Association of size-fractionated particulate matters and their chemical constituents with airway inflammation and lung function among healthy children: A panel study

Evidence is limited regarding size-fractionated particulate matters and their constituents responsible for children's respiratory health. To investigate the short-term effects of size-fractionated particle number counts (PNCs) and their chemical constituents on airway inflammation and lung function in healthy children. We conducted a longitudinal panel study involving 3 repeated surveys among 144 children aged 4–12 years in Guangzhou, China. Lung function and the fractional exhaled nitric oxide (FeNO) were measured during each visit. The real-time multi-size PNCs and their 23 constituent counts were obtained from the environmental monitoring station. We applied linear mixed-effects (LME) models, least absolute shrinkage and selection operator (LASSO) regression, and Bayesian kernel machine regression (BKMR) to evaluate the associations. Each interquartile range (IQR) increase in PNC0.5 was dose-responsive associated with 10.46% (95% CI: 2.54%, 18.98%) increase in FeNO at lag 0 day and 1.12% (95% CI: -1.90%, −0.33%) decrease in the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) at lag 1 day. But results for PNC1.0 and PNC2.5 were not significant. In LASSO regression models, K+, NH4+, and HSO4− were important predictors for FeNO, while Mg+, NH4+, and Mn+ were significant predictors for FEV1/FVC. Additionally, the overall effects of constituent mixture on higher FeNO or lower FEV1/FVC were robust when the mixture was above the 55th or 65th percentiles in PNC0.5 compared to the median. And a significant association between exposure to NH4+ and FeNO increment was identified, when setting all other constituents at the 25th, 50th and 75th percentiles. Short-term exposure to PNC0.5 was dose-responsive related to increased FeNO and decreased FEV1/FVC among healthy children, and NH4+ in PNC0.5 might play a more dominant role in airway inflammation.