Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition [2 ed.] 9781950286126

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Guidance on the recognition, evaluation, and control of Legionella colonization and amplification in common building water systems.

Recognition, Evaluation, and Control of

Legionella

in Building Water Systems 2nd edition

Edited by J. David Krause, PhD, MSPH, CIH; Deborah L. Jaeger, MS; and John P. Springston, MS, CIH, CSP, FAIHA

Recognition, Evaluation, and Control of Legionella in Building Waterand Systems, Recognition, Evaluation, Control of Legionella in 2nd Building Water Systems, edition 2nd edition

Published by AIHA® Falls Church, VA i

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Disclaimer This document is neither a comprehensive treatment of the issues concerning the recognition, evaluation, and control of Legionella in the building water systems, nor is it a stand-alone resource. Scientific and practical knowledge in this area is continuing to accumulate and evolve. This guide is intended to complement existing policies and procedures by other authoritative authors and organizations and should be used by the industrial hygienist and other Competent Professionals in conjunction with prevailing information. AIHA and the authors disclaim any liability, loss, or risk resulting directly or indirectly from the use of the practices and/or theories discussed in this guideline. Moreover, it is the reader’s responsibility to stay informed of policies, statutes, and regulations adopted specifically in the reader’s location of practice. Specific mention of manufacturers, membership organizations, and products in this guideline does not represent an endorsement by AIHA or the authors. Copyright © 2022 by AIHA All rights reserved. No part of this publication may be reproduced in any form or by any other means (graphic, electronic, or mechanical, including photocopying, taping, or information storage or retrieval systems) without written permission from the publisher. Book design by Jim Myers Editorial support provided by Lisa Lyubomirsky Stock Number: LEGG22-781 ISBN-13: 978-1-950286-12-6 AIHA 3141 Fairview Park Drive, Suite 777 Falls Church, VA 22042 Tel: (703) 849-8888 Fax: (703) 207-3561 E-mail: [email protected] http://www.aiha.org

Cover photographs: Photos by J. David Krause; used with permission. Printed in the United States of America

Copyright AIHA®

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Authors and Contributors Primary Authors/Editors J. David Krause, PhD, MSPH, CIH; Project Team Chair Deborah L. Jaeger, MS John P. Springston, MS, CIH, CSP, FAIHA

Contributing Authors Kimberly H. Kirkland, MPH Megan Canright Racicot, MPH, CIH Nathan Sanders, CIH

AIHA Staff Contributors Jim Myers Lisa Lyubomirsky

External Reviewers Clive R. Broadbent, AM, L.AIRAH Stephanie N. Caler, MPH, CIH, CSP Ralph A. Froehlich, MS, CIH, CSP, QEP, FAIHA Alex LeBeau, PhD, MPH, CIH Paul Lilley, CIH Janet E. Stout, PhD

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Foreword by Brian G. Shelton, MPH NOTE: Brian Shelton, William Kerbel, John P. Springston, and J. David Krause were members of the AIHA Indoor Environmental Quality (IEQ) Committee who formed the task force and provided the leadership for the writing and publication of the first edition of Recognition, Evaluation, and Control of Legionella in Building Water Systems (AIHA, 2015). It would be a mistake to write a foreword for this document without mentioning the enormous contribution that James C. Feeley, PhD, made to the understanding and prevention of Legionnaires’ disease. Dr. Feeley developed the microbiological media and laboratory methods that enabled Legionella to be grown in laboratory culture from environmental samples―contributions that are still relied on today. Dr. Feeley, Chief of the Special Pathogens Laboratory at the U.S. Centers for Disease Control and Prevention (CDC) and a member of the Bioaerosols Committee of the American Conference of Governmental Industrial Hygienists, recognized the value and input of industrial hygienists (IHs) in the prevention of this disease transmitted by building water systems. His early and untimely death in 1989 prevented many more contributions to Public Health, and I am sure that this document is indirectly one of those. Dr. Feeley (Legionella feeleii), along with Dr. George Morris and George Gorman (Legionella gormanii), took an early retirement from the CDC to start PathCon Laboratories in 1986 to support prevention for the private sector. I joined in 1989, and our Legionella control strategy was based on detection and quantitation of Legionella in building water systems so that contamination that could not be seen with the naked eye could be reliably detected and then remediated. However, from the mid-1980s onward, the occurrence of Legionnaires’ disease has been increasing, and the U.S. public health response was, unfortunately, reactionary instead of preventive. This reactionary policy was contrary to fundamental IH principles, by waiting for the occurrence of two or more cases of confirmed disease before investigation and discouraging routine testing―the very feedback needed for evidence of treatment efficacy for control of Legionella growth and evaluation of exposure risk. ASHRAE attempted to develop a prevention strategy based on Hazard Analysis and Critical Control Point (HACCP) principles―a strategy entirely experimental for Legionella control in building water systems. Witnessing such a program using unproven principles sparked the idea for this guidance document. Rather than let an experimental approach further delay effective prevention, Bill Kerbel, David Krause, Jack Springston, and I agreed that a Legionella prevention approach based on proven IH principles was necessary. Quantitative feedback to those responsible for maintenance of high-risk building water systems was key―an approach ultimately agreed to by the National Academy of Sciences. With the support of AIHA and many IHs, the first edition of this document was published within a year. Now, with this second edition, the next generation of IHs can continue this most important mission of Legionnaires’ disease prevention.

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Preface As part of revising and updating the first edition, the authors solicited input from users of the guideline. AIHA staff distributed a survey to people who purchased the guideline’s first edition and provided an email address. Recommendations and input from those who submitted responses were used to develop the second edition outline and content. The authors relied on the input of respondents to ensure the update captured, integrated, and addressed the most important issues for users of the guideline. The authors thank everyone who responded to the survey and the AIHA staff who managed and analyzed the survey responses.

Copyright AIHA®

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Copyright AIHA®

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Table of Contents 1.0 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Approaches to Prevention and Control of Legionnaires’ Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3.1 Industrial Hygiene Approach to Source Assessment and Disease Prevention. . . . . . . . . . . . . . . . . . . . 2 1.3.2 Public Health Approach to Disease Assessment and Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.4 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.0 Background on Legionella . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Bacterium and Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3 Ecology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4 Epidemiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.5 Existing Guidance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.6 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.0 Legionella Risk Assessments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1 Goal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.1 Routine Assessment of Legionella Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.1.2 Investigative Assessment of Legionella Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.1.3 Assessment Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2 Inventory of Water Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 Assessing Building Water Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3.1 Cooling Towers and Evaporative Condensers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3.2 Hot Tubs and Spas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.3.3 Decorative Fountains and Water Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.4 Humidifiers and Their Associated Water Sources or Water Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.5 Potable Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.6 Fire Suppression Sprinklers; Emergency Eyewash and Safety Showers . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.7 Industrial Processes (Coolant and Lubricating Fluids). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Other Potential Sources of Legionella . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4.1 Potting Soil and Garden Mulch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.4.2 Ice Machines, Drinking Fountains, and Carbon Filters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.4.3 Computer Room Air Handling Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.4.4 Vehicle-Mounted Water Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.4.5 Car Washes and Pressure Washers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.4.6 Healthcare Devices (CPAP Nebulizers, Ventilators, Heater-Cooler Units). . . . . . . . . . . . . . . . . . . . . . . 19 Copyright AIHA®

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

3.5 Legionella Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.5.1 Developing a Sampling Strategy and Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.5.2 Sample Collection/Shipping and Handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.5.3 Selecting a Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.5.4 Laboratory Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.5.5 Evaluating Data Results and Interpretation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.5.6 Sample Collection Considerations—Number and Frequency of Samples . . . . . . . . . . . . . . . . . . . . . . . 26 3.6 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.0 Prevention, Control, and Remediation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.1 Preventive Measures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.2 Water Treatment Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.2.1 Mechanical Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.2.2 Thermal Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.2.3 Chemical Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.2.4 Biofilm Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.3 Remediation Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4 Interim Measures and Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4.1 Water Restrictions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.4.2 Point-of-Use Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.4.3 Precautionary Emergency Disinfection or Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.4.4 Verifying and Validating Interim Measures, Water Treatment, and System Modifications. . . . . . . . 41 4.5 Remediation Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.5.1 Third-Party Oversight and Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.5.2 Remediating Specific Building Water Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.5.3 Remediating Potable Water Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.5.4 Remediating Cooling Towers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.5.5 Remediating Hot Tubs, Decorative Fountains, and Misters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.5.6 Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.6 Verifying and Validating Remediation and Control Efforts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.6.1 Verifying Remediation Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.6.2 Validating Remediation and Long-Term Control Measures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.7 Long-Term Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.8 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 5.0 Responding to a Legionnaires’ Disease Outbreak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.1 Definition of Legionnaires’ Disease Outbreak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.2 Using the Team Approach. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.3 Role of the Responder Professional. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.3.1 Recommended Steps―Responder Professional and Team. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 5.4 Role of Public Health Authorities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.4.1 Recommended Steps―Public Health Officials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.5 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

