Obesity modifies the association of environmental pyrethroid exposure with glucose homeostasis in the US general adults

Environmental pyrethroids are concerning due to their widespread residues and potential implications on human health. We aimed to assess the association of pyrethroid exposure with glucose homeostasis and examine the interaction between obesity and pyrethroid exposure. A total of 4233 US general adults from the National Health and Nutrition Examination Survey with measured urinary pyrethroid metabolites, fasting plasma glucose (FPG), fasting insulin (FINS), and glycated hemoglobin A1c (HbA1c) were included in the study. The homeostasis model assessment (HOMA2) calculator was utilized to assess insulin resistance (HOMA2-IR), insulin sensitivity (HOMA2-IS), and beta-cell function (HOMA2-β). We estimated the associations of pyrethroid metabolites with glucose homeostasis parameters (FPG, FINS, HbA1c, HOMA2-IR, HOMA2-IS, and HOMA2-β) using multivariate linear regression models and restricted cubic spline models and further assessed the interaction between obesity and pyrethroid metabolites on glucose dyshomeostasis. Urinary 3-phenoxybenzoic acid (3-PBA) was the most detected pyrethroid metabolite (81%) with a median concentration of 0.43 (interquartile range 0.20-1.01) μg/g urinary creatinine. Compared with the participants in the lowest quartile, those in the highest quartile of 3-PBA had a 1.93% (95% confidence interval: 0.46%, 3.42%), 6.69% (1.96%, 11.64%), 1.60% (0.64%, 2.57%), 7.06% (2.33%, 12.01%), -6.59% (-10.72%, -2.28%), and 1.10% (-2.69%, 5.04%) alteration in FPG, FINS, HbA1c, HOMA2-IR, HOMA2-IS, and HOMA2-β, respectively. The restricted cubic spline model displayed a linear positive association between 3-PBA and FPG, FINS, HbA1c, and HOMA2-IR, and a negative association with HOMA2-IS (all P for overall <0.05 and P for non-linear >0.05). Additionally, the association between urinary 3-PBA and FPG was modified by general obesity (P for interaction <0.05), with a more pronounced association observed in obese participants than in non-obese participants. Our findings suggested that pyrethroid exposure was associated with glucose dyshomeostasis. General obesity significantly heightened the association between pyrethroid exposure and increased FPG level.