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More Information of MSMA Use in Turf

October 31, 2012
by Fred Yelverton

EPA Extends Herbicide Use Until NAS Completes Arsenic Risk Review

Posted: October 30, 2012

EPA's pesticides office is extending certain allowed uses of an organic arsenical herbicide known as MSMA until the agency's research office has completed its long-ongoing Integrated Risk Information System (IRIS) assessment of inorganic arsenic, due to undergo National Research Council (NRC) review over the next three years.

The arsenical herbicides industry is anticipating the ongoing IRIS revision and review will result in a weaker inorganic arsenic assessment compared to a draft EPA produced in 2010, which included a cancer potency estimate 17 times stricter than EPA's existing arsenic IRIS assessment.

The research office's IRIS assessment of inorganic arsenic is linked to decisions made about herbicides containing the less-toxic organic arsenic because EPA has in the past raised concerns that organic arsenic can convert to the more toxic inorganic form in soil, and contaminate groundwater.

EPA sought to cancel most remaining uses of arsenical herbicides in the mid-2000s because of these concerns, but reached an agreement with industry in 2009 to cancel just home lawn and related uses.

Per that December 2009 agreement, EPA continued the registration of MSMA for use on cotton indefinitely. As part of the same agreement, EPA planned a phase-out of uses at golf courses, highway rights-of-way and sod farms. These uses were allowed to continue through 2012, with remaining stocks to be used by the end of 2013.

"A significant component of the 2009 agreement was the commitment by EPA [Office of Pesticide Programs (OPP)] to review new scientific data on inorganic arsenic during the first half of 2012 and to have that review conducted by one or more of the EPA peer review bodies. Following that review, OPP would decide whether MSMA could be re-registered unconditionally also for the turf uses," according to an Oct. 1 letter from Organic Arsenical Products Task Force (OAPTF) to users of MSMA.

The letter clarifies that the review is "about inorganic arsenic, not the organic form of the compound because EPA contends that MSMA, the organic form, can transform in soil to the more toxic inorganic form."

EPA and NRC finalized plans for EPA's review of the metalloid over the summer, as EPA continues to work on a draft IRIS assessment intended to address both cancer and non-cancer risks of inorganic arsenic exposure to human health. The review plans include an NRC workshop intended to address challenges in assessing arsenic risk, to be help EPA complete its latest draft assessment. NRC's review will pause until EPA releases its next draft, which it will then peer-review.

This unique peer review is the result of a request that Republicans attached to EPA's fiscal year 2012 appropriations, prompting EPA to seek NRC review of the arsenic assessment and up to two other IRIS assessments released in 2012. NRC recently posted on its website the names of the tentative members of the committee who will perform the arsenic workshop and peer review. NRC is seeking comments on the committee membership.

Peer Review Process

The tentative chair is Joseph Graziano, a professor of environmental health and pharmacology at Columbia University. Among the other committee members is Sandra Baird, a human health toxicologist at the Massachusetts Department of Environmental Health and a member of the NRC committee that critically reviewed EPA's draft IRIS assessment of formaldehyde, leading to the ongoing overhaul of the program, including the NRC arsenic review.

Other committee members include Aaron Barchowsky, a professor in the Department of Environmental and Occupational Health at the University of Pittsburgh and chair of the Society of Toxicology's metals specialty section; Rebecca Fry, an assistant professor in the Department of Environmental Sciences and Engineering at the University of North Carolina who specializes in studying the disease outcomes of populations exposed to arsenic; Gary Ginsberg, a senior toxicologist with Connecticut's Department of Public Health and a member of the NRC committee that wrote "Science and Decisions: Advancing Risk Assessment" and Marie Vahter, a professor at Sweden's Institute of Environmental Medicine at the Karolinska Institute. She served on the 1999 and 2011 NRC committees on arsenic in drinking water.

The NRC website indicates that the review is to be completed in 41 months, and OATPF's letter notes that the EPA's pesticides office has extended its registration of MSMA on golf courses and related uses for three to four years as a result. The herbicide group's website includes a Sept. 14 letter from Richard Kegwein, director of EPA's pesticide registration eligibility division stating that these uses will be "extended until EPA responds to any peer review body's report on the mode of action" of inorganic arsenic.

OAPTF writes, "Recognizing the significance of the [NRC] review, OPP has elected to defer to the [NRC] review process and to use that process to satisfy the terms of the 2009 Agreement with the Task Force to review new scientific information. The Task Force believes this is a prudent course of action. Furthermore, had OPP been concerned with the use of MSMA, they would not agree to continue it for years. The Task Force fully expects the [NRC] review to result in a less stringent risk value for human exposure to inorganic arsenic. Should that be the case, we are confident that we will be able to obtain unconditional re-­registration for the above referenced turf uses of MSMA, and, hopefully, to restore other uses of this important herbicidal product." -- Maria Hegstad (mhegstad@iwpnews.comThis e-mail address is being protected from spambots. You need JavaScript enabled to view it )