Will EPA continue to allow problematic pesticides?

The US Environmental Protection Agency is slated to decide this year whether several controversial pesticides can stay on the market. The agency has been reevaluating the safety of the chemicals in response to court orders and as part of a routine process called registration review that happens every 15 years for pesticides sold in the US.

Here are three of the high-profile pesticides that C&EN will be watching in 2025.

Chlorpyrifos

The organophosphate insecticide chlorpyrifos has been in the EPA’s crosshairs for years because of the chemical’s adverse neurodevelopmental effects in children. The agency proposed banning it twice under Barack Obama’s administration. It then reversed course and denied a petition to ban the pesticide in April 2017 under Donald J. Trump’s first administration. After several court cases, the EPA finalized a ban on chlorpyrifos in 2021 under Joe Biden’s administration. But the US Court of Appeals for the Eighth Circuit overturned that ban in 2023. In response to the court ruling, the EPA banned the use of chlorpyrifos on all but 11 crops in late 2024. As part of the registration review process, the agency plans to issue a proposed decision this year on whether the insecticide can remain on the market, followed by a final decision in 2026.

Neonicotinoids

Neonicotinoids, a class of insecticides blamed for harming bees and other pollinators more than a decade ago, will likely garner renewed attention this year. The EPA is planning to decide whether to reapprove five of them: acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam. Environmental groups say studies in rodents suggest neonicotinoids are harmful to the developing mammalian brain, including the brains of human children. The insecticides were once hailed as safer alternatives to organophosphates. But in a recent review article published in Frontiers in Toxicology, scientists at the Natural Resources Defense Council and the Center for Biological Diversity, two environmental groups, say neonicotinoid makers unduly influenced the EPA’s approval process (2024, DOI: 10.3389/ftox.2024.1438890). The EPA’s exposure limits for neonicotinoids are not supported by the toxicology data submitted by the companies, the groups say.

Dicamba

The EPA will decide this year whether a new product containing the drift-prone herbicide dicamba can be used on genetically modified soybeans and cotton. Bayer applied for registration of the product in May 2024, after a court ruling in February 2024 vacated three previous registrations for dicamba products used on soybeans and cotton. Use of dicamba increased dramatically in 2017 when the EPA allowed it to be sprayed on soybeans and cotton genetically modified to tolerate it. Many weeds have developed resistance to glyphosate, making dicamba an attractive alternative for controlling broadleaf weeds. But dicamba volatilizes and drifts off-site when temperatures spike, even when it is applied properly. States have received thousands of complaints about dicamba damaging nontarget crops and plants on neighboring properties. Environmental groups have sued the EPA twice for approving the drift-prone herbicide and won both cases. A few months after the first ruling in 2020, the Trump administration’s EPA reapproved the products, prompting environmentalists to sue again. The latest ruling, in 2024, vacated the registrations again, but the EPA could approve Bayer’s new product this year.