MSMA Spared by EPA

MSMA on cotton will not be phased out in an U.S. Environmental Protection Agency initiative to discontinue organic arsenicals. Further study will determine for how long the valuable herbicide is available to cotton growers.

Published on: Feb 11, 2009

The U.S. Environmental Protection Agency announced Tuesday that DSMA, CAMA, cacodylic acid and its sodium salt, all organic arsenicals, will be phased out under an agreement with major manufacturers.

MSMA, however, will continue to be labeled for use in cotton. It will be up for re-registration again in 2013.

EPA had announced in its 2006 Re-registration Eligibility Decision that organic arsenicals would not be eligible for re-registration.

"Phasing out these uses is expected to accelerate the transition to new, lower risk herbicides," according to EPA's announcement on Tuesday.

MSMA was spared largely because the cotton industry provided scientific information to refute EPA's decision.

"Following application, these pesticides [organic arsenicals] convert over time to a more toxic form in soil, inorganic arsenic, and potentially contaminate drinking water through soil runoff," EPA explained. "At that time [when the 2006 RED was released], EPA believed that inorganic arsenic also could enter the human food supply through the meat and milk of animals fed cotton by-products treated with MSMA. In completing the RED, EPA determined that the aggregate dietary risks from food and drinking water combined did not meet the food safety standard."

EPA made that decision after reviewing industry-submitted data that showed "that no residues of inorganic arsenic are likely to remain in the meat and milk of animals fed cotton by-products that have been grown in fields treated with MSMA, or in food crops that are rotated with cotton that has been treated with MSMA."

Weed resistance issues also played a role in the decision, according to EPA's announcement.

"Cotton growers also have documented the increasing spread of Palmer amaranth or pigweed, a glyphosate-resistant and economically significant pest, which only MSMA controls at present," EPA reported.

The industry, however, must provide additional data to EPA to continue to use MSMA.

"If these data are not submitted by the August 2010 due date, or if they do not confirm the current scientific understanding, EPA will proceed to cancel the cotton use," EPA reported. "The Agency is also rescheduling the Registration Review of MSMA to begin in 2013. At that time, MSMA's risks and benefits will be reevaluated considering any new toxicity information and the availability of new, lower-risk herbicides that should be entering the market.

That's a slower death than the other organic arsenicals will suffer. Many of the uses, including use on residential lawns, will be canceled this year, according to EPA.

"For products used on cotton and products phased out after 2009, new use restrictions and mitigation measures will be added to increase protections to water resources," EPA announced.

Further, the announcement noted these specifics:

• By mid-March, the registrants must submit voluntary cancellation requests for all uses, other than the use of MSMA on cotton.

• By the end of 2009, many existing uses will be phased out and canceled including use on residential lawns, forestry, non-bearing fruit and nut trees, and citrus orchards.

• Over the next four years, uses on golf courses, sod farms, and highway rights of way will be phased out, promoting transition to alternatives.

EPA will amend the 2006 Organic Arsenicals RED to reflect the provisions of the agreement. Public comment opportunities will be provided when the Agency publishes Federal Register notices announcing its receipt of registrants' requests for voluntarily cancellation of uses.

The organic arsenicals agreement and related information will be available at in Docket EPA-HQ-OPP-2006-0201 and on the re-registration chemical pages for these pesticides at

For additional information, please contact Tom Myers, Office of Pesticide Programs, (703) 308-8589.