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A new document from the Environmental Protection Agency may hold clues to how the agency will move forward in assessing the science when regulating a controversial family of pesticides.
At issue is tetrachlorvinphos, or TCVP, a chemical used in flea collars for dogs and cats, as well as a flea and tick-killer for livestock. TCVP is in the class of organophosphate pesticides, which work by inhibiting a key enzyme for nerve function. In humans, exposures above certain levels can lead to headaches, nausea, convulsions or, in some cases, death.
The Environmental Protection Agency issued a 195-page proposed human health risk assessment last month, the second draft of a document that lays the groundwork for a proposed regulatory decision on TCVP later this year. EPA agreed to revise the initial human health assessment for TCVP to settle a lawsuit from the Natural Resources Defense Council ( NRDC v. EPA , 9th Cir. App., No. 15-70025, 2/11/16 ).
Environmental groups have long sought to prohibit the use of organophosphates, particularly the agricultural insecticide chlorpyrifos. But TCVP also has been targeted in court as a risky chemical for children, who like to pet and hold flea collar-wearing animals.
Specifically, they have called on the EPA to rely on epidemiological studies, investigations of a human population’s exposure to chemicals, in addition to laboratory tests.
This frustrates the pesticide sector’s trade association CropLife America, which petitioned the EPA last month to stop including what they view as flawed studies to justify decisions on whether or not to restrict organophospate pesticides.
“It’s not only overly conservative, we feel as though the information upon which they are drawing to come up with some of their conclusions are not valid,” Janet Collins, executive vice president of CropLife America, told Bloomberg BNA.
The assessment released last month hit on a sore point for industry. In its literature review, the agency cited “cohort” studies, in which a small segment of a population is tracked over a period of time. In particular, the assessment mentions studies from the Columbia University Center for Children’s Health, the Mount Sinai School of Medicine and the University of California—Berkeley, that linked organophosphate exposure to long-term health concerns, like autism and other neurodevelopmental impairments.
In raising these studies, EPA concluded in its assessment that TCVP required an additional ten-fold uncertainty factor to protect children and pregnant women.
The risk assessment also could be a sign of how the EPA will address the suite of organophosphate pesticides slated for review later this year, including chlorpyrifos and malathion. Industry groups are concerned this could hamper the extent to which the pesticides are used, and affect their bottom line.
Epidemiological studies “can have some elements that are factual, the question is what you do with the ‘facts’,” Jim Aidala, senior consultant in the Washington D.C. office of Bergeson & Campbell PC who headed EPA’s chemicals office under President Bill Clinton, told Bloomberg BNA.
CropLife has asked the EPA to write guidelines for the use of epidemiological studies to reach regulatory decision, said Collins. Specifically, the industry would like to see the EPA clarify how it chooses quality studies, and demonstrate how the agency is integrating that data.
EPA had said it would finalize a draft framework for the conduct of epidemiological studies by the end of 2016, said Collins, but to date has not done so.
The decision to include the studies flies in the face of a Science Advisory Panel report on July 20, in which scientists criticized Columbia University’s refusal to submit the raw data for its study. One of Columbia’s deans told the EPA in a letter that the data contains confidential health information on the women and children involved in the study, and that submitting the data would violate the terms to which the participants agreed.
The reliance of the Columbia study indicates that the EPA will continue to rely on the controversial studies, said Collins.
“Nothing has changed in EPA’s approach to a human health risk assessment, from our perspective,” she said.
CropLife America’s Nov. 29, 2016 petition that asked that the agency stop relying on epidemiological studies for their assessments, finding that the data from epidemiological studies should be “closely scrutinized,” and that EPA’s use of a study without disclosing the data is in violation of the Food Quality Protection Act.
“Bias, confounding factors, and in particular, unreliable and invalidated exposure assessments commonly occur in epidemiological studies, limiting the value of the researchers’ conclusions for quantitative risk assessments,” Collins wrote in the petition.
NRDC initially petitioned EPA to take TCVP off the shelves in 2009. Their justification: the agency failed to consider a 2008 study that was the first peer-reviewed paper to rely on real-world samples of chemical residues on pet fur to yield results. The findings concluded that collars transferred high concentrations of residues, but that the collars posed a low toxicological risk.
“That was a huge gap,” Miriam Rotkin-Ellman of the Natural Resources Defense Council, told Bloomberg BNA.
EPA did include the “Davis study,” named for lead researcher Keith Davis, in the most recent risk assessment. They also said that TCVP on flea collars could be considered either a liquid or solid. Dust is a solid, NRDC argued, and more likely to shake off collars and onto people. Liquids, Rotkin-Ellman said, stick to fur and are therefore less likely to get on a child playing with a pet.
“That distinction makes a huge difference,” said Rotkin-Ellman, a senior scientist with NRDC. “We have been arguing that EPA was incorrectly saying that the pesticide was like a liquid.”
The health assessment was not joined with a regulatory decision, such as a voluntary cancellation or phaseout, as NRDC would have preferred. EPA did issue a decision when it released the human health assessment for propuxur, another chemical used to kill fleas.
EPA is expected to propose a decision on TCVP in 2017, and finalize the review the following year.
“They are being incredibly vague at this point,” said Rotkin-Ellman, adding that NRDC is discussing the next steps they are taking to push for a ban of the chemicals in flea collars. “It’s unacceptable from a human health perspective.”
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EPA's revised human health assessment for tetrachlorvinphos is here: http://src.bna.com/ldp
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