Review finds neonicotinoid imidacloprid poses low risk to aquatic invertebrates

A major new ecotoxicological review and risk assessment has been published in the peer-reviewed literature and concluded that registered crop and non-crop uses of imidacloprid in the United States are of minimal risk to sensitive aquatic invertebrate communities. This is also good news for other wildlife, such as birds and fish, since these insects are an important part of their diet.

The neonicotinoid imidacloprid is one of the most widely-used insecticides in the world because of its effectiveness and its relatively favorable human and environmental safety profile. Because aquatic invertebrates serve an important function in nature, many studies have been performed to characterize the potential impact across a variety of species. The publication details the body of research, the careful selection and use of the best available data, and the probabilistic risk assessment. The probabilistic approach better predicts the effects to sensitive species, the relevant exposures and the potential risks to aquatic invertebrate communities in terms of the actual label use directions and the natural environment for these crops and treated landscapes.

The researchers found that higher-tier studies provide the most robust data for regulatory decision making. "Laboratory testing is necessary to establish toxicity endpoints for a wide range of organisms, however such studies have unrealistic exposure conditions which often lead to overestimated toxicity. Fortunately, we had data from many higher-tier mesocosm studies for imidacloprid, which is almost unprecedented," said Dr. Dwayne Moore, Senior VP and Scientist at Intrinsik Environmental Sciences (US) Corp., one of the researchers involved in the review. "The higher tier studies enabled us to look at aquatic invertebrate communities containing a wide array of invertebrate species in realistic environmental settings, which is far more predictive of the biological realities of aquatic ecosystems than are tests on single species in artificial environments in the laboratory."

In the assessment, refined exposure models that better represent pest treatments and the environments where applications could be made were used. The researchers found that their aquatic exposure predictions were consistent with a decade of water sampling data available from public sources, including the U.S. Geological Survey. "We conducted 30-year simulations based on realistic, but conservative, assumptions and found that aquatic communities are unlikely to be at risk from acute or chronic exposures to registered uses of imidacloprid," noted Dr. Moore. "In fact, risks were de minimis, the lowest possible category, for all crop and non-crop uses."