Source: Allied World, EnviroScope, July 2015
Introduction
Nearly 40 years ago, an outbreak of a pneumonia-like illness during an American Legion Convention in Philadelphia resulted in 34 deaths and first brought national awareness to a primarily water-borne bacterium known as Legionella pneumophila. Shortly thereafter, the term “Legionnaires’ Disease” was coined to define this illness which was ultimately traced to bacteria in cooling tower water of the convention hotel. Today, outbreaks of Legionnaires Disease are occurring more frequently in the world impacting some of the finest hotels, cruise ships, healthcare facilities, schools, recreational facilities, and office buildings, most commonly traced to exposure to the bacterium in potable and/or non-potable water, resulting in an ever increasing need to maintain facility water systems and protect the ultimate users of these supplies. “In the United States alone, medical costs for Legionnaires’ Disease are estimated at $321 million per year.”^a In addition to Legionella, other water borne pathogens are becoming more prevalent in our water supply. This paper will focus on prevention strategies to reduce risk and potential liability arising out of the failure to maintain building water systems and resulting water quality as well as examine components of guidelines recently released by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) directed at this emerging and growing issue.
Background
Legionella is found in both natural as well as man-made bodies of fresh water and occasionally in soils as well. Legionellosis describes any illness resulting from exposure to the Legionella bacterium and includes Legionnaires’ Disease as well as less significant respiratory type illnesses (i.e., Pontiac Fever). Epidemiologically, Legionnaires’ Disease presents very similarly to pneumonia and as a result, its incidence is thought to be largely underreported because of this similarity. Legionnaires’ Disease outbreaks in the United States have occurred most often in the northeast, generally impact men more than women, and occur most often in summer and fall months (possibly due to the need to utilize water which has been stagnant over the winter/spring). It has a relatively long incubation period of between 2 and 14 days following exposure, often resulting in a complex and difficult water source identification process, and is extremely rare to contract more than one time.
The following four criteria must be met to have successful transmission of Legionnaires’ Disease because, unlike other respiratory tract infections, this is NOT an infection that is transmitted from person to person:

1. “Species of Legionella in the water must be a species capable of producing illness;”¹

“While there are nearly 50 different species of Legionella, Legionella pneumophila is responsible for the vast majority of infection.”² Therefore, it is critical that if Legionella is identified in the water supply, that the species be identified to validate disease transmissibility. Legionella bacteria will thrive within certain specific water temperature and pH ranges and is often found and protected by biofilms (protective slimy coating of bacteria, protozoa, yeasts, etc.) that adhere to structures within the water distribution piping network and thrive in stagnant conditions.

2. “Person exposed must be a high risk, ‘susceptible’ individual;”³

Those individuals considered to be at highest risk are the elderly, smokers, recent recipients of organ transplants, and immune compromised patients, especially those undergoing chemotherapy.”⁴

3. “Level of contamination in the water source must be sufficient to transmit disease;”⁵

While there is considerable debate as to exactly what level of contamination is required to have documented disease transmission, most would agree that target bacteria levels in water systems should be dependent upon the population/location affected (i.e. healthcare facilities having greater risk due to higher susceptible patient occupancy should have more stringent standards). For example, the OSHA Legionella Technical Manual states that “the viable Legionella concentration should be less than 10 CFU/ml (colony forming unit per milliliter) unless the water system services high risk users which requires a more stringent standard of <1 CFU/ml.”⁶ The main controversy surrounding this issue is that any amount of Legionella in a water supply may be problematic for a susceptible individual, however, just because Legionella is present in a water supply does not equate to the presence of illness in the occupant population of that facility.

