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Chronic obstructive pulmonary disease mortality in railroad workers
1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA. Jaime.hart@channing.harvard.edu
Background:
There is little information describing the risk of non-malignant respiratory disease and occupational exposure to diesel exhaust.
Methods:
US railroad workers have been exposed to diesel exhaust since diesel locomotives were introduced after World War II. In a retrospective cohort study we examined the association of chronic obstructive pulmonary disease (COPD) mortality with years of work in diesel-exposed jobs. To examine the possible confounding effects of smoking, multiple imputation was used to model smoking history. A Cox proportional hazards model was used to estimate an incidence rate ratio, adjusted for age, calendar year, and length of follow-up after leaving work (to reduce bias due to a healthy worker survivor effect).
Results:
Workers in jobs with diesel exhaust exposure had an increased risk of COPD mortality relative to those in unexposed jobs. Workers hired after the introduction of diesel locomotives had a 2.5% increase in COPD mortality risk for each additional year of work in a diesel-exposed job. This risk was only slightly attenuated after adjustment for imputed smoking history.
Conclusions:
These results support an association between occupational exposure to diesel exhaust and COPD mortality.
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