Neonicotinoid insecticide metabolites in seminal plasma: Associations with semen quality

Animal studies have revealed that exposure to neonicotinoid insecticides (NNIs) could compromise male reproductive function; however, related data on the occurrence of NNIs and their specific metabolites in human seminal plasma are scarce. To explore the potential effects of NNI exposure on male semen quality, we determined the concentrations of NNIs and some of their metabolites (collectively defined as mNNIs) in seminal plasma samples collected from men (n = 191) who visited a fertility clinic in Shijiazhuang, North China from 2018 to 2019. Associations between the mNNI concentrations and semen quality parameters were assessed using linear regression models, adjusting for important covariates. In the seminal plasma samples, desmethyl-acetamiprid (DM-ACE, detection frequency: 98.4%), imidacloprid-olefin (IMI-olefin, detection frequency: 86.5%), and desmethyl-clothianidin (DM-CLO, detection frequency: 70.8%) were frequently detected at median concentrations of 0.052, 0.003, and 0.007 ng/mL, respectively; meanwhile other compounds were detected at less than the method detection limits. In the single-mNNI models, the IMI-olefin concentration was associated with decreased progressive motility [IMI-olefin concentration: percent change (%Δ) = -17.0; 95% confidence interval (CI) = -30.3, -0.92; the highest tertile compared with the lowest tertile: %Δ = -21.1; 95% CI = -37.5, -0.23]. Similar results were found in the multiple-mNNIs models. No other inverse associations were found between the other mNNI concentrations and semen quality parameters. This is the first study to identify the occurrence of mNNIs in the seminal plasma and the potential associations of their concentrations with human semen quality parameters. These findings imply an inverse association between the IMI-olefin concentration and semen quality.