Cognitive Development and Prenatal Air Pollution Exposure in the CHAMACOS Cohort

Background: Because fine particulate matter [PM, with aerodynamic diameter $\le 2.5\mu m$ (${\mathrm{PM}}_{2.5}$)] is a ubiquitous environmental exposure, small changes in cognition associated with ${\mathrm{PM}}_{2.5}$ exposure could have great societal costs. Prior studies have demonstrated a relationship between in utero ${\mathrm{PM}}_{2.5}$ exposure and cognitive development in urban populations, but it is not known whether these effects are similar in rural populations and whether they persist into late childhood.

Objectives: In this study, we tested for associations between prenatal ${\mathrm{PM}}_{2.5}$ exposure and both full-scale and subscale measures of IQ among a longitudinal cohort at age 10.5 y.

Methods: This analysis used data from 568 children enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a birth cohort study in California's agricultural Salinas Valley. Exposures were estimated at residential addresses during pregnancy using state of the art, modeled ${\mathrm{PM}}_{2.5}$ surfaces. IQ testing was performed by bilingual psychometricians in the dominant language of the child.

Results: A ${3-\mu g/m}^3$ higher average ${\mathrm{PM}}_{2.5}$ over pregnancy was associated with $-1.79$ full-scale IQ points [95% confidence interval (CI): $-2.98$, $-0.58$], with decrements specifically in Working Memory IQ (WMIQ) and Processing Speed IQ (PSIQ) subscales [WMIQ $-1.72$ (95% CI: $-2.98$, $-0.45$) and PSIQ $-1.19$ (95% CI: $-2.54$, 0.16)]. Flexible modeling over the course of pregnancy illustrated mid-to-late pregnancy (months 5-7) as particularly susceptible times, with sex differences in the timing of susceptible windows and in which subscales were most affected [Verbal Comprehension IQ (VCIQ) and WMIQ in males; and PSIQ in females].

Discussion: We found that small increases in outdoor ${\mathrm{PM}}_{2.5}$ exposure in utero were associated with slightly lower IQ in late childhood, robust to many sensitivity analyses. In this cohort there was a larger effect of ${\mathrm{PM}}_{2.5}$ on childhood IQ than has previously been observed, perhaps due to differences in PM composition or because developmental disruption could alter the cognitive trajectory and thus appear more pronounced as children get older. https://doi.org/10.1289/EHP10812.