6.0 Healthcare Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 6.1 Current Federal Regulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 6.1.1 Veterans Health Administration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 6.1.2 Centers for Medicare and Medicaid Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 6.1.3 Food and Drug Administration 501(k) Clearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 6.1.4 Federal Insecticide, Fungicide and Rodenticide Act. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.2 Current Local and State Regulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.2.1 New York State, 10 NYCRR Chapter 1, Part 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.3 Voluntary Standards with Healthcare Applicability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.3.1 ASHRAE 188-2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.3.2 The Joint Commission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 6.3.3 Foundation for the Accreditation of Cellular Therapy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 6.4 Current Guidance Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 6.4.1 Centers for Disease Control and Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 6.5 Water Management Teams in Healthcare Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.6 Assessing Legionella Sources in Healthcare Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.6.1 Water Systems Inventory Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.6.2 Water Systems Characterization Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 6.6.3 Environmental Sampling Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 6.7 Prevention, Control, and Remediation Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 6.7.1 Prevention Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 6.7.2 Control and Remediation Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 6.8 Medical Surveillance Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 6.9 Responding to Legionnaires’ Disease Outbreak Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 6.10 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 7.0 Competent Professionals and Technicians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 7.1 Definition of Competent Professional. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 7.2 Definition of Competent Technician. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 7.3 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 8.0 Legionella Guidelines, Standards, and Regulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 8.1 Federal Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 8.1.1 Safe Drinking Water Act. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 8.1.2 Federal Insecticide, Fungicide, and Rodenticide Act . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 8.2 Guidelines and Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 8.2.1 Allegheny County Health Department . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 8.2.2 American Society of Heating, Refrigerating and Air-Conditioning Engineers. . . . . . . . . . . . . . . . . . . . 68 8.2.3 Centers for Disease Control and Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.2.4 Association of Water Technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.2.5 World Health Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8.2.5 Cooling Technology Institute. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8.2.7 Environmental Protection Agency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8.2.8 European Guidelines Working Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8.2.9 NSF International . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8.2.10 Council of State and Territorial Epidemiologists. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8.2.11 National Academies of Sciences, Engineering, and Medicine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Copyright AIHA®

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8.3 State and Local Regulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.3.1 California, Title 22, Section 60306. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.3.2 Garland, Texas, Sec. 32.04(D)(6) of Chapter 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.3.3 New York City, Chapter 8 of Title 24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.3.4 New York State, 10 NYCRR Chapter 1, Part 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.3.6 New Orleans, Louisiana, Code of Ordinances 26-17 (sec. 154). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.4 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 APPENDICES Appendix I – Definitions and Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 Appendix II – Supplemental Treatment Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Appendix III – Existing Guidance Documents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Appendix IV – Cooling Tower Cleaning and Disinfection Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Appendix V – Legionella Considerations: Extended Building Closures and Safe Reopening. . . . . . . . . . . . . . . . . . .91 FIGURES AND TABLES Figures Figure 2.1 – Legionnaires’ Disease Chain of Causation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 3.1 – Potable Water Dead Leg Air Column Hammer Arrestors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 3.2 – Aerosolized Water Droplets From a Faucet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Figure 4.1 – Implementing and Monitoring the Control Measures Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Tables Table 3.1 – Sample Data Interpretation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Table 3.2 – Recommended Actions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Table 3.3 – Recommended Minimum Sample Collection Frequencies for Routine Assessments and Monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Table 8.1 – Select Legionella Assessment or Remediation Voluntary Guidance for Industrial Hygienists . . . . . . 67

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Chapter 1 Introduction 1.0 Introduction 1.1 Purpose This document is intended to provide guidance on recognition, evaluation, and control of Legionella colonization and amplification in common building water systems, both with and without any associated disease (legionellosis). This document expands upon information previously presented in the following AIHA publications: Field Guide for the Determination of Biological Contaminants in Environmental Samples, 2nd edition (2005) and Recognition, Evaluation, and Control of Legionella in Building Water Systems (2015).

1.2 Scope Industrial hygienists follow the practice of anticipation, recognition, evaluation, and control of hazards and potential hazards to prevent injury and/or illness in workers and in the community. Legionnaires’ disease and Pontiac fever are building-related diseases. When evaluating a building water system for conditions conducive to growth of Legionella bacteria, the first step is to anticipate and recognize potential amplification and transmission sources. The process of identifying possible sources of Legionella amplification is referred to as either “hazard identification” or “hazard evaluation.” The process of assessing the likelihood of aerosol generation and potential for human exposure to the aerosols produced from a source of Legionella amplification is referred to as a “risk assessment.” Because the infectious dose for Legionella is unknown, and air sampling methods to measure respiratory exposure are unreliable, a complete health risk assessment that estimates the likelihood of disease transmission cannot be performed with today’s technology and information. Therefore, the health risk posed by Legionella amplification in any water sources that can be aerosolized must be mitigated once identified. Building water sources with the potential to amplify Legionella and disseminate aerosols need to be identified and treated, and exposure to aerosols from suspected sources must be minimized or eliminated. However, it is important to remember that the mere presence of Legionella in building water does not always lead to disease in building occupants or members of the surrounding community. Copyright AIHA®

This second edition of Recognition, Evaluation, and Control of Legionella in Building Water Systems supersedes―and is intended to replace―any guidance, information, and recommendations provided in the first edition (published in 2015). Like the first edition of this AIHA publication, the scope of the second edition includes both prescriptive and performance approaches to assess building water systems and other common sources of Legionella amplification. This document does not attempt to address every possible source of Legionella amplification, particularly those associated with medical equipment, dental irrigation, and respiratory therapy equipment. However, this second edition includes a new chapter on considerations when sampling for Legionella in healthcare-related settings. The second edition has also expanded many of the original sections to include more information about water sources (some of which are not building related) that should be considered when assessing Legionella sources, more considerations when investigating a suspect or confirmed cluster or outbreak of Legionnaires’ disease, and updated information on commonly referenced Legionella guidance documents. This guideline describes the basic approaches used to develop Legionella evaluation and sampling strategies and how to perform post-remediation validation (as defined in Appendix 1) that can be applied by a Competent Professional to many situations beyond those described in this document. Competent Professionals, described in Chapter 7, include industrial hygienists, environmental health professionals, engineers, and others with formal education and specific knowledge of Legionella, its habitats, and how to safely find possible sources of its amplification. The information provided in this guideline and the referenced documents are intended to help Competent Professionals understand how Legionella colonizes and amplifies within water sources. With a better understanding of Legionella habitats and ecology, investigators can perform a robust assessment of Legionella amplification sites that pose a hazard to workers, building occupants, and the general public. This document provides guidance on approaches to performing environmental source assessments for Legionella associated with either a routine assessment or an investigative assessment as part of a cluster 1

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or outbreak investigation. By applying the principles of anticipation, recognition, evaluation, and control of environmental factors in the workplace that may cause illness in workers, visitors, or the general public, industrial hygienists can offer a different evaluation approach from those professionals that have been previously relied on for Legionella. Identifying workplace hazards before they cause disease is a primary focus in the field of industrial hygiene and offers the best opportunity to prevent legionellosis.

1.3 Approaches to Prevention and Control of Legionnaires’ Disease 1.3.1 Industrial Hygiene Approach to Source Assessment and Disease Prevention Industrial hygiene is defined as “that science/art devoted to the anticipation, recognition, evaluation, and control of those environmental factors or stresses arising in or from the workplace, which may cause sickness, impaired health and well-being, or significant discomfort among workers or among citizens of the community.” Industrial hygienists use their training and observation skills to identify hazards in the workplace and develop a plan to assess any occupational risks posed by these hazards. Using environmental monitoring and analytical methods to evaluate exposure potential, industrial hygienists can design and implement engineering controls, new or improved workplace practices, and other equipment or control measures to minimize or prevent illness from occupational and community exposure to Legionella sources. The industrial hygiene approach focuses on proactive efforts to anticipate, recognize, and evaluate Legionella hazards and aims to prevent disease through source identification, risk assessment, and control rather than waiting for cases of disease to occur and then responding. The recommended approach to identify potential amplification sites, reservoirs, and sources of exposure is to use validated and reliable laboratory methods to measure viable Legionella concentrations. Indirect or surrogate indicators, such as water temperature, presence or concentration of other bacteria, or residual chlorine levels, often fail to detect conditions and environments where Legionella is present in elevated concentrations indicative of amplification. Because the industrial hygiene approach to Legionella hazard evaluation can be implemented before the first case of disease occurs, it offers the best possibility for anticipation, recognition, evaluation, and control of Legionella and is, therefore, AIHA’s recommended approach. By focusing on specific building water sources where Legionella can grow, and directly assessing if Legionella amplification has occurred and whether aerosols are produced, source

control can be achieved and documented regardless of the occurrence of disease. Because Legionnaires’ disease is contracted from building or other artificial water sources, and not transmitted person-to-person, effectively controlling environmental sources of Legionella can be the most reliable approach to prevention of Legionnaires’ disease. Past efforts have been made to apply Hazard Analysis and Critical Control Points (HACCP), or “Critical Location,” principles to the monitoring and control of Legionella in building water systems. HACCP is a process system that was originally designed for, and primarily used in, food production and safety. As with other novel approaches, including the use of unproven treatment and testing technologies, AIHA cautions users if they choose to integrate such technologies into their water management practice. Because of its track record and history, AIHA endorses the use of traditional industrial hygiene-based assessment and control models, as described in this guideline.

