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.