Evidence of provincial variability in air pollutants-asthma relations in China

Exposure to air pollutants is a significant trigger of asthma in China. However, there is little evidence of which pollutants are associated most with asthma at the national level, and little research on pollutants' critical values based on concentration-response (C-R) curves. Further, the potential influential variables of air pollutants have not been identified clearly. In this study, logistic regression analyses were used to evaluate the associations between air pollutants and asthma based on 14176 samples across 12 provinces in China in 2015. We also fit a generalized additive model to evaluate the nonlinear C-R curves to identify the critical values. Our results showed that PM10-2.5 (odds ratios, 95% confidence intervals: 0.95, 0.90 -1.00) and NOX (odds ratios, 95% confidence intervals: 0.98, 0.96-1.00) were associated significantly with asthma's prevalence (p < 0.05) in China, in which the correlation between NOX pollution and asthma's prevalence was relatively more significant. The risk of asthma increased significantly when the average annual PM10-2.5 and NOX concentrations exceeded approximately 40 mg/m(3) and 67 mg/m(3), respectively. The results of structural equation modelling confirmed that economic scale was the most important driving force for PM10-2.5 and NOX pollution. Economic scale primarily had a direct influence on increased PM10-2.5 concentrations, while it primarily had an indirect influence on increased NOX concentrations. Our findings contribute to the limited evidence on PM10-2.5 and NOX pollution's effects on asthma's prevalence in China. (c) 2019 Elsevier Ltd. All rights reserved.