The U.S. Environmental Protection Agency has approved nearly 100 pesticide products over the past six years that contain mixtures that make them more poisonous and increase the dangers to imperiled pollinators and rare plants, according to an investigation by the Center for Biological Diversity. These “synergistic” combinations have been widely overlooked by the EPA in its approval of pesticides for food, lawns and other uses.

The Center’s new report, Toxic Concoctions: How the EPA Ignores the Dangers of Pesticide Cocktails, involved an intensive search of patent applications for pesticide products containing two or more active ingredients recently approved by the EPA for four major agrochemical companies (Bayer, Dow, Monsanto and Syngenta).

“The EPA is supposed to be the cop on the beat, protecting people and the environment from the dangers of pesticides,” said Nathan Donley, a scientist with the Center and author of the report. “With these synergistic pesticides, the EPA has decided to look the other way, and guess who’s left paying the price?”

Synergy occurs when two or more chemicals interact to enhance their toxic effects. It can turn what would normally be considered a safe level of exposure into one that results in considerable harm. Pesticide mixtures are ubiquitous in the environment and also present in many products for sale on store shelves.

In late 2015, in preparing to defend itself against litigation on the registration of a pesticide product called Enlist Duo, the EPA discovered a new source of information on the product: the U.S. Patent and Trademark Office Database, which contained a patent application indicating the two ingredients in this product, glyphosate and 2,4-D, resulted in synergistic toxicity to plants. This discovery ultimately led the agency to ask the 9th Circuit Court of Appeals to vacate its approval of Enlist Duo because it had not properly considered the potential adverse effects of this synergy on nontarget plants. It also highlighted a previously unknown source of much-needed mixture toxicity data: patent applications.

For this latest analysis, a Center scientist analyzed the patent database for other pesticide products approved in a similar manner.

Among the key findings in the examination of approvals for the four companies:

• 69 percent of these products (96 out of 140) had at least one patent application that claimed or demonstrated synergy between the active ingredients in the product;
• 72 percent of the identified patent applications that claimed or demonstrated synergy involved some of the most highly used pesticides in the United States, including glyphosate, atrazine, 2,4-D, dicamba and the neonicotinoids thiamethoxam, imidacloprid and clothianidin, among others.

“It’s alarming to see just how common it’s been for the EPA to ignore how these chemical mixtures might endanger the health of our environment,” Donley said. “It’s pretty clear that chemical companies knew about these potential dangers, but the EPA never bothered to demand this information from them or dig a little deeper to find it for themselves.”