Wildfire-related PM_2.5 and cardiovascular mortality: A difference-in-differences analysis in Brazil

Brazil has experienced unprecedented wildfires recently. We aimed to investigate the association of wildfire-related fine particulate matter (PM_2.5) with cause-specific cardiovascular mortality, and to estimate the attributable mortality burden. Exposure to wildfire-related PM_2.5 was defined as exposure to annual mean wildfire-related PM_2.5 concentrations in the 1-year prior to death. The variant difference-in-differences method was employed to explore the wildfire-related PM_2.5-cardiovascular mortality association. We found that, in Brazil, compared with the population in the first quartile (Q1: ≤1.82 μg/m³) of wildfire-related PM_2.5 exposure, those in the fourth quartile (Q4: 4.22-17.12 μg/m³) of wildfire-related PM_2.5 exposure had a 2.2% (RR: 1.022, 95% CI: 1.013-1.032) higher risk for total cardiovascular mortality, 3.1% (RR: 1.031, 95% CI: 1.014-1.048) for ischaemic heart disease mortality, and 2.0% (RR: 1.020, 95% CI: 1.002-1.038) for stroke mortality. From 2010 to 2018, an estimation of 35,847 (95% CI: 22,424-49,177) cardiovascular deaths, representing 17.77 (95% CI: 11.12-24.38) per 100,000 population, were attributable to wildfire-related PM_2.5 exposure. Targeted health promotion strategies should be developed for local governments to protect the public from the risk of wildfire-related cardiovascular premature deaths.