Urban-rural differences in the association between long-term exposure to ambient particulate matter (PM) and malnutrition status among children under five years old: A cross-sectional study in China

BACKGROUND: The evidence regarding the relationship between postnatal exposure of air pollution and child malnutrition indicators, as well as the corresponding urban-rural disparities, is limited, especially in low-pollution area of low- and middle-income countries (LMICs). Therefore, our aim was to contrast the effect estimates of varying ambient particulate matter (PM) on malnutrition indicators between urban and rural areas in Tibet, China. METHODS: Six malnutrition indicators were evaluated in this study, namely, Z-scores of height for age (HFA), Z-scores of weight for age (WFA), Z-scores of weight for height (WFH), stunting, underweight, and wasting. Exposure to particles with an aerodynamic diameter ≤2.5 micron (μm) (PM(2.5)), particles with an aerodynamic diameter ≤10 μm (PM(10)) and particles with an aerodynamic diameter between 2.5 and 10 μm (PM(c)) was estimated using satellite-based random forest models. Linear regression and logistic regression models were used to assess the associations between PM and the above malnutrition indicators. Furthermore, the effect estimates of different PM were contrasted between urban and rural areas. RESULTS: A total of 2511 children under five years old were included in this study. We found long-term exposure to PM(2.5), PM(c), and PM(10) was associated with an increased risk of stunting and a decreased risk of underweight. Of these air pollutants, PM(c) had the strongest association for Z-scores of HFA and stunting, while PM(2.5) had the strongest association for underweight. The results showed that the odds ratio (OR) for stunting were 1.36 (95% confidence interval (CI) = 1.06 to 1.75) per interquartile range (IQR) microgrammes per cubic metre (μg/m(3)) increase in PM(2.5), 1.80 (95% CI = 1.30 to 2.50) per IQR μg/m(3) increase in PM(c) and 1.55 (95% CI = 1.17 to 2.05) per IQR μg/m(3) increase in PM(10). The concentrations of PM were higher in urban areas, and the effects of PM on malnutrition indicators among urban children were higher than those of rural children. CONCLUSIONS: Our results suggested that PM exposure might be an important trigger of child malnutrition. Further prospective researches are needed to provide important scientific literature for understanding child malnutrition risk concerning postnatal exposure of air pollutants and formulating synthetically social and environmental policies for malnutrition prevention.