Public Health Hazards of Public Swimming Pools Page 2

In addition, certain free-living aquatic bacteria and amoebae can grow in pool, natural spa or hot tub waters, in the pool or hot tub components or facilities (including heating, ventilation, and air-conditioning [HVAC] systems), or on other wet surfaces within the facility to a point at which some of them may cause a variety of respiratory, dermal or central nervous system infections or diseases.

Outdoor pools may also be subject to microorganisms derived directly from pets and wildlife. The primary water and air quality health challenges to be dealt with are, in typical order of public health priority: controlling clarity to minimize injury hazard; controlling water quality to prevent the transmission of infectious disease, and controlling potential hazards from disinfection by-products.

All of these challenges can be met through a combination of the following factors: treatment (to remove particulates, pollutants, and microorganisms), including filtration and disinfection (to remove/inactivate infectious microorganisms); pool hydraulics (to ensure effective distribution of disinfectant throughout the pool, good mixing and removal of contaminated water); addition of fresh water at frequent intervals (to dilute substances that cannot be removed from the water by treatment); cleaning (to remove biofilms from surfaces, sediments from the pool floor and particulates adsorbed to filter materials); and ventilation of indoor pools (to remove volatile disinfection by-products and radon).

Controlling clarity, the most important water quality criterion, involves adequate water treatment, including filtration. The control of pathogens is typically achieved by a combination of circulation of pool water through treatment (normally requiring some form of filtration plus disinfection) and the application of a chemical residual disinfectant to inactivate microorganisms introduced to the pool itself by, for instance, bathers. As not all infectious agents are killed by the most frequently used residual disinfectants, and as circulation through the physical treatment processes is slow, it is necessary to minimize accidental fecal releases and vomit (and to respond effectively to them when they occur) and to minimize the introduction of bather-shed organisms by pre-swim hygiene.