Manual of Industrial Medicine 9781512817980

Table of contents :
Preface to the third edition
Contents
Introduction
1. Historical Review
2. Orientation and General Considerations
3. Distribution of Industrial Health Services
4. Administration
5. Physical Examinations
6. Industrial Hygiene and Toxicology
7. Non-Occupational Disability—Sickness Absenteeism
8. Psychiatric Problems of Employees
9. Nutrition in Industry
10. The Physician and Workmen's Compensation
11. The Scope of Industrial Medicine. Summary
Bibliography

Citation preview

MANUAL OF INDUSTRIAL MEDICINE

MANUAL OF INDUSTRIAL MEDICINE By LEMUEL C. McGEE, Ph.D., M.D. Medical Director, Hercules Powder Co. Attending Chief, Medical Division, Delaware Hospital, Wilmington Visiting Professor of Industrial Medicine, School of Medicine, University of Pennsylvania

•c-CJCaEXCtt. IJNIVERMHOf

PHILADELPHIA

UNIVERSITY OF PENNSYLVANIA PRESS

Copyright 1950, 1954, and 1956 Lemuel C. McGee, Ph.D., M.D. First Edition, J a n u a r y 1950 Second Edition, J a n u a r y 1954 T h i r d Edition, March 1956

PRINTED IN THE UNITED STATES OF A M E R I C A A M E R I C A N B O O K - S T R A T F O R D PRESS, INC., NEW Y O R K

PREFACE T O T H E T H I R D EDITION In the historical sense occupational medicine may be viewed as an ancient form of medical practice which has recently acquired a name. Our oldest medical literature (the Edwin Smith Surgical Papyrus) presents case reports of patients suffering from trauma, possibly due to accidents while building the step-pyramid of Sakkarah near Memphis, about 3000 B.C. There can be no healthy atmosphere for business or industry without a healthy atmosphere for its essential components—men and women. It is becoming more evident that employee health is of primary concern to industrial management. Surveys of the health needs of men and women on the nation's industrial rolls show that the greater opportunity for constructive medicine lies in the field of prevention of disease and injury rather than in curative medicine. The objective of prevention is approached through improving the working environment (industrial hygiene) on the one hand, and through meeting the health needs of individual worker (clinical medicine) on the other. Medicine is more than an art and a science; it is a potent and distinguished social instrument. Gorgas in 1904, by controlling disease (e.g., malaria and yellow fever), allowed men to build a canal across Panama. He turned a jungle into productive, habitable areas, making it possible for men and women to rise from marginal subsistence to a productivity commensurate with a higher standard of living. Man must be able to work if he is to enjoy the fruits of his labor. v

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PREFACE TO THE THIRD EDITION

Medical training, to be eminently sound, directs its disciplines toward an emphasis on the concept of the "whole man." This concept, that man's many parts must constitute a whole, has no more rewarding application than in industrial medicine. For selective and effective placement of employees in industry, mental and emotional qualities are as important as physical characteristics. Man is more important than the machine. Preservation and utilization of the potentials of man require maximum knowledge of the person as an integrated individual. The demands on the student of medicine are as tremendous as the field of medical knowledge is vast. By summarizing salient features of a subject and condensing the experience of physicians who have preceded the student in practice, time may be saved for that student. It is hoped that this manual will serve to introduce the student to the implications of industrial medicine, to aid his orientation in the industrial society where he will practice. Few, if any, physicians can escape the impact of industrial life on their patients. LEMUEL C.

Wilmington, Delaware March 1956

MCGEE

CONTENTS Introduction 1. 2. 3. 4. 5. 6.

Historical Review Orientation and General Considerations Distribution of Industrial Health Services Administration Physical Examinations Industrial Hygiene and Toxicology 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Page ix 1 7 11 14 23 30

Abnormalities of Air Pressure Ventilation, Temperature and Humidity Illumination and Radiant Energy Noise Fatigue Dusts, Fumes and Gases Poisons Detoxication Mechanisms Industrial Hygiene Codes Infections and Dermatoses Trauma and Disease

31 38 48 65 74 79 103 125 128 135 142

7. Non-Occupational Disability—Sickness Absenteeism 8. Psychiatric Problems of Employees 9. Nutrition in Industry 10. T h e Physician and Workmen's Compensation 11. T h e Scope of Industrial Medicine—Summary

153 160 165 171 189

Bibliography

193

INTRODUCTION There has been a great increase in attention to problems of industrial medicine concomitant with the vast industrial production required by World War II and the efforts at recovery during subsequent years. Forces that have contributed to the growing interest in occupational health problems are: 1) the increasing national importance of industry; 2) the organization and increased strength of labor; 3) the program of "national preparedness" which has catapulted new and untrained millions of workers into industry; 4) the introduction of new materials and processes; 5) a crystallizing recognition of the fact that certain occupations and industries entail unusual and peculiar hazards to health. 1 T h e United States has become a highly industrialized nation. There are few areas where the practicing physician who treats adults does not have patients who are wage earners. Occupation is related to health. Between the ages of 20 to 65 most of us spend one-third or more of each working day in one or more occupations. It is, therefore, essential that the medical undergraduate gain an understanding of the scope and objectives of occupational medicine and its impingements on all forms of medical practice. Although a physician may never be employed by industry his service to his patient is improved by his knowledge of the conditions of the patient's job. T h e bulk of the work of the obstetrician is that concerned with normal pregnancies and deliveries. T h e pediatrician is concerned first with a normal, healthy child and he works to prevent illness in that child. Physicians ix

X

INTRODUCTION

concerned with adult patients can be more effective if they can maintain health instead of merely coping with disease states. In industry the majority of workers are ostensibly healthy; the physician's goal should be to keep workers at a point of optimum health rather than merely to look for and treat disease. Experience has shown that "when a factory management has once employed a medical officer and set up a medical department it is most unlikely to discontinue what it finds to be a great asset to the happiness and efficiency of the workers." 2 It is to be expected that the science and art of medicine will find a larger field of opportunity in industry in the future than it has in the past.

MANUAL OF INDUSTRIAL MEDICINE

I. HISTORICAL REVIEW EARLY RELATIONSHIP OF MEDICINE TO THE TRADES AND PROFESSIONS A. Ancient T h e Edwin Smith Surgical Papyrus 3 representing the oldest medical literature (originating in a period circa 3000 B.C.) describes surgical cases of patients who may have sustained injuries in the building of the Egyptian pyramids. An illustrative case report which suggests the antiquity of industrial surgery follows: A GAPING W O U N D IN T H E HEAD W I T H COMPOUND C O M M I N U T E D F R A C T U R E OF T H E S K U L L AND R U P T U R E OF T H E MENINGEAL MEMBRANES Title Instructions concerning a gaping wound in the head, penetrating to the bone, smashing the skull (and) rending open the brain of the skull. Examination If thou examinest a man having a gaping wound in the head, penetrating to the bone, smashing his skull, (and) rending open the brain of his skull, thou shouldst palpate his wound. Shouldst thou find that smash which is in his skull (like) those corrugations which form in molten copper, (and) something therein throbbing (and) fluttering under thy fingers until the brain of his (the patient's) skull is rent open, (and) he discharge blood from both his nostrils, (and) he suffers with stiffness in his neck, (conclusion in diagnosis). 1

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Diagnosis (Thou shouldst say concerning him:) "An ailment not to be treated." Treatment Thou shouldst anoint that wound with grease. Thou shalt not bind it; thou shalt not apply two strips upon it, until thou knowest that he has reached a decisive point. Gloss A As for: "Smashing his skull, (and) rending open the brain of his skull," (it means) the smash is large, opening to the interior of his skull, (to) the membrane enveloping his brain, so that it breaks open his fluid in the interior of his head. Gloss B As for: "Those corrugations which form on molten copper," it means copper which the coppersmith pours off (rejects) before it is (forced) into the (mould) because of something foreign upon it like (wrinkles). It is said: "It is like ripples of pus." B.Hippocrates (460-359 B . C . ) , Galen (130-200 A . D . ) , Paracelsus (1493-1541 A.D.) and Ramazzini (1633-1714 A.D.) all wrote on diseases of tradesmen Hippocrates reported the sciatica of Scythian horseback riders; gave us the aphorisms "when in a state of hunger, one ought not to undertake labor" and "those who are accustomed to endure habitual labors, although they be weak or old, bear them better than strong and young persons who have not been so accustomed." 4 Galen reported that students and scholars often suffered pains in the chest and dizziness possibly caused by fumes from tallow candles. Galen also visited a copper mine on the Island of Cyprus, and observed that the workmen "who carried a vitriolic liquid ran with all speed from the mine to avoid death in the midst of their labors." 5 Paracelsus gave a masterly description of the symptoms of chronic arsenic poisoning. "This disease may not be

MANUAL OF INDUSTRIAL MEDICINE

3

treated lightly. It causes phthisis, cough, 'stitch' in the side, difficult breathing, spoiled stomach, vomiting, great thirst, finally dropsy and much swelling around the stomach, hard dry stools, following heat palpitations and trembling, rashes on all limbs." Bernardino Ramazzini, 8 an Italian physician who became known as the " T h i r d Hippocrates" (the second or English Hippocrates was Thomas Sydenham, 1624-1689) and the "Father of Industrial Medicine," wrote the first comprehensive textbook on occupational disease. H e wrote many reports and orations which are masterpieces of clinical observation. Ramazzini noted, for example, that miners were liable to difficult breathing, apoplexy, palsy, phthisis, cachexia, swelling of the feet, falling of the teeth, ulcers of the gums, pains and trembling of the joints. C. Nineteenth Century Developments Early in the nineteenth century C. T . Thackrah of London published an important and instructive volume on the relation of occupation to disease.7 In the preface to his second edition Thackrah observes, "If any object, that the cure, not the causes or prevention of disease, is the business of the medical practitioner, I would reply that the scientific treatment of a malady requires a knowledge of its nature, and the nature is b u t imperfectly understood without a knowledge of the cause." Other Thackrah excerpts of interest are: On odors: " T h e atmosphere of the slaughter house, though thoroughly disgusting to the nose, does not appear to be at all injurious to health . . . they (workers) are subject to few ailments and these result of plethora." On tailors: " T h e i r most common effects are dyspepsia, diarrhea, dull headache, giddiness, especially during the summer. They attribute their complaints to two causes, one of which is posture, the body bent for 13 hours a day, the other the heat on the job . . . tailors are the most in-

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temperate set of men in London. A large proportion die annually of phthisis." On coachmen: "Gentlemen's coachmen often suffer from the excess of nourishment: they eat more than they work. Having often to wait for their masters,—to use Dr. Good's phrase,—'They fill up their time by filling up the stomach!' They also take ale too frequently." On a worker in lead: "It is 16 years since he entered the employ, and during this period he has been laid up 28 times from serious disease! Each attack has been worse than its predecessor. . . . This miserable man is now partially paralytic; he has scarcely any motion in either wrist. . . . " On students: "The position of the student is obviously bad. Leaning forward, he keeps most of the muscles wholly inactive . . . and takes a full inspiration only when he sighs. . . . A highly excitable state of the nervous system is not infrequently produced." Also "Pupils sent to distant medical schools at the end of their apprenticeship, and thus placed suddenly in a scene of dissipation, without governor or adviser—mixing, too, with a large mass of young men similarly situated—suffer from the evils and disease which irregularity produces." Another early monograph on occupational diseases was that of a New York physician, Benjamin W. McCready, published in 1837.8 He had difficulty gathering his material because in interviewing workmen he found that they "are so little attentive to the causes which affect their health, and their views are so often warped by prejudice or interest, that little reliance can be placed upon them." McCready reported that "Agriculture is the oldest, the healthiest and the most natural of all employments." He observed that tuberculosis was less prevalent in the country than in the city and emphasized that "one great source of ill-health among laborers and their families is the confined and miserable apartments in which they are lodged."

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He was a backer of municipal "better housing" projects. He described lead poisoning in painters, noted that physicians were prone to cardiovascular disease and considered the clergy the healthiest of professional men. The first Plant Surgeon of record was William J. Middleton at Pennsylvania Steel in 1884. Andrew M. Harvey (1868-1949) became the first Medical Director in the United States at Crane Company, Chicago, 1896. T h e second seems to be Robert T . Legge who became identified with the McCloud Lumber Company, California, in 1899. 9 ' 10 D. Twentieth Century Developments 1. Europe In Great Britain and elsewhere abroad problems of industrial medicine have been more clearly recognized than in the United States. In many European nations industrial hygiene, for example, was fairly well established in the field of medicine prior to the First World War. 2. United States T h e first industrial practice consisted of sewing up cuts and caring for injuries as a result of trauma. It was only after World War I that the preventive concept of industrial medicine made significant progress in the United States. Modern industrial operations have brought new problems to the physician. Some of the landmarks in the growth of industrial medicine in America are as follows: 5 1895—Nurses were first employed by an industrial organization (Proctor, Vermont). 1910—First American Congress on Industrial Diseases. Workmen's

Compensation

Law in New York

State.

1911—First American laws for compulsory reporting of occupational disease (California, New York). T e n more states adopted compensation laws.

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1914—Public Health Service established an office on Industrial Hygiene and Sanitation. 1914—A section covering Industrial Hygiene was organized in the American Public Health Association. 1916—The American Association of Industrial Physicians and Surgeons was founded. 1919—Wisconsin passed the first clear-cut law making occupational diseases compensable. 1923—The Section on Preventive and Industrial Medicine and Public Health of the American Medical Association was formed. 1926—A Committee on Industrial Medicine and T r a u matic Surgery was appointed by the American College of Surgeons. T h e College formulated and adopted the M i n i m u m Standard for Medical Service in Industry. 1935—The Industrial Hygiene Foundation of America was founded. 1937—The American Medical Association established a Council on Industrial Health. 1939—The First Congress on Industrial Health was held by the American Medical Association's Council on Industrial Health. 1950—The American Foundation of Occupational Health agreed to carry on the program of evaluation and certification of medical services in industry which had previously been conducted by the American College of Surgeons.

II. ORIENTATION AND GENERAL CONSIDERATIONS A. Definitions Industrial medicine has been defined as "the practice of medical supervision, preventive medicine and public health within the confines of an industry"; "the practice of medicine applied to the prevention and alleviation of sickness, injury and physical deterioration among industrial workers . . . " (Selby); "a science which deals with prevention, cure and alleviation of disease as it affects gainfully employed individuals" (Seeger); 11 "the contribution of medicine to the industrial life of the country, and as such is concerned with the study and control of the inherent and environmental factors affecting the health and well-being of persons at their place of work." 12 Industrial medical service strives to fit work to man and man to his work. T o reach its highest effectiveness industrial medicine must utilize from time to time all of the specialties and disciplines found in the art and science of medicine. Consider the recognition and control of exposure to benzene when it is used as an industrial solvent. T h e hematologist is needed to develop the true character of the anemias which may appear in workers. For the recognition of hepatic dysfunction the internist is needed; the pathologist and the clinical laboratory to interpret the nature of liver necrosis. A knowledge of dermatology and of physiology of the skin is needed on questions of skin absorption and effects of removal of fat from the skin through contact with benzene. T h e biological chemist 7

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shows us the value of the partition o£ organic and inorganic sulfate in the urine in detecting absorption of benzene. The engineer shows us how to use benzene in chemical operations so as to limit exposure of the workers. On new problems of suspected occupational disease the judicious use of consultants saves time for the investigator, saves money for the plant and helps to avoid error. B. The objectives of industrial medicine are: 1. T o fit the worker to types and quantities of work commensurate with his ability to perform such work without health impairment or injury to himself and his fellow worker 2. T o prevent occupational disease or injury by the exercise of proper control over working conditions 3. T o conserve the health of the worker through individual medical supervision and education 4. T o restore to health the worker suffering from occupational disease or injury C. Attributes of medicine in industry (as contrasted to other patient-physician relationships) are: 1. Close human associations Men select medicine as a career for numerous reasons. High on the list is the desire for close human contacts from birth to death. A plant physician knows hundreds of men from the $100,000-a-year boss to the youngest apprentice by their first names. He in turn is known as "Doc" or by his first name to many close associates—and truly likes it unless the doctor is an incurable "stuffed shirt." He is consulted by men and women in a variety of troubles. He becomes, in fact, a sort of father confessor on matters varying from alopecia to gestation. 2. Opportunity for earlier diagnosis; i.e., before complaints normally lead the worker to seek medical aid

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Earlier aid is sought because o£ the convenience of plant medical quarters. The employee knows the plant nurse and physician from previous contacts. He does not hesitate, from financial reasons, to ask for advice. 3. Increased effectiveness of the physician through application of medical knowledge for health preservation and disease prevention to large groups of people Examples: smallpox vaccination, tuberculosis case finding, blood serology and diabetes case finding. 4. Improved follow-up and controlled observation on his subjects for the student of disease D. Benefits to the employee are: 1. Early recognition of incipient disease 2. Elimination of anxiety over trivial matters; e.g., unimportant peculiarities of the individual worker without health import 3. Protection against contagious disease at work 4. Prevention of the worker being assigned to work which is too great for his physical status or handicap 5. Protection against occupational disease 6. Opportunity for health education 7. Correction of remediable defects E. Benefits to the employer are: 1. Better employee morale and good will 2. Reduction in the amount of time lost from work because of illness 3. Increased efficiency 4. Reduction in compensation and/or group insurance costs. There are appreciable industrial savings from adequate medical service

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MANUAL OF INDUSTRIAL MEDICINE

5. Correction of disabilities and improved health of workers 6. Better placement and less turnover of labor One survey (Heiser) 13 showed the following average industrial savings from an adequate medical service: Reduction

of Loss

Factors

Occupational disease Accident frequency Absenteeism Compensation insurance premiums Labor turnover

Average 62.8 44.9 29.7 28.8 27.3

Reduction per per per per per

cent cent cent cent cent

III. DISTRIBUTION OF INDUSTRIAL HEALTH SERVICES Medical and health programs available to employees range all the way from first-aid kits to extensive medical services and well-appointed medical departments. A. Part-time service of a physician There should be an organized service for small plants with regular visits by the physician; the "on call" physician is insufficient. T h e physician who is employed only "on call" for emergency or special work rarely has either the opportunity or the interest necessary to supervise and maintain adequate health and medical services. "Part-time physicians are employed to: 1) study and analyze health conditions within the company; 2) supervise and develop the plant medical service; 3) examine applicants and employees in companies which do not maintain formal medical departments; 4) substitute for and assist physicians employed in established medical units; and 5) provide medical attention for employees reporting on-the-job injuries or illness." 14 B. T h e full-time industrial physician "Full-time physicians are employed in increasing numbers in the larger plants. T h e size of the plant requiring a full-time physician is not an arbitrary one. A plant of 2,000 or more employees, for example, may be served by one full-time physician or two or more in part-time service. It is rare to find a plant of less than 1,200 personnel using a full-time medical officer." 15 In 1938, 1,399 physicians gave essentially full time to industry; 16 the figure is probably more than 5,000 now. 17 11

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C. The medical industrial hygienist with governmental agencies (federal, state, and city) Prior to 1936 only 8 states conducted official industrial hygiene activities. As of November 1946, there were 52 such units operating in 41 states.18 D. Influence of the character of the plant 1. Size Few plants under 1,200 men require a full-time physician. Thirty per cent of the factory workers in the United States work in plants having less than 100 employees; 65 per cent work in plants having less than 500 employees. Many of these plants have little or no medical supervision at the place of work. This represents an opportunity for consultation and supervision by the part-time physician. 2. Nature of the industrial operation (manufacturing versus packaging; a foundry versus a chemical industry, etc.) Each industry has its own particular problems. 3. Attitude of the employee If the employees have confidence in the aims of the health program and in the professional competence of the physicians and nurses an effective program reaches the men and women for whom it is intended. 4. Attitude of management The responsibility of management for maintaining or improving the physical condition of employees is subject to various interpretations. There are areas of business life where management prefers not to concern themselves with a health program for employees. A Conference Board Report 1 5 states that "the opportunities and responsibilities of the plant physician entitle him to executive rank, where, with the aid of top

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management, he can determine practical policies and procedures for a sound health program." E. Influence of the character of the physician Industrial medicine in the broad sense is a special form of practice for the internist. ". . . T h e surgeon in industry is gradually giving place to the medical man as the idea of preventive medicine is supplanting the repair of the damage done." (Hazlett) 1 9 "If the physician is to take leadership in the health program he must study not only the technique of healing but also such social factors as family income, housing, clothing, nutrition, education and employment." (Levine, quoted by Hazlett) 19 Lack of interest by the physician or a poorly directed program can lead to inadequate health protection together with failure to maintain the good will of employees and the respect of the community. T h e most successful health programs are those where the plant physician has high professional standing, qualities of leadership, an irreproachable character, mature judgment, and an abiding interest in the welfare of his associates.