1.3.2 Public Health Approach to Disease Assessment and Prevention From the discovery of Legionella in 1976 up until 2015, the public health response to Legionnaires’ disease was based on disease surveillance, cluster identification, and investigating possible exposure sources. Disease surveillance involves screening cases of reported disease to detect clusters and then responding to prevent additional cases. Once a cluster of reported cases has been associated with a building water source, remediation and testing is often mandated. Although this model may be effective for controlling infectious diseases that are transmitted from person to person―such as COVID-19, influenza, tuberculosis, and measles―diseases of environmental origin are not effectively prevented using a reactionary approach. Avoiding exposure through effective source identification and control can prevent Legionnaires’ disease and the severe illness, complications, or death that may result. Long-voiced concerns of high costs associated with monitoring and control for Legionella have not been demonstrated. On the other hand, the costs of medical treatment (both short- and long-term) and premature mortality of those who become infected, along with any associated litigation costs, can be significant. The public health approach is based on guidance from the Council of State and Territorial Epidemiologists (CSTE), which focuses exclusively on disease surveillance and outbreak management. The goal of epidemiological disease surveillance is to monitor case

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trends, rapidly recognize cases that occur in similar locations or have similar exposures, identify risk factors for infection, and hopefully identify opportunities for control and prevention. Prior to 2016, it was not recommended by CSTE or the Centers for Disease Control and Prevention (CDC) to implement proactive measures to prevent Legionella contamination of building water systems before an outbreak of Legionnaires’ disease occurred. This policy placed patients at risk and resulted in missed opportunities to prevent outbreaks. Beginning in 2016, the CDC published recommendations in its June issue of VitalsignsTM and released the first edition of Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings: A Practical Guide to Implementing Industry Standards. In January 2021, the CDC published more detailed guidance on evaluating hazardous conditions associated with potable water systems and how to implement Legionella control measures in accordance with ASHRAE Guideline 12-2020; this CDC guidance is entitled Toolkit for Controlling Legionella in Common Sources of Exposure (Legionella Control Toolkit). These documents, along with other guidance from the CDC and state public health agencies, mark a fundamental change from strictly reacting to outbreaks of Legionnaires’ disease to promoting efforts that prevent sources of Legionella from colonizing building water systems and detecting them early if they do. On the heels of new guidance from public health agencies, large healthcare organizations, such as the Veterans Administration (VA), the Centers for Medicare and Medicaid Services (CMS), and The Joint Commission (TJC), have issued mandatory requirements to implement water management programs and practices to control the risk of infections due to Legionella and other waterborne pathogens. Because public health surveillance alone has not effectively prevented either sporadic cases or outbreaks of Legionnaires’ disease, it is not surprising that incidence rates have been steadily rising since 2002. Unfortunately, the rate of disease increases has not declined since the publication of proactive voluntary standards or mandates for healthcare facilities. Still, disease surveillance is of paramount importance for detecting outbreaks when prevention efforts have failed. When a cluster of Legionnaires’ disease has been identified, the guidance described in this document (to identify and assess potential sources of Legionella amplification, aerosol production, and exposure) can prove helpful. Performing Legionella risk assessments, in support of a cluster or outbreak investigation, is described in Section 3.1.2. Copyright AIHA®

1.4 References ASHRAE. ASHRAE Guideline 12-2020: Managing the Risk of Legionellosis Associated with Building Water Systems. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, 2020. Centers for Disease Control and Prevention (CDC). Toolkit: Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings: A Practical Guide to Implementing Industry Standards, Version 1.1. Atlanta, GA: CDC, 2021. https://www.cdc.gov/Legionella/downloads/toolkit. pdf. Centers for Disease Control and Prevention (CDC). Legionnaires’ Disease: Use water management programs in buildings to help prevent outbreaks. VitalSigns (June 2016). https://www.cdc.gov/vitalsigns/pdf/2016-06-vitalsigns.pdf. Centers for Disease Control and Prevention (CDC). Legionellosis – United States, 2000–2009. Morbidity and Mortality Weekly Report (MMWR) Vol. 60, No. 32. Published August 19, 2011. http://www. cdc.gov/mmwr/pdf/wk/mm6032.pdf [Accessed October 23, 2021]. Centers for Disease Control and Prevention (CDC). Toolkit for Controlling Legionella in Common Sources of Exposure (Legionella Control Toolkit): Information for Controlling Legionella in Commonly Implicated Sources of Legionnaires’ Disease Outbreaks, Version 1.1. Atlanta, GA: CDC, 2021. https://www.cdc.gov/Legionella/downloads/Control-Toolkit-All-Modules.pdf. Centers for Medicare & Medicaid Services (CMS). Requirement to Reduce Legionella Risk in Healthcare Facility Water Systems to Prevent Cases and Outbreaks of Legionnaires’ Disease (LD) [Memorandum S&C 17-30-ALL Subject]. June 2, 2017. Collier SA, Deng L, Adam EA, Benedict KM, Beshearse EM, Blackstock AJ, Bruce BB, et al. Estimate of burden and direct healthcare cost of infectious waterborne disease in the United States. Emerg Infect Dis 27(1):140–149, 2021. doi: 10.3201/eid2701.190676 Council of State and Territorial Epidemiologists (CSTE). Position Statement: Strengthening surveillance for travel-associated legionellosis and case definitions for legionellosis. ID No. 05-ID-01. Atlanta, GA: CSTE, 2005. https://cdn.ymaws.com/ www.cste.org/resource/resmgr/PS/05-ID-01FINAL. pdf [Accessed October 23, 2021]. Hung L-L, Miller JD, Dillon HK (eds). Field Guide for the Determination of Biological Contaminants in Environmental Samples, 2nd edition. Fairfax, VA: AIHA, 2005. 3

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Kerbel W, Krause JD, Shelton BG, Springston JP (eds). Recognition, Evaluation, and Control of Legionella in Building Water Systems. Falls Church, VA: AIHA, 2015. Occupational Safety and Health Administration (OSHA). Informational Booklet on Industrial Hygiene (OSHA 3143). Washington, D.C.: U.S. Department of Labor, Occupational Safety and Health Administration,1998.

The Joint Commission. Environment of Care Standard EC.02.05.01 EP 14 and EP 6. Yu VL. Resolving the controversy on environmental cultures for Legionella: a modest proposal. Infect Control Hosp Epidemiol 19(12): 893–897, 1998. doi: 10.2307/30142013. [Erratum in Infect Control Hosp Epidemiol 20(5): 302, 1999].

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Chapter 2 Background on Legionella 2.0 Background on Legionella 2.1 History In the summer of 1976, the deaths of 29 people and illnesses of an additional 180 or more individuals were associated with the American Legion convention held at the Bellevue-Stratford Hotel in Philadelphia, Pennsylvania. Although the media is credited with naming the disease after the Legionnaires that it affected, it was the public health officials and microbiologists at the U.S. CDC who ultimately determined that the causative agent was Legionella pneumophila, an aerobic, Gram-negative rod-shaped bacteria common to freshwater environments, cooling towers, and other artificial water sources. As of the time of this writing, there are 62 known species of Legionella, half of which have been associated with human disease. Legionella pneumophila serogroup 1 causes most cases of Legionnaires’ disease and is frequently detected in building water systems. Despite all that has been learned about Legionella since 1976, incidence rates of Legionnaires’ disease have been rising steadily since 2002. Estimates from the CDC indicate a nearly nine-fold increase of reported cases since 2000, with the number of reported cases rising almost every year. The most recent data available for all reported cases of legionellosis in 2018 indicate that almost 10,000 confirmed cases were reported in the United States. However, the true number of cases is almost assuredly much higher. Recently, a committee of experts for the National Academies of Sciences, Engineering, and Medicine (NAS) estimated that each year there are as many as 52,000 to 70,000 cases of disease in the United States. Some proposed explanations offered in the literature regarding the continued rise of Legionnaires’ disease include the aging population, increased use of immunosuppressant drugs, and more comorbidities in persons, along with aging water distribution infrastructure, transforming building designs (such as greater complexity of building water systems), and emphasis on water conservation measures.

