Ambient Coarse Particulate Matter and Human Health: A Systematic Review and Meta-Analysis

Airborne particles have been linked to increased mortality and morbidity. As most research has focused on fine particles (PM_2.5), the health implications of coarse particles (PM_10-2.5) are not well understood. We conducted a systematic review and meta-analysis of associations for short- and long-term PM_10-2.5 concentrations with mortality and hospital admissions. Using 23 mortality and 10 hospital admissions studies, we documented suggestive evidence of increased morbidity and mortality in relation to higher short-term PM_10-2.5 concentrations, with stronger relationships for respiratory than cardiovascular endpoints. Reported associations were highly heterogeneous, however, especially by geographic region and average PM_10-2.5 concentrations. Adjustment for PM_2.5 and publication bias resulted in weaker and less precise effect estimates, although positive associations remained for short-term PM_10-2.5 concentrations. Inconsistent relationships between effect estimates for PM_10-2.5 and correlations between PM_10-2.5 and PM_2.5 concentrations, however, indicate that PM_10-2.5 associations cannot be solely explained by co-exposure to PM_2.5. While suggestive evidence was found of increased mortality with long-term PM_10-2.5 concentrations, these associations were not robust to control for PM_2.5. Additional research is required to better understand sources of heterogeneity of associations between PM_10-2.5 and adverse health outcomes.