IV. ADMINISTRATION A. Material facilities 1. T h e medical department should be adequately housed and equipped. Physicians generally are particularly inept designers. On the other hand, architects and engineers are not cognizant of the requirements of a plant infirmary. T h e physician and the architect should work together. In planning a unit for a new plant, a careful study of the utility of other medical units (by visiting them and seeing their arrangement, by inquiring of the physicians who have used the facilities just what they would change, etc.) yields dividends in avoiding mistakes. 2. Identify the exact function of the medical facilities at the particular plant; survey the existing hospital facilities in the community. 3. In locating the plant infirmary pay attention to the following: a. Access to natural light and ventilation b. Freedom from noise and vibration c. Accessibility to the greatest number of workmen d. Allowance for expansion e. Accessibility to roads from various parts of the plant and to the nearest hospital. T h e area covered by the plant determines the need for substations. Example: jet-propulsion (rocket) powder plants used first aid buildings on the lines, 3 to 5 miles from the main unit. A textile mill or shoe factory has different requirements. 14

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f. Safe distances from hazardous operations in event of disaster. g. Possibility of its being used for the nonworking population in emergencies. Accessibility to civilians, administrative personnel and other persons should be considered, particularly for plants which are geographically isolated. 4. Space In plants having up to 5,000 employees it is suggested that there should be approximately one square foot of space in the unit per employee on the largest shift. 20 5. Waiting room This should open to the plant side with a receptionist at a control point. T h e location of records for speed in taking care of the cases is necessary. Adequate filing space must be had. 6. Treatment rooms Even in large plants one room divided into cubicles for treatment usually suffices. T h e equipment should be arranged for convenience and speed in handling patients. 7. Operating rooms Operating rooms are rarely used at a plant and are recommended only for the largest plants. How far is the nearest general hospital? T h e control of hemorrhage and the temporary immobilization of fractures are the chief major emergencies at a plant facility. 8. Special eye-examining and treatment rooms Visual testing in industry can be facilitated by special equipment. a. J o b analysis will show the particular visual requirements for: 1) Dangerous jobs

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2) Precision jobs 3) Miscellaneous jobs b. The Snellen chart—long a standard for visual testing at a distance of 20 feet c. The near vision chart (Guibor) using the letter "E" is useful with an illiterate worker. This chart is to be held 14" from the eye with an illumination of not less than 3 foot-candles. d. Color tests for estimation of worker's color sensitivity where quick color recognition is necessary (Ishihara or Wiltberger tests) e. T h e Telebinocular (Keystone View Company) f. The Ortho-Rater (Bausch and Lomb Optical Company) g. The Sight Screener (American Optical Company) 9. Examination rooms need a. Adequate dressing facilities b. Privacy, freedom from noise, good lighting c. Place for convenient collection of urine and other laboratory samples 10. Laboratory space What is the job to be done? T h e laboratory is to be planned to fit the needs. 11. X-ray equipment X-ray equipment is usually not required with less than 2,000 employees at the plant. Where x-ray equipment is used remember a. the hazard of injudicious use, and b. that a well-trained diagnostic radiologist is needed for the interpretation of films.

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12. Physiotherapy equipment Infra-red or other heating unit is the most widely used piece of equipment. Extensive physiotherapy apparatus is undesirable unless the volume of work, the training of a physician and technician in physical medicine justify its use at the plant. 13. Storage space. More of it! There is rarely sufficient storage room. 14. Office space for physicians, nurses and clerical aides is necessary for efficient work. Dispensary floor plans and detailed lists of recommended material facilities may be found in the following references: Hess,21 Hazlett, 22 Lanza and Goldberg, 23 Lasher,24 and Conference Board Report No. 96.14 B. Personnel 1. Qualifications of the medical director Hedley 20 states, "The medical director should be more than a good physician, as important as this may be. He should be possessed of qualities of leadership; a sterling character, and the respect of professional associates, plant officials, and the employees who will be his patients. He should have mature judgment, a sense of values and proportions, and a quiet but radiant sense of humor. He should be able to laugh at situations but not at individuals. He should be able to supervise and direct the manifold operations of a medical department. Whatever his previous background his professional standing should be above reproach." A medical director is bound by all traditions of medicine and should understand their necessity and usefulness to the patient. He should be a specialist in environmental medicine.

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2. Relationship to other plant activities T h e physician should be part of the organization, but in a manner natural to his personality pattern. a. Contacts with management require clarity of purpose, logical thinking, and mutual respect. "Many physicians prefer to report directly to a top company executive because they believe that their programs thereby receive more sympathetic understanding." 14 In practice the position an industrial medical officer will occupy in a business organization depends on himself. An organizational function chart hanging on the plant manager's wall cannot put a physician in a place which is unsupported by training, ability and personality. b. Contacts with supervisors, foremen, laborers. Apply the "Golden Rule" and protect confidences. Select the correct person for effective criticism or suggestion. c. T h e relationship of the physician with the personnel department and employment offices should be a close one. d. Relationship with safety department: "For some generally unexplained reason, friction is more likely to develop between the medical and safety departments than almost any other part of the plant. Judged by any standards this is most regrettable. These two departments have so much in common, and are inter-dependent to so great an extent that every effort should be made to develop harmonious relationships. One of the departments should not be under the direction of the other department." 18 e. Relationship with the legal department for the most part revolves around product liability, toxicology and compensation claims. f. Relations with labor union officials and health committees. Don't earn the title "company doctor." T h e

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physician is not a pawn of management. The laborer should understand through instruction the nature of the medical program. The physician in industry should be impartial and confine his opinions and decisions to health and medical affairs. He must never be a disciplinary agent for management or for a union president. He will be trusted and consulted by management and workers only to the extent that his determination to find the truth and act fairly justifies such trust. 3. The scope of industrial medical department activities has been well defined by the Council on Industrial Health, American Medical Association.25 a. Treatment of compensable injuries and diseases Industry has a responsibility by law to furnish medical or surgical treatment for illness or injury which arises out of and because of the occupation. b. Treatment of non-compensable injuries and diseases This is the normal function of private medical practice. The physician in industry should abstain from such services except in the three following situations: 1) Minor illness. The physician in industry may treat minor physical disorders which temporarily interfere with an employee's comfort or ability to complete a shift, and for the relief of which he may need immediate medical attention. 2) First aid for urgent sickness. The physician in industry should employ such measures as the emergency dictates in all cases of urgent sickness occurring during working hours on the working premises, until such time as prompt notification of the family physician relieves him of further responsibility. 3) Rehabilitation after sickness and injury. The physician in industry can properly assume responsibility for those phases of rehabilitation after disability, indus-

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M A N U A L OF INDUSTRIAL MEDICINE

trially induced or otherwise, which progress best under controlled working conditions. 4. Relationship to other physicians practicing in the community Employees look to the family doctor for advice and help during 16 hours of each day when away from the plant. a. T h e family physician should be acquainted with exposures or lack of them at plant. T h e industrial physician must supply this information. When a private physician suspects the diagnosis of an occupational disease or injury in a patient, he should, with his patient's permission, communicate the information to the plant doctor. A conference between the two physicians should be arranged when differences of opinion exist as to the compensability of medical and surgical conditions. b. T h e basic principles of ethical behavior on the part of physicians must be scrupulously followed in comments made to patients. c. Beware of tale-bearing by patients—misquoting physicians. This can be the basis for serious misunderstandings. Experience leads one to doubt the validity of a patient's derogatory remarks about another physician. d. Compensable Disability: 26 Workmen's compensation laws and policies of medical societies usually govern the provision of medical services for occupationally induced injury or illness. A section of the Principles of Medical Ethics, American Medical Association, has direct reference: Sec. 4.—Free choice of physician is defined as that degree of freedom in choosing a physician which can be exercised under usual conditions of employment between patients and physicians. The interjection of a third party who has a valid interest, or who intervenes between the physician

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and the patient does not per se cause a contract to be unethical. A third party has a valid interest when, by law or volition, the third party assumes legal responsibility and provides for the cost of medical care and indemnity for occupational disability. Additional rules of conduct apply: 1) Adequate care of industrial injuries or occupational disease requires that the chosen or appointed physician seek qualified assistance or consultation for all services beyond his ability. 2) An industrial physician shall not, while caring for an industrial injury or disease, urge a patient to have an unrelated concomitant and coincidental disease treated by himself at the worker's expense. 3) When a case is diagnosed as nonoccupational, the patient is to be referred to the physician of his choice. 4) When an employee's personal physician suspects an occupational disease or injury, or when differences of opinion exist as to the compensability of a medical or surgical condition, he should with the employee's consent confer with the plant physician or appropriate company representative. e. Noncompensable Disability: 26 T h e treatment of injuries or diseases not occupationally induced is the function of private medical practice. T h e physician in his industrial relations should abstain from such services except in the case of (1) absence of accessible independent facilities and (2) minor disorders that temporarily interfere with an employee's comfort or ability to complete a shift, for the relief of which he would not ordinarily seek other medical attention. Established standards of medical practice in the community shall govern case finding and immunization programs in industry. T h e physician in industry should employ such measures as an emergency dictates in all cases of urgent sick-

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ness during working hours on the working premises until such time as he is relieved of further responsibility by the family physician. T h e physician in industry and the employee's personal physician should co-operate in those phases of rehabilitation which progress best under medically approved working conditions.

V. PHYSICAL EXAMINATIONS THE PLACEMENT OF THE

AND SUPERVISION WORKER

A. T h e physician's role in fact-finding N o printed form has been devised which will prove satisfactory for all histories or examinations. For purposes of recording, a medical form is helpful by placing information consistently in the same location for subsequent review in a statistical way. T h e physician must follow leads obtained in history-taking in industry as elsewhere. T h e printed blanks are disadvantageous in that they tempt the physician to assume that he has taken sufficient history after filling out the form. T h e more informative part of the history is usually the narrative notes of the physician. Shirking history-taking is a significant weakness of the examination of the healthy subject (periodic medical examination) in, as well as outside of, industry. From the point of view of the employer a medical examination has value in obtaining qualified employees; that is, m e n w h o are physically able to do the work expected of them. From the point of view of labor such an examination if misused may prove to be discriminatory. If the workmen feel that the physician is an agent of the employer, they may fear that some minor physical defect will lead to denial of employment. Intelligent labor leadership is sincerely interested in the pre-employment examination which will protect employees from infectious disease or from the increased hazard of accidents, and 23

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which will enable a man with a physical handicap to be placed where he can earn a livelihood. T h e physician should maintain his position as a professional man furnishing a professional service and finding the facts. B. The pre-employment examination should be, in effect, a preplacement examination. In this way the examining physician can serve by 1. Detecting communicable disease 2. Uncovering hazards to the health of the individual and to his fellow employees 3. Placing handicapped persons in jobs where the handicap is of no moment Examples of job placement: The loss of an arm or leg: the worker should stay on the ground and not be allowed to climb. Impaired vision and hearing: he should avoid moving machinery. Diabetes mellitus: office work is less hazardous than construction jobs (avoid trauma to the feet). Heart disease: what is the exertion required in the job? It can often be matched to the man's capacity for physical activity. Bronchial asthma: avoid the influence of dust, fumes, vapors, pollens, and other precipitating factors. Liver and gall bladder disease: avoid chemical exposure which may possibly further affect the damaged liver. When the so-called handicapped applicant for employment is matched to a job for which he is suited, the handicap no longer exists in terms of employment. A review of the experience of 1,152 companies shows a steady decline in numbers of companies reporting employment rejection rates in excess of 5 per cent and their movement into the lowest group: 17

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Rejection

Rates

0-5 per cent 6-10 per cent 11-50 per cent Total

25

Percentage of Companies 1924 1930 55.0 60.0 28.0 23.0 17.0 17.0

Reporting 1940 78.0 15.0 7.0

Rates 1951 81.5 13.1 5.4

100.0

100.0

100.0

100.0

4. Protecting the industry against unwarranted or excessive compensation claims Example: Five shipyards which conducted preplacement examinations (during shipbuilding for war) were compared with a similar group of shipyards without examinations. The average employment in each group exceeded 100,000. T h e rate of claim for hernias per month per 1,000 men was three times as high in yards without examination as in yards with preplacement physical examinations. Compensation insurance loss ratios were 50 per cent higher in the "no-examination" yards. 5. Learning job requirements. An examining physician needs to know about the various jobs: a. Particular physical and mental requirements b. Length of hours, shifts, day and night work, overtime pay, etc. c. Occupational health hazards, safety hazards Preplacement code long used in industry: Class A: Physically fit for any work Class B: Negligible or correctible defect which does not interfere with any activity at work Class C: Defect which limits fitness for work and leaves the employee eligible for certain jobs (The defect may or may not be correctible, but usually does require medical supervision.)

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Class D: Defect which requires medical attention, is seriously handicapping and disqualifies for any type of employment The Council on Industrial Health of the American Medical Association has suggested that ratings may be reduced to three major classifications: 1. Individual fit for all work 2. Individual fit for work under periodic medical review 3. Individual unfit for work at the time of the examination. Major findings should be discussed with the worker. Inform the applicant of physical defects found and their influence on the job sought. A transcript of findings should be available to the employee's personal physician or to other community health agencies on the request or consent of the employee. C. The periodic reexamination 1. Why make the periodic health inventory? Every lay person needs advice on health. This can properly be given only by a physician in conference with the individual. Lay health news features are inadequate for this purpose. An opportunity to render service can be exemplified by such subjects as: nonsymptomatic physical handicaps, behavior eccentricities (excesses in any direction—athletic, sexual or occupational), and selfmedication (cathartics and sedatives are frequent offenders).27 2. Special characteristics of the periodic examination a. Signs and symptoms. These are usually not well advanced inasmuch as the examiner often sees the patient before he complains or is aware of being ill. b. The family history. This is an important guide, particularly in the anticipation and early management of

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27

obesity, cardiovascular disease, diabetes, allergy, pernicious anemia, and hereditary disease of the nervous system. c. Importance of the personal history. Jaundice, anemia, recurrent respiratory disease and the like, point to desirable living habits and special preventive considerations on the part of the subject while he is yet in good health. 3. Flexibility in the frequency and extent of examination procedures. What should be included in the periodic examination? Match it to the needs of the examinee. a. The doctor must be willing to devote his time and energy toward making periodic examinations effective. b. The character of the examination should vary with the patient's occupation, age and sex. Example: pelvic examination in women over 40 years of age, electrocardiographic examination in older men, and the diagnostic follow-up of digestive disturbances after the age of 40 years. 4. Proper use of medical findings a. By the worker's personal physician: T h e data which lead to the suspicion of early disease should reach the home physician or the medical specialist (with consent of the employee). Handle the diagnostic data astutely so as to obtain medical supervision for the employee without raising unnecessary fears. Remember that he does not understand the significance of the findings. Skill and sympathy are required in the follow-through on the findings from the periodic examination. b. For health education and advice: Watch for the "introspective worker" and anxiety neuroses. "A little learning is a dangerous thing." Health education involves the art of medicine.

