Asbestos fibers in occupationally exposed individuals relocate from the lung to extrapulmonary sites. A mechanism for relocation is via the lymphatic circulation. Indeed, asbestos fibers have been found in lymph nodes as well as pleural plaques. Our laboratory has recently shown that asbestos fibers also reach the mesentery and omentum in the peritoneal area where a small percentage of mesotheliomas occurs in exposed individuals. The present study uses light and analytical transmission electron microscopy for defining the asbestos burden in digested lung, omentum, and mesentery tissues from individuals considered as representing the general population in East Texas. The findings, when compared with previous data from occupationally exposed individuals, indicate extreme contrasts as to the level and types of fiber burden between individuals representing the groups.

The asbestos body and fiber burden in these cases show variation in tissue burden. Some cases in this study had appreciable burden, which was attributed to secondhand exposure from occupationally exposed family members. Mesothelioma can occur also in individuals with comparatively low tissue burdens of asbestos.

Asbestos is recognized as a lung carcinogen. In the present study, tissue from 20 individuals who died from lung cancer and who had a history of exposure to asbestos was evaluated for the presence of asbestos bodies and uncoated asbestos fibers. A digestion procedure was used to isolate the particulates from the tissue. The samples were evaluated by light microcopy to quantify the numbers of ferruginous bodies in the tissue. The uncoated fibers (which included all fibers equal to or greater than 0.5 microm) were analyzed by analytical transmission electron microscopy. Seventeen of the 20 cases were positive for ferruginous bodies (which were morphologically consistent with asbestos bodies). Five of these were found to have concentrations within the range used in our laboratory for the general population (<20 ferruginous bodies/g wet tissue). Nineteen of the 20 cases were found to have asbestos fibers in the higher magnification scan (either 16 K or 20 K). Some of the asbestos fibers identified were specific for the types of exposures that were reported. Most individuals in this study were found to have mixed populations of asbestos fibers in the lung tissue. This suggests that when there are exposures to products containing commercial asbestos there are likely exposures to dust containing noncommercial asbestos. A contrast exists in the dust burden within the lung of these individuals as compared to samples from the general population in that occupational or "occupational-like" exposures such as in these cases are often reflected by the presence of longer fibers of asbestos in the tissue.

Lavage material was collected from 12 individuals whose work history included working in a cement manufacturing facility. The manufacturing processes of the facility included the use of crocidolite and chrysotile asbestos. Lavage material was prepared via digestion procedure and then analyzed for the presence of ferruginous bodies by light microscopy and for uncoated asbestos fibers by analytical transmission electron microscopy. A comparison was made as to the sensitivity between two analytical methods for linking a past exposure to a specific type of asbestos. The use of analytical transmission electron microscopy for identification of core material in the ferruginous bodies as well as for quantification of the uncoated asbestos fibers increased the sensitivity of the information obtained from lavage samples as necessary for confirming exposure in the past to specific types of asbestos.