Mortality from asthma and cancer among sulfite mill workers

The aims of the present case-referent study were to investigate whether sulfite workers show increased mortality from asthma, chronic obstructive pulmonary disease or certain malignancies of interest in relation to sulfite mill work. The main exposure from the pulping processes is from sulfur dioxide, wood dust and terpenes.

The subjects of the study were all the men who died between 1960 and 1989 and who were aged 40 to 75 years at death (N = 780) in the parishes surrounding 3 sulfite mills. The men who died from asthma (N = 13), COPD (N = 20), lung cancer (N = 33), stomach cancer (N = 35), or brain tumor (N = 10) formed the case group. All the subjects, except the cases in question, were used as referents. As a proxy variable of exposure, job titles from the registers of deaths and burials were used, and 24% of the subjects were classified as exposed.

There was an increased mortality from asthma [odds ratio(OR) 2.8, 90% confidence interval (90% CI) 1.1-6.8] and brain tumors (OR 3.3, 90% CI 1.2-8.9) among the sulfite workers. The mortality due to lung cancer was not significantly increased (OR 1.4, 90% CI 0.7-2.6), and there was a reduced mortality from stomach cancer (OR 0.4, 90% CI 0.2-0.9).

The increased asthma mortality may be due to accidental exposure to irritating gases, such as sulfur dioxide. The increased risk for brain tumors has no obvious explanation.