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

Abstract

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.

Keywords: Air pollution; Cardiovascular; Case-crossover; Coarse particulate matter; Health; Hospitalizations; Mortality; Respiratory; Time-series.

Fig. 1

Forest plot of incidence rate ratios for mortality and hospital admissions per 10 μg/m³ of short-term exposure to PM_10-2.5. Note: Overall estimates are from random-effects models without adjustment for possible publication bias

Fig. 2

Summary incidence rate ratios for short-term exposures to PM_10-2.5 with mortality by study characteristics. Note: Estimates stratified by concentrations include city-specific data from Malig and Ostro [35] and Chock et al. [45] provided via personal correspondence. Estimates were also provided by Zanobetti and Schwartz [••] but ultimately not included because the use of shrunken Bayes estimates could have undue influence on our results

Fig. 3

Summary incidence rate ratios for short-term exposures to PM_10-2.5 with hospital admissions by study characteristics. Note: Estimates stratified by PM concentrations and correlations include city-specific estimates provided by Peng et al. [••] and Host et al. [61] in personal communications

Fig. 4

Incidence rate ratios (RR) for PM_10-2.5 as a function of the correlation between short-term PM_10-2.5 and PM_2.5 concentrations stratified by PM_2.5 associations. Note: Data include city-specific estimates provided by Peng et al. [••] and Host et al. [61] from personal communications

Fig. 5

Summary of rate ratios between long-term exposure to PM_10-2.5 and death per 10 μg/m³