As it turns out, the old adage may be right – what you don’t know can harm you.
The Environmental Protection Agency (EPA) regulates 83 contaminants as part of its primary standard on drinking water.
These contaminants include lead, trihalomethanes, asbestos, bacteria and viruses, which if above a certain level, are a risk to human health.
But the EPA also has another list of 30 contaminants that agency monitors but does not regulate.
For many of these contaminants the science is unclear whether they are a health risk to people, while others clearly pose a risk to people.
“The only concern is something we don’t already know, that just started coming up in the newspaper and we don’t know how to test for it or something some people may say it’s bad, but we don’t know whether it’s really bad,” said Jin Shin a water quality manager at the Washington Suburban Sanitary Commission (WSSC), the primary water utility for people in Montgomery and Prince George's Counties.