4. “Intensity of the exposure to the appropriately contaminated water source must be sufficient to transmit the Legionella ”⁷

The last factor which must be present for successful transmission of Legionella is the dispersion of water into microscopic droplets (1-5 microns in size) which creates the opportunity for inhalation or aspiration into the lungs, since larger water particles will travel into the stomach and not result in disease. For aspiration or inhalation of such small particles to occur, mechanization or aerosolization of water must occur in either potable and/or utility water systems. Some of the most common sources for mechanization/aerosolization of water particles include cooling towers, decorative fountains, whirlpool spas/baths, misting systems, showers, humidifiers, evaporative coolers, but even car washes, hands free faucets, ice machines, grocery vegetable misters, dental water lines, fire sprinklers and steam towel warmers have been implicated as disease sources.
Though the reasons are not exactly clear as to why, cases of Legionellosis (which includes both Legionnaires’ disease as well as the considerably less significant flu-like illness Pontiac Fever) increased 217% between 2001 and 2009.⁸ Some argue this increase is the result of an aging and increasingly deteriorated water infrastructure system while others argue it is the result of increased recognition and ability to rapidly test/diagnose the disease. Green technology and a focus on energy savings (resulting in water temperatures more conducive to Legionella growth) may also be contributing factors as well as climatic change and increased flooding events. In addition, Legionella is chlorine tolerant especially at levels <0.5 ppm and is often brought in with microscopic sediment from the municipal water supply.
Regardless of the precise cause, building owners and managers should begin putting together a knowledgeable water systems team to conduct risk assessments to evaluate potential exposure along with a prevention and response protocol based upon the results of those assessments. The following will detail a prototypical step by step approach towards development of a water risk management program focusing on the control of conditions conducive to growth of Legionella thereby reducing the likelihood of a disease outbreak.
Risk Management
As a first step, building owners and/or other responsible parties should assemble a team of experts knowledgeable about facility water systems. This might include maintenance, engineering, infection prevention (if healthcare related), risk management, consultants, suppliers, contractors, administration, and any other parties involved with the building water delivery systems and their impact. A 10 step water systems review should then be conducted consisting of the following elements. Note that all actions taken should be appropriately reviewed and documented.

1. Review as-built drawings for potable/non-potable facility water systems ensuring that these drawings reflect actual current conditions;
2. Identify any and all water mechanization/aerosolization sources in the building (from the as-built drawings or through an actual building survey) such as such as cooling towers, humidifiers, water fountains, whirlpool spas and other dispersion sources mentioned in item 4 above;
3. Review and evaluate inspection and maintenance procedures, supporting documentation, compliance with manufacturers’ recommendations, prior response actions and outcomes for all water mechanization/aerosolization sources identified above;
4. Review any prior issues relating to water systems including inability to adequately control/ manage water temperatures in ranges conducive to Legionella growth (note that Legionella thrive in temperatures from 95-115°F and that ASHRAE recommends temperatures of 140°F or greater for hot water heater outlets with a minimum temperature of 124°F at the coldest point of hot water storage systems)⁹ and confirm any issues have been resolved;
5. Review any prior water stagnation issues such as those encountered in terminal or non-circulating lengths of pipe (commonly referred to as a dead leg pipes) which contribute to the growth of biofilms which may harbor Legionella bacteria (issues including sludge, scaling,sedimentation, proliferation of algae and other nutrients may also contribute to promoting Legionella bacteria) and confirm any issues have been resolved;
6. Review (and update as necessary) any current water disinfection systems currently utilized to ensure they are functioning properly, documented, and are in compliance with manufacturers’ recommendations;
7. Review any state or local regulations pertaining to water quality management (i.e. anti-scalding provisions, etc.) to ensure compliance;
8. Identify critical control points and develop optimum critical limits in both potable and utility water systems where water quality can be affected by changes to temperature, chemical composition, stagnation, etc. and make improvements/response actions necessary to reduce the likelihood of  Legionella proliferation;
9. Develop an emergency disinfection response program in the event Legionella is found or an outbreak occurs; and,
10. Perform yearly review and monitoring of the above water systems quality management program, update, and make changes when required. Ensure all actions taken are being appropriately documented.

