Exploratory thresholds for ambient PM2.5 constituents in relation to blood pressure levels in Chinese children

This study aimed to examine the associations of fine particulate matter (PM 2.5 ) constituents and their interactions with meteorological factors with blood pressure (BP) among Chinese school-aged children, to inform targeted protection strategies. We analyzed 16,446 children from the Zhongshan Student Growth Cohort, with annual physical examinations conducted from 2006 to 2020 in Southeast China. Bayesian kernel machine regression (BKMR), weighted quantile sum (WQS), distributed lag non-linear models (DLNMs) and restricted cubic splines (RCS) were used to analyze the joint effects, exposure-response threshold, and effect modification by meteorological factors of PM 2.5 constituents on BP. Overall, 20.2% were classified with high blood pressure (HBP). Each IQR increase in PM 2.5 over lag0-14d was associated with a higher risk of HBP ( RR = 1.97, 95% CI : 1.61–2.34) among overweight children. BKMR and WQS models consistently revealed joint effects of PM 2.5 constituents on BP, with Black carbon (BC) as the dominant driver. RCS models established non-linear exposure-response relationships and suggested potential threshold concentrations for key components (BC: 1.98 µg/m³). Notably, both low temperature and low relative humidity (RH) significantly amplified the toxicity of PM 2.5 constituents. PM 2.5 constituents were adversely associated with BP in children, particularly for BC. These associations were modified by meteorological factors, with both low temperature and low RH exacerbating the adverse effects. These findings highlight the importance of considering meteorological factors in developing evidence-based air quality guidelines.