Panelists challenge EPA's position on chlorpyrifos

CropLife America urged the EPA to maintain its high standard of relying on solid scientific evidence in its regulatory decisions. | File photo

A Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) convened in April to discuss the use of a Columbia University epidemiology study entitled, “Chlorpyrifos: Analysis of Biomonitoring Data,” in assessing the human health risk of chlorpyrifos, an insecticide that the study to be moderately toxic to humans. 

But the panelists raised concerns with some of the criteria used in the study.

Following a petition to ban the use of chlorpyrifos in 2014, the U.S. 9th Circuit Court of Appeals denied the Environmental Protection Agency’s request to extend its deadline to make a decision on whether to ban the insecticide to Apr. 15, 2016. Instead, the court set the deadline for Oct. 31, 2015, before the EPA had the chance to complete portions of its chlorpyrifos risk assessment.

During April’s SAP session, speakers offered the panel several limitations of the study, including inadequate access to original data, the exposure measures used, the scope of the study, and the inability of EPA and other agencies to replicate the results of the study.

Marion Ehrich, professor of pharmacology and toxicology at the Virginia-Maryland Regional College of Veterinary Medicine, questioned the stratification used in a growth study on the adverse effects of chlorpyrifos on child neurodevelopment.

“It seems that all the data from this was based on analytical work done right at the beginning,” Ehrich said. “So on that study you're talking about where they got the 6.17, they actually had some values below the detection that they called half-values that they included in. Is that an OK thing to do?”

Ehrich said that the findings were questionable and that she would like to see the original data used to come to the conclusion that chlorpyrifos is harmful to children.

“I work in a forensic lab. You don't quantitate on a level of detection. You quantitate on a level of quantitation,” she said. “And when I go back to look at those papers, have you seen their original data where they have the chromatograms and their calibration grams and so forth? The calibration curves are 1,000-fold higher than what they are giving in their papers. So I'm not quite sure.”

Ehrich added that for a pesticide to be allowed into the market or be re-registered, the data “has to be very rigorous.” Compelling data is also need to pull a pesticide off of the market. The fact that there is some uncertainty regarding the study makes it difficult to make a strong case for the revocation of chlorpyrifos, she said.

“You have to defend your decisions to allow registration. You have to defend your decisions to have certain cutoffs or restricted uses. You certainly have to have enough data, enough strong data, in order to think about a cancellation,” Ehrich said. “So if we’re basing this on one study where it’s not been reproduced, you can’t get the actual hard data, there’s lots and lots of points below levels of detection, one has to give that really serious thought.”

Panos Georgopoulos, professor of Environmental and Occupational Health at Rutgers Biomedical and Health Sciences, raised some concerns after noting that the enormity of the task before the EPA “presents challenges that are insurmountable.”

“I mean, the EPA is facing a very serious challenge here,” Georgopoulos said. “And the quantitative information is currently very uncertain. They’re having to decipher the singer from the noise here. It’s quite a task.”

Georgopoulos went on to emphasize the importance of relying on more than one source to come up with a conclusion in health risk assessment.

“I kept thinking as we were going through these days oh, EPA’s human health risk assessment strategic research action plan for 2016-19, I don’t think the word epidemiology appeared in there. But certainly there were concepts of integrating information from multiple sources -- human, animal, mechanistic,” he said. “And the concept of multicriteria decision analysis is integrating multiple sources of information, qualitative and quantitative, in order to strengthen risk assessment is fundamental in there.”

Another concern raised by the panelists about the Columbia study was that the data the study relies on is not available for the EPA to review and is, therefore, not verifiable. Additionally, the outcomes are limited in time to one biological blood sample without connection to a timeframe for exposure to the pesticide.

In a recent news release, CropLife America urged the EPA to maintain its high standard of relying on solid scientific evidence in its regulatory decisions.

“The EPA’s risk-based approach to crop protection regulation historically has centered on use of relevant, reliable and best available scientific data,” Janet E. Collins, CLA's senior vice president of science and regulatory affairs. said. “Regulatory decisions based on studies that are not yet validated and have many factors lacking adequate scientific control is not responsible.”