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Pesticide News Story: EPA Releases Risk Assessments for Organic Arsenic Herbicides; Seeks Risk Management Ideas

For Release: April 6, 2006

EPA is evaluating the potential risks associated with registered uses of the organic arsenic herbicides MSMA, DSMA, CAMA, and cacodylic acid, and has identified few risks directly associated with use of these herbicides. However, the Agency is concerned about the potential transformation of products applied as organic arsenical herbicides to inorganic arsenic in plants, drinking water, and soil. The Agency seeks public comment by June 5, 2006, on its human health and environmental fate and effects risk assessments for the organic arsenic herbicides, as well as risk management ideas or proposals. Background information and questions to guide comments are provided in a “commenter’s guide,” available in the docket. Responses will be useful to the Agency in revising the risk assessments, if appropriate, and developing an informed, practical, and protective reregistration eligibility decision for the organic arsenicals.

The organic arsenic herbicides are used primarily on cotton and turf, including golf courses, home lawns, recreational areas such as school yards and athletic fields, and rights-of-way. Overall, use in the U.S. appears to be declining. Arsenic is common in the environment and occurs naturally in soil and in surface and groundwater. Arsenic does not degrade over time; it can only transform into other forms of arsenic -- for example, organic arsenic may transform to inorganic arsenic or vice versa -- or be redistributed through runoff, leaching, erosion, volatilization, or plant uptake. State and federal agencies usually monitor for total arsenic in soil and water, so national data for organic arsenic are not available. EPA therefore used a health protective, stepwise approach in its risk assessment, calculating exposure to each of the organic arsenicals alone, as well as considering the potential exposure to inorganic arsenic as a transformation product. Information from the public to clarify the geographic extent of organic arsenical herbicide use, as well as arsenic’s potential for buildup in soil, its contribution to water, and exposure to homeowners and to non-target species, would be useful to the Agency in further refining the organic arsenicals risk assessment.

EPA Pesticide Program’s assessment of organic arsenical herbicides takes into account the possible contribution of these herbicides to vulnerable sources of drinking water. However, it should be noted that EPA’s National Primary Drinking Water Standard for arsenic is based upon the risks of bladder cancer in humans exposed to inorganic arsenic, not organic arsenic. Therefore, the organic arsenical herbicide assessment does not affect or change EPA’s drinking water standard for arsenic.

EPA’s risk assessments, commenter’s guide, and related documents are available in the organic arsenic herbicides docket #EPA-HQ-OPP-2006-0201 at http://www.regulations.gov. The Agency’s April 5, 2006, Federal Register notice is available at http://www.epa.gov/fedrgstr. For additional information, see the Agency’s cacodylic acid and MSMA, DSMA and CAMA reregistration Web pages at http://www.epa.gov/pesticides/reregistration/status.htm.


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