in a single year - 2010 - to collectively lose 1.8 million IQ points, costing the country $44.7 billion in productivity, education, and health costs. Although the true toll of that brain damage is incalculable, pediatrician and environmental health researcher Leonardo Trasande estimates that exposure to organophosphate pesticides, the class to which chlorpyrifos belongs, caused children born in the U.S. And those exposures have since been found to increase the risk of a wide range of neurodevelopmental problems in children, including ADHD and other attention disorders, autism, tremors, and intelligence deficits, as well as memory and motor problems. Countless children and pregnant people were exposed to what we now know were unsafe levels. Between 1992 and 2017, chlorpyrifos was one of the most heavily used pesticides in the U.S., with some 450 million pounds of it sprayed on crops. And yet the consequences of that one statistical sleight of hand, and the government’s failure to notice it, are immense. On one level, the story of the Coultson paper is simple: Decades ago, a seemingly small omission happened to slip past regulators. “When used according to the label, chlorpyrifos is safe for all approved uses, as demonstrated by the more than 4,000 studies and reports examining the product in terms of health, safety and the environment,” Birchmier wrote. In an email, Kacey Birchmier, media relations manager for Corteva Agroscience, which now owns Dow, wrote that the company disagrees with the analysis and conclusions of Sheppard’s paper. And once a study has been around, who goes back and looks after it’s been accepted for 10, 15, or 20 years?” Why didn’t the agency catch Dow’s falsification? “EPA didn’t scrutinize it at the level I did,” Sheppard said. But Sheppard pointed out that the research has been influential even after the EPA officially withdrew the study from consideration for ethical reasons in 2009 and noted that it continues to underly certain assumptions in chlorpyrifos regulation to this day. Asked about the study, EPA spokesperson Kenneth Labbe responded in an email that the Coulston paper was not used in the most recent human health assessment of chlorpyrifos. Coulston’s study was used for decades to set safety levels for chlorpyrifos that were higher than they otherwise would have been. “The outrageous thing was that the group they declared as NOEL was only that because they left out data from their analysis.” In a peer-reviewed paper published in October 2020, Sheppard and her colleagues concluded that “the omission of valid data without justification was a form of data falsification.”īut by the time Sheppard had discovered the falsification, it was too late the injustice of Dow’s experiment had already extended far beyond violating the human rights of incarcerated people. “I realized that in the middle-dose group, which is the one that mattered for the no-effects level, they had conveniently left out one of the two baseline measurement days,” said Sheppard. She also saw how Dow had used the paper to help the EPA set an incorrect “no-effects level,” or NOEL, which is critical for calculating a safety threshold. But while Dow concluded that the middle- and low-range doses had no effect, Sheppard found effects in both groups. Sheppard was able to confirm that finding. The resulting paper, which was written by Dow statisticians based on Coulston’s data, concluded that at the highest dose the pesticide depressed the activity of cholinesterase, an enzyme necessary for neuromuscular function. The research was conducted by an Albany Medical College professor named Frederick Coulston, who exposed 16 incarcerated men to the pesticide, dividing them into four groups - a low-, medium-, and high-dose group as well as a control - and recording their nervous system responses. “I tried to reproduce their analysis, and I couldn’t,” Sheppard said of the study, which was commissioned by Dow Chemical, the maker of chlorpyrifos, in the late 1960s. But when Sheppard, a professor and biostatistician at the University of Washington, looked at the original research that was the basis for the paper and the safety thresholds that were calculated from it, she realized that the underlying data didn’t support its conclusion. Throughout the 1980s and 1990s, the Environmental Protection Agency had used the study to set a safety level for the exposure to the pesticide, which is widely used on fruits and vegetables. L ianne Sheppard was sitting in her office on a Friday afternoon when a colleague approached her with an old study on the safety of chlorpyrifos.
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