(Beyond Pesticides, June 26, 2017) A new report released last week by the U.S. Environmental Protection Agency’s (EPA) Office of the Inspector General finds that the agency must collect and assess information on chemical mixtures and potential synergistic effects in order to improve oversight over pesticide registrations and management of developing herbicide resistance. Synergy results when the mixture of chemicals creates effects greater than the aggregation of individual effects, leading to underestimated toxic impacts on human and environmental health. EPA’s Office of Chemical Safety and Pollution Prevention states it will consider how best to use synergistic effects data for pesticide registration decisions by 2019.

The report, released June 21, 2017, EPA Can Strengthen Its Oversight of Herbicide Resistance With Better Management Controls, is the result of an assessment into EPA’s management and oversight of resistance issues related to herbicide-resistant genetically engineered (GE) crops. The report finds, “EPA uses the pesticide registration process to collect information on human health and environmental risks from pesticides used on herbicide-resistant weeds, but no information is collected regarding synergism.” It states that information on synergy is important because it allows EPA “a greater ability to assess human health and environmental risks combined with real-world pesticide use.” Cited in the report is the case of the herbicide product Enlist Duo, which is a mixture of glyphosate and 2,4-D, and approved for use on GE crops. However, no evaluation of synergy was conducted initially, even though there were patent claims to the U.S. Patent and Trademark Office citing synergism. This was discovered during litigation proceedings of the lawsuit filed challenging the approval of Enlist Duo in 2014. EPA then withdrew its registration approval for Enlist Duo in November 2015. According to EPA, its subsequent review of the synergism claims and data found no synergistic effects. According to the Inspector General, the example of Enlist Duo, “highlights the potential for uncertainty when the EPA does not request data on synergy during the registration process.”