Data omission in key EPA insecticide study shows need for review of industry studies

https://www.eurekalert.org/pub_releases/2020-08/uow-doi081720.php


News Release 18-Aug-2020
University of Washington

For nearly 50 years, a statistical omission tantamount to data falsification sat undiscovered in a critical study at the heart of regulating one of the most controversial and widely used pesticides in America.

Chlorpyrifos, an insecticide created in the late 1960s by the Dow Chemical Co., has been linked to serious health problems, especially in children. It has been the subject of many lawsuits and banned in Europe and California. The EPA itself nearly banned the chemical, but in 2017 the Trump administration backtracked and rejected EPA's own recommendation to take chlorpyrifos off the market. The EPA plans to reconsider the chemical's use by 2022.

In February, the largest producer of chlorpyrifos, Corteva Agriscience (which owns Dow), said it would stop making the chemical because of slumping sales, not out of safety concerns. Corteva has kept up a running defense of the chemical.

So, while chlorpyrifos can still be used on some agricultural products, the chemical appears to be approaching the end of its long run.

However, University of Washington researchers report in a new study that decades of exposure to chlorpyrifos and all the political wrangling and lawsuits surrounding it might have been averted if a 1972 study had been adequately reviewed by the EPA, itself newly established in the early 1970s. The EPA also did not re-analyze the study data when new statistical techniques became available a few years later, the UW researchers added.

Lianne Sheppard, a professor of biostatistics and environmental health in the UW School of Public Health and the study's lead author, explained that the 1972 "Coulston study" established erroneously how much of the chemical a human could be exposed to before adverse effects showed up in a body's chemistry. 

When Sheppard re-ran the study data using the same longhand statistical analysis as the original, she discovered that key data used in two other level-of-exposure tests in the same study had been left out of the central exposure question -- inexplicably. Consequently, the safe exposure limit, called the "no observed adverse effect level," that the EPA used was wrong. 

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