Lung function and radiographic signs of pulmonary fibrosis in oil exposed workers in a cable manufacturing company: a follow up study.

Abstract

Thirty seven workers employed for at least three years in oil impregnation of cables during 1963-83 were followed up in 1990 to study the development of pulmonary fibrosis and consequences for lung function. They had been exposed to concentrations of mineral oil vapours of 50-100 mg/m3, and concentrations of oil mist of 0.5-1.5 mg/m3. All 29 living persons were traced. For each person one control matched for age, height, and smoking habits was selected. Among 25 workers followed up with radiographic studies, 10 cases of pulmonary fibrosis were found, by contrast with one case in the control group (p less than 0.01). Chest radiographs from 1979-80 and 1989-90 were reviewed. The profusion of small opacities increased in seven of 16 persons during 10 years without exposure. Seventeen workers had lung function tests. The bellows function (VC, FEV1, MVV) and lung volumes (TLC, RV) did not differ from those in the matched controls (p greater than 0.05), but the carbon monoxide transfer factor (TLCO) was decreased. The largest reduction of TLCO (1.5 mmol/kPa/min) was found among workers exposed for 10 years or more (p less than 0.05). Arterial blood gases were not affected at rest, but during maximum tread mill exercise, PO2 and HbO2 were reduced in exposed workers compared with controls, particularly among those exposed for at least 10 years (p less than 0.05). Exposure to low viscosity oil mist and vapour is the most plausible cause of the fibrosis. Unaffected bellows function, reduced TLCO, and decreased arterial blood oxygen during exercise is compatible with peribronchiolar fibrosis.