2.2 Bacterium and Disease Legionella species have been found to cause several types of disease. The first is Legionnaires’ disease, Copyright AIHA®

a potentially lethal infection typically resulting in severe pneumonia with fever, myalgia, and cough. The second is Pontiac fever, a flu-like illness with no pneumonia. Pontiac fever was first identified in 1968 in Pontiac, Michigan, when 95 of 100 employees in the Oakland County Health Department became sick. The problem was eventually traced to an evaporative condenser in the basement of the building, which was vented within six feet of the heating, ventilation, and air conditioning (HVAC) system fresh air intake. Legionnaires’ disease is the more severe condition and can be debilitating and life-threatening, whereas Pontiac fever is an influenza-like illness that spontaneously resolves itself without medical treatment. Legionella species can also cause disease at sites outside of the lungs. Illnesses such as endocarditis, wound infections, joint infections, and graft infections have been associated with Legionella infection. These diseases are categorized as extrapulmonary legionellosis and are diagnosed when there is clinical evidence of disease at an extrapulmonary site and associated diagnostic testing indicates evidence of the presence of Legionella at that site. These illnesses are often grouped together as legionellosis, although Pontiac fever and extrapulmonary legionellosis are rarely reported or detected by current disease surveillance systems. Legionnaires’ disease is most commonly contracted from exposure to water aerosols, or small droplets of water, containing viable Legionella. Aspiration is also a mode of transmission, which is well documented in healthcare settings. Cases of Legionnaires’ disease associated with suspected exposure to potting soil contaminated with L. longbeachae have also been reported. This recognized source has predominantly been described in Great Britain, Australia, and New Zealand, with a few reported cases in the United States. Although potting soil as a source of exposure is briefly described in this guideline, building water sources are the primary focus and most common source of exposure leading to Legionnaires’ disease. Legionella amplification typically occurs in heated water sources but can also be found in unheated potable water and other indoor building water systems. Legionella amplification can occur in recirculated water sources, such as cooling towers, hot tubs and spas, decorative water features, and recirculating hot water 5

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

systems in large multistory buildings. Transmission of Legionella does not occur from person-to-person contact but rather from inhaling aerosols or aspirating water from colonized water sources. Legionnaires’ disease is primarily a building-related illness. Legionnaires’ disease is a serious illness, with about one in ten community-acquired cases resulting in death and one in four people dying if they contract the illness while in a healthcare facility. The incubation period is commonly 2–10 days from the time of exposure to the bacterium, sometimes extending to 14 days. Risk factors for contracting Legionnaires’ disease include age (i.e., 50 years or older), gender (males are at higher risk), being a current or former smoker, having chronic lung disease or a weakened immune system, or treatment with immunosuppressive medications such as corticosteroids.

2.3 Ecology Legionella bacteria are naturally occurring in low levels in rivers, lakes, and streams. Water in natural or artificial sources can serve as amplification reservoirs for Legionella when suitable conditions for growth occur. Because it can survive routine water disinfection treatment, Legionella can be found at low concentrations in municipal water supplies. Municipal water is the source of Legionella in buildings, although federal and state regulations do not require testing for Legionella under the Safe Drinking Water Act. Water from natural sources (e.g., rivers and lakes) passes through municipal water treatment plants and into the distribution piping, delivering very low (and often undetectable) concentrations of Legionella bacteria into buildings. Legionella can also be introduced to water distribution lines from soil when a break occurs. Once introduced to building water systems and cooling towers, the bacteria then travel to sites where conditions are favorable for colonization and amplification to occur. Examples of potential Legionella amplification sites in buildings include cooling towers, evaporative condensers, humidifiers, ice machines, carbon filters, water softeners, the potable water system (hot water heaters, hot and cold water pipes and premise plumbing distribution systems, shower heads, electronic faucets, faucet aerators), decorative fountains and other indoor/outdoor water features, nebulizers, mister reservoirs, hot tubs and spas, car washes, and industrial wastewater treatment plants. Legionella bacteria thrive and are protected from harsh environmental conditions in biofilms that routinely develop within most water sources and distribution systems. Once a biofilm develops, it can be difficult to eradicate. Under normal use concentrations, most biocides only impact the exposed surface of the biofilm. As a result, even if desired biocide levels are

achieved, they will not be effective in eliminating all Legionella. Although Legionella do not form endospores, they are able to enter a viable but non-culturable (VBNC) state when exposed to certain chemical or environmental conditions. The VBNC state of stressed bacteria is a well-known phenomenon and is not specific to Legionella. Some of the conditions that have been reported to induce a VBNC state in bacteria include nutrient starvation, low temperatures, high salt concentration, low oxygen concentration, heavy metals, pipe material, and treatment with chemical disinfectants. This phenomenon makes it difficult to know whether chemical treatments have eradicated Legionella growth or simply driven it into a state that makes it undetectable by culture methods. Fortunately, however, Legionella bacteria in the VBNC state have not been found to cause disease until they have been “resuscitated” under favorable conditions. Water temperature is a critical factor for Legionella to thrive in natural or artificial sources. The ideal temperatures for growth of Legionella are approximately 77–115°F (25–46°C), but it can survive at temperatures ranging from 32–145°F (0–63°C). Legionella has also been found to survive in water with pH ranging from 5.0–8.5 and dissolved oxygen concentration of 0.2–15 parts per million (ppm). Other utility and buildingspecific environmental conditions considered to encourage Legionella colonization (and thus increase the risk of human disease) include accumulated debris; scale and biofilm; stagnant water or low flow sections (also known as “dead legs”) in the water distribution system; residual chlorine levels below 0.5 ppm; the presence of algae, amoebae, protozoa, and nutrients; and the type of plumbing materials used. Although chlorine levels are often cited as a potential indicator of risk, recent studies have not shown chlorine levels at or below 0.5 ppm to be predictive of the presence or absence of Legionella in building water systems. However, these levels do seem to be a risk factor. Because cooling towers and other building water systems may become colonized from their make-up water source, and they typically contain warm water and generate aerosols, it is important that such systems are well-maintained, periodically monitored, cleaned, properly treated with biocides, and periodically disinfected to prevent Legionella amplification and exposure.

2.4 Epidemiology Inhaling water aerosols that contain Legionella is by far the most common route of transmission for Legionnaires’ disease. Deposition of Legionella into the alveoli of the lung can lead to infection and development of pneumonia if the individual’s immune system cannot fend off the bacteria. Legionnaires’ disease can also be

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acquired by aspirating drinking water and ice contaminated with Legionella, which can occur during dental procedures or when hospital patients chew on ice chips, for example. However, the aspiration exposure route is not believed to be a common route of exposure outside of healthcare settings. Inhaling aerosolized droplets is believed be–the primary source of exposure Figureto2.1 Legionnaires’ disease chain in of both causation healthcare and community exposures. Currently, there

is little evidence of person-to-person transmission of Legionella, aside from a single case report from Vila Franca de Xira, Portugal, in 2014. Other, less common routes of Legionella transmission have been documented, such as direct instillation via contaminated medical devices or wound infections. For Legionella to cause Legionnaires’ disease, a series of events―referred to as the chain of causa-

Figure 2.1: Legionnaires’ disease chain of causation. Copyright AIHA®

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tion―must occur. Disease transmission can be interrupted if any one of the links in the chain is broken (Figure 2.1). Although breaking any one link reduces the possibility of disease, in general, the greatest opportunity to reliably control Legionella, and thereby prevent Legionnaires’ disease, is to minimize Legionella amplification in building water, i.e., source control (a fundamental tenet of industrial hygiene). Legionella is an ongoing risk related to building water systems and is recognized by the CDC as the single most common etiologic agent associated with outbreaks involving potable water. Since 2000, the number of reported cases of legionellosis has been substantially increasing. During 2013–2014, for all reported drinking water-associated outbreaks in the United States, Legionnaires’ disease accounted for 57% of outbreaks, 13% of illnesses, 88% of hospitalizations, and 13 deaths. Legionella is the most frequently reported etiologic agent among drinking water and other non-recreational outbreaks. This fact underscores the need for improved Legionella prevention, control, and mitigation measures. Legionella amplification is particularly challenging to prevent and control, in part because the organism multiplies in cooling towers, decorative water features, and premise plumbing systems within buildings, which typically fall outside of regulatory oversight. Municipal water systems, which are the primary source of Legionella that seed building water systems, are not routinely tested for Legionella. Additionally, public water system operators typically use unreliable surrogate markers for presumptively addressing Legionella. Current regulations under the U.S. Environmental Protection Agency (EPA) Safe Drinking Water Act (SDWA) do not require any testing for Legionella in public water systems and have not established a maximum contaminant level (MCL) for Legionella. The maximum contaminant level goal (MCLG) for Legionella is zero, but this is not an enforceable level.

2.5 Existing Guidance Refer to Chapter 8 and Appendix 3 for a list of commonly referenced guidance documents on Legionella.

2.6 References Berkelman RL, Pruden A. Prevention of Legionnaire’s disease in the 21st century by advancing science and public health practice. Emerg Infect Dis 23(11): 1905–1907, 2017. doi: 10.3201/eid2311.171429. Blatt SP, Parkinson MD, Pace E, Hoffman P, Dolan D, Lauderdale P, Zajac RA, et al. Nosocomial Legionnaires’ disease: aspiration as a primary mode of disease acquisition. Am J Med 95(1): 16–22, 1993. doi: 10.1016/0002-9343(93)90227-g.

