Estimation of personal exposure to fine particles (PM _2.5 ) of ambient origin for healthy adults in Hong Kong

Personal exposure and ambient fine particles (PM _2.5 ) measurements for 13 adult subjects (ages 19–57) were conducted in Hong Kong between April 2014 and June 2015. Six to 21 personal samples (mean = 19) per subject were obtained throughout the study period. Samples were analyzed for mass by gravimetric analysis, and 19 elements (from Na to Pb) were analyzed using X-Ray Fluorescence. Higher subject-specific correlations between personal and ambient sulfur (r _s = 0.92; p < 0.001) were found as compared to PM _2.5 mass (r _s = 0.79; p < 0.001) and other elements (0.06 < r _s < 0.86). Personal vs. ambient sulfur regression yielded an average exposure factor (F _pex ) of 0.73 ± 0.02, supporting the use of sulfur as a surrogate to estimate personal exposure to PM _2.5 of ambient origin (E _a ). E _a accounted for 41–82% and 57–73% of total personal PM _2.5 exposures (P) by season and by subject, respectively. The importance of both E _a and non-ambient exposures (E _na , 11.2 ± 5.6 μg/m ³ ; 32.5 ± 10.9%) are noted. Mixed-effects models were applied to estimate the relationships between ambient PM _2.5 concentrations and their corresponding exposure variables (E _a , P). Higher correlations for E _a (0.90; p < 0.001) than for P (0.58; p < 0.01) were found. A calibration coefficient < 1 suggests an attenuation of 22% (ranging 16–28%) of the true effect estimates when using average ambient concentrations at central monitoring stations as surrogates for E _a . Stationary ambient data can be used to assess population exposure only if PM exposure is dominated by E _a .