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1) Distinguish between significant and nonsignificant symptoms 2) Discourage self-medication 3) Explain normal physiologic processes 4) Define approved personal hygiene habits 5) Psychologic quirks should be corrected in their incipiency. Examples: (a) fear of halitosis; (b) unreasoning phobias; (c) inability of the worker to accept any point of view except one reached by himself. 6) Advise the older worker as to hobbies, limitations of exercise, eating, sleeping, the use of alcohol, etc. c. For statistical studies and clinical investigations by the physician 5. Special examinations for workers in hazardous occupations or with exposure to toxic chemicals Example: T N T , DNT, tetryl, mercury fulminate, lead azide, carbon tetrachloride, benzene, and lead workers are examined as often as every three to six weeks if the exposure is potentially significant. The type of examination and laboratory work must be appropriate for the physiologic and pathologic changes. (See section on Dusts, Fumes and Gases—VI 6; Poisons—VI 7) 6. Other examinations of employees a. Physical examinations after illness or absence of 3 days, 7 days, or longer. This procedure limits the introduction of infectious disease into the plant, prevents the worker returning to work before he is physically able to do so. b. Transfer examinations: i.e., from one job to another possibly requiring different physical qualifications. c. Examination by request of the employee. Encourage this type of interview.

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d. Termination examinations where knowledge of exact physical status is indicated. e. T h e examination of food handlers—important in control of communicable disease. 7. T h e chief variations from acceptable health standards noted on the periodic reexamination of one group of eight thousand workers were: 28 Disorder Obesity (20 or more pounds overweight) Underweight (20 or more pounds) Dental disease Visual errors Corrected vision (glasses) Uncorrected vision Hypertension (systolic above 150 mm. H g and/or diastolic above 90 mm. H g )

Per cent of Workers 25.6 11.5 18.1 19.4 13.9 5.7 20.9

VI. INDUSTRIAL HYGIENE AND TOXICOLOGY "Industrial hygiene may be defined as the science and art of preserving health through the recognition, evaluation, and control of environmental causes and sources of illness in industry." 1 8 A. Agencies in the field—sources of information 1. Bureaus of industrial hygiene in Federal, state or city governments 2. Independent laboratories of industrial toxicology 3. Departments of biochemistry, physiology, clinical pathology and toxicology in medical schools 4. Various national societies concerned with industrial hygiene are: American Conference of Governmental Industrial Hygienists; American Industrial Hygiene Association; American Standards Association; the Industrial Hygiene Foundation; the Industrial Medical Association; Section on Preventive and Industrial Medicine and Public Health, and Council on Industrial Health, of the American Medical Association; American Association of Industrial Dentists; American Association of Industrial Nurses; American Society of Heating and Ventilating Engineers; Conference of State Sanitary Engineers; the Academy of Occupational Medicine and the National Safety Council. 30

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31

B. Character of industrial health hazards 1. Abnormalities of air pressure a. Abnormally low barometric pressures 1) In acute lowering of barometric pressure there are either no symptoms or slight dizziness, faintness, breathlessness, consciousness of heartbeat, and nausea beyond 10,000 feet for some subjects and up to 18,000 feet for others. This is probably due to the failure to saturate the hemoglobin of the blood with oxygen. Two per cent of one group of subjects showed pallor, sweating, bradycardia, a fall in blood pressure and flaccid unconsciousness (a neurocirculatory collapse) at 18,000 feet without supplementary oxygen. This more severe reaction to anoxemia occurring at such barometric pressures was corrected promptly by the administration of oxygen and/or the removal of the subject from the altitude chamber. By administration of oxygen through a mask the influence of rapid ascent on man can be held back until a level of 35,000 to 40,000 feet is reached. In commercial flying, pressurized cabins are customarily used to protect passengers from symptoms at levels above 10,000 feet. 2) Acute high altitude reactions (generally at 30,000 to 38,000 feet). "Altitude sickness" is a term introduced by E. C. Schneider in 1918.29 a) Neurologic reactions: paresthesias, reflex changes, anesthesias and even paralyses, hemiplegias, asphasias, dysarthrias. b) Myocardial damage. Rarely there is evidence of hypoxia giving alterations in the electrocardiographic tracing which change toward normal in a week or ten days.

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c) High altitude shock. A collapse reaction with hemoconcentration either during the test or an hour or so after the chamber "flight." There may be premonitory signs in the form of aeroembolism (decompression sickness). The symptoms of highest incidence are blurring of vision, nausea and vomiting, transient loss of consciousness, frontal headache, cold extremities, cyanosis and low blood pressure. Death may occur.30 3) Chronic low barometric pressure It was shown by Viault in 1890 that polycythemia follows a sojourn at high altitudes. Natives of the Andes (altitude 18,000 to 22,000 feet) have 7,500,000 to 8,000,000 erythrocytes per cubic millimeter of blood. The change in the blood can be observed in animals as well as in man. The increased cell count may be due in part to contraction of the spleen and expulsion of the cells from this reservoir, and in part because oxygen want probably stimulates new blood formation in the marrow. The stimulating influence of anoxemia on the hemopoietic system is restricted to the formation of red blood cells and hemoglobin. Leukopoietic activity is not affected. 31 a)

Acclimatization

Full acclimatization to a lower oxygen tension is defined as a state allowing "maintenance of growth in young animals, maintenance of normal body weight in mature animals, no loss in appetite, a feeling of general well-being and normal fertility." 32 Chief physiologic mechanisms involved are: (1) Increased ventilation of the lungs which elevates the 0 2 tension in the alveoli while simultaneously reducing the C 0 2 tension. This adjustment may become complete within a few days to a few weeks.

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33

(2) As the blood bicarbonate is reduced, the alkaline reserve becomes lower so that the blood p H remains normal. (3) T h e cardiac output is increased early in the adaptive process. Later the output is normal. Teleoroentgenograms suggest some right-side cardiac hypertrophy. (4) There is an increased vascularity of tissues (greater diameter and tortuosity of smaller vessels) presumably allowing improved diffusion of 0 2 , nutrients and metabolites. (5) There is a marked increase in the total circulating hemoglobin and erythrocytes. T h e hematocrit may show 60 per cent cells at 15,000 feet altitude. (6) Blood bilirubin is doubled at 15,000 feet altitude because of the increased turnover of the red cell mass (higher erythrocyte destruction and formation rate). In the acclimatized human being the plasma volume, resting metabolic rate, growth and body weight are normal. 32 In acclimatized persons Monge 33 found: Cardiovascular

system:

(1) R e d u p l i c a t i o n of t h e

second heart sound, and (2) bradycardia after work with sudden change to tachycardia and back again. Otherwise the response is that of a trained athlete. Respiratory

system: (1) I n the Andeans the chest

is enlarged and the vital capacity is 10 per cent greater than in the Europeans. (2) Workers have periodic hyperventilation. Blood: R.B.C., Hb. and hematocrit are higher than at sea level: R.B.C.—5,840,000 to 8,260,000 Hb—15.93 grams to 20.90 grams Hematocrit (R.B.C. per cent)—56 to 70

MANUAL OF INDUSTRIAL MEDICINE

Blood protein level is somewhat increased, arterial blood oxygen saturation is lower than in residents at sea level. Chiodi 34 made blood studies on 84 subjects in good health who lived permanently at 14,800 feet above sea level. The subjects had been living in that location from 3 months to 57 years. He found the following: Average hemoglobin values were 19.4 grams (range 15.7 to 24.9). Erythrocyte counts averaged 6.46 million per cu.m. (range 5.07 to 9.93). Hematocrit averaged 59.5 per cent (range 50.5 to 73.6). There was found an inverse correlation between red cell number and mean corpuscular volume. No relation was found between the length of residence (duration of hypoxia) and the degree of change in the blood picture. A great increase in hemoglobin took place within the first year of residence at that altitude in most instances. In rare instances almost normal values were found ten years later. Why? T h e possibilities suggested were: 34 A widened range of the normal individual variation found at sea level A different degree of hypoxemia found in subjects living at the same altitude, the response of the hemopoietic system being proportional to the intensity of the hypoxemia stimulus Some unknown factor which would make a great increase in hemoglobin less necessary for the adaptation of the human body to chronic hypoxemia

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35

b) Chronic Mountain Sickness (Soroche, Monge's disease; non-acclimatization or overstrained compensatory mechanism?) After years of adaptation, or at least tolerance, of low oxygen tension (sometimes as long as 20 years) a condition known as chronic mountain sickness may develop. 33 T h e disorder may appear abruptly or insidiously. T h e clinical picture is similar to that of a fully advanced polycythemia vera: (1) T h e patient has a deep ruddy color which turns blue on the least effort. Capillaries are dilated and conspicuous. The hands show clubbing of fingers. " T h e nails appear to be inserted like watch crystals." (2) Hoarseness, aphonia and epistaxis (3) Weakness, drowsiness—possibly 2 or 3 hour periods of coma (4) Dyspnea, emphysema and bronchitis (5) Algesias (of extremities and lumbar back) and paresthesias are common (6) Sexual frigidity with loss of fertility (7) Erythrocyte count, hemoglobin and hematocrit are higher than in acclimatized persons b. Abnormally high barometric pressure Such pressures are found in occupations where compressed air shafts and caissons are used and in diving operations. T h e atmospheric pressure at sea level is equal to 760 mm. of mercury (one atmosphere or 14.7 lb. per square inch). Thirty-two feet below sea level the pressure of water plus the atmosphere is equivalent to 2 atmospheres (29.4 lb. per square inch). High pressures may be tolerated up to 16 atmospheres (235 lb.) without harmful effects on the body, if the pressure of air within the body and outside the body is

36

MANUAL OF INDUSTRIAL MEDICINE

equalized (middle ear, sinuses, viscera, etc. If air passage to these structures is occluded, pain, edema and hemorrhage may result from changes in pressure). If the glottis is kept closed during a rapid change of air pressure lung capillaries may rupture in rare instances. T h e living body is permeated by the atmosphere in which it lives. There are two classes of gas: (1) the biological gases 0 2 and C0 2 —chemical union as well as physical solution in body fluids; (2) the inert gases making up 79 per cent of the normal air, chiefly nitrogen, which are in simple physical solution. 29 Decompression Sickness (The Bends—Caisson Disease— aero-embolism) 35 1) Symptoms When a person who has been exposed to air under high pressure for several hours is brought back to normal pressure too rapidly, the following symptoms may develop: a) Pain in the muscles and joints of the arms and legs (from the formation of gas bubbles in the perivascular and periarticular tissue spaces which, by distorting tissues and nerve endings, cause pain). b) Itching and rash of the skin c) Vertigo d) Nausea and vomiting e) Epigastric pain f) Shallow, rapid respiration, coughing and chest "burning" (the "chokes" from interference with circulation in the lungs) g) Cyanosis or ashen gray appearance, sometimes shock h) Occasionally there are symptoms referable to the central nervous system; e.g., paralysis

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37

These symptoms are believed to be due to the presence of nitrogen bubbles in the blood vessels, forming air emboli which obstruct the flow of blood in small vessels. Nitrogen (and other gases) diffuses into the body during the hours of work under the increased pressure. Time is required for the removal of nitrogen (especially from body fluids and fat) when the ambient pressure is lowered. Decompression sickness may also result from high altitude flying; e.g., sudden loss of pressure in pressurized cabin. 2) Principles underlying prevention of compressed air illness: a) Limit the time of exposure in compressed air or employ helium-oxygen mixtures for saturation in pressure exposures. By way of prevention of compressed air illness, helium may be used instead of nitrogen in the compressed air supply to men working under high pressures. T h e advantages are: Helium is less soluble in fat and body fluids than is nitrogen (ratio of 1 to 4.5 parts). Furthermore, the rate of diffusion of helium in body fluids is greater than that of nitrogen, hence decompression can be done faster. Thus, helium-oxygen mixture has increased the depth for practical diving operations from 150 feet to 500 feet (Behnke).36 Its use allowed the U.S.S. Squalus to be salvaged at a depth of 240 feet. b) Reduce rate of ascent (i.e., decompression). The ascent of a diver should not be more than 25 feet per minute and in stages, reducing the pressure by half in each stage and allowing time for adjustment of the worker to each stage of decompression. 18 c) Slow decompression following long exposures and the inhalation of oxygen at the lower decompression levels

38

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d) Select and maintain personnel in good physical condition. T h e selection of personnel helps to prevent the bends. Excess fat tissues absorb a large proportion of nitrogen when in high pressures. Thus, avoid the obese worker in high pressure work. 3) Treatment: Recompression!! "Perhaps there is no therapeutic procedure more effective than recompression as applied to the asphyxiated, pulseless, cyanotic patient whose blood stream is filled with multiple gas emboli. Even patients presenting incipient lesions of the spinal cord have made complete recovery under immediate and prolonged recompression." (Behnke) 2. Ventilation, T e m p e r a t u r e and Humidity a. Ventilation 1 ) Ventilation may be defined as the process of supplying or removing air by natural or mechanical means to or from any space. Air conditioning is more inclusive and implies the control of some or all the physical and chemical qualities of air. Natural ventilation results from (a) air passing transversely through a space from horizontal wind force (anemotive ventilation) and (b) air movement produced by convection currents (thermal or gravity ventilation). 18 Mechanical ventilation involves suction for removal of air or introduction of air by pressure. Ventilation in a heated room involves a significant heat loss if cool air is used for replacement. 2) Air movement for comfort: When the work is n o t strenuous, the air movement should not be over 40 feet per minute at normal temperatures (the "draft" threshold is approximately 50 f.p.m.). At higher temperatures

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39

and in heavy work, the air movement should be increased; velocities in excess of 150 to 200 feet per minute, however, are considered irritating and undesirable. 3) Purpose of ventilation: a) T o dilute odors, body and other. The need here varies with habits of personal hygiene, the allocation of room space per person, character of odors, etc. It has been calculated that from 7 to 25 c.f.m. (cubic feet per minute) of fresh air are required to control body odors, depending upon the degree of crowding in the work space and the physical activity of the workers (Brandt). 20 b) T o prevent the spread of air-borne infections (control the direction of air currents for removal of dust and floating particles). c) T o remove noxious gases, fumes and mists (up or down currents depending upon specific gravity of a chemical). Do not draw toxic gas across the face of a worker! Industrial process ventilation for specific purposes (e.g., to remove solvent vapors) often utilizes local exhaust air removal to lower the concentration near the site of the hazard (canopy hood or slot on a tank). T h e design of suitable ventilation is an engineering problem. 4) A serious lack of oxygen (suffocation) or true carbon dioxide excess due to human respiration is virtually impossible in buildings constructed above the ground. Carbon dioxide concentrations of 0.10 to 0.50 per cent are not harmful. b. Temperature and humidity: T h e hypothalamus is an integrator for a number of autonomic functions of the body such as temperature regulation, water balance, and vasomotor control of the transport system.

40

MANUAL OF INDUSTRIAL MEDICINE

It has been estimated that in a temperate climate heat is lost chiefly by the body through (1) radiation (wave form as in a vacuum, 60 per cent), (2) evaporation of sweat (25 per cent), (3) conduction and convection (15 per cent). If the air temperature is equal to or above the body temperature, heat cannot be lost by conduction, convection and radiation. If the air is nearly saturated with water vapor, the sweat mechanism is not efficient in losing heat. If the sweat runs off the body, there is little heat lost. Sweat must evaporate to dispose of heat. Air movement facilitates the loss of heat from the body by exchanging the warm moist layer in contact with the skin with cooler and dryer air.37 1) Relation of temperature and humidity to general health and efficiency. Factors affecting thermal comfort 38, 39 are physical (temperature, radiation, humidity, air movement and clothing) and physiological (including the state of health, age, sex, physical activity, and acclimatization). No satisfactory method has yet been found for combining the physical environmental factors into a single index that would indicate the degree of warmth perceived by an individual under various environmental conditions. In studies on adjustments to heat these changes have been described: 40 Initially there is warming of the skin and resulting vasodilation. Such dilation is accompanied by splanchnic constriction with displacement of the blood to the skin. Thermoregulation is more dependent on the changes of temperature in the regulatory centers than on reflex reactions to sensory stimulation. Within an hour, rectal temperature, and presumably brain temperature, is somewhat raised and sweating develops. As long as the physical conditions of the surrounding air will evaporate moisture from

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41

the skin, the body's heat regulation system continues to secrete sweat which, through evaporation, may maintain a relatively cool skin and a stable deep temperature. Thus at low humidities the body may maintain a normal temperature even when air temperature is in excess of that of the body. Respiration is increased, carbon dioxide is removed more efficiently and the blood becomes more alkaline. There may be a fall in blood pressure. There is an increase in blood volume and, after a few days, an increase in blood proteins. Acclimatization to warmth is accomplished mainly during the first week but, like that to cold, it is probably not complete for months. With acclimatization there is a reduction in the salt content of the sweat, presumably because of adrenal cortical activity.41 2) Recommended temperatures and humidities: T h e optimum temperature in American industry during the winter months lies between 68° F. and 73° F., with moderate humidity, for light or sedentary work. For moderately hard work a temperature of 65° F. or even 60° F. is preferred. The humidity is not of great importance, except for high humidities, if the temperature is between 65° F. and 75° F. The higher the temperature, the greater the importance of humidity of the air due to the need for sweat to evaporate. In considering the extremes of temperature and humidity which may be tolerated by man when required, it is noted that at lower humidities somewhat higher temperatures can be tolerated if the air is moving. A dry atmosphere with a temperature of 110° F. is usually better tolerated than is a moist environment of 95° F. T h e wet bulb temperature should be below 91° F. for efficient work. 42 A prolonged stay in a hot humid environment is ac-

42

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companied by feelings of lassitude and irritability, a tendency to forgetfulness and a slowing of one's movements with motor incoordination. 43 Short exposures are better than longer uninterrupted exposures to moderately high temperatures. In outside work extremes of temperature and humidity are encountered. Good physical state, avoidance of excess alcoholic beverages, proper clothing, suitable rest periods, good circulatory efficiency, all increase the tolerance of the worker to extremes of temperature which come under seasonal and other customary climatic changes. It becomes an engineering problem to provide the right temperature and humidity for inside working conditions. Air-conditioning temperatures need to be related to the outdoor temperatures. If the difference is more than 10° F. a "temperature shock" is risked by the sedentary worker entering such a workroom. Vasomotor rhinitis and the phenomenon of "cold allergy" make sudden changes in temperature undesirable. 3) Examples of unfavorable effects of hot weather: a) Increases in the apparent susceptibility of workers to toxic chemicals (e.g., trinitrotoluene, dinitrobenzene). T h e increase in depth and rapidity of respiration may increase the amount of poison a man absorbs through the lungs. Heat aids the volatility of poisons. b) Water-soluble skin irritants, such as soda ash and lime, produce little damage to the dry skin b u t when dissolved in perspiration will cause troublesome irritation. c) Creosote and tars used in preserving wood, exude in hot weather, stick to the skin of the hands and produce burns.

