Health risks associated with the use of water mist systems as a cooling intervention in public places in Australia

The exposure of people to opportunistic premise plumbing pathogens (OPPPs) such as Legionella, Mycobacterium, and Pseudomonas in aerosolized water has been linked to opportunistic infections. Water mist systems (WMS) that are used to cool public places by flash evaporation of tiny water aerosols are gaining prominence in regions with hot climates in Australia. The potential of WMS to be colonized by OPPPs has not been adequately studied. The public health impact of OPPPs is significant, as Legionella accounted for 66% of waterborne disease outbreaks associated with drinking water systems in the U.S. in 2013–2014. Legionella infections caused by the inhalation of contaminated water aerosols in Europe increased from 1,161/year in 1994 to 4,546/year in 2004. As WMS are part of premise plumbing, they have structural characteristics that promote biofilm formation, growth of free-living amebae, inadequate disinfection levels, elevated water temperatures, and oligotrophic conditions—all of which promote OPPP inhabitancy. This special report highlights the potential public health risks of using WMS as a cooling intervention in public places and advocates for their regulation in places of public assembly and entertainment.