PM₁₀ exposure and non-accidental mortality in Asian populations: A meta-analysis of time-series and case-crossover studies

Objectives: We investigated the association between particulate matter less than 10 μm in aerodynamic diameter (PM₁₀) exposure and non-accidental mortality in Asian populations by meta-analysis, using both time-series and case-crossover analysis. Methods: Among the 819 published studies searched from PubMed and EMBASE using key words related to PM ₁₀ exposure and nonaccidental mortality in Asian countries, 8 time-series and 4 case-crossover studies were selected for meta-analysis after exclusion by selection criteria. We obtained the relative risk (RR) and 95% confidence intervals (CI) of non-accidental mortality per 10 μg/m³ increase of daily PM₁₀ from each study. We used Q statistics to test the heterogeneity of the results among the different studies and evaluated for publication bias using Begg funnel plot and Egger test. Results: Testing for heterogeneity showed significance (p<0.001); thus, we applied a random-effects model. RR (95% CI) per 10 μg/m³ increase of daily PM₁₀ for both the time-series and case-crossover studies combined, time-series studies relative risk only, and casecrossover studies only, were 1.0047 (1.0033 to 1.0062), 1.0057 (1.0029 to 1.0086), and 1.0027 (1.0010 to 1.0043), respectively. The nonsignificant Egger test suggested that this analysis was not likely to have a publication bias. Conclusions: We found a significant positive association between PM₁₀ exposure and non-accidental mortality among Asian populations. Continued investigations are encouraged to contribute to the health impact assessment and public health management of air pollution in Asian countries.