by Jill Calabro, PhD
Chlorpyrifos, the most commonly used organophosphate (OP) in the U.S., was banned from most home use in 2000 (except for ant and roach bait) and has faced increased regulation in certain states (California and Hawaii). Regardless, it is still commonly used in agriculture for its broad-spectrum efficacy and short persistence. Many consider it to be an ideal rotation partner to help preserve products with other modes of action, since very few instances of insect resistance have been reported. Environmental horticulture relies on chlorpyrifos as a rotational partner to pyrethroids and neonicotinoids and as an essential product in both the Japanese beetle harmonization plan and to meet imported fire ant quarantine requirements.
At issue is the impact of chlorpyrifos on child development and health. Some research, conducted at Columbia University, suggests that chlorpyrifos negatively impacts children and fetuses. However, the research has come into question due to its relatively small sample size (300 children or less), correlational approach (as opposed to causal), and the emergence of research from other labs showing no such association.
In November 2015, EPA under the Obama administration proposed to ban chlorpyrifos, citing the inability to draw conclusions. The following year, in November 2016, EPA reassessed the proposed ban using a different methodology and still recommended the ban. Administrator Scott Pruitt, under the Trump administration, reversed that decision in March 2017 and sought to better reach a scientific resolution by 2022. That argument was rejected by the 9th Circuit Court.
EPA has the choice to appeal the case to the U.S. Supreme Court or request review by the full panel of 9th Circuit judges, perhaps requesting a delay in enforcement of the ban. Or EPA could abide by the ruling and begin the process of removing chlorpyrifos from the market.
EPA spokesman Michael Abboud commented that the agency was reviewing the decision, but that “The Columbia center’s data underlying the court’s assumptions remain inaccessible and has hindered the agency’s ongoing process to fully evaluate the pesticide using the best available, transparent science.”
Many questions remain. For now, products containing chlorpyrifos are still available for sale and use; that ends in early October. The timeline for when growers and users must cease applications (of products they own) remains unclear. And, further legal maneuvers may delay or ultimately reverse the ban.