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43

4) Clinical disturbances due to heat. Excessive exposure to heat may produce illness of one of the following types: a) Heat cramps (stoker's cramps). These are painful spasms affecting usually the abdominal muscles or those of the arms and legs. The patient has diminished osmolar concentration of body fluids from loss of sodium chloride accompanying copious intake of water. T h e blood and urine show lower sodium chloride content. b) Heat prostration (heat exhaustion), with signs of depression, weakness, faintness and lassitude. This is usually a mild disorder of poorly acclimatized persons. Occasionally syncope and signs of shock may be noted. There is little or no change in body temperature; the sweating mechanism continues to operate in the typical patient. Depression of the vasomotor control has been suggested as the cause of the syndrome. c) Heat stroke (sun stroke, heat pyrexia), with mental excitement followed by unconsciousness, elevated body temperature, headache, dizziness and evidence of dehydration. Heat stroke is more likely under conditions of strenuous muscular exercise in workers poorly acclimatized to heat. T h e onset of illness may be (1) acute with early and persistent coma or delirium, (2) as above with remission and late relapse, or (3) insidious with a progressive course and late coma. 44 Laboratory findings are leukocytosis, a moderate rise in blood nonprotein nitrogen, a decrease in C 0 2 combining power and a thrombocytopenia. Pathologic changes in the central nervous system of men dying from this disorder are: (1) degeneration of neurons and replacement by glia in the cerebellum, cerebral cortex and basal ganglia, and (2) congestion,

M A N U A L OF INDUSTRIAL MEDICINE

edema and petechial hemorrhages, most commonly in the region of the third and fourth ventricles. Hemorrhages occur also in lungs, pericardium, endocardium and adrenal cortex. It is assumed that heat stroke impairs the thermostatic function of the hypothalamus and that as a consequence the autonomic nervous system is unable to maintain sweating or adequate peripheral circulation. The prominent clinical features are the hot dry skin (loss of capacity to sweat) and rapidly mounting body temperature. A combination of these forms of heat disturbance may be seen in the same patient. Saphir described ten cases of unsuspected hypochloremia with symptoms of a psychoneurosis rather than "salt deficiency cramps." 45 (a) Intestinal symptoms were vague epigastric distress, abdominal cramps, nausea and occasional vomiting, (b) Symptoms referable to the nervous system were headaches, dizziness, tremor, hyperreflexia, hyperhidrosis, nervousness, apprehension, restlessness, insomnia, loss of pep and strength, depression, personality changes and even frank anxiety. d) Prevention Reactions to heat are largely preventable through improvement in working and living conditions, rest periods, suitable clothing and adequate salt and water intake. The concentration of sodium chloride in sweat may vary from .05 to 0.5 per cent. 40 Profuse sweating can rob the body of surprisingly large amounts of salt—at the rate of a liter of sweat an hour one can lose thereby 3 or 4 grams of salt per hour. Over an eight-hour period the electrolyte content of the body may become seriously depleted. (Normal daily intake is 8 to 12 grams of salt.) Such a worker needs to take salt in unusual amounts (20 to 30 grams

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daily in extreme salt loss) with his daily food and drink. This can be accomplished by taking salt tablets, by adding more salt to the food or by drinking a dilute aqueous solution of sodium chloride. Of all the substances to be found in sweat, water and NaCl are the principal ones whose loss by sweating may affect homeostasis to a serious degree. 41 Potassium and other minerals, lactic acid, nitrogen, and vitamins may be lost in negligible amounts, have little known effect on the physical state of the worker even in excess sweat loss. e)

Treatment

In instances of heat exhaustion the patient should be treated for shock; i.e., conserve the body heat, keep the patient recumbent and with the head at least as low as the rest of the body, and correct the disparity between the blood volume and the circulatory bed. In sunstroke the patient should be placed in a cool, shady place with the head elevated. A cool sponge bath should be given to facilitate the gradual lowering of the body temperature. Water and salt are required and may be given orally, intravenously, or by hypodermoclysis depending upon the condition of the patient. T h e abdominal cramps of salt deficiency respond quickly and completely to treatment with sufficient sodium chloride. Persons with marked heat exhaustion or suffering from sunstroke should be removed to a hospital after emergency treatment is given. Serious cases are less commonly seen in industry now than a decade or so ago. They are wholly preventable if a few grains of common sense and a few grams of salt are taken prophylactically. As one industrial

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physician quipped, "It isn't the heat—it's the stupidity!" 5) Low temperatures Statistically a fall in temperature in the winter is followed in the next week by an increase in death rate from respiratory diseases, showing predisposition to acute respiratory disease, pneumonia, etc. Some reports indicate a higher incidence of rheumatism associated with this cause. In cold environments the body endeavors to decrease heat loss by cutaneous vaso-constriction. T h e blood becomes concentrated (water loss to organs like spleen, liver, muscle and to connective tissue) in response to a chilled skin and constricted peripheral vascular bed. At the same time more heat is produced by an increase in muscle tone, shivering and voluntary movements (i.e., increased metabolism). If this is not sufficient to maintain the body temperature, the feeling of cold and pain gives way to numbness, muscular weakness, and an inordinate desire to sleep. When the body temperature falls to 80° F. pneumonia often sets in and death probably occurs when the body temperature falls below 70° F. (experiments with hypothermia treatments indicate that body temperature as low as 75° F., for a short time, does not produce any permanent damage to normal tissues). 6) Clinical disturbances due to cold T h e usual effect of cold in industrial workers is that of local changes of exposed parts of the body: fingers, hands, toes, feet, arms, nose and cheeks. These may be: a) Acute transient inflammatory reactions—vaso-constriction is followed by immediate vaso-dilation due to the liberation of a histamine-like substance in the tissues. There is swelling of the tissues with increased fluid.

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T h e term "immersion foot" (trench foot) denotes a disorder that results from prolonged chilling short of freezing. It is an inflammation without thrombotic ischemia or true gangrene. T h e lowered temperature leads to ischemia and tissue anoxia. Montgomery 4 7 suggests that cellular damage may result from 1) ischemia (lack of oxygen and glucose; accumulation of C 0 2 , lactic acid and other metabolites), 2) lowered temperature (decreased metabolism, interference with enzymatic processes within the cell), or 3) failure of nerve conduction (vasoneuropathy). b) Chilbains and allied conditions—prolonged or repeated exposure to cold gives chronic changes in the skin with redness developing into a purple color, tenderness, itching, pain and soreness, edema, blisters, ulcers, and even local necrosis and gangrene, from vascular changes. c) Frostbite—in this there is actual freezing of the skin. Freezing of the skin occurs between 0° and 2° C. Frozen skin appears pale, dull, opaque and yellowish in color. An exudative inflammation with necrosis follows. In severe cold exposure the wet phase (blisters and exudation) does not appear. After thawing, the skin becomes increasingly dark, dry and the tissues mummify. Spontaneous amputation of the parts (example, digits) may take place. This dry gangrene indicates thrombotic occlusion of arterioles supplying the involved tissues. Heparin and anti-infective measures may limit the damage in such patients. For outside work in cold climates prevention of illness from exposure lies in proper clothing. Wool is superior to cotton or linen. If the heat supply to the worker (from metabolism) keeps pace with the heat loss in a cold environment the extremities will remain

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comfortable. Experiments have shown that if the heat loss exceeds the heat supply by more than 15 per cent the hands and feet become cold. 48 It appears that the regulation of the blood flow to the extremities in the normal subject is primarily determined by the thermal state of the body as a whole. Even with the bare hand exposed to temperatures ransino; o O from 0° to minus 30° F. the vasoconstrictive effect of such severe cold was subordinate to the autonomic control of blood flow in the extremities in normal subjects; i.e., if the body is warm the hand skin temperature can be sustained at 70° F. or above. Therefore, artificial application of heat to the extremities is unnecessary for their comfort. In medical treatment of vasospasm of the extremities heat should be supplied to the whole body rather than to the affected part alone. 48 A tendency to undue vascular constriction when the hands are chilled is not uncommon in middle-aged or older adults. Clinically, a marked cold sensitivity of this character is noted in Raynaud's disease. In selecting personnel for exposure to a cold climate the most disadvantageous quality in a worker is early and intense peripheral vasoconstriction in the extremities to cold exposure. Individuals with slight excess of body fat have a decided advantage in emergency cold exposure. Man's range of acclimatization or tolerance to cold stress is smaller than is that to heat stress. Man is essentially a subtropical animal. 3. Illumination and Radiant Energy Physical nature of radiations. Corpuscular (particles): alpha particles, beta particles and neutrons. Electromagnetic radiation: gamma rays (0.005 to 1.5 A.U.), X-rays

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49

(0.01 to 10 A.U.), ultraviolet light, visible radiation, infra-red rays. Illumination

a. Benefits of good illumination 1) Increased accuracy in workmanship. 2) Increased production resulting in decreased costs. 3) Less spoilage. 4) Better utilization of floor space. 5) Less eyestrain and fatigue for workers. 6) Increased vision for older employees and those with subnormal vision. 7) Greater safety. Poor illumination is a factor in the production of accidents. Physicists and engineers have placed the matter of illumination on a scientific basis. There is, however, great variation in individual preferences for illumination for reading or other specific activity. b. Illumination Terms Light is defined as radiant energy with the capacity to produce visual sensation. Brightness "is the luminous intensity of any surface in a given direction per unit of projected area of the surface as viewed from that direction," or, more simply, the amount of light energy that an object sends to the eye. This is expressed in candles per unit area of surface.49 Foot-candle is the illumination upon a surface placed at right angles to the light-rays at a distance of one foot from a light source of one candlepower. Contrast involves variation in brightness and color of two or more objects.

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c. Factors of importance are: 1) Spectral character and color of light. A prompt recognition of colors is essential for workers in transportation, painting, dyeing, lithography, clothing and textile manufacture, and some chemical operations. Color Perception: Each different wave length of lia;ht stimulates a different nerve fiber in the retina. Persons with normal color vision build u p their color appreciation by combining red, green, and violet in various mixtures, aided by white and black at times. It is stated that 160 hues can be differentiated. Since normal persons can distinguish three primary colors and combinations thereof, such persons are called trichromats. T h e common type of color blindness (i.e., redgreen) results from the recognition of only two primary colors. Such persons are called dichromats (the red-blind see red as a green; the green-blind perceive shades of red and pink as green). This type of color blindness is congenital (about 4 per cent of males so affected; only 0.4 per cent of females). There is a transitional group which possesses trichromatic vision yet has poor recognition of red and green and requires a good light for distinction. (These are called anomalous trichromats!) 5 0 2) Quality of light (direction of light, diffusion, absence of glare, etc.). Glare is one of the most detrimental factors encountered in industrial plants. 3) Quantity of light (amount of illumination). T h e r e is a disturbing effect from high brightness ratios, especially with higher intensities of light used; e.g., white on black. T h e contrasts should not be marked. In a factory interior provided with adequate lighting sources, color (of walls, floor, machines, materials, etc.) can mean the difference between good and bad

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visibility. Light color tones reflect more light than do dark color tones. Psychologists say, furthermore, that pleasing color schemes can be conducive to desirable work attitudes, to promotion of efficient performance. Plants, which have paid particular attention to color, report that such attention was worth while. 4) As an aid to safety, color has an important role. Colors call attention to hazards and safety equipment in industry. The color code of the American Standards Association provides the following: 51 Red is the basic color for indicating fire protection equipment, danger, and stop. Orange designates dangerous parts of machines and energized equipment which may cut, crush, shock or otherwise injure. Yellow designates caution and is used for marking physical hazards such as: striking against, stumbling, falling, tripping, "caught in between." Green indicates "Safety" generally and is used on gas masks, first aid kits, the plant dispensary, stretchers, safety deluge showers, etc. Blue is the warning color against starting, the use of, or the movement of equipment under repair. Purple is finding increasing use as the color marking radiation hazards (x-ray, alpha, beta, gamma, neutron, proton, deuteron and meson). Black and white separately or in combination are used for housekeeping and traffic marking. White, for example, is recommended for waste receptacles, room corners, hand rails, and edges of steps. d. Eyestrain We should bear in mind that eyestrain is largely muscular in character—hence the importance of correc-

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tion of visual errors for exacting near vision work, etc. Midsummer daylight is about 10,000 foot-candles. Moonlight intensity may be less than one foot-candle. These extremes require a marked accommodation ability in vision. Contrasts between light and dark areas produce muscular work in adaptations by the iris as the eye is turned from one area to the other. Color and reflectance of the object of work determine the amount of light which should be directed at the object for easiest vision. Practical factors in seeing are size of object, brightness, contrast, time (fast-moving objects not clearly seen), and color. T h e Illuminating Engineering Society has prepared accepted standards for adequate lighting for various work activities. 52 Conditions which produce obvious discomfort should be avoided or eliminated. It should be noted that individuals differ in the amount of light they find optimal for comfortable work. Here physical and engineering standards must compromise to some extent with preference of the worker. Modern artificial lighting is superior to day lighting because of flexibility and precision of control. Flicker is objectionable, predisposes to visual fatigue and is particularly hazardous from a safety viewpoint in the presence of moving machinery. Fluorescent lights have been known to exhibit a stroboscopic effect if not properly installed. Fluorescent tubes should be installed in a manner to eliminate flicker. If the tubes are out of phase with each other so that one is "off" when another is "on," a more continuous, steady light results. Proper cleaning of light sources and reflectors is necessary if the light is to remain at the expected intensity. Radiant

Energy

1) Ultraviolet

light:

T h e division of sunlight into ultraviolet (far 1.0-

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290 millimicrons; near 290-390 millimicrons), visible (400 to 780 millimicrons), and infra-red (near 7701400, far 1400-220,000 millimicrons) is arbitrary, but useful. a) Definition: Angstrom unit = 1/100,000,000 centimeter. A millimicron is 10 times the length of an Angstrom unit (A. U.) 1 A. U. = 1/10,000 micron 1 m. micron == 1/1,000 micron 1 micron = 1/1,000 millimeter Ultraviolet light rays are those shorter than 390 millimicrons. T h e most marked actinic (photochemical) effects are from wave lengths of 300 millimicrons or shorter. T h e range of ultraviolet light has been subdivided into (a) abiotic rays, from 190 to 290 millimicrons and (b) therapeutic rays from 290 to 390 millimicrons. In most ultraviolet lamps the therapeutic range is supplemented by the visible violet range (390 to 425 millimicrons). 63 b) Effects on eyes: T h e effect of ultraviolet light is not thermal, it is chemical (abiotic, i.e., incompatible with life) and consists of swelling of the cytoplasm of the corneal epithelium and conjunctiva with an eosinophilic infiltration (keratitis and conjunctivitis). There is coagulation of protein and death of the cell—the condition is called photophthalmia. Example: Actinic conjunctivitis and keratitis ("flash") from the welder's arc is a complaint of welders. This is an acute disorder. It has not been shown that ultraviolet light produces any permanent corneal or conjunctival injury. It has been believed that wave lengths of 300 millimicrons or shorter constituted the ultraviolet light

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causing most of the visual trouble. Some work (Wolf) 5 4 on chicks (chicks will keep their eyes open under exposure to ultraviolet light) indicates that there may be acute damage to the cornea by wave lengths of 300 to 365 millimicrons. T h e chicks received one hour exposure (quartz lamp and selected filters for the control of light character), then one hour in complete darkness for dark-adaptation. T h e test chicks sometimes required 45 times as much light to recognize a flickering stripe test. Not for 3 days could their eyes see normally again. It has been stated that ultraviolet light from artificial sources causes no retinal damage: " N o concentration of radiation from any artificial illumination is sufficient to produce injury to the retina." (Verhoeff) 5 5 Ultraviolet light from such sources is of an intensity that is well absorbed by the cornea so that effective rays do not reach the retina. c) Sunlight effects on the skin— (1) Abnormal sensitivity: Two general types of skin photosensitivity may be distinguished. 50 Those which represent abnormal response to irradiation which causes merely erythema of a normal skin. Those in which the skin is affected by wave lengths to which normal skin is insensitive (e.g., urticaria solare). Chemical substances, endogenous or exogenous, may make a normal skin photosensitive (dyes, quinine, porphyrins, coal tar are examples). Various systemic diseases are occasionally accompanied by photosensitization (porphyria, epidermolysis bullosa, xeroderma pigmentosum, pellagra, and lupus erythematosus). 87

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(2) Reaction of normal skin (as seen in exposure to sunlight): (a) M i n i m a l erythema is a reddening of skin that disappears in 15 to 20 hours. (b) Sunburn. Dilation of skin capillaries a n d almost imperceptible edema. If exposure has been excessive, edema, blistering and desquamation results. T h e process is that of cellular injury (altering of proteins). (c) Tanning. Browning or "sun tan" is due to: (1) Migration of pigment f r o m basal cells to more superficial layers, eventually reaching the corneum; (2) Elaboration of new melanin in the basal cell layer (a later event). T h e r e is evidence that an enzyme, dopa-oxidase, transforms levo-rotatory, beta-3-4-dioxyphenylalanine (dopa) into melanin within the melanoblasts; (3) A darkening of the preformed melanin. T h i s may appear within the first few minutes of exposure to sunlight, reaching its m a x i m u m within an hour, whereas formation of new m e l a n i n occurs only after several days. Longer wave lengths of the ultraviolet spectrum (300 to 420 millimicrons) can produce pigment darkening b u t n o t (1) or (2). (d) I m m u n i t y to s u n b u r n , according to present belief, is d u e to: (1) Previous pigmentation (however, vitiligo or leukoderma patients and albinos become less sensitive after repeated exposure); (2) T h i c k e n i n g of the horny layer (the corneum is reasonably o p a q u e to wave lengths that cause sunburn); (3) Alteration of the scattering characteristics of the c o r n e u m (changes in proteins, moisture content, etc.). T h e r e is considerable variation in the h u m a n susceptibility to sunlight. Generally, blondes b u r n

