Tap water contains hundreds of different disinfection byproducts. Some of these are toxic, damage DNA, cause birth defects, or cause cancer, according to a 10-year genetic study funded at the University of Illinois by the EPA. The study labeled swimming pools as particularly hazardous.

U. of I. geneticist Michael Plewa described the recent findings of the study, recently published in the journal Mutation Research and described in a U. of I. press release.

One discovery involves water containing iodine, either because the water is mixed with sea water, or because it came from an ancient sea bed now on land. The iodine-containing disinfection byproducts (DBP’s) are much more toxic and genotoxic (damaging DNA) than the DBP’s the EPA currently regulates.

The second and more alarming discovery concerns water containing nitrogen from decomposition of organic matter.  DBPs that contain a nitrogen atom are much more toxic and genotoxic, and in some cases more carcinogenic, than DBPs that don’t contain the nitrogen.  No nitrogen-containing DBPs are currently regulated.

Public pools are particularly hazardous, said Plewa. Organic matter in a pool is broken down by the chlorine, creating DBPs containing nitrogen. The DBPs stay in the pool because they aren’t filtered out and don’t evaporate. This creates higher and higher levels of the toxic compounds, particularly troublesome for young children and infants.

Plewa said the public should be urged to shower before entering a pool, to rinse off sweat and lower the amount of organic material entering the pool. In addition, technologies must be developed to disinfect water without creating these toxic byproducts, he said.

It’s enough to make you think about getting a home water filter.