Diagnosis of “asbestosis”: Observations from a longitudinal survey of shipyard pipe coverers

Abstract

In 1972, to study slight manifestations of pulmonary fibrosis due to asbestos, we evaluated 101 shipyard pipe coverers and 95 control subjects whom we had examined in 1965 and in 1966. Although these workers had been exposed to low levels of asbestos, “asbestosis” was diagnosed in the first survey 11 times more often among pipe coverers than among control subjects. In 1972, clinical, roentgenologic and physiologic tests for monitoring workers were evaluated with respect to (1) ability to separate pipe coverers from control subjects, (2) consistency from the initial to the final survey, (3) predictive value in 1966 with respect to health in 1972 and (4) relationship to duration of exposure. Basilar rales, irregular opacities on chest film, and reduced vital and diffusing capacity were more common in pipe coverers in both surveys. These findings tended to be abnormal in 1972 in those workers in whom they were present in 1966, whereas dyspnea and clubbing were inconsistently found. The predictive value of a single abnormality was minimal, whereas the prognosis was poor in the nine pipe coverers who had three or more of these criteria in 1966. “Asbestosis” was considered present when three or more of the following were present: (1) bibasilar fine rales, (2) irregular x-ray opacifications (International Labour Organization, University of Cincinnati Classification [ILO/UC] 2/1 or more), (3) forced vital capacity (FVC) less than 80 per cent predicted, (4) single breath diffusing capacity (Dsb) less than 80 per cent predicted. There was only one false positive, a worker with significant heart disease. Clusters of findings appear more important for monitoring exposed workers than single findings. An incidence of 1.1 per cent/year of asbestosis, despite an 80 per cent reduction in the total quantity of asbestos used, emphasizes the importance of environment control.