Asbestos Fibers in the General Population1–3

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Abstract
We isolated uncoated asbestos fibers from the lungs of 21 urban dwellers who had fewer than 100 asbestos bodies/gram of lung, a level shown previously to be associated with environmental rather than occupational exposure to asbestos. Lack of occupational history was confirmed in 20 of the 21 patients; history of probable exposure was obtained for 1 patient. Fibers were counted, measured, and identified using a combination of electron optical morphology, diffraction, and energy dispersive x-ray spectroscopy. Eighty per cent of the fibers were chrysotile (mean 130 × 103, range 12 × 103 to 680 × 103 fibers/gram wet lung) and 90% of the chrysotile was less than 5 μ long. Total amphiboles had a mean of 25 × 103 and ranged from 1.3 × 103 to 75 × 103 fibers/g; 95% were noncommercial amphiboles and two thirds were less than 5 μ long. However, 20% of the commercial fibers, amosite/crocidolite, and 20% of the anthophyllite were longer than 10 μ, a finding in accord with the types of fibers seen in asbestos bodies in these patients. Short (1) Substantial amounts of asbestos, mainly chrysotile and noncommercial amphiboles, are present in the average lung in an urban environment; (2) Most of these fibers are too small to form asbestos bodies or to be visible by light microscopy; (3) Asbestos bodies may serve as some indication of exposure to long amphiboles, but offer no information about the bulk of fibers present; and (4) It is probable that most of these fibers reflect general environmental contamination.