[Correlation study between respiratory death and airborne particles in Beijing: Spatiotemporal analysis based on...

To use vertical and humidity correcting method to calibrate aerosol optical depth (AOD), and to explore the feasibility of calibrated-AOD as exposure index to measure the level of air pollutants from the ground and to establish the exposure-response relationship between calibrated-AOD and people's health outcomes.

First of all, we interpolated AOD, PM_2.5, relative humidity and planetary boundary layer height using Kriging method to obtain data at different locations and matched different data with respiratory death in Beijing by geographical coordinates. Then, the planetary boundary layer height and aerosol hygroscopic growth factor calculated based on relative humidity was used to calbrate the AOD. To compare the effects of calibrated-AOD and PM_2.5, we used standardization method to get non dimensionless calibrated-AOD and PM_2.5. At last, we used the generalized additive mixed model (GAMM) to estimate the acute effects of calibrated-AOD and PM_2.5 on respiratory death and chronic obstructive pulmonary disease (COPD) death, after controlling the time trend, temperature and humidity effects, days of the week effect and holiday effects.

The correlation coefficient between calibrated-AOD and PM_2.5 was 0.72. The effects of calibrated-AOD on respiratory death and COPD death was the strongest at lag 0-3, one unit of calibrated-AOD increases was associated with 3.64% (95%CI: 0.58%-6.78%) increase of respiratory death and 4.92% (95%CI: 1.81%-8.14%) increase of COPD death. As for PM_2.5, the strongest effects appeared at lag 0-1, one unit of PM_2.5 (about 155 μg/m³) increases was associated with excess risks of 3.96% (95%CI: 0.82%-7.19%) and 6.12% (95%CI: 1.44%-11.02%) for respiratory death and COPD death respectively. Compared with PM_2.5, the effects of calibrated-AOD on respiratory death and COPD death had narrower confidence intervals. The calibrated-AOD was sensitive to capture the lag effects, and the cumulative lag effects of calibrated-AOD were all significant on multiple lag days which indicated that the calibrated-AOD was sensitive to capture cumulative lag effects of air pollutants on respiratory death and COPD death as well.

We believe that calibrated-AOD can be used as an index to reflect the effects of air pollutants on respiratory death in Beijing. In the absence of ground monitoring, calibrated-AOD can be used to mea-sure the relationship between air pollutants and some health outcomes.