Sulfur Dioxide- and Fluoride-Associated Declines in Lung Function Over an 11-Year Observation Among Aluminum Smelter Workers.

Background: Work exposure-related declines in lung function among aluminum smelter workers are well documented, yet task-varying exposures are likely to contribute differently to respiratory outcomes. This study aimed to assess the association between potroom exposure and lung function changes over time among aluminum smelter workers.

Methods: A retrospective review of spirometric assessments of 265 potroom workers and their exposure to sulfur dioxide (SO₂) and fluoride was conducted. Cumulative exposure was described through job exposure matrices by job titles and exposure across the lifetime of employment. Associations between exposure and lung function were determined using mixed-effect models and a 1-year lag exposure.

Results: Exposures were within the prescribed occupational exposure limits. SO₂ was highest in the maintenance section (mean: 0.4 ppm [range 0.3-0.5 ppm]), while the process control section (mean: 1.1 mg/m³ [range 0.04-2.6 mg/m³]) had the highest level of fluoride. Among those workers who contributed lung function measures at each of the 10 years (n = 98), there was a decline in the percentpredicted forced expiratory volume in 1 second/forced vital capacity ratio (FEV₁/FVC) of 0.21% (95% CI: 0.35-0.07). Within the entire sample, there was an estimated decline of 2.9% (95% CI: -3.9 to -1.9) and 0.15% (95% CI: -0.23 to -0.07) in percentage-predicted FEV₁/FVC, associated with cumulative SO₂ and cumulative fluoride exposure, respectively. A 1-year lagged decline was also seen for the FEV₁/FVC ratio for both pollutants.

Conclusion: SO₂ and fluoride exposure in aluminum smelting is associated with statistically significant lung function declines over the years of exposure.