FIBER SIZE AND NUMBER IN AMPHIBOLE ASBESTOS-INDUCED MESOTHELIOMA

Google Scholar
  • 1 January 1984
    • journal article
    • research article
    • Vol. 115  (3) , 437-442
Abstract
Numbers and sizes of fibers from the lungs of 10 patients who had an amphibole asbestos-induced malignant pleural mesothelioma were analyzed. Amosite was found in 10 lungs and crocidolite in 9; the average ratio of amosite to crocidolite was .apprx. 14:1. In the 8 patients who were not long-time asbestos insulators, the mean number of amosite fibers was 2.3 .times. 106 fibers/g dry lung and of crocidolite fibers, 0.2 .times. 106/g; these values represent an .apprx. 250-fold increase over those found in the general population. Crocidolite fibers were significantly narrower than amosite fibers (mean width, 0.13 vs. 0.23 .mu.), were significantly shorter (mean length, 4.0 vs. 5.8 .mu.) and had a significantly higher mean aspect (legnth to width) ratio (48 vs. 34). Aspect ratios in general increased with increasing fiber length and decreasing fiber width, but the highest values were found for thin amosite fibers at about 13 .mu. in length and thin crocidolite fibers at 8 or 15-17 .mu. in length. Comparison with data from other asbestos-exposed populations indicates that mesothelioma can be induced by relatively small numbers of amphibole fibers and also indicates that amosite is an effective meosthelial carcinogen in humans. Comparison of these data with epidemiologic and experimental predictions of carcinogenic size ranges for mesothelioma induction implies that either the carcinogenic size range is much broader than has been claimed (in particular, fibers considerably shorter than 8 .mu. and broader than 0.05 .mu. can produce mesothelioma), or, alternately, that extraordinarily small absolute numbers of fibers in certain size ranges can induce tumors in humans.