The Environmental Protection Agency under Donald Trump has released a new assessment of the pesticide Chlorpyrifos, claiming the current science is inconclusive as to the amount of exposure necessary to be harmful. Chlorpyrifos is an organophosphate pesticide typically used on crops, animals, and buildings, to kill various pests, including insects and worms. The chemical has been used extensively in grape, almond, soybean, and particularly strawberry production. It acts on the nervous systems of insects by inhibiting the acetylcholinesterase enzyme.

In 2015 the Obama administration announced it would ban chlorpyrifos citing studies by the EPA warning of the chemical’s potential to make farm workers sick and impede brain development in children. However, in 2017, before the ban could be enforced, the EPA Administrator at the time, Scott Pruitt, reversed the decision, igniting a legal uproar. The EPA was ordered by a federal appeals court to make a final ruling by July 2019 on whether to ban Chlorpyrifos. Upon that deadline, Andrew Wheeler, now EPA Administrator, announced the agency would reject the petition to ban the pesticide, questioning the significance of the data around the chemical’s neurological impact on young children. Despite the agency’s continued rejection of a ban, the EPA is required by law to review a pesticide’s uses at least every 15 years, and with another legal case pending in the U.S. 9th Circuit of Appeals, the agency will be due to deliver a new final ruling on the use of Chlorpyrifos in about two years. Meanwhile, the EPA says it will make an interim decision this October.

Preceding the interim decision and final ruling, while pending legal cases loom from a dozen environmental and labor groups demanding an immediate ban, the EPA released this September, a new assessment of the dangers associated with the use of Chlorpyrifos. The report concludes that “Despite several years of study, the science addressing neurodevelopmental effects remains unresolved…. With respect to effects on the developing brain, very little is known about the duration of chlorpyrifos exposure needed to precipitate adverse effects in the developing brain.”


Some farm groups have defended the use of Chlorpyrifos, claiming the chemical has been a safe, effective, and versatile tool for protecting their crops since 1965. The EPA’s new assessment of the pesticide points to Oregon strawberry growers who have been particularly reliant on Chlorpyrifos for controlling symphylans, a pest that feeds on the plant’s roots. However, it should be noted that many certified organic strawberry growers throughout the country use a combination of alternative management practices to control symphylans and other pests, such as solarizing field soils with tarps, flooding fields, compacting growing beds, and incorporating cover crops. They prevent pest outbreaks naturally by maintaining optimal soil and plant nutrition throughout the growing season and establishing a balanced farm ecosystem.

The EPA’s assessment does acknowledge that Chlorpyrifos can have a negative effect on neurodevelopment, and even identifies “concerns about dietary exposure to chlorpyrifos and to pesticide handlers,” mirroring the same concerns expressed by the EPA back in 2015. However, the agency claims the risk of exposure to residential communities is “negligible,” and argues that there is insufficient data to definitively say what level of exposure is dangerous.

Many in the scientific community dispute this claim, pointing to several epidemiological studies, including one from Columbia University, showing “a correlation between prenatal exposure to chlorpyrifos and developmental disorders in toddlers,” such as lower birth weights, lower IQ’s, and higher risk of autism. The EPA’s recent assessment, however, has rejected those findings, citing a lack of access to the raw data of those studies. Spokesman for the EPA, James Hewitt, said in a statement that the agency “remains unable to verify the reported findings” of the Columbia study (despite having been supported by other peer-reviewed studies), deeming its findings inconclusive. This move by the EPA suggests that the agency may be unofficially adopting its proposed “secret science” regulation, aiming to reject or give less weight to scientific studies that do not (or cannot) publicly release their underlying data.

As previously reported by Lisa Friedman at the New York Times, “This controversial policy would eliminate many studies that track the effects of exposure to substances on people’s health over long periods of time, because the data often includes confidential medical records of the subjects.” Trump’s EPA has used this same argument to justify weakening restrictions and rejecting bans on other toxic chemicals and pollutants, such as perchlorate (a water contaminant tied to fetal brain damage) and asbestos, despite repeated objections from agency scientists. The EPA has not finalized or officially adopted the “[secret science] regulation that would officially restrict using such studies in decision-making, but the chlorpyrifos assessment suggests it has moved forward in applying it.”

EPA officials claim they have been prevented from independently assessing the findings of the Columbia University study, by not being provided the study’s raw data. Lawyers supporting a ban on Chlorpyrifos say researchers from the Columbia University study “were willing to show their data to agency officials in a secure location but have not released the information publicly because of privacy concerns.”

EarthJustice attorney, Patti Goldman, criticized the EPA’s new assessment of the pesticide, saying, “Ignoring the demonstrated harm to children doesn’t make chlorpyrifos safe. It shows a commitment to keep a toxic pesticide in the market and in our food at all cost.” Earthjustice has also accused the administration of “fudging the data” in the new assessment, to reach its preferred conclusion. Erik D. Olson, senior director for health at the Natural Resources Defense Council, said of the EPA’s report, “This shows that EPA has completely abandoned any commitment to protecting children from this extremely toxic chemical when their own scientists recommended twice to ban it. The science is being overridden by politics.”

California, New York, Hawaii, and other states have enacted their own bans and restrictions on the use of Chlorpyrifos. Corteva, the world’s largest manufacturer of the pesticide, says it has already ended production of the chemical. Entomologist Allen Felsot of Washington State University claims the use of chlorpyrifos is in decline, and notes, “The market tends to take care of a lot of this.” The EPA’s Draft Ecological Risk Assessment and Revised Human Health Risk Assessment of Chlorpyrifos will be open to scientific review and public comment once the Proposed Interim Decision is released this month. Both documents will remain open for review and comment for 60 days.

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