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Legionella Bacteria Prevention Planning

Thursday, February 28, 2013
Legionella Bacteria Prevention Planning

Legionella Bacteria Prevention PlanningLegionella bacteria can be found in a variety of naturally occurring sources (e.g., soils, ponds and streams) in addition to man-made sources such as cooling towers, potable water systems, and heating, ventilation and air-conditioning (HVAC) systems. Legionella bacteria are present in public and well water supplies at extremely low concentrations. Legionella bacteria grow well in cooling towers and other indoor water systems, primarily because of the presence of warm water and available nutrients. If not properly treated, this warm water can promote the growth of algae, microbiological “slime” and amoebae, which enhance the potential for Legionella bacteria amplification.

Legionella Bacteria Prevention PlanningFollowing the 1976 American Legion convention at the Bellevue Stratford Hotel in Philadelphia, 34 attendees died and 221 people became ill from pneumonia caused by the bacterium Legionella pneumophila. This disease, now commonly known as Legionnaires’ disease, is a respiratory infection that strikes susceptible individuals exposed to virulent Legionella bacteria. Infection results from inhaling airborne water droplets or mist containing viable disease-causing Legionella bacteria, which are small enough to pass deep into the lungs and be deposited in the alveoli, the small pockets in the lungs. The dose of Legionella pneumophila and other Legionella bacteria required to infect humans is not definitively known. Legionnaires’ disease can have an incubation period of two to ten days. Although healthy individuals can develop Legionnaires’ disease, people thought to be at increased risk of infection include smokers and patients with cancer, chronic respiratory disease, kidney disease or any immunosuppressed condition.

Legionella Bacteria Prevention PlanningThe purpose of a Legionella control program is to minimize the presence of Legionella bacteria and other environmentally associated bacteria in building waterside systems and consequently reduce the potential for illnesses associated with these organisms. The mechanism to achieve the above is to limit the ecological conditions (temperature range and nutrients) and physical plant (design) operations and maintenance issues that allow the Legionella bacteria to grow and amplify. However, note that complete elimination of Legionella bacteria in building water systems may not be possible. As such, instituting preventive maintenance procedures is a critical aspect of Legionella bacteria control. A well-designed control program includes the following information and procedures.

  • Source Identification – Review design, operations and maintenance of waterside systems (e.g., hot water tanks, cooling towers, HVAC systems, humidifiers, piping networks, process water and distribution systems) for source identification and to perform a risk assessment to determine the likelihood that the system harbors Legionella bacteria and the potential for exposure to aerosolized water droplets or mist.
  • Preventive Maintenance - Develop site-specific guidelines for preventive maintenance procedures for each of the waterside systems for cleaning and maintenance of environmental conditions, such as temperature ranges and water treatments, to reduce the potential for amplification of Legionella bacteria.
  • Legionella Bacteria Prevention PlanningSampling and Analytical Procedures, and Data Interpretation - Determine the best practices for water sampling, including location, frequency of sampling and data interpretation, in relation to preventive maintenance and risk assessment.
  • Decontamination Guidelines - Develop site-specific guidelines for decontamination of each waterside system, including mechanical cleaning, chemical treatment options and heat pasteurization techniques.
  • Emergency Response Procedures - Identify the appropriate team members from within the facility and outside resources, including facilities/physical plant personnel, safety team, medical workers, experienced industrial hygiene consultant, environmental laboratory technician, chemical treatment vendor and field sample collection team, to efficiently respond to high concentrations of Legionella bacteria in samples or a Legionnaires’ disease outbreak.

For additional information or to request a proposal, please contact Harry M. Neill, CIH, at 610.524.5525, ext. 15, or email.



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