Prenatal exposure to polycyclic aromatic hydrocarbons, reduced hippocampal subfield volumes, and word reading

Reading difficulties and exposure to air pollution are both disproportionately high among youth living in economically disadvantaged contexts. Critically, variance in reading skills in youth living in higher socioeconomic status (SES) contexts largely derives from genetic factors, whereas environmental factors explain more of the variance in reading skills among youth living in lower SES contexts. Although reading research has focused closely on the psychosocial environment, little focus has been paid to the effects of the chemical environment. In this study, we measured prenatal exposure to a common air pollutant, polycyclic aromatic hydrocarbons (PAH), via the presence (versus absence) of PAH-DNA adducts in maternal blood during the third trimester of pregnancy. We examined the impact of prenatal PAH exposure on adolescent hippocampal subfield volume and on word reading in a sample of youth followed prospectively since birth (N = 165). Compared to those without prenatal exposure, those with detectable PAH-DNA adducts (N = 63) exhibited significantly smaller hippocampal volumes (CA2/3 subfield, t = -2.413, p < .05), which was associated with worse pseudoword reading (t = 2.346, p < .05). Exploratory mediation analyses showed a significant effect of PAH on pseudoword reading through CA2/3 vol (p = .028), suggesting that prenatal PAH exposure affects hippocampal volume with downstream effects on reading ability.