Associations between prenatal exposure to a mixture of lead, mercury and polychlorinated biphenyls and executive function in Inuit adolescents

Abstract

Numerous studies have investigated the individual contribution of prenatal exposure to lead (Pb), mercury (Hg) and polychlorinated biphenyls (PCBs) on neurocognitive development, but few have explored their combined influence, particularly on executive function, during adolescence. This study aims to assess the associations between prenatal exposure to Pb, Hg and PCB-153 and executive function in mid-to-late adolescence. Two-hundred twelve Inuit participants (mean age = 18.5 years, range = 16.0 to 21.9) from Nunavik, Canada, completed four tasks assessing executive function: a Stop Task, a 2n-back task, the D-KEFS Trail Making Test and the Tower of London. Exposure to Pb, Hg and PCB-153 was estimated in cord blood samples at birth, and in blood samples at 11 years old and at time of testing. Bayesian Kernel Machine Regression and traditional multiple linear regression models were performed to estimate mixture and individual effects. All models were adjusted for sociodemographic characteristics and fish nutriments as well as for postnatal contaminant exposure in secondary analyses. Mixture modeling of concurrent prenatal exposure to Pb, Hg and PCB-153 did not reveal any statistically significant associations with executive function. However, results from the single-pollutant regression models showed a negative log-linear relationship between cord Pb concentrations and cognitive planning, which remained statistically significant after controlling for postnatal exposure (β = −0.178, 95 % CI = [-0.327, −0.021], p = 0.021). This study suggests that prenatal exposure to Pb is detrimental to executive function in late adolescence. Further research is needed to replicate findings and better understand the functional significance of this long-lasting association and how it might evolve during adulthood.