Associations of early-life exposure to PM2.5 mass and its components with childhood anemia: A cross-sectional study in China, India, and Africa.

Childhood anemia remains a major public health concern, but evidence regarding the associations of early-life exposure to PM2.5 mass and its components with childhood anemia across regions remains limited. We conducted a cross-sectional study of 449,894 children under 5 years from China, India, and 26 African countries. Prenatal, postnatal, and cumulative exposures to PM2.5 and five components, including black carbon, organic carbon, sulfate, dust, and sea salt, were estimated using NASA's MERRA-2 reanalysis data. The prevalence of childhood anemia was 26.9% in China, 62.6% in India, and 64.5% in Africa. In multivariable logistic regression models, each 1 μg/m3 increase in cumulative PM2.5 exposure was associated with higher odds of childhood anemia in China (odds ratio [OR] = 1.019, 95% confidence interval [CI]: 1.009, 1.028), India (OR = 1.009, 95% CI: 1.008, 1.009), and Africa (OR = 1.001, 95% CI: 1.000, 1.002). Organic carbon and dust also showed positive associations across all three regions. The population attributable fractions (PAFs) for cumulative PM2.5 exposure were 28.46% in China, 10.64% in India, and 0.69% in Africa. Among the individual components, organic carbon and black carbon had the largest positive PAF estimates in China, dust had the largest estimate in India, and organic carbon and dust had the largest positive estimates in Africa. Overall, our findings highlight the potential value of region-specific air-quality strategies that address total PM2.5 mass while prioritizing locally relevant components, particularly carbonaceous aerosols in China, dust-related PM2.5 in India, and organic carbon and dust in Africa.