Centers for Disease Control and Prevention (CDC). From the January 18, 1977, special issue of {MMWR} Epidemiologic Notes and Reports Follow-up on Respiratory Illness – Philadelphia. Morbidity and Mortality Weekly Report (MMWR) Vol. 46, No. 03. Published January 24, 1997. https://www.cdc.gov/mmwr/preview/mmwrhtml/00045731.htm [Accessed September 15, 2020]. Centers for Disease Control and Prevention (CDC). Legionella (Legionnaires’ Disease and Pontiac Fever): History, Burden, and Trends. https://www. cdc.gov/Legionella/about/history.html [Accessed March 29, 2022]. Centers for Disease Control and Prevention (CDC). Patient facts: Legionnaires’ disease. http://www. cdc.gov/Legionella/downloads/fs-legionnaires.pdf. [Accessed September 15, 2020]. Centers for Disease Control and Prevention (CDC). Legionella (Legionnaires’ disease and Pontiac fever). https://www.cdc.gov/Legionella/healthdepts/surv-reporting/2016-17-report-tables/index. html#figure1 [Accessed September 15, 2020]. Centers for Disease Control and Prevention (CDC). Drinking Water-associated Outbreak Surveillance Report: Supplemental Tables & Figures. https://www. cdc.gov/healthywater/surveillance/drinking-watertables-figures.html [Accessed September 18, 2020]. Centers for Disease Control and Prevention (CDC). National Notifiable Diseases Surveillance System (NNDSS), 2018 Annual Tables of Infectious Disease Data. Atlanta, GA. CDC Division of Health Informatics and Surveillance, 2019. https://wonder.cdc.gov/ nndss/nndss_annual_tables_menu.asp?mmwr_ year=2018 [Accessed September 18, 2020]. Dietersdorfer E, Kirschner A, Schrammel B, Ohradanova-Repic A, Stockinger H, Sommer R, Walochnik J, et al. Starved viable but non-culturable (VBNC) Legionella strains can infect and replicate in amoebae and human macrophages. Water Res 141: 428–438, 2018. doi: 10.1016/j. watres.2018.01.058. Dooling KL, Toews KA, Hicks LA, Garrison LE, Bachaus B, Zansky S, Carpenter LR, et al. Active Bacterial Core Surveillance for Legionellosis— United States, 2011–2013. Morbidity and Mortality Weekly Report (MMWR) 64(42):1190–1193, 2015. Egan JR, Hall IM, Lemon DJ, Leach S. Modeling Legionnaires’ disease outbreaks: estimating the timing of an aerosolized release using symptomonset dates. Epidemiology. 22(2):188–198, 2011. doi: 10.1097/EDE.0b013e31820937c6. Fields BS, Benson RF, Besser RE. Legionella and Legionnaires’ disease: 25 years of investigation. Clin Microbiol Rev 15(3): 506–226, 2002. doi: 10.1128/ CMR.15.3.506-526.2002.

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Hoge CW, Breiman RF. Advances in the epidemiology and control of Legionella infections. Epidemiol Rev 13: 329–340, 1991. doi: 10.1093/oxfordjournals. epirev.a036076. Htwe TH, Khardori NM. Legionnaire’s disease and immunosuppressive drugs. Infect Dis Clin North Am 31(1): 29–42, 2017. doi: 10.1016/j.idc.2016.10.003. Kirschner AKT. Determination of viable Legionellae in engineered water systems: Do we find what we are looking for? Water Res 93: 276–288, 2016. doi: 10.1016/j.watres.2016.02.016. Lauritano D, Nardone M, Gaudio RM, Candotto V, Carinci F. Risk assessment of colonization of Legionella spp. in dental unit waterlines. Oral Implantol (Rome) 10(3): 283–288, 2017. doi: 10.11138/ orl/2017.10.3.283. Levy P-Y, Teysseire N, Etienne J, Raoult D. A nosocomial outbreak of Legionella pneumophila caused by contaminated transesophageal echocardiography probes. Infect Control Hosp Epidemiol 24(8): 619–622, 2003. doi: 10.1086/502263. Lowry PW, Blankenship RJ, Gridley W, Troup NJ, Tompkins LS. A cluster of Legionella sternalwound infections due to postoperative topical exposure to contaminated tap water. N Engl J Med 324(2): 109–113, 1991. doi: 10.1056/ NEJM199101103240207. Muder RR, Yu VL, Woo AH. Mode of transmission of Legionella pneumophila: A critical review. Arch Intern Med 146: 1607–1612, 1986. doi: Marciano-Cabral F, Jamerson M, Kaneshiro ES. Freeliving amoebae, Legionella and Mycobacterium in tap water supplied by a municipal drinking water utility in the USA. J Water Health 8(1): 71–82, 2010. doi: 10.2166/wh.2009.129. National Academies of Sciences, Engineering, and Medicine: Management of Legionella in Water Systems. Washington, D.C.: The National Academies Press, 2020. https://doi.org/10.17226/25474. National Research Council. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, D.C.: The National Academies Press, 2006. https://doi.org/10.17226/11728.

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Oliver JD. Recent findings on the viable but nonculturable state in pathogenic bacteria (Review Article). FEMS Microbiol Rev 34(4): 415–425, 2010. doi: 10.1111/j.1574-6976.2009.00200.x. Parr A, Whitney EA, Berkelman RL. Legionellosis on the rise: A review of guidelines for prevention in the United States. J Public Health Manag Pract 21(5): E17–E26, 2015. doi: 10.1097/ PHH.0000000000000123. Parte AC. LPSN – List of Prokaryotic names with Standing in Nomenclature (bacterio.net), 20 years on. Int J Syst Evol Microbiol 68(6): 1825–1829, 2018. doi: 10.1099/ijsem.0.002786. Pierre D, Baron JL, Ma X, Sidari FP 3rd, Wagener MM, Stout JE. Water quality as a predictor of Legionella positivity of building water systems. Pathogens 8(4): 295, 2019. doi: 10.3390/pathogens8040295. Shaw P, Barskey A, Binder A, Edens C, Lee S, Smith J, Schrag S, et al. Legionnaires’ Disease Surveillance Summary Report, United States, 2010–2015. Atlanta, GA: CDC, 2018. Soda EA, Barskey AE, Shah PP, Schrag S, Whitney CG, Arduino MJ, Reddy, SC, et al. Vital signs: Health care-associated Legionnaires’ disease surveillance data from 20 states and a large metropolitan area — United States, 2015. MMWR Morb Mortal Wkly Rep 66(22): 584–589, 2017. doi: 10.15585/mmwr.mm6622e1. U.S. Environmental Protection Agency (EPA). Legionella Human Health Criteria Document [EPA822-R-99-001]. Washington, D.C.: EPA, November 1999. U.S. Environmental Protection Agency (EPA). Technologies for Legionella Control in Premise Plumbing Systems: Scientific Literature Review [EPA 810-R-16-001]. Washington, D.C.: EPA, September 2016. Whiley H, Bentham R: Legionella longbeachae and Legionellosis. Emerg Infect Dis 17(4):579–583, 2011. doi: 10.3201/eid1704.100446. Yu VL. Could aspiration be the major mode of transmission for Legionella? Am J Med 95(1): 13–15, 1993. doi: 10.1016/0002-9343(93)90226-f.

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Chapter 3 Assessing Legionella Risks 3.0 Legionella Risk Assessments This section describes two types of Legionella risk assessments that Competent Professionals are likely to perform. Although many aspects are the same between the two types, the underlying purpose of each assessment differs. A Routine Assessment (described in Section 3.1.1) is inherently a proactive effort intended to evaluate whether Legionella amplification is occurring, or likely to occur, in building water system components or other identified sources, or whether current control measures are effectively keeping Legionella populations in check. An Investigative Assessment (described in Section 3.1.2) is performed as part of a disease cluster or outbreak investigation and is intended to identify possible sources of Legionella amplification, dissemination, and aerosol exposure that may have caused illness in workers, visitors, residents, or members of the public. In either case, Legionella risk assessments comprise one part of a larger effort, and results of either a routine or investigative assessment should be interpreted in the context of that effort. It is important to recognize that aerosols generated from equipment, devices, point-of-use fixtures, and other components are not necessarily visible. Although some devices do generate visible aerosols or spray, such as showers, decorative fountains, and cooling towers, other devices may generate substantial aerosols that are not readily visible to the naked eye. Studies have shown that Legionella bacteria can be transported in liquid aerosols as small as 1 micrometer (µm) in size. Inhalation transmission through the mouth or nose occurs when particles containing Legionella enter the respiratory tract, with aerosol sizes of 104 colony-forming units per milliliter [CFU/mL]) and demonstrated the presence of culturable Legionella in aerosols during washer fluid spray. Studies conducted in Spain revealed that larger vehicle-mounted tanks used for asphalt grinding and street washing were a source of Legionella exposure that resulted in community-wide outbreaks and occupational cases of Legionnaires’ disease. Increased use of water spray misting to reduce exposures to silica dust and other airborne particulates at construction sites poses a potential risk for Legionnaires’ disease to both workers and the nearby community if the water used in vehicle-mounted tanks is contaminated with Legionella. This practice is frequently used in the southwestern United States to reduce the risk of Valley fever (coccidioidomydosis) on construction sites where excavation or soil disturbance is occurring.

3.4.5 Car Washes and Pressure Washers Car wash facilities have been recognized as potential sources of Legionella exposure and associated with sporadic community-acquired cases. The use of recycled water (which is required in many areas for water conservation), heated water sources, and high-pressure spraying devices that aerosolize water, as well as accumulation of organic material, all present a favorable environment for Legionella growth. Although not examined frequently during public health investigations of Legionnaires’ disease outbreaks, car washes are ubiquitous and found in many communities and workplaces. Self-service car washes are located throughout many cities and rural communities, at gas stations, and at car dealerships. Car washes can often be found at shipping ports and automotive shipping depots. Aerosols generated during washing activities can travel unimpeded and carry within them bacterial contaminants.

