Cleaning Your Tap Water of Toxins Has Toxic Consequences

This recent NPR story headline, "Chlorine Substitutes in Water May Have Risks," is pretty low-key, considering that the message it delivers is fairly alarming. Since the 1970s, water managers have realized that their all-time favorite disinfectant, chlorine (you know, the stuff that comes in those iconic Chlorox jugs) has some serious down sides, mainly in the form of carcinogenic byproducts.

NPR's story says those carcinogenic byproducts "didn't pose a big risk." But the Environmental Protection Agency wanted water departments to do better in their disinfecting effort.  Unfortunately, their favorite replacement is turning out to pose possibly more serious health risks than the plain old chlorine.

That would be chloramines, which this Water Research Foundation web site describes like this:

Water officials liked chloramines for water disinfection because they were found to not have the same carcinogenic byproducts as chlorine. And, as some critics have noted, chloramines were a fairly cost-effective way for water districts to comply with stiffening EPA regulations.

But as the NPR story goes on to say, chloramines have their own problems, and they may be worse than chlorine's woes.

David Sedlak, civil and envrionmental engineer from the University of California at Berkeley, says that while chlorine doesn't produce the carcinogenic byproducts of chlorine, it produces its own, called nitrosamines.

"Nitrosamines are the compounds that people warned you about when they told you you shouldn't be eating those nitrite-cured hot dogs," Sedlak said to NPR. "They're about a thousand times more carcinogenic than the disinfection byproducts that we'd been worried about with regular old chlorine."

In addition, the NPR article describes the experience of the District of Columbia in going to chloramine disinfecting - the region discovered a vast increase in tap water's lead content, thought to come with chloramines' reactions to the district's many lead pipes.

Most people don't want to know much more about their tap water than that it tastes okay and is safe, free of dangerous contaminants such as cryptosporidium and e-coli. But it turns out that our reliance on chemicals to do that job and our lack as a society of a precautionary principle leaves us open to lots of negative unintended consequences when it comes to keeping drinking water clean.

Sedlak published some of his findings on chlorine and chloramines in this week's Science.