The Facts on Chlorpyrifos

Europe is now considering banning chlorpyrifos because of its effect on childhood development, so we thought it would be a good time to revisit the facts. Both the EPA and its critics say science is on their side in the debate over whether the agricultural insecticide should be banned.


When the Environmental Protection Agency decided to not ban chlorpyrifos, an insecticide widely used in agriculture, both the EPA and its critics claimed “sound” or “solid” science supported their positions. Research does suggest chlorpyrifos impacts human health, but that research has some limitations. 

The EPA, under the Obama administration, proposed to ban chlorpyrifos in November 2015. But EPA Administrator Scott Pruitt reversed that decision last month, arguing he was relying on “sound science.”

Pruitt, March 29: We need to provide regulatory certainty to the thousands of American farms that rely on chlorpyrifos, while still protecting human health and the environment. By reversing the previous Administration’s steps to ban one of the most widely used pesticides in the world, we are returning to using sound science in decision-making – rather than predetermined results.

Sheryl Kunickis, the director of the Office of Pest Management Policy at the U.S. Department of Agriculture, backed Pruitt’s decision, stating it was “grounded in evidence and science.”

But Jim Jones, assistant administrator at the EPA until January, told the New York Times that Pruitt’s decision ignored “science that is pretty solid.” The Times added that Jones — who held various positions at the agency between 1997 and 2017, including director of the EPA’s Office of Pesticides Programs — said that “he believed the ruling would put farm workers and exposed children at unnecessary risk.”

Some studies do suggest that chlorpyrifos exposure can lead to developmental issues in children, for example, but they’re correlational studies, meaning they don’t provide causal links. However, research in rodents has found causal links between chlorpyrifos and developmental issues.

Other studies in human populations have failed to find correlations between chlorpyrifos and development issues in children, but that research may be suffering from what scientists call “confounding variables,” or unrelated factors that may be affecting the study’s results.

In other words, some research does suggest chlorpyrifos poses a threat to human health, but the question is whether or not it’s enough to warrant a complete ban of the insecticide.

We take no position on the EPA’s decisions. But we can outline the strengths and limitations of the research that has been done on chlorpyrifos.

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