Prenatal exposure to fine particulate matter composition and risk of cerebral palsy: a population-based retrospective cohort study in Ontario, Canada

Background — Existing literature suggests an association between prenatal exposure to fine particulate air pollution (PM2.5) and cerebral palsy (CP). However, the impact of individual PM2.5 components (SO42−, NH4+, NO3−, SS, BC, dust, OM) on CP risk remains unknown.

Objective — To examine the associations between prenatal exposure to PM2.5 components, and risk of CP among term births in Ontario, Canada.

Methods — This was a retrospective cohort study that examined term births (gestational age ≥37 completed weeks) from April 2002 to December 2020. PM2.5 total mass and composition measures were assigned to maternal residence at birth using satellite-based estimates and ground-level monitoring data. Cohort data were compiled using health administrative databases. Single-pollutant distributed lag cox proportional hazard models, with and without additional adjustment for PM2.5 residuals, were used to investigate the associations between gestational exposures to PM2.5 total mass and its components.

Results — 2,193,427 mother-infant pairs were identified, of which 3907 were diagnosed with CP during the follow-up period. Increased risk of CP was found for SO42− exposure during early pregnancy in both residual-adjusted (HR: 1.052, 95 % CI: 1.009–1.097, per IQR = 0.94 μg/m3), and non-adjusted models (HR: 1.050, 95 % CI: 1.007–1.095, per IQR = 0.94 μg/m3). The concentration-response relationship between the sensitive window found for SO42− and CP risk (weeks 4–9 of gestation) showcased a supralinear pattern.

Conclusions — Prenatal exposure to SO42− may be associated with increased CP risk during the early pregnancy period. Associations between prenatal PM2.5 total mass and composition exposure and CP risk should be further investigated.