WASHINGTON — The Trump administration has rejected scientific evidence linking the pesticide chlorpyrifos to serious health problems, directly contradicting federal scientists’ conclusions five years ago that it can stunt brain development in children.
The Environmental Protection Agency’s assessment of the pesticide, which is widely used on soybeans, almonds, grapes and other crops, is a fresh victory for chemical makers and the agricultural industry, as well as the latest in a long list of Trump administration regulatory rollbacks.
In announcing its decision, the E.P.A. said on Tuesday that “despite several years of study, the science addressing neurodevelopmental effects remains unresolved.” However, in making its finding, the agency excluded several epidemiological studies, most prominently one conducted at Columbia University, that found a correlation between prenatal exposure to chlorpyrifos and developmental disorders in toddlers.
As a result, the assessment may be the first major test of the Trump administration’s intention, often referred to as its “secret science” proposal, to bar or give less weight to scientific studies that can’t or don’t publicly release their underlying data. This controversial policy would eliminate many studies that track the effects of exposure to substances on people’s health over long periods of time, because the data often includes confidential medical records of the subjects, scientists have said.
The E.P.A. repeatedly cited a lack of access to raw data in the studies it rejected, and came to the conclusion that the findings — though they have been backed up by other peer-reviewed studies — were inconclusive.
The E.P.A. has not finalized the regulation that would officially restrict using such studies in decision making, but the chlorpyrifos assessment suggests it has moved forward in applying it.
“This shows that E.P.A. has completely abandoned any commitment to protecting children from this extremely toxic chemical when their own scientists recommended twice to ban it. The science is being overridden by politics,” said Erik D. Olson, senior director for health at the Natural Resources Defense Council. The environmental group Earthjustice accused the Trump administration of “fudging the data” to reach its conclusion.
James Hewitt, a spokesman for the E.P.A., said in a statement that the agency “remains unable to verify the reported findings” of the Columbia study. Mr. Hewitt said the agency plans to issue an interim decision next month on how or whether to regulate chlorpyrifos that will include additional changes “that may be necessary to address human health and ecological risks.”
Environmental activists said the conclusion announced Tuesday signals the Trump administration is not likely to impose strict regulations on the pesticide in next month’s interim ruling on the issue.
The chlorpyrifos assessment comes on the heels of other E.P.A. moves to weaken restrictions on toxic chemicals. The agency recently pulled back on regulating perchlorate, a water contaminant tied to fetal brain damage, and last year opted not to ban asbestos over the objections of agency scientists.
The debate over banning chlorpyrifos goes back more than 13 years. In 2015 the Obama administration said it would ban the pesticide after scientific studies produced by the E.P.A. showed it had the potential to make farmworkers sick and damage brain development in children. That ban had not yet come into force when, in 2017, Scott Pruitt, then the administrator of the E.P.A., reversed that decision, setting off a wave of legal challenges.
Ultimately a federal appeals court ordered the E.P.A. to issue a final ruling on whether to ban chlorpyrifos by July 2019. That month, the E.P.A. under Mr. Wheeler rejected a petition by environmental and public health groups to ban the pesticide, writing that “critical questions remained regarding the significance of the data” around neurological damage in young children.
The agency criticized the Obama administration’s decision to ban the product as based on epidemiological studies rather than direct tests on animals.
A dozen environmental and labor groups are suing the E.P.A. to try to force an immediate ban.
In a hearing in July before a three-judge panel of the U.S. Court of Appeals for the Ninth Circuit, the E.P.A. argued that the agency does not dispute that chlorpyrifos can cause neurodevelopmental effects. But, an agency attorney argued, there is dispute over what level of exposure is dangerous.
The agency said not being able to see Columbia University’s raw data was problematic and prevented the E.P.A. from independently assessing the findings.
Attorneys supporting a ban on chlorpyrifos said the Columbia University researchers were willing to show their data to agency officials in a secure location, but have not released the information publicly because of privacy concerns.
Several states, including California, New York and Hawaii, already have enacted bans of varying strictness. Corteva, the world’s largest manufacturer of chlorpyrifos, has said it will stop producing the chemical by the end of this year.
Gregg Schmidt, a company spokesman, said Corteva has already stopped production but said “we stand by the safety of the product and its value for the grower community.”