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Daily News Blog

21
Aug

EPA Relied on Flawed Analysis to Allow Use of the Neurotoxic Insecticide Chlorpyrifos

(Beyond Pesticides, August 21, 2020) A foundational study of the toxic insecticide chlorpyrifos left critical data out of its analysis, resulting in decades of an Environmental Protection Agency (EPA) “safe exposure limit” that is flat out wrong, new research says. That 1972 study concluded that the amount of the chemical to which a human could be exposed before adverse effects showed up (the “no observed adverse effect level,” or NOAEL) was more than twice as high as should have been determined had the study not ignored critical data. In addition, the study points to the perennial “fox and hen house” issues at EPA, which include using research commissioned, funded, or even conducted by industry as any basis for regulation. For years, Beyond Pesticides has rung the alarm on this very dangerous pesticide, and advocated for its ban nationwide.

News of this omission from the 1972 “Coulston Study” comes from a team out of the University of Washington. The researchers re-analyzed that human intentional dosing study using both the original statistical methods and modern computational tools that did not exist in the 1970s. (An important side note: such a study is unethical by current research standards.) The new analysis finds two significant flaws: (1) the study design made it less able to identify a treatment effect (an impact of the study subjects’ intentional exposure to chlorpyrifos), and (2) the researchers’ omission of valid and important data obscured a treatment effect that would otherwise have been identified.

In the study paper, the co-authors say plainly, “The Coulston Study misled regulators by omitting valid data for the key treatment group . . . resulting in a finding of no effect. Our updated analysis indicates that even the lowest dose was unlikely to be a NOAEL. A proper analysis of the Coulston Study would have lowered or eliminated the NOAEL. Either action would have reduced the acceptable dose for chlorpyrifos, and may well have led to more restrictions on its use, particularly in scenarios where infants and children were exposed. . . . An earlier reduction in the NOAEL and increased exposure mitigation would have likely reduced the incidence of adverse health effects in children of that era. It is tragic that an omission of valid data from the analysis of the Coulston Study may have adversely impacted public health for at least 15 years.”

Put simply: the “acceptable” chlorpyrifos exposure level established by EPA, on the basis of the 1972 research, was much higher than it should have been, and likely led to many, many dangerous exposures for children, in particular. Lead author Lianne Sheppard, PhD, commented, “This has huge public health implications. This study was the basis of policy for over 15 years and because it concluded that the ‘no observed adverse effect level’ was more than twice as high as it should have been, the standard was a lot less protective than it should have been.”

Chlorpyrifos is a widely deployed and much criticized organophosphate insecticide that has been used on agricultural crops, for turf management, to treat non-structural wood products, and for control of roaches, ants, and adult mosquitoes. Developed as an agricultural pesticide, its use expanded from the 1970s through the 1990s, including approvals for in-home applications. The compound is a central and peripheral nervous system poison and is clearly dangerous. It damages the brains of young children, causing impairment to cognitive function, lower IQs, attention deficit disorder, developmental delays, and other learning and developmental disorders. It can cause damage to human reproductive, endocrine, renal, hepatic, and immune function. Chronic exposure has been linked to the development of lung cancer. In addition, chlorpyrifos is toxic to birds, fish, aquatic organisms, and bees.

In areas where it is used, chlorpyrifos can contaminate indoor air, surface water, and food crops (most commonly, almonds, cotton, citrus, grapes, corn, broccoli, sugar beets, peaches, nectarines, soybeans, Brussels sprouts, cranberries, alfalfa, peanuts, sunflowers, and tree nuts). Farmworkers and their families, as well as pregnant women in such agricultural areas, are at particular risk for damage from the chemical and its drift.

EPA has been sued repeatedly for its allowance of chlorpyrifos use, and has employed epic levels of foot dragging in responding to petitioners and to court orders. Highlights of the litigation and regulatory landscape include many fits and starts over the past two decades. Chlorpyrifos was first registered as an insecticide in 1965. After wide allowances for use during the 1970s, ’80s, and ’90s, EPA banned household uses of the compound (except for ant and roach baits) in 2000. Two years later, the agency reduced allowable application frequencies for a number of food crops. A decade after that, EPA created “buffer zones” around agricultural fields close to “sensitive” sites, such as schools, playing fields, parks, public sidewalks, residences, hospitals, and nursing homes.

