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

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Existing literature suggests an association between prenatal exposure to fine particulate air pollution (PM 2.5 ) and cerebral palsy (CP). However, the impact of individual PM 2.5 components (SO 4 2− , NH 4 + , NO 3 − , SS, BC, dust, OM) on CP risk remains unknown. To examine the associations between prenatal exposure to PM 2.5 components, and risk of CP among term births in Ontario, Canada. This was a retrospective cohort study that examined term births (gestational age ≥37 completed weeks) from April 2002 to December 2020. PM 2.5 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 PM 2.5 residuals, were used to investigate the associations between gestational exposures to PM 2.5 total mass and its components. 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 SO 4 2− exposure during early pregnancy in both residual-adjusted (HR: 1.052, 95 % CI: 1.009–1.097, per IQR = 0.94 μg/m 3 ), and non-adjusted models (HR: 1.050, 95 % CI: 1.007–1.095, per IQR = 0.94 μg/m 3 ). The concentration-response relationship between the sensitive window found for SO 4 2− and CP risk (weeks 4–9 of gestation) showcased a supralinear pattern. Prenatal exposure to SO 4 2− may be associated with increased CP risk during the early pregnancy period. Associations between prenatal PM 2.5 total mass and composition exposure and CP risk should be further investigated. a) Single-pollutant models without residual adjustments b) Single-pollutant models with residual adjustments.c) PM 2.5 residuals. • Cerebral palsy is the most common neurological motor disability in children. • Neurodevelopment may be affected by exposure to ambient air pollution (PM 2.5 ). • PM 2.5 is a mixture of various air pollutants (SO 4 2− , NH 4 + , NO 3 − , SS, BC, dust, OM). • Early pregnancy exposure to sulfate (SO 4 2− ) may increase the risk of cerebral palsy.