MANUAL OF INDUSTRIAL MEDICINE

more readily than do brunettes, men more readily than women, persons between the ages of 20 and 50 years more readily than persons who are younger or older. Protection against sunburn is provided by any material which absorbs wave lengths of the short ultraviolet group before they reach the skin. Ointments and "suntan" lotions furnish some protection (carbolated petrolatum, para-aminobenzoic acid or isobutyl para-aminobenzoate are significantly effective screeners for the sunburn range of 290 to 320 millimicrons). 57 (e) Effects of prolonged exposure to sunlightfreckles. Skin repeatedly exposed may become reddened owing to prolonged irradiation of the minute vessels, may develop pigmented splotches or freckles (ephelis, ephelides; lentigo, lentigines) and may show degenerative changes in the corneum. (f) Neoplasms of the skin. Evidence for relation to exposure to sunlight: 68 1. Sunlight or mercurial arc irradiation increases the incidence of tumors of the skin in rats and mice. 2. Cancer of the skin is more common in regions receiving the most sunlight (highest insolation). 3. Cancer of the skin is generally distributed on the parts of the body habitually exposed to sunlight (90 per cent occur on the face). 4. Cancer of the skin is less prevalent among Negroes and dark-skinned races. 5. Skin cancer is said to be more common in outdoor workers than in indoor workers. (3) Mercury vapor lamps in industries, hospitals and homes are popular as health-promoting agents. This

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implies proper use; misuse can be harmful. General irradiation of the body has been practiced for a variety of nonspecific syndromes. Local irradiation has been used for its exfoliative effect; e.g., acne. "The formation of vitamin D, and the resultant anti-rachitic action is the one clear-cut, beneficial effect known to be produced by sunlight impinging upon human skin." 59 2) Infra-red Rays, Effect on Eyes (For systemic effects of heat see section VI. B. 2. b.—Temperature and humidity) Infra-red rays in the main are absorbed by the media of the eyes. Glassblower's cataract (two to five times as frequent as cataracts in other persons) is probably due to overheating of eyes as a whole with consequent disturbed nutrition of the lens. "Infra-red" cataracts occur only after exposure to intense heat for many years. These start as saucer-like opacities in the posterior cortical area of the lens.60 Recent experience suggests that the disease is currently rare, possibly due to better control of industrial exposures to heat. 61 Sunlight has sufficient intensity of light energy to produce a condition, with lesions in the retina, called "eclipse blindness" or solar retinitis. This is largely a thermic effect. A late result of sun-gazing, without eye protection, is the appearance of one or more small perforated holes in the fovea centralis. "The macula forms a crater of deep crimson color, one-eighth of the disc diameter in width, the edges of which are sharply cut and irregular in shape; it is surrounded by a soft cloud of pigment." 62 T h e atomic bomb has given us a similar hazard of retinal burns. As an intense source of infra-red and visible light energy, which is focused on the retina and

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choroid during an explosion, tissue coagulation and damage not unlike that of "eclipse b u r n " may be expected. Byrnes and his associates 63 exposed rabbits to detonations at the Nevada proving ground and found "the typical fresh lesion in the rabbit eye as seen with the ophthalmoscope is almost perfectly r o u n d and sharply circumscribed and consists of a central and peripheral zone. In animals exposed near the detonation flash (within about 8 miles) the lesion has a deep central hole with a glistening white base that appears to be sclera. . . . Hemorrhage a n d / o r coagulated debris may or may not exude from the hole. Surrounding the central hole is a 'halo' of dirty-gray color, often twice the diameter of the hole." In this man-made exposure to a high energy source, pupillary and blink reflexes are too slow to prevent retinal heat lesions. T h e hazard is greater at night when the pupil is dilated. Because of the focusing (concentrating energy) action of the optical system these burns may occur at distances greater than the distances at which other harmful effect of the atomic bomb occurs. 3) Miners'

Nystagmus

"Miners' nystagmus" is an occupational disease of obscure origin. In some respects it appears to be a neurosis. T h e majority of such patients are workers who have spent twenty years or more in British coal mines. Complaints, usually appearing when the worker is between the age of 40 and 50 years, are of a constant oscillation of objects, particularly of light sources; giddiness; photophobia; and occipital headache. T h e eyes frequently show active oscillations of a rotary type with a tremor of the lids (sometimes tremors of the whole body). T h e evidence from Great Britain suggests that the

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low level of illumination in the mines is responsible. In America, where good cap lamps have been used for years, nystagmus of this specific type is unknown. In Great Britain nystagmus does not occur in the "naked light" pits, where illumination is much better than in "safety light" pits. 64 4) Roentgen Rays and Radioactive Materials—efiects of overexposure to ionizing radiation 05 Roentgen, who discovered x-rays in 1895, escaped injury chiefly because his experiments were photographic and he used x-ray tubes placed in a zinc box and protected by lead screens. a) Skin: (1) Loss of hair (epilation) by radiation. (2) Cell death. Acute x-ray burn of the skin may vary from erythema to necrosis and ulceration. (3) Chronic x-ray dermatitis—atrophy and regeneration—telangiectases, areas of pigmentation and atrophy, warty growths, ulceration from obliterative endarteritis. Carcinoma may arise in the site of injury. b) Blood changes from exposure to x-rays and other gamma rays: (1) Leucopenia first (bone marrow effect?). Later leukemia possibly. (Subsequent hyperplasia of a hypoplastic marrow?) (2) Thrombocytopenia. P u r p u r a is common in persons dying three to six weeks from irradiation effects. (3) Low-grade anemia and aplastic bone marrow. c) Bone: Necrosis (osteomyelitis). Possibly induction of t u m o r (sarcoma).

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d) Generative organs—sterility, male and female e) Injury to fetus. Malformation of central nervous system with injury to eyes and limbs may occur if pelvis of the mother is irradiated before third month of gestation. Fetus may be killed. A common defect is microcephaly. f) Gastroenteritis (inflammation of stomach a n d / o r intestine) requires large doses of x-ray and is seldom seen except as a complication of tumor therapy. g) Radiation cataracts. Roentgen rays damage the dividing cells of the lens equator. This is followed by slowly developing opacities which appear most characteristically in the posterior subcapsular region. 60 Recently young physicists have developed such cataracts—suggesting that neutrons may be more active on lens tissue than has been thought heretofore. 6 8 Industrial uses of x-ray: For the detection of flaws in casings, weldings, cables, gas cylinders, concrete and other materials. Diagnostic radiology equipment is occasionally misused. In a shipbuilding plant operating during World War II there were burns from misuse of the fluoroscope by improperly trained personnel. 5) Radium—radiation forms: Alpha particles (92 per cent of the energy)—most destructive potential but least penetrating; travel b u t 4 cm. in air and penetrate tissue 0.1 m m . or less! Radon is a colorless gas, without taste or smell, which is being continuously formed from radium and is itself continuously being transformed into the next radioactive element—Radium A—by loss of an alpha particle (i.e., a degradation product). Beta particles (3.2 per cent of the energy) are less destructive than alpha particles. These need several

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millimeters of metal or glass for complete screening. Chief action on skin: radium dermatitis. Beta rays can travel through tissue a distance of about 10 mm. Gamma radiation (4.8 per cent of the energy) is true electromagnetic radiation of great penetrating power; only half of its intensity is lost after passing through 1.5 cm. lead. Radium is stored in the body and distributed as is lead and calcium. It is reported that sufficient radium has produced (1) necrosis of the jaw, (2) severe aplastic anemias and (3) osteogenic sarcoma. Industrial

exposure

to

radium:

Ingestion or inhalation of radium—"pointing" brushes with lips in luminous dial painting is no longer allowed. Manufacture of radium applicators and needles. Handling of ores. T h e pulmonary carcinoma in miners of cobalt and pitchblende miners in Central Europe is not well understood. Evidence is that a derangement of the chromosomes unleashes a restraining influence on cell multiplication. Liver carcinoma, a rare disease in our population, accounts for 90 per cent of all cases of cancer among the South African Bantu working in the Witwatersrand Gold Mines. Why? T h e diet of these workers (corn pap, meal, plus fermented milk) when fed to rats gave abnormal livers (fatty degeneration to multilobular cirrhosis).67 Maybe the liver cancers are not actually occupational in origin. So long as the ultimate cause of growth of the cancer cell is unknown, "occupational cancer" entails much in undesirable guesswork. (See Section VI—B—11—h., Trauma and Neoplasms.) The importance of protection against exposure to radiation may be illustrated by the following account:

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LAST RADIUM VICTIM DIES T h e 28th recorded victim of radium poisoning among former employees of the United States R a d i u m Corporation died November 18, in Orange, N. J., at 52 years of age. She was the last to survive of five women who sued the corporation for damages in 1927 and won an out-of-court settlement. T h e poisoning resulted from the workers swallowing small particles of radioactive substances while moistening brushes with their lips, in painting luminous dials on watches. T h e plant closed in 1926 following discovery of the incurable disease after the death of the first victim.—New York Times—November 18, 1946. Reference: Industrial Hygiene Digest, 10: 3 (paragraph 1163) December 1946. R e c e n t case r e p o r t s of two persons w h o d i e d of aplastic a n e m i a f o l l o w i n g w o r k in a r a d i u m - d i a l painting p l a n t emphasize the n e e d f o r c o n t i n u i n g supervision of e x p o s u r e to e x t e r n a l r a d i a t i o n as well as that to i n t e r n a l radiation. 6 8 T h e m a x i m u m permissible dose of r a d i a t i o n for adults presently agreed u p o n is 0.3 r e p ( r o e n t g e n equivalent physical). T h e r e p c o r r e s p o n d s to a n ionizing energy a b s o r p t i o n of 93 ergs p e r g r a m of tissue. T h e r e m (roentgen e q u i v a l e n t m a n ) is t h a t a m o u n t of ionizing r a d i a t i o n w h i c h p r o d u c e s t h e same d a m a g e to m a n as o n e r o e n t g e n of x-radiation. (1 r e m = 1 r e p X R B E in which R B E is the relative biological effectiveness of the r a d i a t i o n . ) e 9 M A X I M U M PERMISSIBLE T I S S U E D O S E L I M I T S Maximum Exposure to Maximum Exposure Type of Blood-forming Organs of Skin Radiation (rep/wk) (rem/wk) RBE Entire Body Hands Only X or Gamma Iieta Thermal Neutron Proton or Fast Neutron Alpha

0.3 0.3

0.3 0.3

1 1

0.5 0.5

1.5 1.5

0.06

0.3

5

0.1

0.3

0.03 0.015

0.3 0.3

10 20

0.05 0.025

0.15 0.075

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For measuring the roentgens of radiation to which a worker is exposed, he may wear a calibrated (varying with the character of the radiation being measured) ionization chamber throughout a working day. Another useful instrument is the Geiger-Müller counter or a modification thereof which indicates the presence of radioactive particles or rays (energy of the photons) having sufficient energy to trip the relay of the sensitive instrument. Calibration by a physicist is essential to get a reliable indication of the hazard. Photographic radiation meters are usually dental x-ray films covered with wrappings calibrated as filters of varying radiation filtering abilities. A f t e r a measured period of exposure the blackness of the processed film is measured with a densitometer or compared with calibrated films (exposed to known strength radiation sources). T h e danger of harmful exposures to radiation is incurred by persons inadequately experienced in using various forms of ionizing radiation or by persons who become careless. Intensive indoctrination of personnel who are to work with ionizing radiation is basic to their protection. T h e r e is no attendant physical sensation to radiation exposure, its effects are insidious and cumulative. It is difficult for a worker to be continuously attentive to a hazard that cannot be seen, felt or heard. 6) Nuclear Energy T h e atomic age has brought new responsibilities in preventing radiation hazards which may be of two classes: a) External (skin) irradiation, beta and gamma rays b) Internal irradiation, alpha, beta and gamma, from general overdosage, or pick-up of radioactive isotopes by inhalation, ingestion or absorption through skin A careful study of the few instances of significant

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accidental radiation exposure occurring under the Atomic Energy Program have added to the physician's understanding o£ the acute radiation syndrome.10 T h e medium lethal dose of radiation for man is apparently about 400 ( ± 100) roentgens of gamma rays. Warren and Bowers 70 list the tissues of the body in the order of decreasing sensitivity to ionization radiation as follows: a) Lymphocytes b) Erythroblasts c) Germinal epithelium of the testis d) Myeloblasts e) Epithelium of intestinal crypts f) Germinal cells of the ovary

g) Basal cells of the skin Connective tissue h) Bone i) i) Liver k) Pancreas 1) Kidney m) Nerve n ) Brain o) Muscle

Cellular effects include cessation of mitosis followed by disorganization of the structural detail and swelling of the cell. These effects are presumably due to chemical changes induced by radiation. Stromal effects are manifest by swelling which may be followed by fibrosis and hyalinization. Initial vascular effects are thrombosis, then follows fibrosis, hyalinization and telangiectasia. 7) Acute Radiation Syndrome 70 T h e acute radiation syndrome is produced by total or near total body exposure to excessive amounts of radiation, not by localized exposure. Symptoms: (a) asthenia, (b) diarrhea, (c) nausea and vomiting, (d) petechiae and purpura, (e) mucosal ulcerations, (f) epilation, (g) fever. Clinical course: (a) Fulminating form—Many of

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above symptoms appear within two to six hours of exposure. Death occurs from the fifth to the tenth day. (b) Hemorrhagic form—The initial nausea, vomiting, diarrhea and prostration lasts for two days and is followed by a fairly symptomless period of about five days. T h e n the initial symptoms recur and are accompanied by petechiae, purpura and frank bleeding from body orifices. Death occurs three to six weeks after exposure. (c) Pancytopenic form—A number of patients survive the hemorrhagic period but exhibit continued weakness, pallor and ulcerative lesions in association with a pancytopenia. Finally cachexia may become pronounced and the patient dies after a prolonged period of illness. There is no known specific agent which, when given after exposure to radiation, will significantly ameliorate the injury. Therefore, treatment is symptomatic and supportive. 4. Noise a. Noise is believed to contribute to: 1) Fatigue 2) Impaired hearing (boilermaker's deafness) 3) Decreased working efficiency 4) Emotional disturbances and neuroses b. Definitions: 1) Sound is the sensation produced by airborne vibrations reaching the ear. 2) Noise is a type of sound which is generally considered to be unmusical, confused, discordant, irksome, and disturbing. Noise consists of wave motions in the air (or sensations in the ear) which are unrelated in frequency and in time. Noise has been classified as (a) steady state noises in which discrete tones stand out,

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(b) steady state noises in which no discrete tones predominate, and (c) transient (not steady) noises. 3) Besides frequency or pitch (number of vibrations or cycles per second) sounds have two closely related attributes: intensity and loudness. Intensity and loudness are not synonymous because of the fact that the ear is not uniformly sensitive throughout the entire range of audible frequencies. The human ear can detect frequencies from 16 to 22,000 vibrations or cycles per second but it is most sensitive between 1,000 and 5,000 cycles. Frequencies of speech sounds usually lie between 200 and 6,000 cycles.23 4) Decibels. Because of the enormous range of intensity experienced with audible sounds, a logarithmic scale is more convenient than an arithmetic scale for the measurement or comparison of sound intensity. This logarithmic scale employs the term "bel" (Alexander Graham Bell is the eponym). If the intensity of sound increases ten times, its intensity level is said to have risen one bel; if 100 times, two bels. T h e "decibel" is one-tenth of a bel. This decibel (db) unit is the common expression for sound intensity measurements. T h e smallest intensity of sound required to produce a sensation (threshold of audibility or the threshold of hearing) is zero on the decibel scale. W h e n the intensity of sound increases until it is felt as well as heard, it is said to be on the threshold of feeling. T h i s point, known as the upper limit of audibility, is nearly 120 decibels for certain sound frequencies. Sound level meters are satisfactory for measuring sound between 25 to 140 decibels. Octave Band Analyzers measure noise in selected frequency bands: e.g. below 75 cps (cycles per second), 75-150 cps, 150-300 cps, etc., u p to 2,400-4,800 cps and 4,800 to 9,600 cps.71

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Approximate relations of certain sounds to the threshold of hearing: 71 Sound Condition Pain T h r e s h o l d Feeling T h r e s h o l d A i r p l a n e , DC-6 (inside) Very Noisy Factory Subway Car Automobile New P T C Streetcar Street C o r n e r Traffic, L a r g e City Loud Radio T y p i c a l Office Average Living R o o m Very Q u i e t H o m e Audibility T h r e s h o l d

Pressure

Level, 130-140 120 104 100 94 92 90 75 74 60 40 20 0

db

Sound

Pressure,

Microbars 600-2000 200 32 20 10 8 6 1.1 1 0.2 0.02 0.002 0.0002

c. Effects of noise on hearing 1) Exposure to extremely loud sounds over a long period of time results in impaired hearing. The damage appears to involve the organ of Corti and the auditory nerve endings. Such damage is permanent; no method of repairing the injury from loud noises is known. (Committee on Conservation of Hearing, American Academy of Ophthalmology and Otolaryngology.) 2) The lower part of the organ of Corti, which is the area concerned with the perception of higher frequencies of sound, appears to be especially vulnerable. Early cases of noise deafness show a characteristic loss of hearing near the 4,096 frequency cycle. Audiometer tests will reveal a characteristic dip in this frequency before the patient becomes aware of any loss of hearing. T h e differential diagnosis of advanced acoustic trauma is more difficult. Hence, pre-employment and subsequent periodic audiograms on workers are essential not only to establish a diagnosis but to detect acoustic trauma at the earliest moment, so as to avoid further damage. 72, 73