3.4.6 Healthcare Devices (CPAP Nebulizers, Ventilators, Heater-Cooler Units) The use of medical devices that include a humidification or nebulizing reservoir poses a risk of contamination with Legionella if tap water or another source of contaminated water is used. The risk of disease has been recognized by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the Centers for Medicare and Medicaid Services (CMS), the Veterans Administration (VA), and the CDC. Even a single use of water from a contaminated water source (e.g., to fill the reservoir or to wash or rinse the equipment) could introduce the bacterium. Examples of medical devices that use water to humidCopyright AIHA®

ify the airstream include oxygen tanks and generators, CPAP and BiPAP devices, nebulizers, and ventilators. Humidifiers and heater-cooler units used in healthcare have been found to aerosolize Legionella when contaminated with tap water. Devices such as these tend to generate an aerosol that spreads throughout a room or larger area.

3.5 Legionella Sampling 3.5.1 Developing a Sampling Strategy and Plan Environmental monitoring that includes sampling for viable Legionella is essential for evaluating the effectiveness of control measures in minimizing or eliminating Legionella growth. In the case of proactive sampling and verification/validation of water management plans, Legionella results can assist facility personnel in evaluating the efficacy of maintenance and water treatment protocols by directly detecting Legionella, ideally before amplification occurs and high levels are aerosolized. As part of an outbreak investigation, water sampling can allow the investigator to identify Legionella amplification and transmission sources throughout a building water system, and ideally determine the environmental water source associated with disease. Legionella culture analysis provides quantitative results (CFU/mL) that can be used to evaluate the effectiveness of Legionella control measures and identify water systems that pose a hazard. It is the responsibility of a Competent Professional to design and implement the Legionella sampling strategy. A thorough and well-planned sampling strategy should ensure that sample results will be useful in addressing questions about building water sources and their potential to grow and amplify Legionella. Additional guidance is available elsewhere, including the NAS publication, Management of Legionella in Water Systems (2020). The sampling strategy should include or consider the following actions: • Identify the source(s) of incoming water supply to the building; • Identify potential sampling sites (include sample type and specific locations); • Determine sample collection methods and the order they are collected; • Outline the number of samples for each source or system and indicate whether they should be “first draw” (pre-flush) and/or “flushed” (postflush) samples; • Specify any special instructions for sample collection, handling, shipping, or analysis; • Specify other measurements to document when evaluating water sources, including temperature, pH, dissolved oxygen, turbidity, residual (free) 19

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chlorine or other disinfectant levels from cold water sources, and water flow rates; • Identify the water treatment schedule and any recent cleaning, maintenance, and renovations; and • If the water system has undergone recent disinfection and/or cleaning protocols, allow sufficient time to pass so that residual levels of disinfectants, pH, temperature, and flow rates return to normal operating conditions before sample collection. A sampling plan should be thorough and well thought out. Identify all possible sampling sites. Consult with facilities personnel and decide on sampling locations that are appropriate for the scope of the project. Be sure to include collection of samples from any storage tanks, make-up water, or municipal water supply sources. Proactive Sampling. In the case of a routine source assessment or proactive sampling, when identifying sampling sites, keep in mind the characteristics of water sources that have the potential to amplify Legionella and produce sprays or aerosols, including the following: • Water sources that are maintained between 60 and 130°F (15–55°C)*; • Hot water storage tanks and sections of the building water that are recirculated; • Water sources that are stagnant or experiencing low flow (no longer in use or temporarily out of use); • Water sources that contain microbial nutrient sources (such as rust, sludge, scale, biofilm, etc.); • Water sources where building occupants or guests are likely to be exposed to the spray or aerosol; and • Water sources in locations where recent construction or renovation has taken place. Investigative Sampling. In the case of sampling performed as part of an investigative source assessment, either resulting from suspect, probable, or confirmed cases of legionellosis or following remediation efforts, identify sampling sites necessary to characterize potential for amplification of Legionella and/ or validate remediation efforts. (Refer to the list under Proactive Sampling.) Consult with

the public health authorities conducting the investigation.

3.5.1.1 Air Sampling Air sampling for Legionella is strongly discouraged as a reliable means of assessing Legionella levels in the environment. Legionella bacteria have a short lifespan in air and can easily become desiccated during air sample collection. Air sampling often leads to falsenegative results and is an inaccurate assessment of airborne Legionella levels in the building environment. Air sampling should never be the sole method of Legionella testing. Water samples (and possibly swab samples) are the preferred types of samples recommended. If used to evaluate an air pathway of exposure or some other specific hypothesis, culturable air samples for Legionella should be collected using a size-selective orifice volumetric air sampler (e.g., single-stage Andersen N6 microbial sampler) containing suitable Legionella-specific growth media, such as Buffered Charcoal Yeast Extract (BCYE) agar. Sampling equipment and protocols should be selected under the guidance of a Competent Professional with special expertise in bioaerosol sampling in consultation with microbiologists from the laboratory that will analyze the samples.

3.5.2 Sample Collection/Shipping and Handling 3.5.2.1 Sample Collection Sampling protocols for the collection of water and swab samples from potable and non-potable sources have been adequately described elsewhere in the published literature. Consult with the testing laboratory about sample collection materials, methods, paperwork, and transport. Because Legionella species are known human pathogens, personal protective equipment (PPE) should be considered when performing sampling, particularly when conducting an investigative source assessment involving known cases of legionellosis. However, respiratory protection is often unnecessary if water aerosol generation can be prevented while samples are being collected. (Refer to the NAS 2020 publication, Management of Legionella in Water Systems and ASHRAE Guideline 12-2020.)

*Note: Refer to call-out box (at the beginning of Section 3.1) for further discussion on ideal temperatures for Legionella growth and recommended temperature ranges for sampling in building water systems. 20

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Sampling is performed to determine the concentration of culturable Legionella in water. The CDC recently clarified information for routine versus outbreak investigations in their 2021 CDC Toolkit for Controlling Legionella in Common Sources of Exposure (Legionella Control Toolkit). The following are some sampling recommendations: 1. At each chosen sampling location, collect at least 125 milliliters (mL) of water for routine sampling. Collect 1000 mL if investigating a disease cluster or outbreak. For water samples, use sterile sample collection containers that are pre-treated with sodium thiosulfate (to bind free chlorine in the sample and prevent any reduction in the concentration of culturable Legionella during sample transit). Wide-mouth sterile polypropylene bottles are commonly used. 2. If collecting swab samples, use a sterile swab (Dacron/polypropylene-tipped; not cotton) to collect the sample from the sampling surface, including any residual liquid, if present. (Refer to Section 3.5.2.3 for more instructions on swab sample collection.) 3. Using a sample collection chain-of-custody form, record a specific description for each sample, along with other details (secondary parameters such as temperature, pH, biocide levels). Submit samples to the laboratory using a chain-of-custody form to minimize the risk of mixing up samples and to document the times, dates, and locations of sample collection, how long samples were stored before shipping, and length of time for samples to be received at the laboratory. Be sure to include names of persons responsible for collecting the samples. 4. For some sampling projects, photographic images of some or all sampling sites may be appropriate. Consult with facilities personnel for permission.

3.5.2.2 Water Sampling Sampling of cooling tower water requires similar volumes as described in Section 3.5.2.1. At each chosen sampling location, collect 125–250 mL water for routine sampling. Collect 1000 mL of water for a disease cluster or outbreak investigation. Collect the water in a sterile sample collection container that contains sodium thiosulfate neutralizer. It is recommended that the cooling tower fan be turned off before sample collection but the Copyright AIHA®

water circulation pump and make-up water supply remain operating. Typically, the water sample is collected from the cooling tower basin in a single, one-direction swooping motion to fill the sample collection bottle, always keeping the hand behind the bottle so as not to potentially contaminate the sample and to prevent the loss of neutralizer. Debris or sediment should not be included in the water samples, unless there is a specific concern about the presence of Legionella in these materials. Sampling of potable water requires using a sterile sample collection bottle to collect 125–250 mL of water for routine sampling or 1000 mL of water if investigating a disease cluster or outbreak. When collecting samples from potable water systems that are treated with halogens (i.e., chlorine, bromine), containers should contain sodium thiosulfate. Sampling of pre-flush water samples may be useful, followed by post-flush samples collected when the water temperature has stabilized. Pre-flush samples are collected from the water that immediately exits the fixture and may indicate the presence of Legionella within the fixture itself (e.g., faucet aerator, showerhead). Post-flush samples are collected after the hot or cold water has run for an established amount of time (typically 1–2 minutes), an established volume (typically 1–2 gallons), or until water temperature stabilizes. Results of post-flush samples may reveal conditions supporting Legionella amplification within the premise plumbing system itself or water storage tanks serving the fixture. Water samples collected from other potable and non-potable sources (e.g., hot tubs, decorative fountains, hot water heaters, water storage tanks, etc.) are collected in sterile sample collection containers containing sodium thiosulfate; sample volume should be between 125 and 250 mL for routine sampling and 1000 mL for disease investigation. Sample bottles with a volume of 250 mL are most commonly used for routine assessments. At each water source, the on-site investigator must make decisions about sample collection details (e.g., from a particular water spigot or basin) on a case-by-case basis. When filtering systems are present, samples collected from the filter media and residual water can sometimes detect bacteria when the basins of water features have been drained and before the media is dry. However, interpreting 21

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Legionella concentrations in filter media samples is difficult and lacking in clear guidance. In general, when collecting water samples, it is useful to measure and record water temperature and other secondary parameters, such as pH and biocide levels, to document on-site conditions at the time of sample collection.

