A dispute over the toxicity of arsenic, a ubiquitous element found mostly at low levels in soil and water the world over, threatens to poison the nation’s public water supplies. A group within the U.S. Environmental Protection Agency’s Office of Research and Development (ORD) is pushing hard to redefine on a large scale the level at which arsenic should be considered toxic by EPA’s Integrated Risk Information System (IRIS), even though scientists at regional EPA offices and others have questioned the science behind such a change. Some critics of the move also stress that ORD is bypassing the regular review process by which such changes are made.
The EPA action would redefine the toxicity level — referred to as the “toxicity slope” — for inorganic arsenic, essentially increasing it by 20 times, according to an October 2008 agency paper that has been circulating among scientists and the affected industries since March. That 404-page paper met with intense criticism from EPA regional offices, the nation’s municipal water suppliers and others, and has since been revised. ORD is now proposing a 17-fold increase in the standard — still a radical change, according to critics. Ratcheting up the cancer slope (from a level of 1.5 per unit dose of arsenic in milligrams per kilogram of bodyweight per day (mg/kg/day) to about 26 per mg/kg/day) could result in the reclassification of much of the nation’s natural water supply and soils as carcinogenic.
Susan Griffin, Ph.D., from EPA’s Region 8 based in Denver, Colo., challenged the ORD view in an April 16 letter to IRIS program director Abdel Kadry, PhD, “We cannot concur with the final arsenic file,” Griffin said in the letter. “In our previous comments we also noted the vast majority of studies conducted in the U.S., Mexico, Finland, Denmark, and Australia with low levels of arsenic in the drinking water found no statistically significant associations between bladder cancer and arsenic exposure.”
“Not only was the 20-fold increase in the oral slope factor unexpected and bewildering, it didn’t make any sense from an actual exposure perspective,” Griffin wrote.
The ORD report cites controversial studies from Taiwan as evidence that the long-term ingestion of inorganic arsenic in drinking water could lead to bladder cancer. Studies in the United States have not found conditions similar to those in Taiwan. “A case-control led study of bladder cancer in Utah did not find an association with ingested arsenic,” says a 1999 report in the science journal Environmental Health Perspectives. Similarly, a 2008 analysis in the journal Human and Ecological Risk Assessment concludes that “exposures to ingested inorganic arsenic from typical U.S. background sources do not present any elevated risk of carcinogenicity.”
Arsenic naturally occurs in organic and inorganic forms, with the latter being the more toxic, according to a National Institutes of Health (NIH) report, (Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc).
Ground water in most populated areas of the United States contains inorganic arsenic in the 1 to 3 ppb (parts per billion) range, according to U.S. Geographical Survey maps. The rates are considerably higher in the sparsely populated U.S. North Central and Western regions where they routinely range from 10 to 50 ppb.
Revising the cancer slope could effectively move the current drinking water standard for inorganic arsenic — the maximum containment level (MCL) — from 10 ppb to just tenths of a ppb. Such a move would put pressure on municipalities to spend additional billions of dollars in attempts to meet the new standard with minimal benefit, if any, according to numerous sources.
Meeting that standard “may not be achievable except at enormous cost,” says an April 15 letter to Lek G. Kedeli, acting assistant administrator of EPA’s Office of Research and Development, from 13 diverse groups ranging from the American Farm Bureau Federation to the Edison Electric Institute.
In parts of New Mexico inorganic arsenic in groundwater may be as high 30 to 40 ppb for some municipalities, said Mark Sanchez, executive director of the Albuquerque Bernalillo County Water Utility Authority. Albuquerque’s drinking water is currently six ppb inorganic arsenic, Sanchez said. “Part of our strategy has been to treat surface water, blend it with ground water and couple that with the use of an advanced microfiltration system,” he said. Without access to relatively arsenic-free Colorado River water, meeting EPA’s current MCL would have cost the Water Authority over $200 million, Sanchez said.
“The practicality of trying to revise the risk slope is confusing,” said Pankaj Parekh, director for water quality for the City of Los Angeles Department of Water and Power, where he has worked for 24 years.
Parekh said he was unaware of any epidemiological study implicating arsenic in any U.S. water supply as a cause of cancer at levels below the current standard. According to the NIH report published in 2001, when the MCL for inorganic arsenic in water was 50 ppb, “Studies in U.S. populations exposed to arsenic in drinking water have not identified cancer increases.”
“The management of contaminants must be seen as a cradle-to-grave issue,” Parekh said. Reducing the MCL for arsenic would have wide-ranging implications. For example, arsenic may be removed from water, but then municipalities are faced with the problem of its disposal. Would landfills accept arsenic in the concentrated levels resulting from water treatment? Tightening water regulations usually influences allowances by other agencies for arsenic management and disposal. In addition to the problems of water remediation cost and disposal, there could be implications for a wide range of consumer food and beverage products, the regulators of which take EPA’s lead on recommendations for toxicity.
Risk assessments must be balanced by cost and practicality, Parekh said. “Unfortunately, sometimes these things are pursued in the absence of clearly articulated and balanced public health policy.”
Given the ubiquity of arsenic, “establishing a risk goal that leads the agency into risk-management policy decisions with extraordinary costs and uncertain public health benefits deserves more caution than this decision appears to be receiving,” says an April 17 joint letter from the American Water Works Association and the Association of Metropolitan Water Agencies to Lek G. Kadeli, acting assistant administrator at EPA’s ORD.
The 15 groups that have written Kadeli in two letters also complain that ORD in its bid to implement a new arsenic cancer slope is attempting to bypass the established review process.
“We believe it essential that EPA make clear its intent to follow the IRIS process and to refrain from issuing the assessment until it has been the subject of a properly focused peer review and public comment,” says the April 15 letter from the 13 industry groups.
That review process, as outlined in the group’s letter, would require anther 11-17 months from the date of the letter. However, EPA Administrator Lisa Jackson revised the review process in a May 21 memorandum in which roughly parallel steps are now to be completed in about 11 months. While both scenarios would have the review process completed sometime in 2010, the new cancer slope is on track for implementation by the third quarter of 2009, said IRIS Arsenic Hotline Manager Bernard King.
Paul Anastas, the Obama Administration nominee to head ORD, told Senate Environment and Public Works Committee members after a query from Sen. James Inhofe (R.-Okla.) that he would review the new arsenic risk assessment if nominated, according to a June 24 report in “Inside EPA,” an Arlington, Va.-based publication that tracks the federal agency. That report also included a comment from Sen. Barbara Boxer (D.-Calif.) that EPA should “follow the science” in finalizing the arsenic study.
Arsenic, while ubiquitous and found at some level in most water and foods, is largely misunderstood by many consumers, who become alarmed at the mention of toxicity and cancer, no matter how small the risk. EPA’s Region III has said that the proposed cancer slope change “may lead to an increase in public relations frenzies related to the potential increase cancer rates suggested by this assessment but not yet substantiated by background cancer deaths related to inorganic arsenic exposure,” said “Inside EPA” in a June 6 report.
Several EPA officials, including Lek Kadeli, did not respond to queries about why ORD was attempting to bypass established review procedures or about what evidence in the United States necessitates such a large revision in the arsenic cancer slope given that it had just been revised in 2006 for water based on an arsenic cancer slope of 3.67 mg/kg/day.
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