Long-Term PM2.5 Exposure and Timing of Pubertal Development in Boys and Girls: A Prospective Cohort Study in Chongqing, China.
BACKGROUND PM2.5, a ubiquitous air pollutant with endocrine-disrupting potential, may contribute to the global trend of earlier puberty, yet evidence remains limited to isolated milestones and largely excludes boys. METHODS We analyzed 3,833 children from the Chongqing Child Health Cohort (2014-2024). Time-varying PM2.5 exposure was defined as cumulative average residential PM2.5 from the prenatal period to milestone onset or censoring. Cox models were used to examine associations between cumulative average PM2.5 exposure and the timing of multiple pubertal milestones, with stratification by weight status and underlying health conditions and evaluation of whether these associations varied according to long-term average temperature and relative humidity. RESULTS In girls, each 1 μg/m3 increase in cumulative average PM2.5 exposure was associated with earlier breast development (HR = 1.044, 95% CI: 1.039-1.050), pubic hair (HR = 1.038, 95% CI: 1.032-1.045) and menarche (HR = 1.033, 95% CI: 1.025-1.040), with a weaker association for axillary hair development (HR = 1.012, 95% CI: 1.005-1.020). In boys, each 1 μg/m3 increase was associated with earlier testicular development (HR = 1.065, 95% CI: 1.056-1.073), penile development (HR = 1.063, 95% CI: 1.055-1.071), pubic hair (HR = 1.032, 95% CI: 1.022-1.041), and beard development (HR = 1.032, 95% CI: 1.023-1.041), with a weaker association for spermatorrhea (HR = 1.024, 95% CI: 1.003-1.046). Associations varied by weight status and according to long-term average temperature and relative humidity, with stronger associations for several milestones among overweight/obese girls and stronger associations overall in areas with higher long-term average temperatures and lower long-term relative humidity. CONCLUSION Long-term PM2.5 exposure is associated with earlier onset of secondary sexual characteristics and key reproductive milestones across the pubertal trajectory. The observed associations varied according to long-term average temperature, relative humidity, and weight status, suggesting heterogeneity according to both background environmental conditions and individual susceptibility.