Reducing Indoor Levels of "Outdoor PM" in Urban China: Impact on Mortalities.

This study estimates adult mortalities attributed to PM across urban China in 2015 and the corresponding mortalities that might be avoided by meeting the yearly averaged indoor PM threshold in the newly established Assessment Standard for Healthy Building (ASHB) and seven other potential thresholds. We use outdoor PM concentrations from ∼1500 monitoring sites in 339 Chinese cities, coupled with a detailed exposure model, to estimate outdoor and indoor exposures to PM originating outdoors. We proceed to calculate premature mortality attributable to PM exposure using an integrated exposure-response model. Results indicate that indoor exposures accounted for 66%-87% of total exposure to PM of outdoor origin and 81% (95% confidence interval (CI), 71%-87%), i.e., 316 000 (95% CI, 176 000-435 000), of the 389 000 (95% CI, 245 000-501 000) mortalities attributable to "outdoor PM" for the urban population ≥25 years of age in China in 2015. Potentially 14 000 (95% CI, 8000-20 000) deaths might be avoided if indoor PM of outdoor origin met the ASHB guideline of 35 μg/m for annual mean indoor PM, and 162 000 (95% CI, 79 000-237 000) deaths might be avoided by meeting a 10 μg/m threshold. The analysis in this work should be helpful in formulating indoor air quality policies.