Tests Confirm High Chromium-6 Levels in Tap Water
By Staff in News on Aug 10, 2011 2:00PM
The results are in and they are hard to swallow: Chicago’s drinking water contains levels of the toxic metal chromium-6 11 times higher than a public health standard established recently in California.
City officials responded to a memo from the EPA in January urging public water departments to check their drinking water for the hazardous compound chromium-6, also called hexavalent chromium — a contaminant perhaps best known from the 2000 film Erin Brockovich and the real-life crusade of its titular character.
Chicago’s Department of Water Management said they would begin quarterly tests for the heavy metal. The Tribune’s Michael Hawthorne reported Saturday on the results.
Test results obtained by the Tribune show that treated Lake Michigan water pumped to 7 million people in Chicago and its suburbs contains up to 0.23 parts per billion of the toxic metal, well above an amount that researchers say could increase the long-term risk of cancer.
The National Toxicology Program’s most recent Report on Carcinogens identifies chromium-6 as a known human carcinogen. Scientists once thought stomach acids converted most chromium-6 into chromium-3 (or trivalent chromium), an essential nutrient. But studies have affirmed the chemical’s link to cancer in animal experiments.
In 1991, EPA established a standard of 100 parts per billion for total chromium, which includes both hexavalent and trivalent chromium. The Obama administration is finishing a scientific review, which may result in the first national standard for the toxic hexavalent variety.
EPA’s own memo came on the heels of a report published by the non-profit Environmental Working Group in December 2010. The report is a snapshot of chromium-6 levels in the water supplies of 35 U.S. cities.
Chicago is one of 25 cities identified in the report with concerning levels of chromium-6. The amount then was 0.18 ppb, over 20 percent less than more recent measurements.
Chromium-6 does occur naturally, but EPA identifies industrial chemical manufacturing and steelworks as major sources of the carcinogen. Lake Michigan’s southern shores in Northwest Indiana are home to several large steel mills, some of which dump wastewater into Chicago’s source of drinking water.
Reverse osmosis filters are a good precaution against water contaminants in general, but cheaper, more widely available carbon filters won’t reduce chromium levels. And no need to stock up on bottled water (again, Hawthorne):
Bottled water is no different. Food and Drug Administration regulations for bottled water limit most of the same contaminants monitored in tap water but are silent when it comes to hexavalent chromium, drug residues or other unregulated substances. Moreover, some brands of bottled water use municipal tap water supplies.
Tap water is still safe to drink in Chicago, city officials urge. Levels are even worse elsewhere. Environmental Working Group’s report found a chromium-6 level of 12.9 parts per billion in Oklahoma city — more than 70 times that found in Chicago.
— Chris Bentley