The association between gaseous pollutants and non-accidental mortality: a time series study

To evaluate the effects of gaseous pollutants (SO₂, NO₂) on non-accidental mortality of residents in Hefei city, we collected non-accidental deaths, air pollutants and meteorological data of Hefei city from 2014 to 2017. After controlling confounding factors with Poisson generalized additive model, we analyzed the relationship between air pollutants and non-accidental mortality and used subgroup analysis to identify susceptible groups. The number of non-accidental deaths during the study period was 42,116, with an average of 28.83 per day. The average concentrations of SO₂ and NO₂ were 16.08 μg/m³ and 39.10 μg/m³, respectively. In the single-pollutant model, every 10 μg/m³ increase in SO₂ and NO₂ concentrations was significantly associated with non-accidental mortality, and there was a significant lag effect. SO₂ increased the risk of non-accidental death by 4.93% (95% CI: 1.94% ~ 8.00%) at lag0-3. In addition, male, the elderly, non-elderly and low-education people were more susceptible (P < 0.05). NO₂ increased the risk of non-accidental death by 2.11% (95% CI: 1.18% ~ 3.05%) at lag0-1 and had an effect on all subgroups (P < 0.05). For every 10 μg/m³ increase in SO₂ and NO₂, the two-pollutant model showed that the risk of non-accidental death, respectively, increased by 3.34% (95% CI: 0.29% ~ 6.50%) and 1.82% (95% CI: 0.85% ~ 2.79%), suggesting that the effect was weakened. Our study suggested that SO₂ and NO₂ were associated with non-accidental mortality, and there were lag effects. Therefore, environmental management should be strengthened and health protection education should be carried out for different groups.