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3) It has been observed that the noisier the industrial occupation, the higher the incidence of deafness in the workers. The longer the period of exposure to the same level the greater is the hearing impairment. 4) Exposure of the human ear to noise at 115 db above the threshold of hearing for 10 minutes results in marked temporary elevation of the hearing threshold. Pre-test hearing acuity is regained within 30 minutes. Gallagher and Goodwin used test tones of 2,048, 4,096 and 8,192 cycles for the determination of the threshold of hearing in studies on the temporary influence of noise on hearing acuity.74 Exposure for 30 minutes inside a boiler during repair work produces a hearingloss of 30 to 45 decibels (at a frequency of 4,096 cycles) for several hours. "The recovery of threshold in riveters after a full day's work may take fifteen hours. . . . There is agreement in regard to the cumulative effect of noise, finally resulting in permanent hearing loss." 75 5) Davis 76 states: "We do not have rigid proof of permanent impairment of hearing by noises of less than 115 or 120 decibels." Grove 77 quotes opinions to the contrary. Concern about the deafening effects of noise below levels of 85 decibels is probably not justified except for the particularly susceptible person. More evidence is needed to fix the dangerous level of intensity. The spectrum of a noise must be analyzed before its deafening value can be estimated. The current estimate of a probable safe maximum intensity is 85 decibels above 0.0002 dyne/cm. 78 (The designation "0.0002 dyne/cm" is the standard reference level adopted by the American Standards Association. Ninety decibels above standard reference is about the average of the loudest orchestral music.) d. Effects of noise on working efficiency—Aside from hearing loss, there is evidence that noise is undesirable:

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1) The output of weavers was increased about 3 per cent by a decrease in noise of 15 decibels when ear defenders were used.23 2) A 12 per cent increase in the output of office workers followed a reduction of a noise level from 45 to 35 decibels. 23 3) Long continued exposure to sound increases fatigue and may lead to a neurasthenic or psychasthenic state.79 4) T h e Aetna Insurance Company found that as a result of lowering the noise levels of their offices, general efficiency rose 9.2 per cent, typing errors decreased 29 per cent, machine operator errors decreased 52 per cent and employee turn-over was reduced by 47 per cent. The company concluded that it had effected net savings of $58.00 per employee in the first year.80 5) The Bell Telephone Laboratories estimated that noise which decreases the efficiency of a routine worker by 5 per cent will decrease the output of an executive by as much as 30 per cent. 80 Kryter 81 suggests the following criteria in determining the allowable noise level: a) For perfect work conditions in offices or other work situations where person-to-person voice communication at conversational intensities is required, the "unwanted sound spectra" should not exceed 40 decibels re 0.0002 dyne/sq.cm. at 2,000 cps or for the critical band at that point and even less at higher frequencies. b) For work situations requiring minimal amounts of voice communication the maximum safe intensity for exposure for indefinite periods is around 85 decibels re 0.0002 dyne/sq.cm. for tones or critical bands in the case of noise of continuous spectra. The 85 decibels criterion is a conservative guess at present; fur-

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ther research will likely revise this value upward for the frequencies below 1,000 cps and above 3,500 cps. c) For nonauditory work output (disregarding possible damage to the ear) noise as high as 100 to 110 decibels re 0.0002 dyne/sq.cm. per critical band can be tolerated with no significant psychologic or physiologic effects in most workers, provided they have had time to adapt to the noisy environment. e. Prevention of noise 1) Elimination of noise at its source. Examples: Later model streetcars, substitution of welding for riveting, redesigning noisy machines. 2) Isolation of noisy operations by soundproofing enclosures. 3) Reduction of noise by sound insulation: acoustical treatment of walls and ceilings. 4) Use of personal protective devices against noise; e.g., ear defenders of soft rubber. Gunners and artillerymen have used a V-51 R ear warden. This device is said to attenuate noise by 30 decibels or more. (A cotton plug reduces noise by 5 or 10 decibels only.) A well-fitting ear protector should be made compulsory during unavoidable exposure to loud noise of an injurious nature. f. Differential diagnosis of hearing loss Three common elements in loss of hearing must be considered in evaluating deafness: (1) Presbycusis, (2) acoustic fatigue—a temporary condition after short exposure to a loud noise, (3) nerve degeneration due to exposure to intonations above the critical level for a period of time. A distinction between these three conditions has proved to be difficult. Removal from the noisy occupation for 6 to 12 months will remove factor (2) above.

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Presbycusis (the lessening of acuteness in hearing which characterizes old age) is an unknown quantity in evaluating occupational deafness in the older worker. Technics for differential diagnosis are needed. With a pure tone audiometer hearing loss can be measured in decibels for tones of different frequency but this measurement does not denote the degree of disability, especially in terms of loss for hearing speech. Exploratory work is being conducted on the use of speech test materials as an aid to hearing evaluation by the Subcommittee on Noise in Industry of the Committee on Conservation of Hearing of the American Academy of Ophthalmology and Otolaryngology. 8 2 In attempting a clinical evaluation of hearing loss the A.M.A. Council on Physical Medicine and Rehabilitation 83 cautions recognition of the fact that " n o r m a l " hearing actually involves a range of thresholds for hearing (either for pure tones or for speech). In clinical audiometry a hearing loss of 15 db (decibels) may be within the limits of normal variability under usual testing conditions. Audiograms at appropriate intervals are required to distinguish temporary from permanent hearing loss. Since audiometric measurements at any instant involve the attentive cooperation of the test-subject, psychological factors can alter the recorded threshold for hearing a tone. Only instruments which meet minimal acceptance standards should be employed in making audiometric tests from which disability of hearing is to be calculated. 8 3 What frequency (cycles per second) range should receive chief attention in evaluating deafness? T h e healthy human ear may detect frequencies ranging from 16 to 22,000 vibrations per second. Speech sounds lie chiefly between 200 and 6,000 cycles. 23 In diagnostic testing frequencies between 250 and 8,000 cycles are customarily used by otologists. Many workers on the subject of occu-

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pational deafness pay more attention to hearing acuity at 500, 1,000 and 2,000 cps (cycles per second). In assigning a cause for hearing loss which has been established in a worker, what must the physician consider? A complete "otologic history" will include 1) Childhood and adult life experience with infections: streptococcal, pneumococcal and other bacterial or viral invasions of sinuses, tonsils, middle ear and central nervous system. 2) Physical and chemical injury to the nose, throat, ear or central nervous system. 3) Military service factors such as exposure to blasts, excess noise, combat or other injuries. A second step in establishing cause is the determination of the character of noise sources to which the patient has been exposed. What are the spectral qualities (frequencies of the sound energy) in the noise? Is it continuous or intermittent? What protective or sound suppressive devices were in use; how long used and with what effect? Is the hearing loss one of conduction? If so, it cannot be attributed to prolonged or repeated exposure to noise. A long-standing conduction lesion serves to protect the inner ear from injury by noise. Suitable records of the state of hearing before exposure to a noisy environment gives one a base line for estimating the degree of change which occurs subsequent to such employment. Some loss of hearing, especially for higher tones, is characteristic of advancing age in the absence of specific, presently known causes. One report states that for the frequency of 2,000 cps, this loss on the average will amount to about 5 db in the sixth decade and 10 db in the seventh decade. For 4,000 cps tones the averages were given as about 10 and 20 db, respectively, for the indicated age decades.83 Large-scale

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population hearing surveys by the Bell Telephone Laboratories and the U. S. Navy Electronic Laboratory support presbycusis curves indicating 1) For 2,000 cps hearing: Significant losses begin about 30 years and progress about 5 db each decade to 50 years when the rate increases to 10 db for the next two decades. 2) For 4,000 cps hearing: Losses are apparent soon after the age of 25 years and progress at the approximate rate of 10 db per decade of age. In view of the complexity of the problem presented to the physician, how should an industrial commission proceed to adjudicate a claim for loss of hearing due to occupational exposure to noise? One state director of Workmen's Compensation has presented the following view on the administration of the law covering occupational loss of hearing in his state: 84 The claimant must establish a loss of hearing as the result of prolonged exposure to noise in a given employer's service for a total period of at least 90 days. If he has ceased such employment "since it is inadvisable for him to continue in it because of impairment of hearing" or otherwise can establish wage loss, "he may receive benefits not to exceed $3,500." Sound intensity below 90 decibels, as measured on a C scale of an approved sound level meter, is not to be considered hazardous regardless of length of exposure. An advisory committee was studying a formula, at the time of the report, to determine its usefulness by the commission in administering thé law. This formula provides that: 84 "Pure tone air conduction audiometric tests are to be used in evaluating hearing acuity only in the 3 readings of 500, 1,000, and 2,000 cycles. These are the frequencies ordinarily produced in speech conversation.

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(The American Medical Association table also includes the frequency of 4,000.) Frequencies between 250 and 8,000 cycles are to be used for diagnostic purposes. " T o get the average decibel loss, losses in the 3 frequencies are to be divided by 3. Losses averaging 16 decibels or less are to be held not to constitute hearing disability, and losses of 80 decibels and over are to constitute total deafness. Between these points, each average decibel loss between 17 and 79 is prescribed a percentage of compensable hearing loss. "For binaural loss (both ears), the statutory formula is to be used with the recommendation that for purposes of legislation the relative value of loss as between 1 and both ears should be as 1 to 5. "Loss for presbycusis (age deafness) is to be subtracted at the rate of one-half per cent at age 50, plus an additional one-half per cent for each year thereafter. Some recovery of hearing may be expected after removal from a noisy environment. Just how much will depend on factors of years of exposure, degrees of loss, and individual susceptibility. A first examination for hearing loss should be made after 48 hours' removal from the noise environment followed by closely spaced periodic tests. Five decibels are to be deducted from each of the average ratings of the 500, 1,000, and 2,000 frequencies to allow for the 'recovery factor.' T h e result will be the final permanent loss except for those individuals who have been removed from noise for 6 months or longer." 5. Fatigue: Ennui and boredom of repetitive actions Ramazzini, 6 in 1710, quoted Borelli to the effect that standing

is particularly

fatiguing

because of " t h e con-

tinual and uninterrupted Action of the same Muscles for, he says, Nature delights in alternate and interpolated Actions; and for that Reason walking does not tire us so much. . . . This alternate Succession of Action is

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agreeable to N a t u r e , n o t only in the Motion of the Body but in almost all the n a t u r a l Functions; For if we look steadily u p o n one Object, if we listen with o u r Ears to one sound, if the same Meat be often served u p at the Table, if o u r Nostrils be long exposed to the same Smells, we are uneasy; so m u c h does N a t u r e delight in Vicissitude a n d Change. Accordingly we see the Jews when they were fed with Heavenly M a n n a in the Wilderness, began to long for the Egyptian Garlic and Onions." a. W h a t is fatigue? T h e mechanism of fatigue is actually not well understood. Experimental physiologists have taught us that the energy f r o m muscular contraction comes f r o m or is associated with the breakdown of a phosphate c o m p o u n d (phosphocreatin) into creatin and phosphoric acid. These are subsequently resynthesized with the formation of lactic acid. Glycogen is presumably the source of lactic acid. Lactic acid formation does n o t take place until after muscular contraction and relaxation. In the physiology laboratory demonstration of muscular contraction (muscle-nerve preparation of the frog), the failure of contraction after repeated stimulation of the nerve comes at the myoneural junction (the nerve continues to transmit the impulse and the muscle will contract if stimulated directly). Industrial fatigue is not simple. It is made u p of complex factors. O n e may speak of a lower fatigue which is muscular a n d a higher fatigue which is psychological. One also should distinguish between fatigue which is: 1) Physiologic fatigue (a normal sense of tiredness relieved by rest, food a n d sleep), and 2) Pathologic fatigue (exhaustion of nervous a n d muscular systems, not restored overnight or over week end by food, sleep and rest). If this condition persists there

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may be reduced capacity for work, accident proneness and serious ill health. b. Fatigue of the central nervous system plays a much more important role in industry than does strictly muscular fatigue. 85 If one analyzes his own experiences of fatigue he observes that 1) One can feel extremely tired without having exerted oneself. 2) Fatigue can disappear abruptly if something interesting occurs. 3) Fatigue can develop quickly in unpleasant social situations. 4) The mere thought of doing certain types of work creates a sensation of fatigue. 5) When tired, one makes mistakes more frequently, the mistakes in turn increase tiredness. 6) After a day of pleasant physical activity one may not feel tired, but be ready for further activity. 7) In an emergency situation one can undergo unusual emotional and physical strain without feeling correspondingly tired. c. Causes of fatigue 86 1) At-work factors: Excessive speed-up of work, boredom due to repetitive work, awkward work movements, lack of properly spaced rest periods, improper posture, excessive noise, excessive heat, inadequate illumination. 2) Off-the-job or away-from-work factors: Loss of sleep, intemperance, emotional disturbances, inadequate nutrition, etc. Infections or other disease and drugs may aid and abet fatigue. d. How does fatigue show itself?

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1) Decreased quantity of work 2) Decreased quality of work 3) Increase of accidents 4) Physiologic and psychologic effects (these are difficult to interpret): a) Digestive disturbances b) Loss of muscular control c) Insomnia d) Backache e) Vague debilities, possibly increased susceptibility to respiratory infections f) Irritability and unstable emotions—stubbornness. How many faulty decisions are the result of fatigue? e. Measuring fatigue A study of truck drivers 86 found that the four factors which showed the closest relationship with the hours of driving were: (1) speed of tapping, (2) simple reaction time, (3) reaction-coordination time, and (4) manual steadiness. There are but a few jobs and under unusual conditions in industry where excessively long hours must be worked. Wage and hour laws have corrected situations formerly causing physical exhaustion. The psychological adjustment of the worker to his personal environment (boss, associates, hobbies, family) and his lack of joie de vivre have more to do with work decrement (reduced output) than has his physical environment. "The fatigue of the ordinary factory worker is too subtle to yield to the ordinary test of the physiologist." 87 The British have studied the effects of long hours of work during World War I and World War II. Their observations may be summarized as follows: 87

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1) T h e extension of the usual hours, except for a short period, does not yield a proportional increase in output. 2) After an extended period of overtime has been discontinued, weeks are required before the original steady output is obtained. 3) More than 60 hours a week lead to increased lost time during work, and increased absenteeism. One day's rest in 7 is essential. T h e British experience has shoiun 56 hours a week to be the optimum, standard for men. 4) Organized or enforced rest periods, particularly with an opportunity to take food during the period, assist in the maintenance of a high output level. f. Prevention of fatigue In spite of our ignorance of many unmeasurable factors which cause stress and fatigue in industry, there are certain physical factors which undoubtedly contribute to that state, in the opinion of some investigators. 88 A change in the job or in the environment which will reduce physiological stress during the performance of work will lead to decrease in complaints of fatigue. Brouha 88 has demonstrated benefits through reducing stress as follows: 1) Reduction of the work load. This can involve position of the body (static muscle contraction), nature of motion (dynamic contraction) and speed of motion (rate of contraction), as well as weight times distance lifted ("mechanical work"), alterations in the requirements of a job. 2) Reduction of the heat load. In hot climates cooling the environment or the worker through temperature and humidity control postpones fatigue from physiological stress.

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3) Adequate rest periods. Rest intervals should be long enough to insure complete or near complete recovery from effects of stress of the job. 4) Adequate teams of workers for the job. Enough men for the job decreases the need for physical exertion and increases the resting time for each individual in the working crew. 5) Adequate water and salt intake. Manual labor in hot surroundings requires attention to these factors. 6) Selection of workers. T h e capacity to perform tasks requiring the use of muscles depends on the natural physical fitness of an individual and his degree of training for the specific tasks. Such procedures for limiting stress and reducing the resulting incidence of fatigue require the collaboration of the physiologist, the engineer, the physician, management, and labor. 6. Dusts, Fumes and Gases A dust implies finely divided solid particles in the air. The engineer's unit for measuring airborne debris is the micron (one-thousandth of a millimeter, one twenty-five thousandth of an inch). Examples: tobacco-smoke particles (carbon) average 0.3 micron, face-powder particles are about ten microns in diameter. Air under normal conditions contains some dust. Clean country air may contain 0.2 mg. dust per cubic meter of air, while city air shows 0.5 mg. per cubic meter of air. 18 Industrial dusts are generated by handling, crushing, grinding and detonation of rock, ore, coal, wood, grain, organic and inorganic chemical compounds. Dusts do not tend to flocculate except under electrostatic forces. A fume is composed of solid particles which have condensed from the gaseous state, usually after volatilization from molten metal. Fumes flocculate and sometimes coalesce.

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Liquid particulate matter is known as a mist or fog. These suspended droplets are generated by condensation from the gaseous to the liquid state or by direct dispersion of a liquid (splashing, foaming and atomizing). Gas is a formless fluid which diffuses unless confined by enclosure. The term is preferably reserved for material which exists in the gaseous state at 25° C. and 760 mm. Hg. pressure. Increased pressure or decreased temperature (or both) change a gas into the liquid or solid state. A vapor is the gaseous phase of a substance ordinarily liquid or solid at 25° C. and 760 mm. Hg. pressure. The Division of Occupational Hygiene of a highly industrialized state reported that 80 per cent (4 out of 5) of the inquiries received from physicians, and others interested in the protection of the worker, concerned the poisonous nature of dusts, fumes and gases. a. Dusts, Fumes and Gases: General

Effects

Air pollution has been defined as "an excessive atmospheric concentration of foreign matter that may adversely affect the well-being of any person, or cause damage to property." 89 If one divides possible air pollutants into (1) those which are known to affect health and (2) those which are not known to affect health, it must be emphasized that most suggested pollutants are in the latter group; i.e., contaminants with doubtful, unknown or no measurable influence on health. Some air contaminants which appear to be relatively harmless (e.g., inert dusts) are annoying and disagreeable. The appraisal of a nuisance in the air we breath is difficult. Its nuisance value varies with individuals. Inhaled toxic agents may be associated with one or more of four general types of reactions: 1) Chemical or physical irritation leading to pulmonary edema, pneumonitis, lung fibrosis, etc.

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2) Systemic poisoning following lung absorption of dusts, gases or fumes, as with lead, cadmium, radium, arsenic, beryllium, mercury, manganese, chromium, and selenium. 3) Acute febrile reactions: a) Infection. Example—cotton mill fever (gin fever). A small gram-negative bacillus (genus aerobacter) was found on stained cotton dust by Neal and co-workers 90 as the causative agent in an outbreak of illness among mattress makers. T h e illness was characterized by sudden onset 2 to 3 hours after inhaling contaminated dust. T h e symptoms were headache, cough, skeletal aching, tightness of chest, dryness in throat, sneezing, chills, nausea, dyspnea, insomnia and vertigo. There was fever, tachycardia and a leukocytosis. T h e illness lasted twenty-four to forty-eight hours. Dust serves as a carrier of a variety of agents such as common respiratory infections, psittacosis, Q fever, and fungus infections. b) Metal fume fever—zinc and others. Metals as fumes when inhaled in sufficient quantity can produce metal-fume fever (brass founder's ague). T h e symptoms are thought to be due to the absorption of the foreign protein formed when metal fumes (metal oxides?) contact the alveolar cells and cause their necrosis. 91 Typically, some four to eight hours after exposure the worker notices dryness in the throat, pains in the muscles and joints, weakness, chills and fever. A mild leukocytosis occurs. Recovery is complete in 24 to 36 hours; no pulmonary damage has been demonstrated. No permanent disability has occurred following this acute "influenza-like" syndrome. 4) Allergic reactions to pollens, pulverized wood and flour, etc.

