Associations between air pollution and surrounding greenness with internalizing and externalizing behaviors among...

Air pollution and greenness are emerging as modifiable risk and protective factors, respectively, in child psychopathology. However, research shows inconsistencies. Here, we examined associations between air pollution and surrounding greenness with internalizing and externalizing behaviors. In addition, the potential modifying role of the genetic susceptibility for these traits and socioeconomic status (SES) was explored.

This population-based study included 4485 schoolchildren aged 5-18 years from Spain. Internalizing and externalizing behaviors were assessed using the Child Behavior Checklist (CBCL). Average air pollution (NO₂, PM_2.5, PM₁₀, PM_coarse, and PM_2.5 absorbance) and surrounding greenness (NDVI within 100-m, 300-m, and 500-m buffers) school exposure were estimated for 12 months before outcome assessment. Genetic liability was assessed by computing polygenic risk scores (PRS) and SES was calculated using the Hollingshead Four-Factor Index. Associations were analyzed using negative binomial mixed-effects models.

Although no associations survived multiple testing, we found that increases of 5.48 μg/m³ in PM₁₀ and 2.93 μg/m³ in PM_coarse were associated with a 6% (Mean Ratio (MR) = 1.06; 95% CI: 1.01-1.12) and a 4% (MR = 1.04; 95% CI: 1.00-1.09) increase in internalizing behavior scores. A 0.1 increase in NDVI within a 100-m buffer was associated with a 6% decrease in externalizing behavior (MR = 0.94; 95% CI: 0.89-0.99). Neither differences by sex or age, or moderation effects by PRS or SES, were observed.

We found preliminary evidence of detrimental effects of air pollution on internalizing behavior and protective effects of greenness on externalizing behavior, which were not modified by sex, age, SES, or genetic liability. If confirmed, these results reinforce the need for improving air quality, especially around schools, as part of preventive strategies focused on childhood psychopathology.