S209: Control of Legionella in Cooling Towers

Cooling towers are structures that re-circulate and cool water in heat exchangers and air conditioning systems of large buildings including businesses, hospitals, schools and other public venues such as museums and shopping centers. The design and environmental conditions of cooling towers appear to enhance growth of biofilm microorganisms, including pathogens such as Legionella.  Amoebae and other protozoa are also abundant in such structures and have been shown to enhance the growth and virulence of Legionella species. Aerosols from cooling towers have been implicated in outbreaks of Legionnaire’s disease.  Therefore, monitoring and control of Legionella and protozoa are important for health risks; however, current detection and remediation methods may not be adequate for addressing the risk for respiratory illnesses associated with cooling towers. This presentation will include discussions of potential problems with guidelines and recommendations for cooling tower treatment, monitoring and detection of Legionella, and acceptable levels of Legionella in relation to infectious dose, microbial interactions and biocide efficacy.