Environmental and Occupational Health

BACKGROUND: Evidence from developed countries suggests that fine particulate matter (≤2.5 µm [PM]) contributes to childhood respiratory morbidity and mortality. However, few analyses have focused on resource-limited settings, where much of this burden occurs. We aimed to investigate the cross-sectional associations between annual average exposure to ambient PM and acute respiratory infection (ARI) in children aged <5 years living in low- and middle-income countries (LMICs).

METHODS: We combined Demographic and Health Survey (DHS) data from 35 countries with gridded global estimates of annual PM mass concentrations. We analysed the association between PM and maternal-reported ARI in the two weeks preceding the survey among children aged <5 years living in 35 LMICs. We used multivariable logistic regression models that adjusted for child, maternal, household and cluster-level factors. We also fitted multi-pollutant models (adjusted for nitrogen dioxide [NO] and surface-level ozone [O]), among other sensitivity analyses. We assessed whether the associations between PM and ARI were modified by sex, age and place of residence.

RESULTS: The analysis comprised 573,950 children, among whom the prevalence of ARI was 22,506 (3.92%). The mean (±SD) estimated annual concentration of PM to which children were exposed was 48.2 (±31.0) µg/m. The 5th and 95th percentiles of PM were 9.8 µg/m and 110.9 µg/m, respectively. A 10 µg/m increase in PM was associated with greater odds of having an ARI (OR: 1.06; 95% CI: 1.05-1.07). The association between PM and ARI was robust to adjustment for NO and O. We observed evidence of effect modification by sex, age and place of residence, suggesting greater effects of PM on ARI in boys, in younger children, and in children living in rural areas.

CONCLUSIONS: Annual average ambient PM, as an indicator for long-term exposure, was associated with greater odds of maternal-reported ARI in children aged <5 years living in 35 LMICs. Longitudinal studies in LMICs are required to corroborate our cross-sectional findings, to further elucidate the extent to which lowering PM may have a role in the global challenge of reducing ARI-related morbidity and mortality in children.