Using Publicly Available Tools to Assess Ecological Risks Associated with Agricultural Pesticide Use in California: The Case of Glyphosate

Herbicides are formulated to manage undesired vegetation; however, the potential adverse effects of herbicides on non-target species are of interest to the scientific community, regulators, communities, and industry alike. In this study, using glyphosate as an example, the use of publicly available tools to assess potential risks to several ecological receptors was demonstrated. To this end, data on glyphosate application rates in California were gathered from the 2022 California Department of Pesticide Regulation (CDPR) report and glyphosate toxicity data were gathered from Ecotoxicology Knowledgebase (ECOTOX) and relevant agency reports. Subsequently, the U.S. Environmental Protection Agency (EPA) models (BeeREX, T-HERPS, and T-REX) were used to assess the screening level risk to honeybees, herpetofauna, birds, and mammals. It was demonstrated that the risk potential was the highest in honeybees compared to other species considered, since the application rate not anticipated to exceed the acute and chronic levels of concern (LOCs) was estimated at 8.85×10 ^− 6 lbs/A, which was lower than the minimal glyphosate application rate in California of 7.70×10 ^− 5 lbs/A. In comparison, the risk potential was lower in herpetofauna, birds, and mammals, for which the application rates not anticipated to exceed the acute and chronic LOCs were estimated at 0.58, 0.53, and 0.29 lbs/A, respectively; these estimated rates were between the median and mean glyphosate application rates of 0.142 and 0.701 lbs/A, respectively. It was concluded that the available models can be effective tools to use during pesticide development in understanding potential risks to various ecological receptors, which can then inform decision making as it relates to appropriate application rates and mitigation strategies.