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b.

Pneumoconiosis

For purely sesquipedalian interest, it should be pointed out here that the longest word said to be found in a recent edition of Webster's International Dictionary is a term found in industrial medicine. T h e word is: pneumonoultramicroscopicsilicovolcanokoniosis. T h e various pneumoconioses are named by the character of the dust which is inhaled. Anthracosis is from coal dust; siderosis from iron dust; chalicosis from stone cutting (calcium); silicosis from dust containing silica; byssinosis from cotton particles, etc. In a broad sense the term "pneumoconiosis" means simply "dust in the lungs." Most pneumoconioses do not result in recognizable disability or disease. Of the few dusts which cause fibrotic reactions in the human lung, free silica and asbestos have received the greater amount of attention. T h e inhalation of diatomaceous earth recently has been implicated in the development of pulmonary fibrosis, possibly due to the form of its silica content after being calcined. 9 2 Surveys suggest that noncrystalline forms of silica may produce a pneumoconiosis "which is not silicosis per se but closely related to i t . " 9 3 Silicates (talc, mica, soapstone), 94 ' 95 largely from epidemiologic association, have been suspected as agents which may cause lung fibrosis. Usually there is some silicon dioxide present in such dusts, which could contribute to the clinical and pathologic findings. Sericite (a hydrated aluminum and potassium silicate) in animal experimentation has been reported to be a potent lung fibrosing agent. 12 Beryllium (see section on beryllium under Illustrative Poisons—d) can produce pulmonary fibrosis and sarcoid-like miliary granulomata in man. 90 Pulmonary fibrosis in soft coal miners has not been

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fully accepted as a clear-cut clinical entity. T h e disability which occurs in miners with prolonged exposures to soft coal dust often manifests focal emphysema and bronchiolitis, with associated poor pulmonary function, and may or may not show roentgenologic changes in the chest. T h e condition has not been proved to be a fibrosing form of pneumoconiosis. 97 Sander has offered a classification of Respirable Dusts: 98 "Pneumoconiosis is a condition in which dust particles are retained in the lymphatic depots of the lungs. T h e term itself carries no implication of fibrosis or other reaction of the lung tissue to the dust, nor is it specific with relation to the type of dust. Dust likely to be inhaled may be classified as follows: 1) Organic Dusts: a) Non-living: (1) Animal (dander, fur, hair, etc.). Reaction is allergic only; occurs in occasional individuals. (2) Vegetable (pollens, grains, cotton, bagasse, etc.). Allergic reaction only, if any. (Byssinosis and bagassosis—probably not toxic fibroses. Any lung changes are more likely to be infectious pneumonitis, mechanical plugging of the bronchioles by fibers, or both.) b) Living: (1) Bacteria] Irritants, fibrogenic and allergic; ocL casionally occupational in etiology. (2) Fungi J N o t t r u e pneumoconioses. 2) Inorganic Dusts: Finely divided particulate matter. Particles must be less than 10, and probably less than 5 microns, in diameter to reach the alveoli. Larger particles are caught along upper respiratory tract. Particles reaching the alveoli are removed by phagocytosis.

MANUAL OF INDUSTRIAL MEDICINE

a) Inert Dusts: (Produce the so-called "benign pneumoconioses") N o fibrous reaction; d o r m a n t deposits in pulmonary lymphatics a n d root lymph nodes. Small dosages completely absorbed—deposition only after prolonged large doses. Visualized by x-ray when material is radiopaque. N o predisposing effect to tuberculosis or other infections. N o i m p a i r m e n t of lung function. (1) Carbon: (smoke-soot) Most anthracosis due to coal deposits also benign, b u t excessive deposition over many years may be proliferative (see below). (2) Calcium: (when excessive?—small quantities absorbed) Cement, gypsum. (3) Iron: (when excessive, as after m u c h confined welding, grinding, steel cutting) R a d i o p a q u e deposits visualized by x-ray. Siderosis. (4) C a r b o r u n d u m , emery, a l u m i n u m oxide, etc.: (from artificial abrasive grinding wheels). (5) A l u m i n u m : (used in some areas in prevention and treatment of silicosis). (6) Barium, tin, etc.: (radiopaque deposits) Baritosis, stannosis, etc. b) Proliferative conioses):

Dusts

(Produce

fibrotic

pneumo-

(1) Silica: (crystalline free silica (Si0 2 ) as quartz, flint, etc.) Typical fibrous nodules spread throughout both lungs a n d can be visualized by x-ray. Silicosis. (a) Modified silicosis more common t h a n classical, because most industrial dusts are mixtures of numerous components. Non-silica components tend to prevent development of typical fibrous nodules (Ca, Al, Fe, C, etc.).

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(b) No disability unless advanced or complicated with tuberculosis and marked emphysema. (c) Relationship of silicosis and tuberculosis: Primarily a reactivation and spread of pre-existing tuberculosis foci. Combined lesions frequently result in chronic progressive massive fibrosis. (d) Relationship with heart disease: Right heart strain (cor pulmonale) only with advanced stages of silicosis and emphysema. (2) Asbestos: (hydrated magnesium silicate) Mechanical plugging of bronchioles by long fibers and peribronchiolar fibrosis. Asbestosis. (3) Other silicates?: (talc, soapstone, mica, feldspar) Reported fibrosis with some silicates may be due to quartz impurities. (4) Beryllium compounds: Generalized granulomatosis with pulmonary manifestations due to fluorescent powders and the oxides. May be an allergic response and not a true pneumoconiosis. Beryllosis. (5) Bauxite (processing): Diffuse fibrosis with marked emphysema and frequent pneumothorax. Due to silica fume modified by aluminum fume? Shaver's Disease. (6) Diatomaceous earth: Amorphous and only slightly reactive before calcining; then cristobalite formed, causing diffuse fibrosis. (7) Coal dust: (coal workers' pneumoconiosis) Focal emphysema and minimal fibrosis, which may be disabling when advanced. c. Silicosis

Silica is the name given to the chemical compound silicon dioxide (Si0 2 ). In nature it occurs most commonly in the crystalline form as quartz. Other minerals

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contain silica, example: tridymite, cristobalite, opal (granite, for example, contains about 30 per cent quartz and other complex salts containing silica). T h e silicates are usually bound by chemical structure so that they are not released to act as a harmful agent to the lungs." Chief interest has been in the free silica (silicon dioxide) present in a material to which a worker is exposed. 1) Definition: The condition "silicosis" has been defined by the Committee on Pneumoconiosis of the American Public Health Association as: "A disease due to breathing air containing silica (Si0 2 ) characterized anatomically by generalized fibrotic changes and the development of miliary nodulation in both lungs, and clinically by shortness of breath, decreased chest expansion, lessened capacity for work, absence of fever, increased susceptibility to tuberculosis (some or all of which symptoms may be present), and by characteristic x-ray findings." The exposure is prolonged, rarely as short as one year. Often it may be 20 years before symptoms appear. Particle size for silica (as with any dust) is critical. Large particles settle rapidly from the air. In the nose and upper respiratory passages particles larger than 10 microns are trapped. At the size of one micron for mineral particles, alveolar deposition appears to be maximal for a given concentration in inspired air. The deposition (or retention) of particles in the alveoli is reduced, in experimental work, as the size varies from one micron in diameter (for both larger and smaller particles).100 Such observations are pertinent inasmuch as only that silica which remains in the lung can be harmful. It has been believed that phagocytes and other cells pick up the sharp angular silica particles which are in-

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haled and carry them through the lymphatics to the pulmonary lymph nodes. Recently the role of the macrophage in the movement o£ the dust particles from air sacs has been questioned. Gross and Westrick 101 find that particulate matter may penetrate air sacs and reach perivascular and peribronchial positions without being carried by phagocytes. Silica dust in excessive amounts poisons the lymphatics. T o what extent the marked proliferation of fibroblasts results from a physical or a chemical stimulation by the particle of silicon dioxide is still debated. Dale and King 102 suggest that "the silicic acid which dissolves from the surface of quartz particles in the tissues becomes in part colloidal and that this colloidal silicic acid may in some way be related to the formation of silicotic lesions." In any event, when the lymphatic channels become blocked and no dust can be removed in that direction, the silica is deposited in the walls of the air sacs and nodules of fibrous tissue are formed in these areas. 2) Symptoms: Early in the disease there are no symptoms and no impairment of capacity for work. Later there is coughing, shortness of breath, pains in the chest, fatigue on exertion. There is no relationship between the x-ray appearance of the lungs and the severity of the patient's symptoms. In late stages there is reduced vital capacity (decreased chest expansion), marked dyspnea and lessened capacity for work. Tuberculosis is usually the fatal complication of advanced silicosis. When conglomerate silicosis develops, one usually finds in the patient at rest reduced maximum breathing capacity, increased residual volume, and the oxygen ventilation equivalent at normal or above (findings typical of diffuse obstructive emphysema). Virtually

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all the blood that flows through the lung, at rest, appears to flow through adequately functioning lung tissue. 103 3) Differential Diagnosis: Chest conditions whose x-ray patterns simulate silicosis may come from dusts of cotton, sugar cane, tobacco, limestone, chalk, marble, carbon and cement. Mycotic diseases (aspergillosis, moniliasis, histoplasmosis, coccidiomycosis, blastomycosis and actinomycosis) may produce x-ray patterns in the lungs which are difficult to distinguish from nodular silicosis. Occasionally confusion in the x-ray interpretation comes from miliary tuberculosis; metastatic carcinoma of the lungs; vascular changes associated with hypertension; mitral stenosis; bronchiolitis; polycythemia vera and Boeck's sarcoid. 104 ' 105 It is essential to know that the subject has actually had significant silica exposure when making an etiologic interpretation of his chest roentgenogram. Marked changes in x-ray films may result from symptomless deposits of iron, tin, barium oxide, and other inert dusts. 108 Many patients thought to have silicosis in the past, it is now known have roentgenographic shadows of little or no significance to health. 107 4) Prevention: Silicosis is preventable. Small amounts of silica appear not to be harmful. If free silica does not exceed 5 million particles per cubic foot of air breathed during the working day, silicosis apparently will not develop. Fundamental to prevention is engineering control: (a) enclosed processes, (b) exhaust ventilation, (c) wetting dust (wet drilling), (d) hose masks for operators. Medical control involves a periodic physical examination with chest x-ray films of good quality. Because

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of better protective measures, the incidence of silicosis (in industries where such exposure has occurred in the past) has diminished during the past decade. 5) Treatment: Inhalations of aluminum hydroxide and metallic aluminum powder have been used by some workers. This is based on the experimental work of Denny, Robson and Irwin 108 who reported that the development of silicosis in animals could be prevented by the inhalation of small quantities of metallic aluminum powder. T h e inhalation of powder by the worker is allowed for from 5 minutes up to 30 minutes daily. Fifty-five per cent of the cases are reported to have shown clinical improvement; i.e., lessening of the shortness of breath, cough, pain in the chest and fatigue. Other cases have remained stationary, none having become worse. In the group of workers receiving no aluminum dust, 66 per cent grew progressively worse in the same period of time. Explanation? The work lacks confirmation and is contrary to our concept of the fibrotic lung changes. Other investigators 10fl ' 110 have found no benefit beyond the psychologic lift given the workers with silicosis (boost in morale from the use of the dusting equipment, reassurance that something was being done for them). A large number of subjects have inhaled aluminum dust without reported harm. Its actual usefulness, once silicotic changes have appeared in the lungs, is unproved. 6) Chief Occupational Hazards for Silicosis: 99 a) Mining of hard siliceous rock (copper, gold, silver, zinc, iron and hard coal) b) Quarrying of granite, sandstone, quartz, slate rock, and crystal

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c) Ceramic industries—pottery-making d) Glass-manufacturing e) Abrasives f) Stone-finishing g) Construction work (tubes, tunnels, aqueducts, etc.) d. Asbestosis T h e occupational fibrosis which results from the inhalation of asbestos fibers is due chiefly to the mechanical plugging of the alveoli or in the formation of fibrotic sleeves along the terminal bronchioles. T h e condition has been noted in workers mining and crushing crude asbestos. In 1940 Gardner stated that 27 per cent of workers so exposed had lung x-ray changes. I n those with more than 15 years exposure the percentage rose to 60.104 T h e characteristic x-ray finding is the so-called "ground glass" appearance which differs from the nodular pattern of silicosis. Lynch and C a n n o n 1 1 1 described the characteristic lesion in 40 necropsied cases as an "asbestosis body" consisting of a central asbestos fiber with a shiny yellowbrown coating, found in terminal bronchioles and peribronchial lymph nodes. Some of these bodies may appear in the sputum. A feature of the disease in advanced form was pleural thickening with some adhesive obliteration of the pleural spaces. In 8 cases there was nodular fibrosis of the lungs, in 6 some form of active pulmonary tuberculosis, and in 3 carcinoma of the lung. Wright 1 0 3 found in patients with asbestosis evidence of a marked inadequacy of oxygen transfer from the lung air to the lung blood (subnormal 0 2 content of arterial blood) along with increased breathing or ventilation rates. In well-developed asbestosis he believes that lung tissue changes are more widespread, hence the oxygen transport defect in alveolar walls (increased

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thickness). Many workers in asbestos, receiving intense exposure, fail to develop evidence of either physiologic or roentgenographic abnormality. Behrens 112 stated that post-mortem reports from the literature indicate that in 309 cases of asbestosis there were 44 lung carcinomas (14.2 per cent), whereas in 2,204 cases of silicosis only 32 carcinomas were found (1.4 per cent). Pulmonary tuberculosis is less often associated with asbestosis than it is with silicosis. e.Fume Exposure A brasives 113

in the Manufacture

of

Alumina

An interesting pulmonary disorder has been described in workers who inhaled fumes from molten bauxite (aluminum oxide with clay, iron oxide, titanium dioxide and other impurities). The calcined bauxite is raised to a temperature of about 2,000° C. in furnaces. Chemical analyses of the fumes show alumina and silica as the chief constituents. Symptoms: Cough, aggravated by exertion; moderate sputum, dyspnea; and pain, usually pleuritic, occasionally of a substernal discomfort type. Findings: Physical examination in well-established disease shows restricted movement of the thorax, retraction of rib interspaces after spontaneous pneumothorax, rales and rhonchi inconstantly, and pleural friction rubs. There is reduced vital capacity. Roentgenograms show granular shadowing in lung apexes spreading later over the lung field. T h e mediastinum and heart shadow broadens and the diaphragm becomes elevated and shows adhesions. All except one patient in a group of forty-six had bilateral pneumothorax (spontaneous) sometime during the course of their disease. In some men the condition appeared after 3 years of exposure; others had 20 to 30 years of exposure. Cardiac failure,

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contributed to by extensive lung collapse, is a common mechanism of death. Post-mortem examinations: Diffuse interstitial fibrosis with extensive emphysema characterizes this disease. T h e fibrous changes occur first about the lung apexes in the interalveolar septums and then in the interlobular tissue. Perivascular and peribronchial fibroses occur early. T h e r e are numerous emphysematous bullae which contribute to pneumothoraxes. It is stated to be unlike any other well-recognized lung disease but closely resembles a condition which has been found following the inhalation of aluminum dust. 113 f. Noxious Gases Many toxic gases and vapors in industry are from volatile solvents. Between 350 and 400 different solvents have been listed in texts on the subject. 29 Classification: 1) Asphyxiants There are numerous places in industrial operations where the worker may inadvertently get into an atmosphere which will not support life. In storage tanks which have been emptied of solvent there may be sufficient solvent vapors remaining to prevent the entry into the tank of appreciable amounts of air for days. Inert gases are sometimes used to replace air and thereby remove the possibility of combustion where combustible material (usually a flammable vapor or gas) is used in the industrial process. In grain elevator bins the bacterial consumption of oxygen has been known to deplete the atmosphere above the grain to the point that a man becomes asphyxiated if he enters the bin without an oxygen hose and mask. Occasionally, the deficient oxygen supply is not suspected or is simply forgotten by the worker. Skilled workers have been known to enter an inert atmosphere when they

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93

were actually aware of the low oxygen content but momentarily forgot that fact. When asphyxiation has occurred the immediate need is for oxygen. Henderson and Haggard 29 define asphyxiation as a perversion of the chemical processes of the tissues under a deficiency of oxygen. From experiments on dogs it is stated that if there is complete anoxia for as long as eight minutes, death ensues; if oxygen is supplied within six minutes, recovery may occur; if oxygen is supplied within four minutes, recovery is expected. Artificial respiration may be provided in a variety of ways. Speed and simplicity of the method are factors which are of life-saving importance. The critical examination of manual artificial respiration procedures has shown significant variations in efficiency as judged by the tidal air volumes obtained. 114 MEAN T I D A L VOLUMES (cu. cm.) R E S U L T I N G FROM VARIOUS M A N U A L M E T H O D S OF ARTIFICIAL R E S P I R A T I O N IN COMP A R A T I V E STUDIES BY F O U R D I F F E R E N T RESEARCH GROUPS University of Illinois

Method

(1) Prone pressure Hip lift Arm lift-chest (Silvester) Arm lift-back (Nielsen) Hip roll-back Hip lift-back

(Schafer)

University of Pennsylvania (2A)

485 635

155

1,069

285

1,056 967 1,140

245 350 405

(2B)

Harvard University

Springfield College

(3)

(4A)

(4B)

365 352

296 753

466 871

795

1,087

748 858

1,060 1,140

pressure pressure pressure pressure

474

577

864

680

The American Medical Association's Council on Physical Medicine and Rehabilitation and the American Red Cross recommend the back pressure-arm lift method (essentially that originally proposed by Holger

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Nielsen and used successfully for the past 20 years in the Scandinavian countries). 115 Technique of the Back Pressure-Arm, Lift Method of Artificial Respiration " T h e subject is placed prone, elbows bent, arms overhead with one hand upon the other. T h e cheek is placed on the hand, the face turned slightly to one side. T h e operator kneels on one knee at the head of the subject and puts the foot of the opposite leg near the elbow. He places his hands on the subject's back, in such a way that the thumbs just touch, the heels of the hands being just below a line running between the armpits. H e rocks slowly forward, elbows straight, until his arms are approximately vertical, exerting steady pressure upon the chest. T h e n he commences to rock backward slowly and slides his hands to the subject's arms just above the elbows. H e raises the arms until resistance and tension are felt at the subject's shoulders. T h e n he drops the arms. This completes a full cycle. T h e cycles are repeated 12 times per minute, the expansion and compression phases being of equal length, the release periods being of minimum duration." 115 Eve Method of Artificial Respiration Eve in 1932 proposed a rocking method whereby the force of gravity causes the abdominal organs to shift and move the diaphragm in and out like a bellows in victims of drowning. 116 T h e subject is laid face down on a stretcher (or a suitable board), wrapped in blankets, his wrists and ankles are lashed to the stretcher handles. He is hoisted on a trestle or sling and rocking is begun. T h e procedure has been used on British warships with success. T h e method is safe and said to be effective. Its disadvantage is that the equipment, although simple, may not be on hand in emergency cases.

