On September 28, 2023, the Environmental Protection Agency (EPA), the national agency responsible for evaluating and approving plant protection products in the United States, rejected a request from several NGOs concerning the failure to take account of the cocktail effect when assessing risk.

In a legal petition dated July 10, 2017, the Center for food safety (CFS) had asked the EPA to revise the methodology for assessing the toxicity of pesticides submitted for authorization, so that not only the toxicity of the active substance is apprehended, but also that of co-formulants (which represent the majority of components in plant protection products), and the synergistic effects of interactions between all substances present in the products.

In view of the EPA's failure to respond, CFS, along with three other NGOs (Center for Environmental Health, Pesticide Action Network of North America, Californians for Pesticide Reform), took the agency to the U.S. District Court for the Northern District of California in October 2022. A deadline for response was set following a compromise reached between the complaining associations and the agency on October 24, 2022.

On September 28, 2023, the EPA finally rejected the petition, considering that "the information provided in the petition is insufficient to compel any change
to EPA’s current understanding of the science", and that the current method of assessing the product's ecotoxicity on the basis of the active substance alone is sufficiently protective of the environment and human health. The agency also stresses the importance of the scientific corpus used to assess the product's toxicity, and the existence of additional documentation in cases where information on co-formulants is deemed necessary.