THE DETAILS: Dentists have long known that swimming can damage tooth enamel, particularly if a pool isn't properly maintained. In fact, as far back as 1986, a survey of 747 swimmers published in the American Journal of Epidemiology found that 39 percent of competitive swimmers suffered from dental enamel erosion. In this recent paper, dentists from the New York University College of Dentistry analyzed the case of a 52-year-old man who complained of sensitive teeth, dark tooth staining, and enamel loss that came on quickly and had lasted for just five months. The only logical explanation for these sudden changes the researchers could pinpoint was his newly adopted, 90-minutes-per-day swimming routine.
WHAT IT MEANS: Damage to tooth enamel occurs when the pH balance of swimming pool water drops too low, or becomes too acidic. If you've ever been to a pool and your eyes start to water or your nose burns just from smelling the pool water, that's due to low pH (not necessarily too much chlorine). When the pH drops too low, the water becomes corrosive and can stain surfaces like teeth, and irritate your skin. In the 1986 study, the pH of the pool water was discovered to be 2.7, much lower than the recommended pH of 7.2 to 7.8. The man in the NYU case study admitted that he'd never had his pool professionally maintained, and didn't know the pool's pH.
Another reason to be concerned about an improper pool pH is that it can affect how well the chlorine works. When the pH becomes too low or too high, chlorine either dissipates too quickly or its ability to disinfect the water slows. As a result, disease-causing bacteria like chriptosporidium and giardia can thrive.
To protect yourself, you can buy inexpensive pool pH test strips online; the optimal pool pH is between 7.2 and 7.8. Use your test strips at both swimming pools and splash parks, playgrounds with lots of toys shooting water; they should have the same pH as swimming pool water.
For more tips on swimming pool safety, see:
Splash Parks = Germ Parks?
Even Chlorine Can't Clean Up All the Pool Pee
Peeing in the Public Pool: One in Five People Do It