Landscape fire PM_2.5 and hospital admissions for cause-specific cardiovascular disease in urban China

There is a growing interest in the health impacts of PM_2.5 originating from landscape fires. We conducted a time-series study to investigate the association between daily exposure to landscape fire PM_2.5 and hospital admissions for cardiovascular events in 184 major Chinese cities. We developed a machine learning model combining outputs from chemical transport models, meteorological information and observed air pollution data to determine daily concentrations of landscape fire PM_2.5. Furthermore, we fitted quasi-Poisson regression to evaluate the link between landscape fire PM_2.5 concentrations and cardiovascular hospitalizations in each city, and conducted random-effects meta-analysis to pool the city-specific estimates. Here we show that, on a national scale, a rise of 1-μg/m³ in landscape fire PM_2.5 concentrations is positively related to a same-day 0.16% (95% confidence interval: 0.01%–0.32%) increase in hospital admissions for cardiovascular disease, 0.28% (0.12%–0.44%) for ischemic heart disease, and 0.25% (0.02%–0.47%) for ischemic stroke. The associations remain significant even after adjusting for other sources of PM_2.5. Our findings indicate that transient elevation in landscape fire PM_2.5 levels may increase risk of cardiovascular diseases.