A comparison of the ferruginous body and uncoated fiber content in the lungs of former asbestos workers.

Tissue samples from 12 former asbestos workers were digested and analyzed for ferruginous body and uncoated fiber populations. It was noted that there were large numbers of nonasbestos fibers in each of the samples. In some samples, these fibers constituted over 80% of the total uncoated fibers, and they could greatly influence the data as to asbestos content of the tissue unless differentiated by light and electron microscopic techniques, such as X-ray energy-dispersive analysis. There were great variations in the numbers of uncoated fibers per ferruginous body between the individual workers. The digested samples from lungs of 2 workers yielded no ferruginous bodies by light microscopy, even though these samples by electron microscopy contained respective loads of 780,000 and 1.2 million uncoated amphibole fibers per gram. Light microscopy examination of adjacent tissues confirmed mild fibrosis in both workers. Ferruginous bodies serve as a general marker for asbestos exposure. However, our data suggest that their absence in tissue with interstitial fibrosis from a worker with previous occupational exposure may not be sufficiently conclusive to rule out asbestos-induced disease. Rather, as shown by our data, individual exceptions may require correlated analysis by analytical electron microscopy in order to define particulate load and support the diagnosis of the disease.