Politicized Science: The 'Erin Brockovich Chemical'

If you believe the Environmental Working Group’s latest “study,” your drinking water might be contaminated with dangerous levels of a chemical that the group has conveniently dubbed the “Erin Brockovich chemical” -- aka chromium-6. By hyping risks and by capitalizing on Hollywood sensationalism created by the 2000 film Erin Brockovich, the group has begun to build pressure for expensive regulations that could drain the already strained budgets of small towns and cities across America.

EWG’s “study” has captured headlines, the attention of policymakers on Capitol Hill and at the Environmental Protection Agency, and it is the subject of hearings before the Senate Environment and Public Works Committee this week.

EWG claims to have found harmful levels of hexavalent chromium (aka., chromium-6) in the drinking water of 35 U.S cities, and it is calling for swift federal regulatory actions. The group timed their study to coincide with the Environmental Protection Agency’s (EPA) routine review of its drinking water standard for chromium -- but the EPA review doesn’t support EWG’s claims.

The evidence of significant risk from chromium in U.S. drinking water is weak. EPA’s draft risk assessment on chromium-6 (September 2010) states, “The epidemiologic data are not sufficient to establish a causal association between exposure to hexavalent chromium by ingestion and cancer.”

It is true that some studies have linked chromium-6 to lung cancer among workers who inhaled high levels of chromium-6 over a relatively long time period, but those studies are not very relevant to ingestion of trace levels in drinking water.

Still, EWG says the chemical is dangerous because it has produced tumors in rodents. But those studies, which were conducted by the National Toxicology Program in 2007 and 2009, involved rodents that ingested relatively high levels -- between 5,000  to 180,000 parts per billion -- of the chemical in drinking water over two years, a long time frame in the life of a rat.

These very high, long-term exposures of rodents to chromium tell us little about impacts on humans who are periodically exposed to levels that are thousands of times lower. For example, the amounts of chromium-6 that EWG found in U.S. drinking water averaged at just 0.18 parts per billion, with the highest rate of 12.9 parts per billion in Norman, Oklahoma.