[S]ome municipal water in Vermont contains minuscule amounts of a suspected carcinogen for which the Environmental Protection Agency is considering setting new limits.
Chromium-6 was found in 11 Vermont public water systems during EPA tests that were compiled recently by an advocacy organization called the Environmental Working Group.
The levels found in Vermont are far below the current EPA standards for chromium and the stricter limits that apply in California — the only state to have an enforceable limit.
However, several Vermont results were higher than what California scientists recommended as the limit to prevent a significant risk to public health.
This oxidation state of the element chromium has in recent studies caused rats to develop cancer, said David Andrews, a senior scientist at the Environmental Working Group. It also can burn human skin, cause birth complications and lead to other maladies even in very small doses, he said.
The EPA in 1991 set a limit of 100 parts per billion total for three of the element’s oxidation states in public drinking water supplies, and Vermont’s levels do not exceed that, said Bryan Redmond, director of the Vermont Department of Environmental Conservation’s Drinking Water and Groundwater Protection Division.
The highest concentration of chromium-6 found in Vermont during this round of EPA testing — in at least one sample in Caledonia County — was 0.39 parts per billion.
The 100 parts per billion limit applies to the total amount of chromium, chromium-3 and chromium-6 in drinking water, although the EPA says its regulation assumes that a given level represents 100 percent chromium-6, the more toxic form.
The EPA’s current limit is based on the amount required to cause skin rashes, irritation and other acute effects and does not address the possibility of cancer over time, Andrews said.
The EPA is investigating both chromium-3 and chromium-6 to find whether it’s time to set a lower limit for either, Redmond said. That determination will consider the health risks as well as technical feasibility and costs of a lower limit, he said.
Scientists have known for decades that inhalation of chromium-6 significantly raises the risk of lung and nasal cancer, Andrews said. They’ve learned in the last 10 years that ingestion of chromium-6 causes stomach and intestinal cancer in rats, he said.
California recently set a public health goal for chromium-6 in public drinking water of less than 0.02 parts per billion, Andrews said. That concentration — if consumed in liquids throughout a lifetime — is expected to cause one incidence of cancer per million people, he said.
California regulators, taking into account the technical and economic demands of compliance, then established a chromium-6 limit of 10 parts per billion.
Vermont doesn’t have the resources California does, though, and it may not be feasible to establish such a low limit in Vermont without a change in federal regulations, Redmond said.
The EPA found chromium-6 in water supplies in or around Jay Peak, St. Johnsbury, Lyndonville, Barre City, Burlington, South Burlington, Rutland, Bennington, Shaftsbury, Brattleboro and Stratton, according to information tabulated by the Environmental Working Group.
The element occurs naturally, and Andrews said it is likely to have been introduced into many U.S. water supplies from natural sources. Chromium-6 is also a component of certain industrial processes, however, and industrial sources are thought to be responsible for at least some instances of contamination, he said.
The EPA carried out the tests as part of a program required every five years by the federal Safe Drinking Water Act.
The Environmental Working Group is publicizing the EPA’s chromium-6 findings in hopes the agency will lower the standard for it in public drinking water, Andrews said.
The EPA published a draft assessment of the element’s potential health risks in 2011, and the agency is currently reviewing the draft in light of findings in a 2008 study naming chromium-6 a carcinogen.
Home filters are available that effectively remove chromium-6 from drinking water, Andrews said. They include filters that work using a process called reverse osmosis, he said.
Countywide average test results across the state ranged from levels too low to detect to 0.39 parts per billion, which was in Caledonia County. Many systems had detectable levels only in some samples.
Chittenden County tests showed on average 0.0308 parts per billion between Burlington’s and South Burlington’s public water systems.
Washington County averaged 0.0693 parts per billion of chromium-6 in samples from Barre’s water supply — the sole system tested in that county. Rutland City had an average of 0.0214 parts per billion.
Two Bennington County water systems showed on average 0.0529 parts per billion, and two systems in Windham County returned an average of 0.0683.
Caledonia County averaged 0.109 parts per billion in the two public water systems the EPA tested there. Results in Orleans County showed an average of 0.139 parts per billion.
