Legionella & Building Water Systems

A new report from the Centers for Disease Control (CDC) provides an update on infections associated with potable (drinking) water in the United States. During 2011-2012, a total of 32 outbreaks were reported causing at least 431 infections and 14 deaths. Two-thirds of these outbreaks were caused by Legionella.   Additionally, CDC reported that non-potable water from cooling towers, showerheads and fountains was responsible for an even larger number of cases, of which nearly all were caused by Legionella.

More recently, an outbreak of Legionnaires’ Disease in New York City resulted in twelve deaths and more than two hundred illnesses. The outbreak has been tentatively linked to a cooling tower on the roof of a new boutique hotel. This resulted in an administrative order to test and clean all cooling towers in New York City. Additionally, this summer, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) released a new standard, 188(2015), designed to prevent Legionellosis associated with building water systems.

Legionnaires’ Disease is caused by infection from a water-borne bacterium, Legionella pneumophila, although other species of Legionella bacteria have been associated with the disease as well. While the bacterium has been around for a long time, it has only recently been identified. It received its name from the incident that occurred at the 1976 American Legion conference in Philadelphia, where many attendees suffered from an outbreak of a type of bacterial pneumonia that resulted in 34 deaths. Legionella pneumophila is spread by the release of small droplets of contaminated water into the air from equipment such as air conditioning cooling towers, fountains, showers, sinks, misters, and humidifiers. In the Philadelphia Legionnaires’ Disease outbreak, the hotel’s cooling tower was identified as the likely source of the disease, although domestic water sources were never evaluated. Fresh air intakes located close to the cooling towers provided a pathway into the hotel.

Legionnaires’ Disease is considered to be fairly common yet serious in the U.S. It is often characterized as an “opportunistic” disease that most frequently affects the elderly, and individuals with underlying heart/lung illness or weakened immune system. The disease is not transmitted from person to person, only through exposure to the airborne aerosols. Although approximately 1,000 cases are reported annually to the CDC, it is estimated that more than 25,000 cases occur each year – causing more than 4,000 deaths. Many of its symptoms are flu-like and may not be observed for as long as fourteen days after exposure.

ASHRAE’S New Standard 188(2015)

The goal of ASHRAE’s standard – applicable to human-occupied buildings, excluding single-family residences – is to assist those in building design and facility management in preventing the occurrence of  Legionellosis associated with building water systems. The standard defines minimum risk management practices for the design, construction, commissioning, operation, maintenance, repair, replacement and expansion of new and existing building systems.

The central aspect of the standard identifies the development of a site-specific management plan for the control of Legionellosis in a building or buildings. Since every building is different, the plan should be customized to address specific building-related issues. Hospitals and healthcare facilities, for example, are especially susceptible because of the large number of at-risk individuals. The management plan includes a description of the building water systems, analysis of risk of the water systems, applicable control measures, verification procedures, validation and documentation. The standard leaves the goal of developing specific control strategies to the management program team.

Identification/Characterization of Hazards – Determining the risk hazards at a facility is the first step to reducing potential exposure to Legionella pneumophila. The risk characterization typically includes evaluating:

  • Type of facility (healthcare facility, multiple housing units, etc.)
  • Facility occupants (immuno-compromised, etc.)
  • Aerosol-generating features (ornamental fountains, misters, humidifiers, evaporative coolers, etc.)
  • Existing potable water treatment systems
  • Cooling towers and evaporative condensers

Based on the results of the initial survey, risk management techniques can be used to reduce the potential for the bacterium to thrive and cause illness.

Design and Operation of the Potable Water System – The potable water system should be evaluated and designed to reduce the potential of Legionellosis. Areas that are critical to this design include hot water heater and storage vessel components. Potable water systems with deficiencies in these areas may require secondary disinfection systems. Operation parameters include the storage and distribution temperatures of designated cold and hot water systems.

Maintenance of the Potable Water System – Proper maintenance includes scheduled inspections of thermostats, draining of hot water tanks, and inspection and cleaning of raised water storage systems.

There is ongoing discussion among professionals about the value of routine periodic testing of cooling towers and potable water systems, as well as the most effective treatment for water systems. The ASHRAE standard does not address these two issues.

OSHA’s Stand

Although the ASHRAE standard is not enforceable as an Occupational Safety & Health Administration (OSHA) regulation, several states have proposed rules for management of water systems. 188(2015) establishes an enforceable “standard of care” essential to a defense in Legionella claims. It helps to outline what steps should have been taken to protect employees and building occupants and provides a level of   protection when the management plans are implemented. Chapter 7 of the OSHA Technical Manual specifically addresses controlling Legionellosis by identifying the source of potential contamination, implementing controls, and employee training. The General Duty Clause of the Occupational Safety and Health Act requires that employees protect their employees and visitors from known hazards.

HETI…Helping Prevent Exposures

By establishing adequate barriers to transmission of Legionella bacteria, implementing sound maintenance procedures, and utilizing consistent and effective control mechanisms, users of the ASHRAE standard can reduce the possibility of exposure of at-risk individuals.

HETI can assist in assessing a facility for the risk of Legionella pneumophila exposure. Whether developing a site-specific management plan, conducting a risk characterization assessment, developing controls/measures to reduce the risk of Legionellosis, or assessing implemented controls and programs, HETI has the experience and technical expertise to aid our clients in reducing the risk of Legionellosis at a facility.