Characterising neonicotinoid insecticide exposures among the Irish population using human biomonitoring

Neonicotinoid and neonicotinoid-like insecticides (NNIs) are the most widely used class of insecticides in the world, with previous large-scale human biomonitoring studies of NNIs showing widespread exposure. They have been identified as priority substances requiring further toxicological and human exposure research by numerous initiatives, including the Partnership for the Assessment of Risks from Chemicals (PARC). The study aimed to conduct the first human biomonitoring study investigating exposures to NNIs in Ireland by analysing 227 urine samples from the Irish population. Samples were collected between 2019 and 2020 from 14 farm and 54 non-farm families throughout Ireland and analysed for seven NNIs (acetamiprid, clothianidin, imidacloprid, thiacloprid, thiamethoxam, flupyradifurone, and sulfoxaflor) and nine of their metabolites using online-solid phase extraction coupled to liquid chromatography-tandem mass-spectrometry (online-SPE-LC-MS/MS). The results found that 75 % of samples had quantifiable levels of at least one parent compound or metabolite. N-desmethyl acetamiprid (dme-ACE) and imidacloprid-olefin (IMI-olefin), the main metabolites of acetamiprid and imidacloprid, were the most widely detected analytes and could be quantified in 57 % and 34 % of the urine samples, respectively. Based on reverse dosimetry, the maximum urinary concentration of dme-ACE corresponded to 31.7 % of the acceptable daily intakes (ADI) for acetamiprid, which has been recently reduced five-fold. In comparison, the maximum urinary concentrations of all other NNIs analysed in the study corresponded to less than 3 % of the ADIs of the respective parent NNIs. Though NNI exposure was widespread among this study group, the exposure levels were below current regulatory guidance values.