Disrupting effects of neonicotinoids and their interaction with metals on thyroid hormone, an evidence of children in a rural area, South China.

Neonicotinoids exposure was found to induce thyroid dysfunction. However, there lack of direct evidence between neonicotinoids exposure and thyroid hormone (TH) disruption in population study, especially in children, which limits the understanding on their health hazard. To fill this knowledge gap, we conducted a cross-sectional study on children of a rural area in South China (n = 88), and analyzed urinary ten neonicotinoids (including metabolites), serum TH, thyroxine-binding globulin (TBG), and thyroid stimulating hormone (TSH) levels. Based on linear regression, generalized additive model, and Bayesian kernel machine regression, neonicotinoids levels were found to be correlated with TH, TBG, and TSH levels, with stronger effects for metabolites than parent compounds in most cases. Mixture exposure of neonicotinoids had significantly positive effect on free triiodothyronine (T3). N-desmethyl-acetamiprid (N-dm-ACE) was negatively associated with T3 for female, which corresponded to much lower T3 levels for female than for male. Also, N-dm-ACE was found to non-monotonic associated with free thyroxine for male. Some neonicotinoids had interactive effects with lead and cadmium on TH disruption. The results provide an evidence on TH disruption of neonicotinoids in children, and highlight the need to explore TH disruption of neonicotinoids and safeguard the health of children.