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 = 184,954) who lived within a 5-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 neuro-toxicity 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 (RR = 1:24; 95% CI: 1.08, 1.43) or metals (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.