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April 22 — Scientists on a panel convened by the Environmental Protection Agency to look at new human health studies of a widely used insecticide expressed frustration at the agency's lack of access to the studies' underlying data.
The EPA is asking the panel to evaluate whether the findings from the studies can be used to set new legal limits on the use of the chemical chlorpyrifos.
If the 15 scientists on the panel come down in the affirmative, it could lead to a sea change in the way the agency determines how much of a pesticide can be safely used—not just for chlorpyrifos, but for all the other chemicals within its class and potentially for all other pesticides as well.
But, at a three-day meeting of the panel this week at EPA headquarters in Arlington, Va., the scientists said it will be very difficult, if not impossible, to determine if the studies are valid without having access to the raw data used to generate them.
“It anchors everything [the studies' authors are] doing here,” panelist Jeffrey Fisher, a toxicologist with the Food and Drug Administration, told EPA officials at the meeting. “Not having data was just amazing, flabbergasting. What’s going on here?”
The studies at issue came out of Columbia University, where researchers followed a cohort of several hundred children from birth through infancy and beyond.
Using blood samples taken at birth from their mothers and from their umbilical cords, the researchers found that the children who had greater pre- and post-natal exposure to chlorpyrifos were more likely to experience a host of serious neurodevelopmental problems—from lower IQ scores to greater incidences of attention deficit disorders.
Currently, the EPA calculates the safe limit of chlorpyrifos use by looking at how much of the chemical triggers suppression of an enzyme called acetylcholinesterase, or AChE, which is a crucial neurotransmitter between muscles and the brain.
The Columbia studies were especially troubling because they found that chlorpyrifos can harm fetuses and infants even at very low levels that don't lead to significant AChE suppression.
The EPA convened the panel of scientists to get feedback on whether it should stop regulating chlorpyrifos based on its capacity to suppress AChE, as it has done for decades, and instead move to a different measure of how the insecticide affects the human body.
If the agency does take this new scientific approach, the implications for the pesticide industry could be profound, as chemicals once believed to be safe could be forced to come off the market. That would apply especially to chlorpyrifos itself, which EPA's top pesticides regulator, Jack Housenger, said was the most used insecticide in the U.S.
The shift would also be significant because the EPA would be using human-based epidemiology studies in a regulatory decision rather than the traditional lab-based toxicology studies conducted on test animals (40 CRR 450, 4/18/16).
“What we have before us today is a proposed paradigm shift,” Daland Juberg, head of human health assessments at Dow Chemical, the leading manufacturer of chlorpyrifos, told the panelists.
Without access to the raw data from the studies, all the scientists had to go on were the charts included in the Columbia researchers' published journal articles.
This was problematic for some of the panelists because a large number of the cord blood samples analyzed by the researchers contained undetectable levels of chlorpyrifos. Based on the published charts, it was not totally clear how the researchers incorporated these undetectable results into their statistics, Marion Ehrich, a neurotoxicologist at Virginia Tech University, said.
“We’re basing things on such low levels,” she said. “How can you regulate if you can’t even measure?”
However, other panel members pushed back on this, arguing that all of the Columbia studies had been peer-reviewed before being published and that there's no evidence the researchers had erred.
“It seems that some of you would not be satisfied until you get to analyze this data yourself,” Stella Koutros, an epidemiologist at the National Cancer Institute, said. “That is shocking to me from a group of scientists. I would expect that from industry … but not from a group of scientists.”
The reasons why the scientists, and the EPA itself, don't have access to the Columbia data are murky.
In an April 12 e-mail, Columbia University spokesman Peter Taback told Bloomberg BNA that “if we have a formal request from EPA, we will, of course, share all data that were gathered with the support of the U.S. government.”
Taback also said Columbia has offered to make its data available “under protocols that ensure the confidentiality of the children who are the subjects of our research.”
Housenger told the panel that, based on Taback's statements to Bloomberg BNA, he sent a formal request for the data to Columbia in an April 19 letter.
However, the EPA also contended that access to Columbia's raw data was not strictly necessary. Mark Dyner, an official in the agency's Office of General Counsel, told the panel that there is no legal requirement that academic researchers turn over their data to the EPA.
“If there were, this would require us to discard a lot of sound science” because the agency couldn't get access to the raw data, Dyner said.
He also said that the EPA is under a court order in a lawsuit filed by several environmental activist groups, which requires the agency to make a final decision on whether or not to ban chlorpyrifos by the end of this year (Pesticide Action Network v. EPA, 9th Cir., 14-72794, 9/10/14; 39 CRR 1301, 11/2/15).
The panel of scientists is scheduled to issue its final report on the matter by July 21. The scientists' recommendations will be nonbinding on the EPA, which has ultimate authority to regulate how pesticides can be used.
Though there was widespread doubt among the scientists about whether the studies support the EPA's shift to a new way of regulating the safety of chlorpyrifos, there was much more agreement that the agency should impose conservative safety factors to account for the uncertainty surrounding the effects of the chemical. This could also have the effect of forcing many pesticide products off the market as EPA tries to address the amplified effects pesticide exposure can have on newborns and infants.
“We’re kind of in a limbo area in terms of our knowledge,” University of Colorado reproductive scientist James McManaman, the chairman of the panel, said.
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More information about the scientific advisory panel is available at https://www.epa.gov/sap.
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