In an article published on July 12, 2011 in the New York Times, Jane E. Brody discussed the prevalence of waterborne illnesses in natural and man-made water sources, along with a number of protection strategies. “Recreational water illnesses,” or RWIs, so dubbed by the CDC, may result not only from swimming in natural, untreated water sources, such as lakes or rivers, but also from chemically treated water sources, like pools and hot tubs; in fact, 94% of RWI cases investigated in a 2006 study by the CDC were associated with treated water sources. A common cause in this study was the bacterium Cryptosporidium, which, thanks to a tough outer shell it develops in its spore phase, is resistant to chlorine and can survive for an extended period of time outside a host. Cryptosporidium, like Legionella, is one of the leading causes of RWIs in the United States.
A study like this highlights the fact that even if a pool or hot tub has been treated with chlorine, bacteria may still survive. It is always important to ensure that the pH and chlorine levels in pools and hot tubs are maintained at an effective range for killing bacteria; public pools and hot tubs should be tested for this twice a day. The CDC advises that chlorine levels fall between 1.0 and 4.0 ppm, and that pH levels fall between 7.2 and 7.8. While it is the responsibility of the pool or hot tub management to monitor disinfectant levels, pool and hot tub users are also encouraged to check themselves using chlorine and pH test strips which are widely available for purchase.