First national-scale reconnaissance of neonicotinoid insecticides in streams across the USA

Environmental context Neonicotinoids are under increased scrutiny because they have been implicated in pollinator declines and, more recently, as potential aquatic toxicants. Nevertheless, there is currently little information on concentrations of multiple neonicotinoids in surface water. This paper presents a summary of concentrations of six neonicotinoids in streams from across the United States in both urban and agricultural areas. These environmental data are important in determining the potential risk of neonicotinoids to non-target aquatic and terrestrial organisms. Abstract To better understand the fate and transport of neonicotinoid insecticides, water samples were collected from streams across the United States. In a nationwide study, at least one neonicotinoid was detected in 53% of the samples collected, with imidacloprid detected most frequently (37%), followed by clothianidin (24%), thiamethoxam (21%), dinotefuran (13%), acetamiprid (3%) and thiacloprid (0%). Clothianidin and thiamethoxam concentrations were positively related to the percentage of the land use in cultivated crop production and imidacloprid concentrations were positively related to the percentage of urban area within the basin. Additional sampling was also conducted in targeted research areas to complement these national-scale results, including determining: (1) neonicotinoid concentrations during elevated flow conditions in an intensely agricultural region; (2) temporal patterns of neonicotinoids in heavily urbanised basins; (3) neonicotinoid concentrations in agricultural basins in a nationally important ecosystem; and (4) in-stream transport of neonicotinoids near a wastewater treatment plant. Across all study areas, at least one neonicotinoid was detected in 63% of the 48 streams sampled.