Thousands of US water systems show dangerous levels of cancer-causing chemicals
By Carey Gillam
Millions of people across the United States could be drinking water contaminated with dangerous levels of substances created when utilities disinfect water tainted with animal manure and other pollutants, according to a report released Thursday.
An analysis of testing results from community water systems in 49 states found that nearly 6,000 such systems serving 122 million people recorded an unsafe level of chemicals known as trihalomethanes at least once during testing from 2019 to 2023.
The chemicals are byproducts created when chlorine or other disinfectants used by water systems interact with organic matter, such as decaying leaves, vegetation, human or animal waste and other substances. One or more of these chemicals – chloroform, bromodichloromethane, dibromochloromethane, and bromoform – have been linked to various human health risks, including cancers. As a result, the Environmental Protection Agency (EPA) has set a maximum allowable annual average level of 80 parts per billion (ppb) for what the agency calls “total trihalomethanes” or TTHMs. The rule, which applies to public water systems, has been in place for more than two decades.
Texas water systems had the highest prevalence of water systems with unsafe levels of TTHMs, with more than 700 such systems serving over 8.6 million people reporting the contaminants above the EPA’s 80 ppb, according to the report issued April 10 by the Environmental Working Group (EWG).
New York, Oklahoma, California and Illinois followed Texas with hundreds of water systems in each of those states showing higher-than-allowed levels of TTHMs during the testing period, the EWG report found. More than 64.5 million people are served by 3,170 systems in the ten states that had the most violations.