Effect of mortality risk from combined exposure to five metal components in ambient PM_2.5 in Harbin

Objective To quantitatively assess the exposure-response relationship and joint effects of combined exposure to metal components in fine particulate matter (PM_2.5) on population mortality in Harbin.

Methods Daily mortality data as well as daily meteorological and ambient air pollution data of Harbin city between 2013 and 2018 were collected from the monitoring system. Ambient PM_2.5 was collected to determine the concentrations of metal components, and the daily concentrations of metal components were predicted using a random forest model. Quantile g-computation (qgcomp) was used to estimate the joint effect of combined exposure to metals in PM_2.5 on non-accidental, cardiovascular, and respiratory mortalities, and to identify the susceptible populations. Sensitivity analysis was performed using weighted quantile sum regression (WQS).

Results From 2013 to 2018, the median daily average numbers of non-accidental, cardiovascular, and respiratory deaths in Harbin city were 75, 42, and 7, respectively. For every one quartile increase in combined PM_2.5 metal exposure, the relative risk was 1.026 (95% confidence interval CI: 1.010-1.043) for non-accidental mortality and 1.038 (95% CI: 1.016-1.060) for cardiovascular mortality. Stratified analysis showed that males and elderly individuals (≥60 years old) were susceptible to combined PM_2.5 metal exposure. Sensitivity analysis further confirmed the robustness of the above results and indicated that arsenic had the greatest contribution to population mortality.

Conclusion Combined exposure to metal components in PM_2.5 increases the risks of non-accidental and cardiovascular mortalities, and males and people aged 60 and above are susceptible to combined metal exposure.