Center for Biological Diversity

For Immediate Release, April 14, 2022


Nathan Donley, (971) 717-6406,

Independent Scientific Review Panel: EPA’s Weakening of Groundwater Protections From Pesticides Is Not Justified

EPA Rejection of Panel’s Findings Coincided With Promise to Ensure Science Guides Its Decisions

WASHINGTON— In a peer-review report released this week, an independent panel of scientists gave a scathing critique of recent changes made by the Environmental Protection Agency to weaken its estimates of pesticide pollution in U.S. groundwater.

The EPA’s weakened modelling is based on questionable research about the depths at which pesticides breakdown in soil — research the peer-review scientists found to be “not adequate.”

And the less-protective modeling input has already been used to reverse an agency finding that a pesticide called spirodiclofen, widely used on tree fruits, may be present at high enough concentrations in groundwater to cause cancer in people.

Although the peer-review report was supposed to be made available to the public at the time of the decision in February, it was only posted publicly this week after multiple inquiries by the Center for Biological Diversity.

“If the EPA had submitted this proposal to a peer-reviewed journal for publication it would have been rejected for its glaring lack of scientific support,” said Nathan Donley, environmental health science director at the Center. “It’s unsettling that when it comes to protecting the health of people and wildlife, the EPA has decided to completely ignore the experts it asked for advice and pretend it never happened.”

Widely accepted research shows that microscopic organisms like bacteria can work to break down pesticides at depths of up to 3 feet in soil. But the changes to the groundwater model are based on limited evidence that the metabolic breakdown of pesticides can continue to occur at depths of up to 6 feet.

While some research suggests that biotic metabolism of pesticides can take place at lower soil depths, the peer-review committee noted that “the presented data do not provide enough evidence to justify changes in the conceptual model.” The panel further concluded that the EPA’s data were “not adequate for assessment of different degradation zones.”

The peer-review panel, consisting of academic and government researchers, took issue not only with the underlying data the EPA used to justify its decisions but also with the agency’s rationale for even considering weakening such a consequential tool for protecting groundwater.

The EPA noted that the proposed changes have the support of the U.S. Department of Agriculture and the pesticide industry group Croplife America. The agency explained that there were “differences in opinions” on this topic and noted multiple times that this was a “policy decision” as opposed to a scientific one.

Despite the fact that the modeling change was only finalized a little over a month ago, the EPA has already put it into practice for the pesticide spirodiclofen, a pesticide the agency designates as “likely to be carcinogenic to humans.”

In a previous assessment, the agency found that spirodiclofen, which is used on crops like oranges, pears, walnut and cherries, would lead to levels in groundwater that could put nearby communities at high risk of developing cancer.

However, in its updated assessment, the agency found that its new modeling input, together with a 75-foot buffer from wells, was sufficient to find that no concerning risk existed. That change puts the pesticide on track to be reapproved and continue to contaminate groundwater for the next 15 years.

Paradoxically the changes to the EPA’s model that were strongly opposed by the peer-review committee were finalized on the same day EPA administrator Michael Regan announced that the agency would further strengthen the independence of its peer-review panels and ensure that the agency properly considers peer-reviewed science early in its decisions.

“This is a striking example of how the EPA’s pesticide office routinely shuns the concerns of independent researchers in favor of the industry it’s supposed to regulate,” said Donley. “It shows just how far out of touch this office is with the communities it’s supposed to protect.”

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.7 million members and online activists dedicated to the protection of endangered species and wild places.

center locations