Critical CHD often requires surgical intervention or results in infant mortality. We aimed to determine the association between critical CHD categories and exposure levels to pollutants.

A retrospective study of n = 1484 infants who underwent complex cardiac surgery in early infancy from 1996 to 2021. The association between critical CHD categories (compared to a reference category with chromosomal abnormality) and exposure levels during early pregnancy to nitrogen dioxide, ozone, fine particulate matter (<2.5 micrometers diameter), and air quality from smoke was determined. Spatial heterogeneity was accounted for using geographically weighted multinomial logistic regression.

For fine particulate matter exposure, 0.34% of locations displayed statistically significant negative associations with critical CHD categories, clustered in Saskatchewan and Manitoba. These regions exhibited small spatial extents. For ozone exposure, 15.1% of locations exhibited statistically significant negative associations with critical CHD categories, with the majority originating from Alberta and a smaller fraction in Saskatchewan. Differences in significant associations with locations were observed before and after spatial adjustment. Air quality from smoke and nitrogen dioxide exposure demonstrated no statistically significant associations with critical CHD categories.

Differences before and after geographic spatial adjustment underscored the importance of accounting for spatial heterogeneity to uncover patterns of association between environmental pollutants and critical CHD categories. The negative associations likely reflected pollution acting as a second hit to markedly increase the risk for critical CHD in those with genetic predisposition.