Pagalan L, et al. - In a large population cohort, researchers assessed the relationship between prenatal exposures to airborne pollutants and autism spectrum disorder (ASD). An association was found between exposure to nitric oxide (NO) and ASD but no significant association with PM_2.5 and nitrogen dioxide (NO₂) in a population-based birth cohort. Findings suggested that reducing the exposure of pregnant women to environmental NO might lead to a reduction in the incidence of ASD in their children.

Methods

• This population-based cohort included almost all births in Metro Vancouver, British Columbia, Canada between 2004 and 2009, followed by 2014.
• ASD was diagnosed in children using a standardized assessment with the Autism Diagnostic Interview–Revised and Autism Diagnostic Observation Schedule.
• Monthly mean exposures to particulate matter smaller than 2.5 μm (PM_2.5) in diameter, NO, and NO₂ during pregnancy at maternal residence were estimated using temporally adjusted, high-resolution land use regression models.
• Using logistic regression adjusted for child sex, birth month, birth year, maternal age, maternal birthplace, and neighborhood-level urbanicity and income band, the relationship between prenatal air pollution exposures and the odds of developing ASD was assessed.
• The analysis of data took place between June 2016 and May 2018.
• Using temporally adjusted, high-resolution land use regression models, mean monthly concentrations of ambient PM_2.5, NO, and NO₂ at the maternal residence during pregnancy, calculated retrospectively.
• Main outcomes and measures included autism spectrum disorder diagnoses based on standardized assessment of the Autism Diagnostic Interview–Revised and Autism Diagnostic Observation Schedule.
• The hypothesis was formulated during the collection of data.

Results

• One thousand, three hundred seven children (1.0%) were diagnosed with ASD at the age of five years in a cohort of 132,256 births.
• The final sample size for the PM_2.5-adjusted model was 129,439 children and 129,436 children were diagnosed with ASD for NO and NO₂, of whom 1276 (1.0%) were diagnosed.
• Findings revealed that adjusted odds ratios for ASD per interquartile range (IQR) were not significant for exposure to PM_2.5 during pregnancy (1.04 [95% CI, 0.98-1.10] per 1.5 μg/m3increase [IQR] in PM_2.5) or NO₂ (1.06 [95% CI, 0.99-1.12] per 4.8 ppb [IQR] increase in NO₂), however, the odds ratio was significant for NO (1.07 [95% CI, 1.01-1.13] per 10.7 ppb [IQR] increase in NO).
• It was noted that odds ratios for male children were 1.04 (95% CI, 0.98-1.10) for PM_2.5; 1.09 (95% CI, 1.02-1.15) for NO; and 1.07 (95% CI, 1.00-1.13) for NO₂.
• Odds ratios for female children were 1.03 (95% CI, 0.90-1.18) for PM_2.5; 0.98 (95% CI, 0.83-1.13) for NO; and 1.00 (95% CI, 0.86-1.16) for NO₂.