Reacción a "A study claims that exposure to fine particulate matter pollution during pregnancy is associated with an increase in autism diagnoses"

In this study, the authors observe a positive association between prenatal exposure to certain air pollutants (sulfate and ammonium anions) and the risk of autism spectrum disorders (ASD). The study analyzes more than 2 million births in the Ontario region (Canada) between 2002 and 2022.

Although there was previous epidemiological evidence on the relationship between air pollution and ASD, this is the largest study conducted to date, covering a long period of time. Therefore, the importance and significance of this study lies not only in the enormous size of the population sample analyzed, but also in its individual analysis of the effect of individual chemical components and specific periods during pregnancy and early childhood, establishing the last two trimesters of pregnancy as those of greatest susceptibility and risk to these pollutants. Furthermore, they also observe a positive association between postnatal exposure to ozone and an increased risk of ASD.

The study has several limitations:

1. Exposure estimates were assigned to residential zip codes, so they may not fully capture individual-level variability, especially in rural areas. They also did not account for temporal activity patterns, daily mobility, maternal physical activity, housing, or air filtration, which may influence personal exposure.
2. The study does not provide data on the mechanisms of action of pollutants that explain their association with ASD, based on the limited number of previous studies.
3. Potential interactions between air pollutants or factors such as race, ethnicity, lifestyle, differential access to medical care, and behavioral patterns, which may affect associations between prenatal exposure to pollutants and ASD risk, were not considered. Additional studies with more detailed individual-level data would be useful to clarify the observed patterns.