Study Finds Probable Carcinogen in 31 U.S. Cities' Tap Water

A new analysis showing the presence of a probable carcinogen in the tap water of 31 cities across the country, including the District and Bethesda, has raised questions about what consumers in those communities can do to reduce their exposure.

The chemical, hexavalent chromium, got public attention via the 2000 film "Erin Brockovich" and has been deemed a "probable carcinogen" by the National Toxicology Program, part of the National Institutes of Health.

Although basic water filters such as those made by Brita and PUR do not remove hexavalent chromium, several reverse-osmosis systems designed for home use can take the chemical out of water.

The analysis, released Monday by the Environmental Working Group, is the first nationwide look at hexavalent chromium in drinking water to be made public. The advocacy group sampled tap water from 35 cities and detected hexavalent chromium in 31 of those communities. Of those, 25 had levels that were higher than a health goal proposed last year by the state of California.

The federal government has not set a limit for hexavalent chromium in drinking water but is reexamining the chemical to decide whether it should impose such restrictions. Last year, California proposed a "public health goal" for a safe level of hexavalent chromium in drinking water: 0.06 parts per billion. If the state sets a limit, it would be the first in the nation. Hexavalent chromium was a commonly used industrial chemical until the early 1990s. It is still used in some industries, such as chrome plating and the manufacturing of plastics and dyes. The chemical can also leach into groundwater from natural ores.

Public awareness about the possible health effects of hexavalent chromium was heightened when residents of Hinkley, Calif., accused Pacific Gas & Electric of leaking the chemical into groundwater for more than 30 years. The company paid $333 million in damages in 1996 and pledged to clean up the contamination. The case was the basis for the movie "Erin Brockovich," which starred Julia Roberts.

But a recent California study found that cancer levels in Hinkley are not elevated. The California Cancer Registry's third study on the town, released this month, found that cancer rates remained unremarkable from 1988 to 2008. The state survey did not explain why any individual in Hinkley got cancer. State epidemiologist John W. Morgan has said it is still important that PG&E clean up the groundwater contamination, which continues to migrate despite efforts to contain it.

PG&E has been giving affected residents bottled water and has sent letters to about 100 property owners expressing interest in buying their property. The company has said it will continue those efforts despite the recent cancer study.