Associations between parental and postnatal metal mixture exposure and developmental delays in a Taiwanese longitudinal birth cohort of preschool children

Studies have evaluated the impact of environmental exposure to neurotoxic metals on developmental delays (DDs). However, comprehensive understanding regarding the associations between parental and postnatal exposure to metal mixtures and the occurrence of DDs in offspring is limited. In this study, we assessed the relationships between parental and postnatal exposure to three metals (arsenic [As], cadmium [Cd], and lead [Pb], levels of which were measured in toenails) and suspected DDs (SDDs) in preschool children within a Taiwanese longitudinal birth cohort. In total between 2017 and 2021, 154 pairs of parents and their children under the age of 6 years were recruited, and 462 toenail samples and 154 completed questionnaires were collected. Metal concentrations in toenails were quantified using inductively coupled plasma-mass spectrometry after acid digestion of the toenails. We applied multivariable logistic regression and Bayesian kernel machine regression to evaluate the overall effect and to identify key components of the metal mixture that were associated with the SDD risk. Higher concentrations of As, Cd, and Pb were found in the toenails of the parents of children with SDDs compared with the toenails of the parents of children without SDDs. Our examination of the combined effects of exposure to the metal mixture revealed that As concentration in the father's toenail and Cd concentration in the mother's toenail were positively correlated with the risk of SDDs in their offspring. Notably, the effect of exposure to the metal mixture on the risk of SDDs was stronger in boys than in girls. Our findings suggest that parents taking measures to minimize their exposure to metals might enhance their children's developmental outcomes.