Long-Term Ambient Multipollutant Exposures and Mortality

Abstract

Rationale: Population-based studies have demonstrated associations between ambient air pollution exposures and mortality, but few have been able to adjust for occupational exposures. Additionally, two studies have observed higher risks in individuals with occupational dust, gas, or fume exposure. Objectives: We examined the association of ambient residential exposure to particulate matter less than 10 μm in diameter (PM₁₀), particulate matter less than 2.5 μm in diameter (PM_2.5), NO₂, SO₂, and mortality in 53,814 men in the U.S. trucking industry. Methods: Exposures for PM₁₀, NO₂, and SO₂ at each residential address were assigned using models combining spatial smoothing and geographic covariates. PM_2.5 exposures in 2000 were assigned from the nearest available monitor. Single and multipollutant Cox proportional hazard models were used to examine the association of an interquartile range (IQR) change (6 μg/m³ for PM₁₀, 4 μg/m³ for PM_2.5, 4ppb for SO₂, and 8ppb for NO₂) and the risk of all-cause and cause-specific mortality. Measurements and Main Results: An IQR change in ambient residential exposures to PM₁₀ was associated with a 4.3% (95% confidence interval [CI], 1.1–7.7%) increased risk of all-cause mortality. The increase for an IQR change in SO₂ was 6.9% (95% CI, 2.3–11.6%), for NO₂ was 8.2% (95% CI, 4.5–12.1%), and for PM_2.5 was 3.9% (95% CI, 1.0–6.9%). Elevated associations with cause-specific mortality (lung cancer, cardiovascular and respiratory disease) were observed for PM_2.5, SO₂, and NO₂, but not PM₁₀. None of the pollutants were confounded by occupational exposures. In multipollutant models, overall, the associations were attenuated, most strongly for PM₁₀. In sensitivity analyses excluding long-haul drivers, who spend days away from home, larger hazard ratios were observed. Conclusions: In this population of men, residential ambient air pollution exposures were associated with mortality.