3.5.2.3 Swab/Surface Sampling Swab sampling may be performed to document the concentration of culturable Legionella in surface biofilms found on showerheads, faucet aerators, cooling tower sumps, and various other surface components (e.g., hot tubs, internal pipe surfaces, etc.). Sterile swabs (Dacron/polypropylene-tipped; not cotton) are recommended for the collection of surface samples. During swab sample collection, care should be taken to avoid contamination of the swab by contact with unintended surfaces or hands. Interpreting Legionella concentrations in swab samples is difficult and lacking in clear guidance. In general, swab samples are considered qualitative and primarily used to identify environmental isolates present in water sources. To date, most recommendations have been that no transport medium is necessary for swab samples. However, current CDC guidance (CDC Legionella Toolkit: Sampling Procedure and Potential Sampling Sites, 2019) states that a swab should be moistened with approximately 3–5 mL of source water (if possible), followed by the addition of 0.1N sodium thiosulfate, to prevent drying and loss of viability during transport. Commercial swab transport systems are sufficient to keep the swab moist in transport and do not require sodium thiosulfate.

3.5.2.4 Personal Protective Equipment During sample collection (routine sampling or legionellosis investigation), PPE may be worn to minimize exposure of the on-site investigator to Legionella-contaminated aerosols and chemicals or other hazards related to the building water system. PPE is usually worn during a disease cluster or outbreak investigation if significant aerosol exposure is possible; however, it may not always be necessary, and this decision should be left to the Competent Professional. When deemed necessary, high-efficiency particulate air (HEPA)-filtered (N100) respirators are recommended if mist or

aerosol generation cannot be prevented during sample collection. Other PPE (e.g., nitrile or latex gloves, disposable coveralls, etc.) may be used during sampling to minimize skin contact and prevent sample contamination. Skin protection is most often needed to protect investigators from chemical disinfectants often used in cooling towers. Choice of PPE should be determined on a case-by-case basis by the Competent Professional with guidance from a knowledgeable and informed Industrial Hygienist.

3.5.2.5 Shipping and Handling of Samples During sample collection, the laboratory sample submission or chain-of-custody form should be completely filled out, including investigator contact information. Sampling containers should be clearly labeled using water-resistant labels and/ or permanent marker. Labeled sample containers should be sealed, packed, and shipped in an insulated container or cooler to the microbiology laboratory via overnight courier. Ideally, samples should be received by the laboratory within 24–48 hours of sample collection. Use of ice or dry ice is not recommended because the goal is to transport the samples to the laboratory at ambient temperatures while avoiding temperature extremes.

3.5.3 Selecting a Laboratory Selection of a Legionella laboratory is one of the most important steps in performing a Legionella hazard assessment. Investigators should ensure that the chosen laboratory is qualified and experienced in microbiological methods for Legionella. Analysis for Legionella is not a routine procedure that can be performed by all microbiology laboratories, and it requires specialized training, media, and reagents. Legionella can be difficult to grow and requires specialized culture media, detection and identification procedures, and laboratory expertise in order to obtain reliable analytical results, which are critical to an accurate risk assessment. Before sending the samples to any lab, the Competent Professional should verify that the laboratory’s limit of detection (LOD) is appropriate for the water sources being evaluated.

3.5.3.1 ELITE and Other Environmental Certifications When selecting a Legionella laboratory, the Competent Professional should consider the following factors:

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

• Is the laboratory accredited for Legionella analysis according to the international laboratory quality standard ISO 17025:2017 by an accreditation body that is itself accredited according to ISO 17011:2017 (e.g., AIHA LAP or others)? • Is the laboratory certified by the CDC Environmental Legionella Isolation Techniques Evaluation (ELITE) program? (http://www. cdc.gov/Legionella/elite.html) – Does the laboratory participate in any Legionella proficiency testing programs other than the CDC ELITE program? – What are the credentials, education, experience, and training of the laboratory personnel responsible for Legionella analysis? – How many years of experience does the laboratory have in Legionella analysis? – What is the laboratory’s LOD for Legionella analysis? Selection and training of laboratory personnel should be defined in the laboratory’s standard operating procedures (SOPs). Procedures for determining initial and ongoing competence of laboratory personnel should be described. Laboratory SOPs should define the education requirements for laboratory analysts (e.g., BS or BA degree in Biology or other natural science from an accredited university) as well as any required or recommended laboratory experience. Laboratory analysts should undergo a specific training period, during which all laboratory work should be under the review of a senior member of the laboratory staff (e.g., Senior Lab Analyst, Laboratory Manager, or Laboratory Director). After laboratory personnel are trained specifically for Legionella analysis, laboratories should be able to demonstrate initial and ongoing competence for each analyst involved in Legionella analysis. At a minimum, laboratories should participate in a Legionella proficiency testing (PT) program administered by an independent PT vendor laboratory. At regular intervals, the Legionella PT program ships “blind” environmental samples with known quantities of Legionella to participant laboratories. Participant laboratories then analyze them and report the concentration and types of Legionella detected in the samples. After all participants submit their results, the Legionella PT program generates a scored report that the laboratory can keep as a record of proficiency Copyright AIHA®

of their laboratory analysis. Typically, if a laboratory scores below the program-determined minimum for two subsequent rounds, then they are categorized as “non-proficient” by the PT program until their scores improve. The CDC ELITE program is one of many Legionella PT programs available to laboratories. In addition to the CDC ELITE and other PT programs in the United States, laboratories may also choose Legionella PT programs offered in other countries, such as England and Australia. Section 7.7.2 of ISO 17025:2017 recommends that proficiency testing providers meet the requirements of ISO/IEC 17043. Although proficiency testing is an essential tool in determining performance of Legionella laboratory analysts, it is only part of the overall picture of competency of a laboratory. ISO 17025:2017 accreditation goes further and requires that laboratories have a quality management system that meets specified requirements. Laboratories should have a well-defined quality management program that establishes the laboratory’s organization, personnel training, evidence of personnel competency, procedures for corrective action and customer complaints, risk identification and mitigation, regular internal quality audits and management reviews, participation in a relevant PT program, and a regularly scheduled on-site assessment with an accreditation body that meets the requirements of ISO 17011:2017. If a laboratory participates and maintains a proficient rating in a Legionella PT program, it has demonstrated that its laboratory analysts are capable of identifying Legionella. However, if those same analysts work in a laboratory accredited to ISO 17025:2017, they not only accurately identify Legionella, but they also function in an organization where the overall quality management system is continually reviewed and meets ISO 17025 requirements. This shows that competent, trained personnel are reporting accurate, reliable, and traceable laboratory results in a quality management structure that subjects itself to checks and balances.

3.5.4 Laboratory Analysis A comprehensive overview of analytical methods to detect, enumerate, and identify Legionella in environmental samples is beyond the scope of this document. Readers should understand that Legionella bacteria are not detected by the same microbiological methods 23

Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

used to detect other common heterotrophic bacteria and that no correlation exists between the levels of heterotrophic bacteria (or other bacteria) and the concentration of Legionella present within the same samples. The following is a statement about Legionella detection methods from the 2020 NAS report entitled Management of Legionella in Water Systems (Page 128): “The detection methods applied should include more than one technology (likely a culture method and a molecular method, e.g., qPCR) and be quantitative. Laboratories will continue to use culture but may use more than one medium; this may be unnecessary if, for example, qPCR or droplet digital PCR (ddPCR) was used first to examine more rapidly the concentrations of specific species or L. pneumophila serogroup 1. The detection limit should be carefully documented, addressing both the volume collected and concentrated. More experience is needed where both types of results (culture and molecular methods) are available, thus providing knowledge on their comparability.”

3.5.4.1 Legionella Culture Method The Legionella culture method (based on ISO 11731:2017 and/or the U.S. CDC methods published in 2005) is considered the gold standard of quantifying the level of Legionella in environmental samples because it can yield the following: • Quantitation of viable and culturable Legionella; • Quantitation of any species from the Legionella genus (instead of only L. pneumophila, for example); and • Environmental isolates of Legionella cultured from the samples (which may be useful for further identification and/or matching patient isolates with environmental isolates during an outbreak). Legionella culture methods are typically based on methods described in ISO Standard ISO 11731:2017 Water quality – Enumeration of Legionella and/or the U.S. CDC methods originally published in Procedures for the Recovery of Legionella from the Environment (January 2005). Laboratories must use specialized culture media to isolate Legionella and specific sample treatment methods to prevent other environmental bacteria from outcom-

peting and obscuring Legionella growth on culture plates. Culture results for Legionella can take 7–10 days to be completed; however, preliminary results can be obtained after 4–5 days of incubation, which allows for some positive samples to be identified. Results are reported in CFU/mL or CFU per liter (CFU/L) of sample. Some experienced Legionella laboratories are able to provide a detection limit of 1 CFU/mL or lower.

