The Environmental Working Group (EWG) has done Duhigg one better by actually ranking American cities according to how "toxic" their water supply is.
"EWG is again doing what it does best: scaring Americans about hypothetical or nonexistent health risks," says Dr. Ross. "In this case, much like the New York Times' campaign against 'toxic' water, EWG has analyzed various water systems for pollutants, and of course they found some. As we say again and again, the fact that you can find a substance in the water at minute levels does not mean that it's a threat to health. Certainly water systems should adhere to federal standards for levels of chemicals present, but to try and scare us over how one city's water compares to that of other cities is not productive. It does generate publicity, however, which is what EWG is all about."
For more information on the detection of trace levels of chemicals, see ACSH's publication on biomonitoring.