Environmental group targets disinfection byproducts

The Environmental Working Group (EWG) has charged that existing federal regulatory limits for disinfection byproducts in drinking water are inadequate to protect the public from the dangers of trihalomethanes.

by Patrick Crow, Washington Correspondent

The Environmental Working Group (EWG) has charged that existing federal regulatory limits for disinfection byproducts in drinking water are inadequate to protect the public from the dangers of trihalomethanes.

The trihalomethanes (THMs) are chloroform, bromodichloromethane, dibromochloromethane, and bromoform. They are formed when chlorine, added to treated water as a disinfectant, reacts with rotting organic matter such as farm runoff, sewage or dead animals and vegetation. Their concentrations tend to rise when storms increase organic pollution in waters that serve as sources for tap water.

EWG said scientists suspect that THMs in drinking water may cause thousands of cases of bladder cancer every year. THMs also have been linked to colon and rectal cancer, miscarriages, birth defects and low birth weight.

The environmental group analyzed water quality tests conducted in 2011 by 201 large municipal water systems that serve more than 100 million people.

THM levels fluctuated monthly at water systems, sometimes above the 80 ppb limit set by the Environmental Protection Agency. Only the Davenport, Iowa, system exceeded the limit for the entire year.

"Many people are likely exposed to far higher concentrations of trihalomethanes than anyone really knows," said Renee Sharp, a senior scientist at EWG.

EWG said that since EPA set the 80 ppb limit in 1998, subsequent scientific research has indicated that THMs cause serious disorders at much lower concentrations.

The research included Taiwanese studies conducted in 2007 and 2012 that associated increased risks of bladder cancer and stillbirth to long-term consumption of tap water with THMs of more than 21 ppb.

EWG said 168 (or 84%) of the 201 large water systems reporting data in 2011 had average annual concentrations greater than 21 ppb.

It said California public health officials reviewed THM research in 2010 and determined that to reduce the risk of bladder cancer to no more than 1 in a million, the drinking water standard would need to be set at 0.8 ppb, or 100 times lower than the EPA standard.

The environmental group said EPA has listed chloroform, a member of the THM family, as a "probable" human carcinogen. California health officials consider it a "known" carcinogen.

It said EPA does not regulate hundreds of other types of contaminants formed by water treatment chemicals. One of those is nitrosamine, which is formed when a chloramine, a chlorine compound used for water treatment, reacts with organic matter. EPA has begun an investigation of nitrosamine.

EWG said a thimbleful of THM prevention is worth a gallon of cure. It noted that EPA has reported that every $1 spent to protect source water reduced water treatment costs by an average of $27.

"We must do a better job of keeping farm runoff, sewage and other pollutants from getting into our drinking water in the first place," said Sharp. "By failing to do so, Congress, the EPA, and polluters leave no choice for water utilities but to treat dirty water with chemical disinfectants. Americans are left to drink dangerous residual chemicals generated by the treatment process."

EWG urged federal officials to:

  • Reform farm policies to provide more funds to programs designed to keep agriculture pollutants (such as manure, fertilizer, pesticides and soil) out of tap water.
  • Renew the conservation compliance provision by tying wetland and soil protection requirements to crop insurance programs and requiring farms that receive subsidies to update their conservation plans.
  • Strengthen and adequately fund conservation programs that reward farmers who take steps to protect sources of drinking water.
  • Fund more research on the identity of and toxicological profiles for hundreds of water treatment contaminants in drinking water.
  • Reevaluate the measurement of water treatment contaminants so that consumers cannot be legally exposed to spikes of toxic chemicals.
  • Expand source water protection programs to prevent and reduce pollution and to conserve land in buffer zones around public water supplies.

To reduce exposure to THM and other pollutants in drinking water, EWG said consumers should use a water filtration system.

Sharp said EWG has received "a lot of positive feedback" on the report although "not from the water community directly." She added, "We went out of our way not to scare people about THMs and that seemed to be appreciated."

"Many people are likely exposed to far higher concentrations of trihalomethanes than anyone really knows," – Renee Sharp, EWG

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