Swimming Pools and Hot Tubs: Worse than You Thought

By Jane Farrell

Even when hot tubs and swimming pools are disinfected, they’re not as clean as you might think, according to new research.

A study published in the American Chemical Society’s journal Environmental Science & Technology showed that the more these facilities are used, the more potentially harmful compounds they contain.

Disinfectants such as chlorine kill pathogens in hot tubs and swimming pools, whether they are personal or public facilities. But disinfectants also react with sweat, urine and other substances that users add to the water. Studies of swimming pools have identified many of the resulting compounds, called disinfection byproducts. And testing has shown that they can cause genetic damage to cells in lab settings.

Other reports have found that some people who swim or work in and around pools have higher rates of certain health problems, including respiratory symptoms and bladder cancer. Susan D. Richardson, of the University of South Carolina, and colleagues took a closer look at hot tubs, in addition to pools, to help flesh out potential problems with disinfection byproducts.

The researchers sampled water from public and private hot tubs and pools from tap to basin, and after both normal and intense use. They identified more than 100 disinfection byproducts in the water and tested extracts of the samples for their potential to cause genetic damage to cells in the lab.

On average, pool and hot tub samples were 2.4 and 4.1 times more mutagenic, respectively, than the original tap water used to fill them. Heavy use increased mutagenic potencies further. But, the researchers say, pool and hot tub operators could reduce disinfection byproducts by cleaning facilities and changing water more frequently. In addition, they could encourage swimmers to shower before sliding in and to use toilets when needed.