The U.S. Environmental Protection Agency (EPA) is proposing to revoke all food tolerances for the organophosphate insecticide chlorpyrifos (also known as Dursban), a neurotoxic pesticide produced by Dow AgroSciences that poses particular risks to children and farmworkers. If EPA’s rule is finalized, chlorpyrifos would be effectively eliminated from use in agriculture 15 years after consumer uses were discontinued. However, other non-food uses, including golf courses, turf, green house and mosquito control are not affected by this decision and will remain.

EPA’s proposed rule came on the day of a court-ordered deadline from the U.S. Court of Appeals Judge for the Ninth Circuit, M. Margaret McKeown. In August of this year, Judge McKeown ordered EPA to respond to a petition filed by Pesticide Action Network North America and the Natural Resources Defense Council nearly nine years ago. The lawsuit called on the agency to ban all uses of the insecticide in light of scientific evidence and public comments ignored by the agency after its cumulative risk assessment for organophosphate insecticides.

In 2012, EPA imposed “no-spray” buffer zones around public spaces, including recreational areas, schools, and homes to reduce bystander exposure risks. Earlier this year, the agency updated its 2011 preliminary human health risk assessment for chlorpyrifos, a report that was widely criticized by health and environmental groups. The update identified significant risks to children, farmworkers, and drinking water as a result of the chemical’s use.

Chlorpyrifos is highly neurotoxic. It is a cholinesterase inhibitor, which means that it can bind irreversibly to acetylcholine esterase (AchE), an essential enzyme for normal nerve impulse transmission, inactivating the enzyme. Studies have documented that exposure to even low levels of organophosphates like chlorpyrifos during pregnancy can impair learning, change brain function, and alter thyroid levels of offspring into adulthood. The evidence of the neurotoxic dangers associated with chlorpyrifos’ exposure is extensive and consistent. See the Pesticide Induced-Disease Database (PIDD) for more information.

While EPA had requested the Judge give the agency until April 15, 2016 to revoke food tolerances for chlorpyrifos, the court rejected this timeline, ordering EPA to deny the petition or issue a revocation rule by October 31, 2015. EPA indicates it is proposing the rule rather than issuing a final rule in order to provide for public comment, and the agency indicates it will release its final rule in December 2016.

EPA’s decision to revoke food tolerances for chlorpyrifos was based upon aggregate risk calculated under the Federal Food, Drug, and Cosmetic Act (FFDCA). The law requires the agency to consider all sources of exposure to a certain chemical. Though EPA asserted that food exposure was not of concern, when aggregated with potential exposure through drinking water, safety standards were exceeded in certain watersheds where chlorpyrifos is heavily used.