MANUAL OF INDUSTRIAL MEDICINE

Requirements

of Artificial

95

Respiration

In efforts at artificial respiration one must (1) be sure that there is actually good air interchange by noting the character of the stream of air passing back and forth through the patient's mouth and nose (clear the mouth and nose of obstruction and alter the head position if necessary), (2) keep the rate of artifical respiration slow, and (3) lose no time starting the efforts to supply oxygen. A delay can be fatal. An often overlooked, speedy method of administering air is the simple method known best to obstetricians in starting breathing in the new-born; i.e., blowing air into the lungs of the patient by the mouth-to-mouth technic. A pocket handkerchief will suffice to cover the mouth of the patient during this procedure. Mechanical means of artificial respiration can be effective when used properly. 116 Such machines are rarely at the scene of immediate need in asphyxiation and one must start with manual or the mouth-to-mouth methods if critical minutes are to be saved. Resuscitators create positive and negative pressure alternately by means of a mechanical device. Inhalators provide an atmosphere of oxygen through a face mask under slightly higher than atmospheric pressure and may be added to efforts at manual artificial respiration. Artificial respiration can save life only when the cause for cessation of breathing has been removed. An irreversible pathologic process will prevent a return to normal respiration and life. Types of

Asphyxiants

a) Physical asphyxiants (irrespirable gases)—hydrogen, helium and nitrogen are examples. b) Chemical asphyxiants may act in either of two ways:

M A N U A L OF INDUSTRIAL MEDICINE

(1) Prevent the formation of oxyhemoglobin. Carbon monoxide is formed when organic (carbonaceous) material is burned in the absence of sufficient oxygen; i.e., incomplete combustion of carbonaceous material. Carbon monoxide poisoning is characterized by the formation of CO-hemoglobin. T h e amount of CO-hemoglobin formed depends upon the concentration of CO in the respired air, the rate of respiration and the duration of exposure. Blood concentrations of CO-hemoglobin below 20 per cent of the circulating hemoglobin are accompanied by mild to moderate subjective complaints; these become serious with blood concentrations of 30 per cent and higher. Symptoms are those of asphyxiation, tightness across the head, headache, throbbing in temples, weakness, dizziness, nausea, vomiting, collapse and coma. Meigs and Hughes 117 found that rapid pulse, abnormal blood pressure (high or low), irregular cardiac rhythms, flushing of the mucous membranes, tremor, headache, vomiting, elevation of the erythrocyte count and glycosuria are commonly seen in "mild" cases of CO poisoning. Neurological abnormalities (altered reflexes, spasticity, incontinence, tremors, paralyses), abnormal skin color, chest signs (rales, rhonchi and dullness to percussion), skin lesions (papules, vesicles, edema, ulceration, gangrene), enlarged liver, fever, hyperpnea, albuminuria, and leukocytosis of 18,000 or higher are significantly commoner in "severe" CO poisoning. Hypoxic injury to the brain and associated stimulation of the pituitary-adrenal mechanism is probably the common denominator in this group. Cherry-coloring or pink skin and lips have been stressed in CO exposure. Actually, the abnormal skin

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and mucous membrane color may be that of dark suffusion or cyanosis. Treatment: Prompt elimination of CO from the body (administration of 0 2 ) is important in treatment. Artificial respiration may be required. Chilling and exertion in the victim should be avoided. Venesection, spinal puncture and intravenous injection of hypertonic solutions have been used in efforts to reduce hyperemia and edema of the brain. Antibiotics may be required to control pulmonary and other infections. Morphine and atropine are contraindicated. 1 1 8 Sequelae: Only about one in 500 of those acutely affected by and who survive carbon monoxide poisoning have permanent damage. 119 T h e changes most frequently seen are psychoses and Parkinsonism. T h e degree of permanent residual damage is related to the duration of unconsciousness of the patient. " C h r o n i c " carbon monoxide poisoning is a doubtful entity. Since carbon monoxide is not stored in the body, but rather is excreted in a matter of hours, it is difficult to see how so-called "safe," i.e., low, doses can cause damage even when repeated over a long period of time. (2) Prevent the utilization of oxygen by the tissues. Hydrogen cyanide (hydrocyanic acid) and derivatives (cyanogen and vinyl cyanide) act in this manner. Interference with tissue enzyme systems prevents the utilization of oxygen (inhibits cytochrome oxidases, e.g., ferricytochrome oxidase). Symptoms of acute cyanide poisoning: constriction of the throat, dizziness, nausea and vomiting—convulsions, cold sweat, frothing at mouth, shallow slow respiration, paralysis. T h e skin may show cyanosis or a rosy red color (usually the latter).

M A N U A L O F INDUSTRIAL M E D I C I N E

Chronic poisoning: Exceedingly rare. Symptoms are said to be flatulence, abdominal cramps, vomiting, obstipation, nervousness, dizziness, headache. Treatment: Cyanide poisoning is rapidly fatal. However, no case can be considered hopeless unless the heartbeat has completely stopped. The prevention of death demands a quick diagnosis and the prompt use of specific antidotes. Even though the diagnosis may be doubtful, the recommended therapy should be instituted immediately.120 Cyanide has an affinity for methemoglobin and hence treatment consists of converting some hemoglobin to methemoglobin by use of amyl (or sodium) nitrite. In experimental work with dogs sodium nitrite will detoxify about four lethal doses. Sodium thiosulfate potentiates the action of the nitrite to a point that the median lethal dose of cyanide is raised about 18-fold. The mechanism of poisoning and detoxification is described by Chen and Rose 120 as follows: Ferricytochrome oxidase

NaCN ?=£ ferricytochrome oxidase cyanide NaN0 2 -f- hemoglobin methemoglobin Methemoglobin -j- NaCN cyanmethemoglobin Under the influence of the enzyme rhodanese: Na 2 S 2 0 3 + NaCN + O

NaSCN + Na 2 S0 4

Fortunately the first reaction above is reversible as long as the heart continues to beat. Speed in instituting treatment is obviously essential. Proceed as follows: (a) Instruct an assistant to break, one at a time, pearls of amyl nitrite in a handkerchief and hold the latter over the victim's nose for 15 to 30 seconds per minute. At the same time, the physician quickly loads his syringes, one with a 3 per cent solution of

99 sodium nitrite, and the other with a 25 per cent solution of sodium thiosulfate. MANUAL OF INDUSTRIAL MEDICINE

(b) Stop the administration of amyl nitrite and inject intravenously 10 cc. of a 3 per cent solution of sodium nitrite at the rate of 2.5 to 5.0 cc. per minute. (c) Inject by the same needle and vein, or by a larger needle and a new vein, 50 cc. of a 25 per cent solution of sodium thiosulfate. Oxygen therapy is of little use. The patient is watched for 24 to 48 hours, and, if signs of poisoning reappear, injections of both sodium nitrite and sodium thiosulfate are repeated in one-half the original dose. Sources

of

Poisoning

Sodium or potassium cyanide is widely used in metallurgy for extracting gold and silver from ore, in electroplating, in metal-cleaning and in organic synthesis. Hydrogen cyanide is an effective poison for ridding ships, freight cars, and buildings of rodents and insects. Most cyanide poisoning is intentional (suicidal); rarely is it industrial in origin. 2) Irritants These gases cause inflammation and sometimes necrosis of the tissues of lungs. Examples: acids, ammonia and aldehydes. T h e more soluble the gas in water the more readily will it dissolve in the moisture of the upper respiratory tract; e.g., ammonia and formaldehyde. Lower respiratory tract effects are seen after exposure to oxides of nitrogen or phosgene. Chlorine is intermediate in location of its action.29 These gases have similar effects on all animals. T h e concentration factor is of greater significance than duration of exposure and pulmonary effects are primary; i.e., systemic

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M A N U A L OF INDUSTRIAL MEDICINE

effects are secondary to the pulmonary irritant effect. A common form of pulmonary irritation in industry is that resulting from exposure to oxides of nitrogen. Oxides of Nitrogen: The gases and mist which form during the reaction of nitric acid with organic material contain a mixture of nitrogen dioxide (N0 2 ), nitrogen tetroxide (N 2 0 4 ), nitrous oxide (N 2 0), nitric oxide (NO), nitrogen trioxide (N 2 0 3 ), nitrogen pentoxide (N 2 O s ), and a mist of nitrous and nitric acids. Nitrous oxide has no irritating action and has been used extensively as an anesthetic for surgical operations and dental extractions. The chief offender long was thought to be nitrogen dioxide existing in equilibrium with its polymer, nitrogen tetroxide (NO a ±5 N 2 0 4 ). At body temperature about 70 per cent of the gas is in the form of the tetroxide. Recent British studies show nitrogen pentoxide (N 2 0 5 ) to be a potent irritant and possibly the important factor in causing pulmonary edema following exposure to mixed oxides of nitrogen. 121 Acute pulmonary edema in rats was produced by a four-hour exposure to as low as 2 ppm (9.7 mg/m 3 ) nitrogen pentoxide in the air. Recent reexamination of the content of gases formed at high temperatures (e.g., carbon arc, oxyacetylene torch, and cellulose nitrate combustion) show that at such temperatures the oxide which predominates is nitric oxide (NO).122 Elkins 123 has made the following calculations based on theoretical considerations of the rate of conversion of nitric oxide to nitrogen dioxide: if the concentration of NO is 200 ppm (parts per million), N 0 2 will be formed at the rate of 11 ppm per minute; if the concentration is 100 ppm, N 0 2 will be formed at the rate of 2.8 ppm per minute; if the concentration of NO is 25 ppm, N 0 2 will be formed at the rate of 0.18 ppm per minute. Thus, if the initial

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101

percentage of N O is high, appreciable quantities of NO will persist for a considerable period after exposure to air. Heretofore, it has been assumed that nitric oxide would not exist for a significant time in air (being converted in the presence of moisture and oxygen to the dioxide). Nitric oxide in laboratory animals is not an irritant but acts on the central nervous system as a depressant, and on the blood to form methemoglobin (in high concentration causing cyanosis). Nitrogen dioxide, on the other hand, is an irritant gas, damaging lung tissue in a manner similar to that of phosgene. 122 T h e clinical picture of "nitrous fume" poisoning, as this is incorrectly called, may be one of several types.124 Typically, there is bronchial irritation with chest pain, burning, choking in the throat, coughing and yellowish or blood-tinged sputum. Pursuant to the initial symptoms the exposed man may feel quite comfortable and consider himself to be recovered. Clinical Types of

Poisoning:124

a) Six to twelve hours after exposure (or longer in exceptional cases) the victim characteristically becomes dyspneic, develops a severe cough, extensive pulmonary edema, and cyanosis. He may die rapidly by "drowning" in his own fluids. b) On the other hand, the patient early may show dyspnea, cyanosis, vomiting, methemoglobinemia, and evidence of severe intoxication with little pulmonary edema. Most of the latter group recover, if placed at complete rest. c) Another type of oxides of nitrogen poisoning is one wherein the shock syndrome dominates the clinical picture. Such patients show asphyxia, cyanosis and circulatory collapse rapidly leading to death.

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MANUAL OF INDUSTRIAL MEDICINE

d) Still other victims of this irritant inhalation show a mixed symptomatology with vertigo, incoordination and similar evidence of impaired function of the central nervous system. The most constant of these effects are those which refer to the respiratory tract. Poisoning by oxides of nitrogen usually leads to some degree of edema of the lung. The treachery of this exposure lies in the seeming mildness of damage to the exposed man, initially. The effects of exposure are notably insidious. While evidence of untoward effects of the gas usually appear within 12 to 24 hours after inhalation, it has been reported that the symptoms may be delayed for a week or more. Treatment:125'126

The patient should have complete rest from physical activity. If there is pulmonary irritation the platelet count in the venous blood may rise before clinical signs of pulmonary irritation appear. Oxygen should be administered, preferably before the untoward effects of anoxemia begin. Carlisle 126 found that oxygen given with a provision for expiration against a resistance of a few centimeters of water pressure is beneficial. Other therapeutic suggestions include the use of epinephrine in an oral nebulizer, blood-letting for right ventricular strain, mercurial diuretics, dextrose, plasma, codeine and barbiturates. Obviously the desideratum is prevention of exposure. If there has been sufficient chemical damage to enough alveolar sacs no combination of therapeutic agents would appear to be life-saving. Great care is required to protect the workman who receives what he considers to be an insignificant exposure. That worker often feels too well immediately after the accidental contact to be properly receptive to

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103

medical recommendations made in his behalf. The supervisor of a nitric acid plant, a skilled chemist who knew and could describe accurately the effects of contact with nitrogen dioxide, allowed himself such exposure that he required hospital treatment for pulmonary edema. He was greatly chagrined that it should have happened to himl 3) Anesthetics and Narcotics This group has a predominant anesthetic effect with other less obvious systemic effects. Such materials are: 18 acetylene hydrocarbons, olefin hydrocarbons (ethylene), ethers, paraffin hydrocarbons, and aliphatic alcohols and ketones. T h e anesthetic properties of diethyl ether, as an example, are well-known. A concentration of ether of some 35,000 ppm (parts per million) inhaled for 30 minutes or longer is required to induce unconsciousness.29 For surgical anesthesia the arterial blood concentration must be above 1.5 g. per liter. It is rare that ethers cause symptoms in industrial workers. In the manufacture of smokeless powder, air concentrations of 3,000 or 4,000 ppm cause no ill effects to most workers. An occasional man develops a slight dizziness, may become a devotee of the "ether jag" (the observation which led Crawford Long to find its analgesic qualities) and deliberately invite intoxication by overexposure when supervision is lax. The effects are entirely acute— a cheap form of drunkenness. 7. Poisons Most of the systemic poisons in industry reach the worker in the vapor state. They may be classed either as gases or solvents. Some salient differences between poisoning at home and in industry should be noted:

104

MANUAL OF INDUSTRIAL MEDICINE

Poisoning

at

Home

Industrial

Poisoning

usually

usually

(a) acute (b) taken by mouth (c) a single poison

(a) chronic (b) received through the lungs and skin (c) mixed chemicals

These poisons may be subdivided on the basis of chief effects as: a. Materials which cause injury to visceral organs: example—halogenated hydrocarbons b. Materials damaging the hematopoietic system: example—benzene (which has been mentioned previously for its anesthetic effect) c. Nerve poisons: example—carbon disulfide d. Toxic metals: examples—lead, mercury, cadmium e. Toxic nonmetal inorganic compounds: examples—arsenicals, phosphorus, fluorides Definition

A product meeting any of the following criteria should carry a POISON label with skull and crossbones, according to the Manufacturing Chemists Association: 127 a. Produces death within 48 hours in half or more of a group of ten or more white rats weighing 200-300 grams at a single dose of 50 milligrams or less per kilogram of body weight, when administered orally; or b. Produces death within 48 hours in half or more of a group of ten or more white rats weighing 200-300 grams when inhaled continuously for a period of one hour or less at an atmospheric concentration of 2 milligrams or less per liter of gas, vapor, mist, or dust, provided such concentration is likely to be encountered by man when the product is used in any reasonable foreseeable manner; or c. Produces death within 48 hours in half or more of a group of ten or more rabbits tested in a dosage of 200

M A N U A L OF INDUSTRIAL MEDICINE

105

milligrams or less per kilogram of body weight, when administered by continuous contact with the bare skin for 24 hours or less. If available data on h u m a n experience with any chemical in the above-named concentrations indicate results different f r o m those obtained on animals, the h u m a n exposure data shall take precedence. Since "toxicity" is a relative term attempts have been made to establish significance for qualifying adjectives. T h e industrial toxicologist needs 1) to describe toxic properties in a simple way that is understandable to others and 2) to translate the data on toxicity into terms of an industrial "hazard." U n d e r the first need, toxicity may be characterized for acute exposures as suggested by Hodge and Sterner 128 on the basis of data dealing with oral administration, intraperitoneal administration, inhalation and skin absorption. An example of classification of toxicity by single dose ingestion appears on page 106. Illustrative

poisons:

a. C a r b o n disulfide

3

In France in 1865, August Delpech remarked on the devastating effects of carbon disulfide (CS2) as follows: " H e who works in sulfur is no longer a man." (Delpech reported in 1856 on 24 cases of CS2 poisoning. T h i s was later extended to 80 more cases in 1863.) 1)

Properties

C a r b o n disulfide is a clear liquid with a molecular weight of 76.12, a specific gravity of 1.263 at 20°C., and a boiling point of 46.3°C. T h e vapor has a density of 2.63 compared to air. T h i s vapor belongs to the anesthetic g r o u p of noxious gases. At 20°C. the vapor pressure is 298 m m . Hg., at 30°C. it is 433 mm., and at 40°C. it is 617 m m . P u r e CS 2 is colorless b u t after long standing in the

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