A new report released Monday says a suspected cancer-causing form of chromium is contaminating the water supply in at least 31 U.S. cities.
The report by the nonprofit Environmental Working Group found chromium-6, also known as hexavalent chromium, in the public water supplies of 89 percent of the cities it sampled.
Chromium-6 is the same chemical discovered by legal researcher Erin Brokovich in the water supply of Hinkley, California. That discovery led to the largest medical settlement in history paid by Pacific Gas and Electric.
The EWG report is the result of laboratory tests of tap water in 35 cities across the U.S. The U.S. Environmental Protection Agency requires water utilities to test for total chromium, which includes chromium-3 or trivalent chromium, and chromium-6, but does not require tests specific for Chromium-6.
Chromium-3 is a naturally occurring chemical often found in runoff from surface disturbances such as construction, road building and mining. It is not thought to be carcinogenic. Chromium-6 can occur naturally in some geologies, but is typically the result of human activities. It is an ingredient in industrial lubricants and degreasers, and has been shown to cause intestinal tumors in laboratory animals in some studies. The U.S. Environmental Protection Agency has not yet made a definitive statement that chromium-6 causes cancer.
In my own community of Letcher County, Kentucky, hexavalent chromium was found in three streams during initial tests in 2005. Retesting in 2007 did not show hexavalent chromium, though chromium-3 was still present. The tests were conducted by Headwaters Inc., a nonprofit watershed group on whose board of directors I serve.
Tests on tap water for Letcher County were not immediately available.