Ambient Toxic Air Contaminants in the Maternal Residential Area during Pregnancy and Cerebral Palsy in the Offspring.

Abstract

Background: Cerebral palsy (CP) is the most common permanent neuromotor disorder diagnosed in childhood. Although most cases have unknown etiology, emerging evidence suggests environmental risk factors of CP.

Objectives: We investigated whether ambient toxic air contaminants (TACs) in the maternal residential area during pregnancy, specifically volatile organic compounds (VOCs) and metals, were associated with offspring CP risk in California.

Methods: We conducted a case-cohort study that included CP cases ($N=906$) and a 20% random sample of all live singleton births ($N=\mathrm{184,954}$) who lived within a $5\text{-mile}$ (8-km) radius of air toxics monitoring stations in California during 2005-2015 as the control comparison group. CP cases were ascertained from diagnostic records of the California Department of Developmental Services. We a priori selected TACs with suspected neurotoxicity and developmental toxicity, including 14 VOCs and 6 metals. We estimated the adjusted risk ratio (RR) and 95% confidence interval (CI) for CP and the average maternal residential exposures to each TAC over the entire pregnancy using modified Poisson regression. For air contaminant mixtures, we used quantile-based g-computation to estimate the effects of mixtures of VOCs or metals. Finally, we performed a negative control exposure analysis on exposure estimates of 36-48 months after delivery to evaluate uncontrolled confounding bias.

Results: Maternal residential exposures to six VOCs (benzene, toluene, 1,3-butadiene, acetone, acetonitrile, and methylene chloride) and four metals (antimony, lead, nickel, and vanadium) were associated with 3%-25% higher risk of CP per interquartile range increase, and the estimated mixture effects of VOCs ($\text{RR}=1.24$; 95% CI: 1.08, 1.43) or metals ($\text{RR}=1.38$; 95% CI: 1.20, 1.58) were stronger. The observed associations were close to null for negative control exposures (36-48 months after delivery) to mixtures of VOCs or metals and CP.

Discussion: In California, maternal prenatal residential exposure to VOCs and metals in the outdoor air, largely attributed to mobile traffic emission sources, was associated with an increased risk of CP in offspring. https://doi.org/10.1289/EHP14742.