Joint effects of PM 2.5 pollution and cold waves exposure on population health risks in Shijiazhuang, China.
Li M, Li F, Chen S, Ding Y, Chen F, Shen Q, Bao L, Wang Y, Ji Y, Kang H
Abstract
Against the backdrop of global climate change, joint exposure events involving cold waves and PM 2.5 pollution pose a serious threat to public health. However, research on the joint effects of these factors on mortality risk among residents, particularly in North China, remains limited. This study employed a "joint exposure" analytical framework, utilizing mortality data, meteorological records, and PM 2.5 concentration data from Shijiazhuang City between 2017 and 2024. Events where cold waves and PM 2.5 pollution occurred simultaneously were defined as joint exposures. Twelve exposure combinations were constructed using three cold waves thresholds (T1-T3) and four PM 2.5 pollution thresholds (P1-P4). A distributed lag nonlinear model assessed their risks for non-accidental mortality, circulatory disease mortality, and respiratory disease mortality. The findings showed that joint exposure to cold waves and PM 2.5 was significantly associated with increased mortality risks. The relative risks for non-accidental mortality and circulatory/respiratory disease mortality peaked at the P4T1 combination, reaching 2.55 (95% CI: 1.82, 3.57), 2.62 (95% CI: 1.76, 3.92), and 2.34 (95% CI: 1.18, 4.65), respectively. Interaction analysis revealed a significant synergistic effect, with a synergy index of 1.54 (95% CI: 1.05, 2.03) for the P3T2 combination, indicating significant super-additivity. Attribution analysis indicated a substantial disease burden attributable to the joint events, with the attributable fraction for non-accidental mortality reaching 60.8% under the P4T1 combination, corresponding to 883 attributable deaths. Subgroup analysis revealed greater vulnerability among the elderly (≥ 75 years), males, and individuals with lower education levels. Joint exposure to cold waves and PM 2.5 pollution was significantly associated with elevated mortality risk among Shijiazhuang residents. It was recommended that such joint environmental events be incorporated into public health early warning systems to implement targeted health protection measures.