3.5.4.2 Polymerase Chain Reaction (PCR) The PCR method of analysis for Legionella bacteria is recognized as a useful tool to complement laboratory culture methods and for academic research. The availability of rapid results makes Legionella PCR analysis desirable when results are needed quickly. Data interpretation of PCR results can be difficult for environmental professionals, especially when Legionella culture results and Legionella PCR results do not correlate. PCR analysis can also vary greatly between laboratories. When using Legionella PCR analysis, it is important to understand which part of the Legionella genome a laboratory’s PCR method is trying to detect. In other words, does the PCR analysis detect a specific species (e.g., L. pneumophila) or just the genus? If the method only detects L. pneumophila, does it include all the different serogroups, or only serogroup 1? PCR is comprehensively reviewed in the ISO standard ISO/TS/12869:2019 entitled Water Quality-Detection and Quantification of Legionella spp. and/or Legionella pneumophila by Concentration and Genic Amplification by Quantitative Polymerase Chain Reaction (qPCR). Used with culture analysis, Legionella PCR can be useful; however, it has some limitations. It can be difficult to explain discordant results between the two methods. PCR can be positive and culture negative, and culture can be positive and PCR negative. Also, PCR analysis does not distinguish between viable and non-viable (live and dead) or virulent and non-virulent strains of Legionella. Additionally, unlike the culture method, PCR does not yield actual cultures of Legionella from positive samples (that can then be saved for future use). During a Legionnaires’ disease investigation, Legionella isolates cultured from environmental samples may need to be further identified and compared to clinical isolates

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

cultured from Legionella-positive patients. Further identification of environmental and clinical isolates can be used to epidemiologically link an environmental source with confirmed case(s) of Legionnaires’ disease. As a complementary analysis to the culture method, PCR can be useful and provide rapid information during a Legionella source investigation, but it cannot replace the information gained from environmental isolates yielded by the Legionella culture method. The 2020 NAS report entitled Management of Legionella in Water Systems describes the future potential for Legionella PCR assays: “Now that there is an ISO method for qPCR detection of Legionella (ISO, 2019), it would be appropriate to compare the two methods (qPCR and a culture method) for a variety of buildings and water systems in order to help interpret qPCRgenerated data. It is likely that greater application of qPCR will occur in the future given the speed with which qPCR can provide information.” Next-Generation DNA Sequencing and Whole Genome Sequencing The 2020 NAS report discusses next-generation DNA sequencing and whole genome sequencing. However, these methods are currently not available on a commercial basis for use in environmental monitoring for Legionella because they are still being used mostly in research applications and by public health laboratories. One advantage of this method is that there is no need for pre-amplification of DNA, as there is in traditional PCR/qPCR and subsequent DNA sequencing. Also known as metagenomic sequencing, next-generation DNA sequencing can be performed directly on a DNA extract from a water sample and can theoretically identify all organisms (if at a certain level of relative abundance) that populate the water sample, providing valuable information such as the relative levels of each organism type. However, this method only identifies organisms to the

genus level. Although it provides information on the types of Legionella and non-Legionella organisms present in water, it remains costly and is not an ideal choice for routine Legionella monitoring of environmental samples. Next-generation DNA sequencing, such as whole genome sequencing of individual Legionella isolates, is a method of subtyping Legionella isolates for epidemiologic investigations. This method has implications for Legionnaires’ disease outbreaks, where it can be used to characterize the Legionella strains causing disease in an outbreak and compare them with clinical isolates from individuals diagnosed with Legionnaires’ disease who were exposed to the suspected source.

3.5.4.3 Other Test Methods to Analyze Environmental Samples for Legionella A growing number of Legionella test systems are being marketed as replacements for the traditional culture method. These tests are culture-based, immunologic, and/or PCRbased. If an individual or laboratory chooses to use one of these “non-traditional” methods for Legionella detection, they should thoroughly research the advantages, disadvantages, and limitations of the method. Three examples of currently available rapid Legionella detection methods are as follows: Legiolert*: The Legiolert test (IDEXX Laboratories, Westbrook, Maine) screens for L. pneumophila in water samples. Based on bacterial enzyme detection technology that indicates the presence of L. pneumophila through a color change (utilization of a substrate), L. pneumophila cells grow and produce a brown color in the Legiolert medium. The number of brown wells is then used to estimate the most probable number (MPN) of Legionella in the sample. Legiolert kits detect only L. pneumophila with a detection limit of one (1) organism in 100 mL, and a maximum MPN of 2,272 organisms per 100 mL. The kits can potentially produce false-positive results. Veriflow® Legionella*: The Veriflow Legionella test (Invisible Sentinel, a bioMerieux company, Philadelphia, Pennsylvania) is a molecular-based Legionella test system that can

*Note: These alternative Legionella tests are some examples of products currently available to laboratory and industrial hygiene professionals for rapid Legionella testing. No AIHA endorsement is being made for any brand or company of rapid Legionella testing. More information about new and emerging methods for Legionella testing can be found in Chapter 3 of the NAS document Management of Legionella in Water Systems (2020). Copyright AIHA®

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

provide results from water or swab samples in under four hours. Designed to be a simple laboratory procedure, no filtration or enrichment steps are necessary. Legionella is detected using the proprietary Veriflow DNA Signature Capturing method. The manufacturer claims that this test can distinguish between living and dead cells, thereby decreasing the chance of false-positive results. Invisible Sentinel reports this test to have broad inclusivity of 13 Legionella types. Spartan Cube*: Genomadix (formerly Spartan Biosciences based in Ottawa, Ontario, Canada) manufactures an on-site qPCR testing system for rapid detection of Legionella pneumophila in water samples. The manufacturer advertises that this system can preferentially detect live Legionella (and not dead cells) in contrast to traditional qPCR, which does not differentiate between living and dead cells. Results for viable Legionella are reported in genomic units per milliliter of sample (GU/mL). The manufacturer reports that the system is calibrated so that 1 GU/mL = 1 CFU/mL, making interpretation of results comparable to that of culture results. Testing takes 45 minutes to run, and the system detects L. pneumophila serogroups 1–15. A major disadvantage of the Spartan Cube Legionella test is that it allows for only one water sample to be tested at a time and does not detect other Legionella species.

3.5.5 Evaluating Data Results and Interpretation For the purpose of evaluating the effectiveness of remediation and control measures, Legionella sample results should be categorized in levels ranging from “non-detectable” to “high.” Although the categories are somewhat arbitrary, they attempt to estimate the degree of Legionella growth or amplification that may be occurring in a water system or at specific sites within a water system. Legionella amplification is one of the links in the chain of causation of Legionnaires’ disease (Figure 2.1). Viable, culturable, and pathogenic Legionella concentration in an environmental water sample is an indicator of whether amplification has occurred and quantifies the level of amplification in that source. The goal for system treatment and remediation is non-detectable levels of Legionella; however,

100% of samples being non-detectable for Legionella is not necessary to prevent further cases of disease. Water sources with “high” levels of Legionella pose a potential health hazard to workers and the public if there is an exposure pathway. In such a situation, prompt remediation should begin or interim measures should be taken to mitigate exposure. Water samples with detectable, but still “low,” concentrations of Legionella should typically remain under surveillance but may not require additional remediation. Several different agencies and organizations have published guidelines on interpreting Legionella levels in water samples and the hazard they may represent, including CDC, OSHA, NYCDOHMH, NYSDOH, and NAS. However, none of those guideline levels are based on a quantitative risk assessment. Tables 3.1 and 3.2 represent AIHA’s recommendations for interpreting Legionella culture sample results and suggested remedial actions based on currently available guidance and knowledge. Ultimately, it is the responsibility of the Competent Professional to apply guidelines that are most appropriate for the situation being evaluated and the population at risk.

3.5.6 Sample Collection Considerations― Number and Frequency of Samples A common question asked by industrial hygienists, public health authorities, water management team members, and building operators is how often Legionella sampling should be performed and how many samples should be collected. Fundamentally, there is no single answer to this question, and each facility will likely need a different assessment strategy and sampling plan. The most useful answer to the question of how often and how many samples to collect is that an assessment of water sources requires an overarching strategy that includes sampling to answer a specific question or hypothesis. Sampling results can indicate the effectiveness of control measures that have been put in place to control the growth of Legionella. An assessment strategy that relies on too few samples, or one where samples are collected infrequently, may be deemed unreliable and is likely to not detect potentially hazardous conditions or contaminants. On the other hand, an assessment strategy that samples and measures every fixture, outlet, and potential exposure source is likely to drain available financial resources and disrupt operations to the point that ongoing monitoring is prematurely ended. A middle ground is usually sufficient to meet the needs

*Note: These alternative Legionella tests are some examples of products currently available to laboratory and industrial hygiene professionals for rapid Legionella testing. No AIHA endorsement is being made for any brand or company of rapid Legionella testing. More information about new and emerging methods for Legionella testing can be found in Chapter 3 of the NAS document Management of Legionella in Water Systems (2020). 26

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Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2nd edition

Table 3.1: Sample Data Interpretation Guidelines No Action Required*

Potential for Growth (CFU/mL

Action **

Possible Growth (CFU/mL)

Action **

Indicates Growth (CFU/mL)

Humidifiers and Misters; Decorative Fountains and Water Features; Hot Tubs, Whirlpools, and Spas

Non-Detectable