A review and analysis of personal and ambient PM2.5 measurements: Implications for epidemiology studies.

Abstract Background In epidemiology studies, ambient measurements of PM2.5 are often used as surrogates for personal exposures. However, it is unclear the degree to which ambient PM2.5 reflects personal exposures. Objective In order to examine potential sources of bias in epidemiology studies, we conducted a review and meta-analysis of studies to determine the extent to which short-term measurements of ambient PM2.5 levels are related to short-term measurements of personal PM2.5 levels. Methods We conducted a literature search of studies reporting both personal and ambient measurements of PM2.5 published in the last 10 years (2009–2019) and incorporated studies published prior to 2009 from reviews. Results Seventy-one studies were identified. Based on 17 studies reporting slopes, a meta-analysis revealed an overall slope of 0.56 μg/m3 (95% CI: [0.39, 0.73]) personal PM2.5 per μg/m3 increase in ambient PM2.5. Slopes for summer months were higher (slope = 0.73, 95% CI: [0.64, 0.81]) than for winter (slope = 0.46, 95% CI: [0.36, 0.57]). Based on 44 studies reporting correlations, we calculated an overall personal-ambient PM2.5 correlation of 0.63 (95% CI: [0.55, 0.71]). Correlations were stronger in studies conducted in Canada (r = 0.86, 95% CI: [0.67, 0.94]) compared to the USA (r = 0.60, 95% CI: [0.49, 0.70]) and China (r = 0.60, 95% CI: [0.46, 0.71]). Correlations also were stronger in urban areas (r = 0.53, 95% CI: [0.43, 0.62]) vs. suburban areas (r = 0.36, 95% CI: [0.21, 0.49]). Significance Our results suggest a large degree of variability in the personal-ambient PM2.5 association and the potential for exposure misclassification and measurement error in PM2.5 epidemiology studies.