*2.1. PM2.5 Air Pollution Exposure*

The yearly mean PM2.5 concentration over China was assessed by using the satellite remote sensing technology. Firstly, spectral data from the two moderate resolution imaging spectroradiometer (MODIS) instruments aboard the Terra and Aqua satellites were used to build aerosol optical depth (AOD) data at a resolution of 0.01◦ × 0.01◦, over China [21]. Secondly, an observational data-driven algorithm, which took the ground-observed visibility and relative humidity data as inputs, was developed to derive the yearly mean ground-level PM2.5 concentration from the AOD [22]. Evaluation of the long-term satellitederived PM2.5 concentration against the ground observations demonstrated a correlation coefficient of >0.9 and a mean absolute percentage error within ±20% [23]. The mean concentration of PM2.5 over a single year was registered, corresponding to the study year of each subject.
