The EPA standard of 100 parts per billion measures all types of chromium in public drinking water and does not set a separate limit for chromium-6. Another form included in the EPA standard, chromium-3, is found naturally at low levels in foods.
The report released by EWG used a much stricter public health goal of 0.02 parts per billion recommended by the California Environmental Protection Agency. According to the California EPA, “for every million people who drink two liters of water with that level of chromium-6 daily for 70 years, no more than one person would be expected to develop cancer from exposure to chromium-6."
“Americans deserve to know if there are potentially harmful levels of a cancer-causing chemical in their tap water,” David Andrews, a senior scientist at EWG and co-author of the report, said in a statement. “But the test results on the EPA's website are hard to find and even harder to understand. So we compiled and sorted the data, and we found that the scope of the contamination is startling. It's long past time for the EPA to take action to protect Americans from chromium-6.”
The EPA has authority over the nation's drinking water and started looking at the health effects of chromium-6 in 2008. The EWG report alleges that the agency has taken too long to decide if a rule is needed to regulate chromium-6.
The EPA said in a statement today that it is evaluating the possible health effects from hexavalent chromium as part of the agency's risk assessment process for chemicals found in the environment. A version of that assessment is expected to be released to the public next year.
"Ensuring safe drinking water for all Americans is a top priority for EPA," an EPA representative said in a statement. "The agency has taken many actions to improve information on chromium and its potential health risks in drinking water. EPA and states are responsible for ensuring that public water systems are in compliance with the current standard for total chromium."
It's unclear why levels of chromium 6 are higher in some places than others. It can be a result of runoff from industrial operations but it can also be naturally higher in certain parts of the country, according to experts.