Prenatal Diesel Exposure and Cognitive Ability in the Early Autism Risk Longitudinal Investigation

Abstract

Intro: Results from several epidemiologic studies suggest that prenatal air pollution exposure, particularly from traffic sources, increases risk for autism spectrum disorder (ASD). We examined the relationship of prenatal diesel exhaust exposure with measurements of cognitive ability and early autistic traits in Early Autism Risk Longitudinal Investigation (EARLI). Methods: EARLI is an enriched-for-high-familial-ASD-risk pregnancy cohort with longitudinal follow-up of infants through 36 months. Cognitive ability was assessed at 6 and 12 months using the Mullen Scales of Early Learning (MSEL). The Autism Observational Scales for Infants (AOSI) was administered at 6 and 12 months to assess the presence of early autistic traits. We quantified hemoglobin (Hb) adducts of 1-nitropyrene (a diesel exhaust specific compound) in 235 mid-pregnancy maternal blood samples using HPLC-MS-MS. The relationship between the adduct and outcome was examined using linear regression. Analyses were adjusted for season of sample collection and study site (Philadelphia, Baltimore, Sacramento, San Francisco). Results: Level of the Hb adduct was not associated with MSEL composite or cognitive scores at 6 months. At 12 months, a 2 standard deviation (SD) increase in adduct level was associated with poorer performance on the MSEL overall (beta= -4.19, p=0.05) and on the cognitive subscale (-8.73, 0.05). When stratified by study site, increasing adduct level was associated with poorer MSEL overall only in the San Francisco site (-7.16, 0.03) after adjusting for season. No associations were found between the adduct and AOSI score. Conclusion: Preliminary results suggest that increasing diesel exhaust exposure during pregnancy may result in decreased overall cognitive ability at 12 months of age. Further analyses of adduct measures with additional longitudinal outcome data are needed to understand if associations with ASD may be present.