Lung function and respiratory health of long-term fiber-exposed stonewool factory workers

The present study was undertaken to examine the respiratory health of a Dan ish workforce exposed to man-made vitreous fibers (MMVF) during production. Workers with more than 5 yr occupational exposure to MMVF (n = 377) were c ompared to a group without MMVF exposure (n = 381). Respiratory health was assessed by questionnaire, dynamic spirometry, and measurement of transfer factor. Overall response rate was 63%. A sample of nonresponders was assess ed by questionnaire and spirometry. On most spirometric indices the two gro ups had comparable values. However, a larger proportion (14.5%) of the expo sed subjects had an obstructive flow pattern compared with the control subj ects (5.3%). Subgroup analyses showed that the elevated risk of airways obs truction associated with exposure was restricted to heavy smokers. Transfer factor and prevalences of symptoms and self-reported disease were similar in the two groups. There is no indication of excess risk of lung fibrosis. However, a number of exposed workers have some degree of airflow obstructio n, which cannot be explained by known confounders. An additive or synergist ic action between smoking and fiber exposure on airflow obstruction can be speculated.