When you ask people if they believe they are at risk of contracting Legionnaires’ disease (LD), most respond with another question. “Didn’t they cure that problem in the ’70s?” “Isn’t that only a problem in VA hospitals?” This lack of public awareness and understanding of LD, a growing public health concern threatening the most vulnerable among us, has contributed to the current situation, where most politicians, policy makers, and bureaucrats know practically nothing about the disease.
In the United States, LD has proven to be the most lethal building-related illness associated with water-borne bacteria. The gram negative bacteria Legionella causes an acute infection of the lower respiratory tract. The resulting pneumonia can be fatal, with a mortality rate of 5-30 percent. Those who survive the illness often require extensive medical treatment and can experience long-lasting health effects. Although most people who contract LD suffer from a compromised immune system, otherwise healthy people are also frequently affected during disease outbreaks.
Ever since the causative agent for LD was first identified, following the 1976 outbreak at the American Legion Convention in Philadelphia, LD has been on the national list of notifiable diseases. The Centers for Disease Control and Prevention (CDC) has maintained this passive surveillance program through state and local health departments. Clinical tests for LD have become more rapid and specific, but can detect only strains of Legionella pneumophila serogroup 1. The rapid clinical assay is blind to the numerous other strains of Legionella that cause human illness. The passive surveillance system and annual reporting by the CDC has, however, accomplished one major thing: it has documented the failure of public health efforts, water authorities, and building owners to prevent LD. CLIMATE CHANGE COLLIDES WITH PUBLIC HEALTH In response to droughts believed to be associated with climate change, a number of energy and water conservation measures are being implemented throughout the U.S. Misguided energy conservation measures that recommend lowering water temperatures or shutting off hot water heaters for long periods of time can help create an ideal environment for Legionella bacteria amplification in the potable water systems of homes, hospitals, and hotels. Water conservation measures intended to save this precious resource, including low-flow toilets, shower heads, and motion sensor-activated faucets, inadvertently increase the chance that Legionella bacteria will colonize and thrive in a building’s potable water systems.
An executive order issued in January 2014 by the Governor of California mandates efforts to reduce potable water use by 25 percent in urban areas of the nation’s most populous state. However, no actions have been identified or funded to assess or mitigate the inevitable public health consequences. Existing potable water delivery systems are old, degraded, and corroded, and have entrenched biofilm and sediment microenvironments from years of service. Reducing overall water usage in communities and buildings has been found to increase the “residence time” of water in distribution lines, eventually reducing the chlorine levels used to keep waterborne bacterial pathogens, including Legionella, in check.
Chlorine can react with microorganisms and organic debris in the water, and with the corrosion, sediment, and biofilm lining the internal surfaces of the pipes. As a result, the amount of chlorine can drop below levels that protect against Legionella. The water that reaches a building may therefore have insufficient chlorine levels to prevent colonization and amplification of Legionella. Adding more chlorine, however, can cause an inadvertent increase in levels of carcinogenic disinfectant byproducts including chloroform and total trihalomethanes (TTHMs). LEGIONNAIRES’ DISEASE ON THE RISE According to CDC, reported cases of LD in the U.S. rose from 1,110 in the year 2000 to 4,954 in 2013—a nearly 350 percent increase. While CDC identifies increasing populations of older people and people living with compromised immune systems as contributing factors, the agency has also indicated that the increase is probably not a result of better surveillance by health professionals. In fact, CDC recognizes that LD is probably significantly under- reported. Efforts to improve surveillance for LD have not progressed from a passive system to an active one, either.
It appears that public health officials see only the tip of the iceberg and investigate only those cases determined to be part of an outbreak. Historical data suggest that the number of reported cases of LD could represent less than 8 percent of actual cases. Blindly proceeding with water conservation efforts without increasing surveillance of water-borne diseases in people, monitoring water-borne disease-causing microorganisms, and taking steps to counter the predictable rise in pathogens is a recipe for disaster.
Several non-binding guidelines provide guidance for architects, facility owners, and building operators on ways to mitigate Legionella and, hopefully, reduce the number of LD cases. Chief among these guidance documents are ASHRAE Guideline 12-2000, ASTM Standard Guide D5952-08, and guidance from the Association of Water Technologies. Despite these well-intentioned efforts, outbreaks of LD have continued to occur worldwide, and the number of reported cases has grown significantly over the past 15 years. Either the control measures outlined within these voluntary guidelines are ineffective, the guidance hasn’t been properly followed, or both.
NEW GUIDANCE Most available guidance recommends investigating sources only after there have been verified cases of LD, or as a means to verify the effectiveness of remediation and cleaning efforts. Therefore, the likelihood that existing guidance documents would work to prevent disease is low.
Two new documents offer significantly more guidance on prevention. Industrial hygiene professionals and others who assess building water systems for potential sources of LD should be aware of how these documents will affect the standard of care throughout the industry.
