Respiratory Health in Workers Exposed to Man-made Vitreous Fibers1–3

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Abstract
A study of the respiratory health of workers who produce man-made vitreous fibers (MMVF) included 1,028 men (median length of employment, 18 yr) in 7 fibrous glass and mineral wool plants. Health assessment was by respiratory questionnaire, ILO 1980 Classification chest radiograph readings, and pulmonary function testing. Results from an earlier environmental survey were combined with job histories to derive individual exposure estimates. The study population was found to be generally healthy, with respiratory symptoms not related to the fiber exposure and no detected adverse lung function consequences of that exposure. Radiograph readings revealed low category profusion of small opacities: of 941, 63 (7%) in category 0/1, 25 (3%) in 1/0, and 6 in 1/1, with none in higher categories. Prevalence of small opacities increased with age and cigarette smoking. A greater prevalence of small opacities was found among current smokers in the two plants producing both ordinary and fine fibers (for profusion ⩾ 1/0, 15% in these plants, 2% in all others). Among ex-smokers and never smokers, greater prevalence was observed in only one of these plants (14% versus 1%), the plant having the higher airborne concentrations of fibers less than 1 μm in diameter. Among current smokers, prevalence of small opacities of profusion ⩾ 0/1 increased with lengthening employment (beyond age and pack-years of smoking) in both plants producing ordinary and fine fibers and the five other plants combined. It is concluded that exposure to MMVF with small diameters may lead to low-level profusion of small opacities. However, without high-level profusion of these opacities in a population with a considerable range of exposure durations, a diffuse tissue reaction (e.g., fibrosis) seems unlikely but cannot be excluded.

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