Chemicals used to treat drinking water actually might raise the risk of cancer or cause other health hazards by creating toxic byproducts that need tighter federal regulation, according to an environmental advocacy group.

Fair Warning reports that the Environmental Working Group, a Washington, D.C.,-based advocacy organization, also wants the government to reduce the need for chemical treatment by cleaning up sources of public drinking water.

The Environmental Working Group says the problem is that chlorine and other chemicals that public utilities add to drinking water to kill microorganisms can react with other material – such as sewage and manure – to create hundreds of toxic byproducts, many of which aren’t regulated at all.

According to Fair Warning’s post:

Researchers analyzed results from water quality tests done in 2011 at 201 large municipal water systems that serve more than 100 million people in 43 states. They found trihalomethanes, a byproduct of chlorination, in every system. The EPA calls some members of this class of chemicals “probable human carcinogens” and studies have linked them to bladder cancer, birth defects and miscarriages. However, only one water treatment system exceeded the EPA’s limits for the chemicals, which was set at 80 parts per billion in 1998.

But the report argued that the EPA’s limits are too lax, citing several studies linking even lower levels of the chemicals to health problems. For example, in 2011 a French research team analyzing data from three countries found that men exposed to more than 50 parts per billion of trihalomethanes [try-hal-o-MEH-thanes] had significantly increased cancer risks.

You can read the full Environmental Working Group report here.

Read more from Fair Warning here.

Here’s more coverage from Open Channel on drinking water and health issues:

• NC neighbors aghast to learn drinking water contaminated for years
• How an EPA project backfired, endangering drinking water with lead
• Farming communities facing crisis over nitrate pollution, study says