AIHA Publishes Guidance 
on Assessing Water 
Systems in Buildings
BSR/ASHRAE Standard 188P Legionellosis: Risk Management for Building Water Systems, forthcoming from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), is poised to establish a significant standard of care related to the monitoring and assessment of potable water systems in buildings. In principle, ASHRAE Standard 188P establishes “minimum Legionellosis risk management requirements for building water systems” and is intended for use by “owners and managers of human-occupied buildings.” Almost entirely dedicated to establishing a comprehensive prevention program for practically every building in the U.S., the ASHRAE standard mandates building owners to establish a “water management program” and a “program team.”
Developing and documenting the water management program would involve identifying potable and non-potable water systems within each building and creating a process flow diagram to identify areas where Legionella may amplify. Without directing users to collect samples for the pathogenic bacteria itself, the standard prescribes that “control measures” be established, monitored, and maintained to prevent the amplification and dissemination of Legionella bacteria.
It is left to the discretion of the program team to establish procedures to confirm whether the program is being implemented as designed and effectively controlling the Legionella hazard. The critical aspects of verification and validation of the water management program are essentially where the guidance ends. The ASHRAE standard directs building owners and operators to think about Legionella risk and how it should be managed, but it does not discuss how a team might determine whether its efforts are effectively controlling Legionella amplification.
A facility may be in compliance with the ASHRAE standard without ever having sampled its water sources for the presence of the bacteria that causes LD. It is up to the program team ​to decide which control point monitoring approaches to use to verify and validate their efforts. It appears to be possible for the program team to settle upon secondary metrics that may track temperature, disinfectant levels, or other indicators without ever collecting samples for Legionella bacteria. In industrial hygiene terms, this is akin to measuring temperature and ventilation rates at a refinery to gauge the effectiveness of controlling benzene exposure, rather than sampling for benzene itself and determining the actual exposure hazard. AIHA Guidance In early 2014, members of AIHA’s Indoor Environmental Quality (IEQ) Committee recognized the need for more comprehensive guidance on routine assessments performed before any disease has occurred and approaches to validating the effectiveness of Legionella control measures. Building upon guidance provided in the 2005 AIHA Field Guide for the Determination of Biological Contaminants in Environmental Samples and other authoritative sources, the committee developed a guideline for competent professionals and technicians to follow when assessing Legionella hazards using the fundamental principles of industrial hygiene. This guideline, Recognition, Evaluation, and Control of Legionella in Building Water Systems, was published in May 2015 and is available for purchase from the AIHA store. (Note: the authors of this article are editors of the guideline.)
Recognizing the need for clear guidance on planning and executing a proactive routine assessment, the guideline describes the components, techniques, methods, and observations that should be included. This approach differs from the current public health approach to LD—that of passive surveillance and evaluation of sources only after two or more cases have been confirmed. The industrial hygiene approach advocates the fundamental principles of anticipation, recognition, evaluation, and control of workplace and environmental hazards, including Legionella.
In many ways the AIHA guidance document picks up where the ASHRAE standard leaves off. Where the ASHRAE standard requires that validation of control measures be performed, it is all but silent on how to validate the effectiveness of control measures used to prevent Legionella amplification. The AIHA guideline provides extensive guidance for the competent professional to design and execute a successful assessment of building water systems before disease occurs.
The IEQ committee believes that some level of testing to measure the concentrations of Legionella bacteria in a water source is necessary to determine whether control measures are effective. The availability of sample analysis by accredited laboratories, at a reasonable cost, ensures an adequate level of certainty in the results. The guideline provides guidance on interpreting results as well as recommended courses of action. Whether or not a facility achieves compliance with the ASHRAE standard, the periodic assessment of water sources for Legionella hazards can be a powerful tool in overall risk management and prevention of LD.
Industrial hygienists will likely be among those called upon to respond to outbreaks, perform proactive assessments, and evaluate preventive and remedial measures. The fundamentals presented in the new AIHA guideline have proven to be effective at early recognition of other workplace hazards and long-term management of the risks they pose.
J. DAVID KRAUSE, CIH, MSPH, PhD, is a toxicologist and industrial hygienist with Geosyntec Consultants in Tallahassee, Fla. While serving as the Florida Department of Health’s State Toxicologist, he authored the Guidelines for the Surveillance, Investigation, and Control of Legionnaires’ Disease in Florida in 2009. He can be reached at (850) 766-1938 or dkrause@geosyntec.com. WILLIAM KERBEL, CIH, is a consultant with Environmental Health Investigations, Inc., in Sparta, N.J. He can be reached at (973) 729-5649 or bkerbel@ehi-inc.com. BRIAN G. SHELTON, MPH, is president and owner of Pathogen Control Associates Inc. in Norcross, Ga. He can be reached at (770) 446-0540 or bshelton@pathcon.com. JOHN P. SPRINGSTON, CIH, CSP, MS, is industrial hygiene program manager at TRC Environmental in New York City. He can be reached at (212) 221-7822 or jspringston@trcso lutions.com.
California Executive Order B-29-15 (January 2014).
CDC: Morbidity and Mortality Weekly Report (July 2013).
Water Research: “Impact of advanced water conservation features and new copper pipe on rapid chloramine decay and microbial regrowth” (2012).
The New Age of Legionella