Identifying child growth effects of elevated pollution levels during pregnancy

Abstract

Poor air quality is known to be one of the leading contributors to poor child health globally, and a wealth of evidence has linked pollution exposure during pregnancy to adverse birth and early-life outcomes. While there is some evidence pollution exposure during pregnancy is associated with slowed child growth, this evidence is largely limited to empirical settings in which it is difficult to disentangle the role of pollution from other co-varying factors. Here we rely on quasi-random variation in pollution conditions induced by thermal inversions to estimate the impact of pollution spikes during pregnancy on childhood stunting. We find that thermal inversions during pregnancy worsen air quality and increase the likelihood of childhood stunting, but only in places with poor baseline air quality and particularly for younger children and in lower-wealth communities. Our estimates imply that a 1  µg m⁻³ increase in average PM_2.5 concentration during pregnancy increases the probability of stunting by an average of 4.1 percentage points (95% CI: 0.2–8.0). This translates to an 11.2% increase (95% CI: 0.6%–21.9%) in stunting risk from the sample baseline of 37% children stunted. Our results suggest that policies that limit baseline daily PM_2.5 levels, particularly during seasons when thermal inversions are more frequent, have potential to generate meaningful improvements in long-run child outcomes.