ASHRAE 188
Despite the prevalence of Legionella in many building water systems (i.e. recent studies have estimated that 70% of building water systems may be at least colonized with Legionella),¹⁰ continuous outbreaks of Legionnaires’ Disease, and a multitude of guidelines (ASHRAE, CDC, AIA, EPA, WHO, OSHA, TJC, etc.), there has been little agreement among regulatory agencies on this issue and no definitive standard – at least until now. For the last several years, ASHRAE has been working on a recently released standard (ASHRAE 188) directed at establishing risk management practices for the prevention of Legionellosis in most buildings with potable and utility water systems.
This standard is written in code ready language facilitating integration into existing building codes and where adopted, will have the force of law. Based on the specific details of the standard, it is clear that emphasis is placed on building owners/managers to appropriately assess their risk of facility water conditions (i.e. temperature, stagnation, composition, etc.) conducive to the growth of Legionella, and once those conditions are identified, to comply with best prevention, control, and response methodologies to mitigate those risks. Establishing critical control limits for the conditions known to promote Legionella growth, ensuring those limits are not exceeded (with appropriate response actions when they are) along with supporting and legally defendable documentation to validate compliance appear to be the cornerstones of this new standard. Furthermore, the standard imposes stricter requirements on those facilities housing “susceptible” populations.
Having been finalized and accepted, ASHRAE 188 will create a benchmark standard for Legionella prevention. Documented compliance with the standard will help to refute allegations of negligence, minimize liability exposure and create underwriting standards from which insurability can be determined. The risk management recommendations identified in the 10 step process above should assist in attaining compliance with the primary goals of ASHRAE 188 in instances where the standard requires these additional preventive and/or evaluative steps be taken.
Significance of Risk and Liability for Legionella Exposure on Your Business
The importance of developing a preventive water risk management and quality control program becomes abundantly clear once the significance and detrimental impact that an outbreak of Legionnaires’ Disease can have upon your facilities and your business is understood. In addition to the obvious bodily injury costs, there can be significant property damage, negative publicity (stigma), relocation, business interruption, remediation, and legal fees. While many of the Legionella outbreak costs/settlements have been kept confidential, some of the more notable lawsuits filed in recent years have sought compensatory and punitive damages ranging from $193 – $600 million. Along with the lawsuit costs comes potential tort, contractual and even criminal liability. As a result, anyone involved in the owning, managing, design, engineering, construction, manufacturing, installation, maintenance, and repair of the building and its water systems could have liability exposure in the event of a Legionella outbreak and therefore, with the advent of the new ASHRAE 188 standard, serious consideration should be given to implementation of a proactive risk management program.
Documented adherence to a water quality control program directed at preventing and responding to the growth of Legionella (along with compliance with any applicable regulations) will help to successfully minimize liability and cost exposure as well as facilitate compliance with the ASHRAE 188 standard.
Endnotes
^aSmith, Susan E., Bernier, Thomas P., Legionnaires Disease and Premises Liability, June 21, 2013. Claims Management; www.claims-mgmt.theclm.org/legionnaires-diseaseandpremises-liability.
¹U.S. Department of Labor, Occupational Health and Safety Administration (OSHA) Technical Manual, Legionnaires’ Disease, section III, chapter 7. www.osha.gov/dts/osta/otm/legionnaires/diseaserec.html#risk.
²ASHRAE Guideline 12-2000, Minimizing the Risk of Legionellosis Associated with Building Water Systems, February,2000.
³U.S. Department of Labor, Occupational Health and Safety Administration (OSHA) Technical Manual, Legionnaires’ Disease, section III, chapter 7. www.osha.gov/dts/osta/otm/legionnaires/diseaserec.html#risk.
⁴State of Maryland, “Report of the Maryland Scientific Working Group to Study Legionella in Water Systems in Healthcare Institutions,” Department of Health and Mental Hygiene, June, 2000. www.dhmh.state.md.us/html/legionella.htm.
⁵U.S. Department of Labor, Occupational Health and Safety Administration (OSHA) Technical Manual, Legionnaires’ Disease, section III, chapter 7. www.osha.gov/dts/osta/otm/legionnaires/diseaserec.html#risk.
⁶Ibid. ⁷Ibid.
⁸Centers for Disease Control and Prevention, 2011. Legionellosis-United States, 2000-2009. Morbidity and Mortality Weekly Report 60(32);1083-86.
⁹ASHRAE Guideline 12-2000, Minimizing the Risk of Legionellosis Associated With Building Water Systems, February, 2000.
¹⁰McCoy, William F., 2006, Preventing Legionellosis, Rx for Healthcare HVAC, A Supplement to ASHRAE Journal, June:27-32