Production of silicon alloys is associated with respiratory symptoms among employees in Norwegian smelters

Objectives: To develop a qualitative exposure classification of employees in Norwegian smelters and to investigate the relationship between respiratory symptoms and occupational exposure using this classification. Methods: The 3,924 participants completed a standardised questionnaire including questions of respiratory symptoms, familial asthma, allergy, doctor-diagnosed asthma, smoking habits, previous exposure and occupation. The employees were classified according to their current job function: (1) line operators were employed full time on the production line, (2) non-exposed employees did not work in production, (3) the remaining employees were classified as non-line operators. The association between the prevalence of respiratory symptoms and job category was examined using multivariate logistic regression. Results: The mean age of the participants was 38.6 years (standard deviation 9.2 years), 88.5% were males. The odds ratios (OR) (95% confidence intervals in parenthesis) for dyspnoea, cough and phlegm regarding previous exposure compared with no previous exposure were 1.4 (1.1–1.7), 1.4 (1.2–1.8) and 1.3 (1.0–1.7), respectively. The OR in line operators compared with non-exposed employees was 1.2 (0.9–1.7) for dyspnoea, 1.3 (1.0–1.8) for cough and 1.9 (1.4–2.7) for phlegm. The OR for respiratory symptoms was higher in relation to previous exposure than current job function except for phlegm. Conclusion: In Norwegian smelters respiratory...