Short-term exposure to sulfur dioxide and daily mortality in Brazil: A nationwide time-series study between 2003-2017.

Sulfur dioxide (SO2), despite its ubiquitousness, there is relatively less epidemiological evidence regarding the health risks associated with SO2 compared to other pollutants, especially in low-income countries where there are high levels of SO2 emissions. In this study, we estimated the association between ambient SO2 exposure and daily mortality in Brazil over a period of 15 years (2003-2017). We used an extension of the two-stage time-series design in a time-series analytic approach with a distributed lag model. The study population consisted of 2,872,084 death records, with a higher proportion of male deaths observed across all-cause mortality (58%). The majority of the individuals were aged above 65 years. The mean SO2 concentration across the study period was 1.5 μg/m³ (range: 0.0 to 71.0). The national meta-analysis for the whole dataset (without stratification by sex and age) showed an uncertain association, in which a 10 μg/m3 increase in daily SO2 was associated with an RR of mortality of 1.015 (95%CI: 0.992; 1.037). Robust associations were observed only for the subgroup analysis of people 46-65 years old [RR = 1.050 (95%CI: 1.004; 1.096)] and men 46-65 years old [RR = 1.064 (95%CI: 1.005; 1.122)]. We found moderate heterogeneity in the national analysis, with an I2 of 21% for the subgroup of people 46-65 years old. Excess mortality fraction for people between 46 and 65 years old attributable to per 10 μg/m3 increase in SO2 was 2.93% (95% eCI: 0.29%-6.78%). These results highlight the need for targeted air pollution control policies to reduce the health burden of SO2 exposure in Brazil. Further research is needed to fully understand the mechanisms behind the age-specific and regional effects of SO2 on mortality.