A new health study found drinking water in 31 out of 35 U.S. cities contaminated by a dangerous form of chromium known as hexavalent chromium. Another study found that hexavalent chromium, a known carcinogen when inhaled and a suspected carcinogen when ingested, often contaminates water leaching from coal ash impoundments. The revelations expose the need for greater monitoring of public drinking water and stronger protections against contamination.

The recent studies by environmental and public health groups shed new light on the extent of drinking water contamination in America and the potential sources of that contamination. The Environmental Working Group (EWG) commissioned water sampling and testing for hexavalent chromium, also known as chromium-6. The results, published in the report Chromium-6 in U.S. Tap Water, found that more than 26 million people are serviced by the water utilities in the 31 cities where chromium-6 was detected. However, the report represents a one-time "snapshot" of the water quality in 35 cities, and without regular monitoring, the full threat to public health is unknown.

Chromium is found in many forms, and the two most prevalent forms are trivalent chromium (chromium-3) and chromium-6. In small amounts, chromium-3 is a vital nutrient needed for healthy human metabolism, but chromium-6 is a known carcinogen and dangerous even in small amounts. Chromium-6 was the toxin contaminating the drinking water of Hinkley, CA, the case made famous by the 2000 film Erin Brockovich. California is currently the only state that requires water utilities to test for hexavalent chromium.

California environmental officials recently revised a proposed "public health goal" for chromium-6 in drinking water. The state's environmental agency originally proposed a goal of 0.06 parts per billion (ppb) of hexavalent chromium in tap water. That figure was lowered to 0.02 ppb to better protect vulnerable populations such as children. However, the EWG report states that California's water testing methods cannot detect levels of hexavalent chromium in amounts below 1 ppb, 16 times higher than what the state considers the maximum safe level.

According to the EWG report, drinking water can be contaminated by hexavalent chromium released by steel and pulp mills, as well as metal-plating and leather-tanning facilities. However, researchers from Earthjustice, Physicians for Social Responsibility, and the Environmental Integrity Project contributed to a report released last week linking numerous cases of chromium-6 groundwater contamination to pollution from coal ash impoundments. Coal ash, a major byproduct of burning coal for energy, is often disposed of in huge landfills or surface impoundments. One such site, a coal ash impoundment operated by the Tennessee Valley Authority (TVA), collapsed in December 2008. The resulting spill at the Kingston Fossil Plant sent more than one billion gallons of toxic sludge flowing into the nearby community and the Emory River.

The report, EPA's Blind Spot: Hexavalent Chromium in Coal Ash, draws on U.S. Environmental Protection Agency (EPA) reports and other studies to identify 28 coal ash dump sites in 17 states that have contaminated groundwater with chromium at levels far above the public health goal proposed by the state of California. According to the report's authors, the contaminated coal ash dump sites "are likely the tip of the iceberg," and EPA regulators are operating with a "blind spot" that misses this significant source of water contamination.

The report also uncovered a study by an electric utility industry group, Electric Power Research Institute (EPRI), that found that 97 to 100 percent of the chromium leaching from coal ash impoundments is the deadly chromium-6. This industry study tested water at 29 coal ash landfills and ponds, finding chromium-6 at 15 coal ash dump sites at levels hundreds of times greater than the proposed California goal. However, the locations of these dumps are unknown, identified only by a number.

The report cautions that "the high levels of hexavalent chromium at the sites may pose a danger to those living near the landfills." The report warns that at these contaminated sites, "there may be little attempt to monitor [the contamination's] migration offsite to protect well users from harmful exposure to hexavalent chromium or other toxic metals commonly found in coal ash leachate."

According to the National Toxicology Program (NTP), "Hexavalent chromium compounds have been shown to cause lung cancer in humans when inhaled." In addition, the NTP states that "hexavalent chromium can also cause cancer in animals when administered orally." The EPA listed chromium-6 as a priority for evaluation under its Integrated Risk Information System (IRIS), and the agency released a draft toxicological review in 2010 stating that chromium-6 in drinking water is "likely to be carcinogenic to humans."

In January 2011, the EPA recommended that water utilities nationwide test for chromium-6. According to EPA, "Systems that perform the enhanced monitoring will be able to better inform their consumers about any presence of chromium-6 in their drinking water." Currently, EPA only requires public water utilities to test for total chromium, which lumps the essential nutrient chromium-3 with the carcinogenic chromium-6. EPA's drinking water standard for total chromium, set back in 1991, is 100 ppb, or 5,000 times higher than California's recent proposed goal for chromium-6 in drinking water. There are no federal regulations requiring water utilities to monitor drinking water for hexavalent chromium, and chromium in leachate from coal ash dumps also is mostly unmonitored.

At a recent Senate oversight hearing on the safety of drinking water, Sen. Frank Lautenberg (D-NJ) announced plans to introduce legislation to require greater monitoring and disclosure of pollutants in drinking water. According to the senator, the public "has no idea that they might be drinking water laden with unregulated contaminants like chromium six, gasoline additives or other toxics." Lautenberg's planned Drinking Water Right to Know Act would allow EPA "to require a targeted increase in monitoring for unregulated pollutants that could be hazardous." The bill would also require EPA "to make information on contaminants in drinking water more readily available online and in simple English."

According to Lautenberg, "More information on contaminants will empower citizens and help government make better decisions on pollutants in the water supply."

Environmental advocates are calling for strong federal regulation of the disposal of coal ash to prevent water contamination, as well as setting a legal limit for chromium-6 in drinking water and requiring water utilities to regularly test for the contaminant. Coal ash disposal proposals have met with fierce industry opposition. TVA, for example, was allowed to comment on EPA's coal ash proposal before it was made available for general public comment, and evidence indicates that EPA may have weakened its original proposal in the face of strong pushback from industry interests and entities within government itself.