Chlorine is not be perfect, but it’s better for you than the nasty bugs it’s put in pools to kill.
Among the “recreational water illnesses” listed by the federal Centers for Disease Control and Prevention is diarrhea caused by Cryptosporidium, E. coli, Giardia and Shigella, all spread, as the CDC delicately puts it, by “accidentally swallowing water that has been contaminated with fecal matter.” Unsanitized pool water can also cause respiratory illnesses, as well as skin, ear and eye infections. ( For more than you ever wanted to know about such things, check out the CDC website, www.cdc.gov/healthyswimming, and look up the recommendations for pool staff to follow in the event of “fecal accidents.”)
The downside of chlorination – like stinging eyes and the strong odor – is not from the chlorine itself, said CDC epidemiologist Michael Beach, but from the byproducts formed when chlorine binds to organic material in the pool (like hair, feces, sweat, urine, etc.) These compounds are volatile and accumulate in the water and air, a major reason why indoor swimming pools should not just recycle air but ventilate with fresh air as well. Some data suggest that these volatile compounds can exacerbate asthma, though more data on this is needed, said Beach.
One alternative to chlorine is bromine, though this can discolor the water and some people’s skin is more sensitive to it than to chlorine. Another product called PHMB (polyhexamethylene biguanide) is also “registered” by the federal government as an acceptable pool “sanitizer,” said Ed Lightcap, chairman of the recreational water quality committee of The National Spa and Pool Institute, an industry association.
And then there are the “ionizers,” pool sanitizing systems that use copper and silver ions to kill microbes. At the West End House Boys and Girls Clubs in Allston, executive director Andrea Howard said that “people love it,” especially those who believe they have allergies to chlorine. For some, she said, “it’s the difference between being able to go into the pool or not.”
But ionizing is “never meant to be used alone,” said Beach of CDC, but just to reduce the amount of chlorine needed. It’s also not clear yet, he said, whether ionization kills pathogens as quickly as chlorine.