Chlorpyrifos was first registered for use as an insecticide in the United States in 1965. It was reregistered in 2006. Its use has ranged from corn and soybeans to fruit and nut trees. It is an organophosphate insecticide which binds to cholinesterase enzymes to prevent the breakdown of acetylcholine. This causes the target insect to experience overstimulation of the nervous system and, in time, death. Due to their acute toxicity to humans, most organophosphate insecticides have already been phased out of production.
A petition regarding chlorpyrifos was filed in 2007 by the Pesticide Action Network North America (PANNA) and the Natural Resources Defense Council (NRDC). The petition asked the EPA to revoke all chlorpyrifos tolerances on food because of the potential for neurodevelopmental effects in children. Tolerances are EPA-set maximum residue levels of an active ingredient or chemical that are permitted in or on food for humans or animals.
In 2015, an EPA statement indicated that there was a plan to “revoke all food residue tolerances for chlorpyrifos.” One year later, the Agency released a revised human health risk assessment that stated food and drinking water exposure to chlorpyrifos was unsafe, and that its use in agriculture was therefore also unsafe.
The next administration rejected the PANNA/NRDC petition in 2017 and again in 2019. These rejections were challenged in 2019. In April of 2021, the Ninth Circuit Court of Appeals ordered the EPA to issue a final rule with new guidelines regarding the tolerances for chlorpyrifos.
On August 18, 2021, the EPA released a final rule “revoking all tolerances for chlorpyrifos” on food for humans or animals. A Notice of Intent to Cancel will also be issued in the near future by the Agency to cancel all food-use registrations of chlorpyrifos. These cancelations, combined with the tolerance revocations, will effectively bar chlorpyrifos from food crop production.
Food security is an important part of the United States economy and this ruling is not expected to impact the food supply. Though chlorpyrifos has historically been used as a crop protection tool, its use has declined in recent years as alternative, less toxic products have been registered for use.
See the EPA release at this link:
https://www.epa.gov/newsreleases/epa-takes-action-address-risk-chlorpyrifos-and-protect-childrens-health