Long-Term Exposure to Fine Particulate Matter (PM2.5) Components and Precocious Puberty Among School-Aged Children: Cross-Sectional Study

Background: The increasing incidence of precocious puberty is a major health challenge for Chinese children, while related risk factors remain less well explored. Exposure to ambient fine particulate matter (PM2.5) is a leading environmental hazard in China. Although certain components of PM2.5 have been reported to be endocrine disruptors for sex hormones, population-based evidence is still lacking on the association between PM2.5 exposure and precocious puberty in China. Objective: Based on a cross-sectional survey covering 30 cities in 2017 to 2019, this study was designed to explore the association between long-term exposure to PM2.5 and its 5 major components with precocious puberty in China and to check the potential modifying effects of family-related and personal factors. Methods: We included 34,105 children aged 6 to 9 years. We collected the 5-year average concentrations of PM2.5 and its 5 major components (sulfate, nitrate, ammonium, organic matter, and black carbon) in the area (at a spatial resolution of 0.1 degrees x 0.1 degrees) where each school was located. We used mixed effect logistic regression to estimate the effect sizes of the total mass of PM2.5 and each of its components on precocious puberty, and we examined the modifying effects of family-related and personal factors using an additional interactive term. A weighted quantile sum (WQS) regression model was applied to identify the weights of each component in explaining the effect size of the total mass of PM2.5. Results: We found that the odds ratio (OR) for precocious puberty per IQR increase in the concentration of total PM2.5 mass was 1.27 (95% CI 0.92-1.75) for the whole population, 2.12 (95% CI 1.27-3.55) for girls, and 0.90 (95% CI 0.62-1.30) for boys. Similarly, the effect sizes of the 5 major components were all substantial for girls but minimal for boys. Results of the WQS analysis showed that organic matter could explain the highest proportion of the effect of PM2.5, with the weight of its contribution being 0.71. Modification effects of family income and dietary habits were only observed in certain population subgroups. Conclusions: Long-term exposure to total PM2.5 mass was significantly associated with precocious puberty in girls, with organic matter identified as the major effect contributor. The results add evidence on the detrimental effects of PM2.5 on children's development and growth.