How much hexavalent chromium is too much when it’s in your drinking water?
That is one of many questions lingering in the wake of The Environmental Working Group’s report on carcinogenic chromium in tap water across the country. Water samples taken by volunteers showed 31 of 35 cities tested had more hexavalent chromium in their tap water than the proposed legal limit in California.
The Environmental Protection Agency says hexavalent chromium is definitely a carcinogen when inhaled, but it is still reviewing how dangerous it is when ingested, as it is in drinking water.
A draft review this year concluded orally ingested hexavalent chromium is “likely to be carcinogenic to humans” based on science showing ingestion increased the risk of gastrointestinal tumors in laboratory rats and mice, evidence tying oral exposure to stomach cancer in humans, and tests indicating that chromium can damage DNA.
There are two well-known types of chromium that can be found in drinking water; hexavalent chromium, or chromium-6 is the more dangerous of the two (chromium-3 can actually have health benefits). It can find its way into drinking water through erosion of natural sources and through discharges from manufacturers of stainless steel, metal plating, wood products and textiles. A reverse osmosis filtration system will remove the contaminant.
In Bend, the samples showed hexavalent chromium levels at .78 parts per billion – 13 times the proposed limit in California. And that’s the only city in Oregon that was tested; the report doesn’t tell us anything about tap water in Portland, Salem, Eugene, Corvallis or elsewhere. Though The Oregonian reports Bend was chosen because its tap water had elevated chromium levels in the past:
“The nonprofit selected cities in 23 states that had elevated levels of total chromium in past water quality reports. Bend had registered two spikes in total chromium in 2004, although both were nearly 100 times less than the EPA’s legal limit, state water quality officials said.”
Why are we talking about proposed limits in California? Well, the EPA hasn’t set a limit on chromium-6 in drinking water. It only regulates total chromium. California, however, is the notorious home of Hinkley, where Erin Brockovich made history by exposing chromium-6 contamination in the groundwater and winning a tort settlement for the locals who had been affected by it. The state allows just half the national limit for total chromium and has set a tap water goal of .06 parts per billion for chromium-6 – the first step toward establishing a binding limit.
Bend officials say the city’s water has always been within the EPA’s total chromium limit of 100 parts per billion – most of the water samples have detected no chromium at all since 1987 – and that the water is safe to drink. But the Environmental Working Group says the EPA should be paying more attention to chromium-6 in particular.
Here’s what the Environmental Working Group said after completing the tests:
“Given the scope of exposure and the magnitude of the potential risk, EWG believes the EPA should move expeditiously to establish a legal limit for chromium-6 and require public water suppliers to test for it.”