Association of short-term exposure to air pollutants with mortality from respiratory diseases: a case-crossover study of individual cases based in Hefei, China.

BACKGROUND

Although short-term exposure to air pollutants has been linked to heightened hospital admissions for respiratory diseases (RDs), evidence regarding its association with the risk of mortality from such diseases remains scarce. We aimed to examine the impact of short-term exposure to air pollutants on RD-related mortality.

METHODS

We employed a time-stratified case-crossover design to explore the impact of short-term exposure to various air pollutants (fine particulate matter (PM), coarse particulate matter (PM), nitrogen dioxide (NO2), sulfur dioxide (SO), carbon monoxide (CO), and ozone (O)) on mortality due to RDs. Our sample comprised 15 878 RD-related deaths that occurred between 2017 and 2020 in Hefei, Anhui province. We delineated daily exposure to air pollutants using raster data corresponding to the residential addresses of the study subjects. We used conditional logistic regression to assess the relationship between pollutant exposure and the risk of mortality. To improve precision in identifying vulnerable populations, we stratified individuals by gender and age. Lastly, we used interrupted time series (ITS) analysis to explore COVID-19's impact on RD mortality.

RESULTS

We found that every 10 μg/m3 increase in PM, PM, and CO at a lag of zero days was associated with the largest significant effect on increased mortality from RDs (excess mortality risks of 0.735%, 1.349%, and 0.160%, respectively). We observed the highest positive associations between NO and O with delays of one and two days, resulting in excess mortality risks of 1.965% and 0.861%, respectively. We obtained consistent findings through moving average concentration analysis, while our stratified analysis showed that females and the elderly exhibited a heightened susceptibility to mortality from RDs attributable to short-term exposure to pollutants. Additionally, the ITS analysis confirmed that the COVID-19 outbreak did not significantly alter the level and trend of RD deaths.

CONCLUSIONS

Our findings indicate that short-term exposure to air pollutants, excluding SO, increases mortality rates from RDs, particularly among women and the elderly. In the context of Hefei, our findings highlight the public health imperative for reducing local residents' exposure to air pollutants, particularly through targeted protection of vulnerable populations, to minimise preventable RD mortality.