Cumulative Household Solid Fuel Use, Mediating Factors, and All-Cause and Cardiovascular Mortality in Chinese Adults: A Prospective Cohort Study

Household air pollution from solid fuel use affects approximately 2.67 billion people globally. However, robust evidence on cumulative dose-response relationships and underlying mediating mechanisms remains limited. We conducted a prospective cohort study among 45170 Chinese adults followed for a median of 10.8 years. Cumulative exposure indices were developed for cooking and heating using information on fuel type, duration, and intensity. Mortality outcomes were ascertained through registry linkage. Fuel stacking was reported by 25.4% of participants for cooking and 12.9% for heating. After adjusting for concurrent fuel use, each 50 h-year increase in biomass use for cooking was associated with higher risks of all-cause mortality (hazard ratio [HR] = 1.18, 95% CI 1.09-1.28) and cardiovascular mortality (HR = 1.22, 95% CI 1.10-1.35), compared with clean fuel use. Biomass and coal use for heating showed similar positive associations, with HRs ranging from 1.09 to 1.15. These associations followed monotonic linear exposure-response patterns. Mediation analyses indicated that pulmonary function indices, blood pressure, and specific hematological markers partially explain the observed mortality risks. These findings underscore the importance of reducing cumulative solid fuel use and strengthening early clinical risk monitoring to mitigate the fatal health burden among populations with persistent exposure.