Mixtures of multiple pesticides in products not evaluated for increased toxicity

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(Beyond Pesticides, July 21, 2016) An investigative report released yesterday by Center for Biological Diversity (CBD) concludes that, over the past six years, the U.S. Environmental Protection Agency (EPA) has approved nearly 100 pesticide products with chemical mixtures that elevate the formulations’ toxicity, but are not specifically evaluated by the agency. CBD finds that these formulations add more stress to already-jeopardized pollinators and rare plants. The reportToxic Concoctions: How the EPA Ignores the Dangers of Pesticide Cocktails, highlights a long-running blind spot within EPA’s pesticide evaluation program, which Beyond Pesticides has long sounded the alarm on: the risk associated with combining mixtures of different pesticide active ingredients, which independent science shows may be more toxic than a single active ingredient by itself, also known as pesticide synergism. The mixtures occur as a result of multiple ingredients in individual products or because of exposure to multiple pesticide product residues in food, air, water, and land areas, such as lawns, playing fields, and parks.

“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,” said Nathan Donley, Ph.D., a scientist with the CBD, and author of the report. “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.”

Dr. Donley’s research was fueled in part from the fact that  EPA did not analyze patent applications for toxicity data back in 2014, when despite opposition from many farmers and environmental groups, the agency approved Dow AgroSciences’ Enlist Duo, an herbicide that incorporates a mix of glyphosate and a formulation of 2,4-D, for use on genetically engineered (GE) crops. This approval was done before a patent application from the U.S. Patent and Trademark Office Database was discovered, which included information on the potential toxic synergistic effects these two ingredients have on non-target plants, including endangered species. This finding led EPA to ask the 9th U.S. Circuit Court of Appeals to vacate its approval of Enlist Duo, due to a lack of proper knowledge and evaluation of the adverse effects the product had on the environment.

The report specifically looks at recently approved patent applications for four major agrichemical companies (Bayer, Dow, Monsanto, and Syngenta) for pesticide products containing two or more active ingredients. 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;
• A breakdown of the patent synergy claims by company indicates that 71 percent (35/49), 46 percent (12/26), 40 percent (2/5) and 78 percent (47/60) of Bayer, Dow, Monsanto and Syngenta products had patent applications that claimed synergy between at least two of the active ingredients in the product, respectively;
• 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.

The report adds to the growing body of research on the interactive effects of pesticides on human health and the environment. A 2002 study by Warren Porter, PhD., professor of zoology and environmental toxicology at the University of Wisconsin, Madison, examined the effect of fetal exposures to a mixture of 2,4-D, mecoprop, and dicamba exposure —frequently used together in lawn products like Weed B Gone Max and Trillion— on the mother’s ability to successfully bring young to birth and weaning. Researchers looked at pesticide concentrations diluted to levels that are considered “safe” by EPA and found that it is capable of inducing abortions and resorptions of fetuses at very low parts per billion. The greatest effect was at the lowest dose. Research by Tyrone Hayes, PhD, professor of integrative biology at UC has compared the impact of exposure to realistic combinations of small concentrations of pesticides on frogs, finding that frog tadpoles exposed to mixtures of pesticides took longer to metamorphose to adults and were smaller at metamorphosis than those exposed to single pesticides, with consequences for frog survival. The study revealed that “estimating ecological risk and the impact of pesticides on amphibians using studies that examine only single pesticides at high concentrations may lead to gross underestimations of the role of pesticides in amphibian declines.”

Other studies note that the synergistic combinations of different pesticide combinations (especially fungicides and insecticides like pyrethroids and neonicotinoids) are of great concern to pollinators, since the toxicity of the individual compounds is already very high. Current risks to bees from neonicotinoids are underestimated because of their cumulative toxicity, synergistic effects with fungicides, and additive effects in combination with pyrethroids are not well understood.

In an interview process with stakeholders for the March 2016 report done by the Government Accountability Office (GAO), EPA took the position that it did not know where to find information on common pesticide mixtures: “EPA officials agreed that such mixtures may pose risks to bees but said that EPA does not have data on commonly used mixtures and does not know how it would identify them.” However, the GAO report, in its critique of EPA’s efforts to protect pollinators, notes that EPA can collect and source data on commonly used mixtures from farmers, pesticide manufacturers, and many others. This current report, in utilizing the data from the U.S. Patent and Trademark Office (a publicly available information source), to provide a report on the potential hazards of different chemical mixtures that EPA has already approved is a direct refute of EPA’s position.

The report concludes that potential additive and synergistic impacts of chemical mixtures must be evaluated: “Clearly pesticide synergy is not a rare occurrence and should no longer be treated as such. The EPA must take into account relevant patent data and other lines of evidence and fundamentally alter its approach to assessing pesticide mixtures.”

Beyond Pesticides has long been critical of EPA’s risk assessment process, which only evaluates the toxicity of an active pesticide ingredient alone, and does not consider the hazards of pesticide mixtures (or inert ingredients) in common pesticide products. For more information on pesticide synergy, see our 2004 article, “Synergy: The Big Unknowns of Pesticide Exposure.” For information on individual pesticide health effects, see the Pesticide Gateway.

Dr. Donley joined Aaron Blair, Ph.D., Warren Porter, Ph.D. and others as part of the Environmental Health and Law Workshop at Beyond Pesticides’ 34th National Pesticide Forum April 16, 2016 in Portland, Maine. You can watch the discussion here.

All unattributed positions and opinions in this piece are those of Beyond Pesticides.

Source: Press Release