Association between compound PM2.5-cold events and population-specific mortality: a time-trend ecologic study of damage amplification in Zigong, China

Abstract Background With the global increase in extreme weather events, understanding the effects of consecutive extreme PM 2.5 (EPM) and cold spells (CS) events on specific mortality is vital. Methods Daily meteorological, air pollution, and mortality data were collected in Zigong. Using the Distributed Lag Nonlinear Model (DLNM), we defined the lag as 14 days and quantified the risk effect of EPM-CS events (P 95 for EPM, P 7.5 for CS) on resident mortality and explored the potential amplification of damage resulting from different patterns of sequential extreme events. Additionally, we calculated the attributable fraction (AF) of extreme events and conducted stratified analyses based on age, gender, marital status, etc. Results Exposure to cold spells, PM 2.5 , and compound events was statistically associated with an increased risk of mortality. The cumulative rate ratios (CRRs) of EPM-CS events for total non-accidental mortality was 1.56(1.44,1.69). The mortality risks of EPM-CS events in females, elderly people ≥ 65 years, low level of education, and widowed, divorced, and never married were higher, with AF were 6.64%(95%CI: 5.42%, 7.89%),6.51%(95%CI: 5.52%, 7.51%), 6.10%(95%CI: 5.17%, 7.06%) and 7.73%(95%CI: 6.07%, 8.51%), respectively. The attributable fraction of specific mortality due to the EPM-CS events was the highest for cerebrovascular disease. Exposure to combined events was associated with a substantial increase in mortality risk, and the damaging effect of combined events occurring in the short term was more significant. Conclusion Our findings demonstrated synergistic mortality risks from compound cold and pollution exposure, highlighting a disproportionate impact on vulnerable populations. This evidence supports the rationale for developing integrated early warning systems as a targeted intervention.