In 2015 the Ninth Circuit Court of Appeals ordered EPA to respond to a petition by the Natural Resources Defense Council and Pesticide Action Network North America to ban all uses of chlorpyrifos. Following that, EPA proposed to revoke all food tolerances for the compound. In March of 2017, the newly installed Trump administration’s EPA contravened the conclusions of its own scientists, as well as those of independent researchers, by reversing that 2015 decision to revoke food residue tolerances because of the chemical’s neurotoxic impacts. In a suit brought by a coalition of labor and health organizations represented by EarthJustice, in 2018 the Ninth Circuit Court of Appeals ordered EPA to finalize its ban on chlorpyrifos. In April 2019, the Ninth Circuit gave EPA 90 days to justify a decision to allow chlorpyrifos to remain on the market. In July of that year, EPA announced it would allow continued use of the toxic pesticide.

Absent protective action by EPA, some states have acted on this toxic threat. Hawaii became the first state to ban chlorpyrifos in 2018. In 2019, six states (California, New York, Massachusetts, Washington, Maryland, and Vermont) sued EPA, arguing that chlorpyrifos should be banned because of the dangers of its use to people’s health. Also in 2019, the New York State legislature voted to phase out and eventually ban use of the neurotoxic insecticide. Maryland passed a limited ban in 2020.

In February of 2020, Corteva AgriScience (formerly DowDuPont), the largest manufacturer of chlorpyrifos pesticide products, announced that it would cease production of those products by the end of 2020, citing declining sales as the reason for the move — no doubt fueled by both states’ actions and momentum against use of the products because of their dire health consequences. The problem behind that welcome news is the difference between one company stopping production and EPA cancellation of the registration of chlorpyrifos. Continued EPA registration permits other generic manufacturers to continue to produce and sell such products.

The UW researchers charge 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. . . . The EPA also did not re-analyze the study data when new statistical techniques became available a few years later [in the 1980s].” UW News reports that if the Coulston data had been re-evaluated with the newer statistical tools that became available in the ‘80s (as should have been done, and as the UW researchers did), “EPA’s reviewers would have seen that chlorpyrifos’ effect on the body’s chemistry accumulated over time and that the study had not discovered the ‘no observed adverse effect level’ used by regulators to set safe levels of exposure.” Dr. Sheppard commented, “All kinds of approvals were allowed for uses that never should have been allowed and quite well wouldn’t have been allowed if the Coulston study authors had properly reported their results.”

The co-authors note that their re-analysis points to issues of concern beyond those specific to chlorpyrifos. One is that EPA reliance on research results that have not been properly peer reviewed can endanger public health. As they write, “The original analysis, conducted by Dow-employed statisticians, did not undergo formal peer review; nevertheless, EPA cited the Coulston study as credible research and kept its reported NOAEL as a point of departure for risk assessments throughout much of the 1980s and 1990s. During that period, EPA allowed chlorpyrifos to be registered for multiple residential uses that were later cancelled to reduce potential health impacts to children and infants. Had appropriate analyses been employed in the evaluation of this study, it is likely that many of those registered uses of chlorpyrifos would not have been authorized by EPA.”

Emeritus professor in the UW School of Public Health’s Department of Environmental & Occupational Health Sciences, Dr. Richard Fenske, notes that the reasons for the failure of EPA to review the Coulston study — when EPA began a supposedly systematic review of such older studies in 2006 by its inaugural Human Studies Review Board — are a mystery. That said, UW News reports that when EPA began that review of such human-subject studies, the chief manufacturer of chlorpyrifos products (then Dow Chemical) specifically pulled that study from the review process, according to Dr. Fenske, a member of the initial review board. “You can speculate why they did, but they formally asked the Human Studies Review Board not to review this study and so it was never reviewed.”

Dr. Fenske also said, “It is a cautionary tale that data being submitted for pesticide registration may not have undergone proper review, and that could be happening today.” Dr. Sheppard aserted that, minimally, studies funded by companies developing a chemical that is under review need to be opened to outside scrutiny, adding, “I’m not sure industry should be doing these studies at all. I don’t think the fox should be guarding the hen house.”

Sources: https://www.washington.edu/news/2020/08/18/data-omission-in-key-epa-insecticide-study-shows-need-for-review-of-industry-analysis/ and https://www.sciencedirect.com/science/article/pii/S0160412020318602#!

All unattributed positions and opinions in this piece are those of Beyond Pesticides.

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