Environmental household exposures to asbestos and occurrence of pleural mesothelioma.

We reviewed the certificates of 39,650 deaths which occurred in the period 1975-1988 in Leghorn and of 45,900 in La Spezia (Italy) in the period 1958-1988. In total 262 cases have been recorded as pleural mesothelioma. The main occupational exposures occurred in the shipbuilding industry. Regarding non-occupational exposures to asbestos, 13 cases of mesothelioma were found in women who had washed the work clothes of their relatives at home; we also found other domestic uses of asbestos which were rarely or never discussed previously in the literature: six cases might be explained by the installation of fireproof or non-conductive materials in the domestic environment. These exposures probably are more frequent than realized until now.     

Malignant mesothelioma from neighborhood exposure to anthophyllite asbestos

BACKGROUND: Anthophyllite asbestos has been reported to cause asbestosis, lung cancer, mesothelioma, and pleural plaques in occupationally exposed workers. Anthophyllite has also been associated with pleural plaques in Finland and Japan among those who live near mines and mills and have neighborhood or environmental exposure. METHODS: We evaluated a 38-year-old patient with pleural mesothelioma who lived, attended school, and delivered newspapers near a manufacturing facility that used exclusively anthophyllite asbestos fiber from ages 8-17 years. He had no work exposure to asbestos. RESULTS: The pleural mesothelioma was an epithelial type with tubulopapillary structures and was treated with an extrapleural pneumonectomy followed by radiation therapy. The malignant cells were positive by immunohistochemistry for cytokeratin but negative for carcinoembryonic antigen, S100, B72.3, and leu M1 antigen. Anthophyllite fibers were > 5 microm in length in lung tissue compared to 3 microm from a general population study. CONCLUSIONS: Anthophyllite asbestos has been associated with neighborhood environmental exposure and pleural plaques; we now report a neighborhood exposure and pleural mesothelioma.     

Malignant mesothelioma caused by childhood exposure to long-fiber low aspect ratio tremolite

A 41-year-old man was found to have a malignant mesothelioma of the pleura. During childhood in Corsica, he had been exposed at home to chrysotile ore from the Canari mine. Analysis of lung mineral content revealed background levels of chrysotile but an elevated level of tremolite and actinolite asbestos. The latter had a geometric mean length of 3.7 μm, a value considerably longer than we have found for tremolite and actinolite from Quebec chrysotile miners but roughly the same as the mean length of amosite and crocidolite in workers with occupational amphibole exposure. No tremolite or actinolite fibers of length greater than 8 μm microns and width less than 0.25 μm were observed. The mean aspect ratio of the tremolite and actinolite fibers was 7, a value similar to that found in chrysotile miners with mesothelioma but considerably less than the mean aspect ratio of amosite and crocidolite from those with occupational expsoure. These data suggest that long-fiber tremolite is a potential mesothelial carcinogen in humans, and that fiber length is more important than fiber aspect ratio in this regard.     

Asbestos burden predicts survival in pleural mesothelioma

BACKGROUND: Malignant pleural mesothelioma (MPM) is a rapidly fatal asbestos-associated malignancy with a median survival time of <1 year following diagnosis. Treatment strategy is determined in part using known prognostic factors. OBJECTIVE: The aim of this study was to examine the relationship between asbestos exposure and survival outcome in MPM in an effort to advance the understanding of the contribution of asbestos exposure to MPM prognosis. METHODS: We studied incident cases of MPM patients enrolled through the International Mesothelioma Program at Brigham and Women's Hospital in Boston, Massachusetts, using survival follow-up, self-reported asbestos exposure (n=128), and a subset of cases (n=80) with quantitative asbestos fiber burden measures. RESULTS: Consistent with the established literature, we found independent, significant associations between male sex and reduced survival (p<0.04), as well as between nonepithelioid tumor histology and reduced survival (p<0.02). Although self-reported exposure to asbestos was not predictive of survival among our cases, stratifying quantitative asbestos fiber burden [number of asbestos bodies per gram of lung (wet weight)] into groups of low (0-99 asbestos bodies), moderate (100-1,099), and high fiber burden (>1,099), suggested a survival duration association among these groups (p=0.06). After adjusting for covariates in a Cox model, we found that patients with a low asbestos burden had a 3-fold elevated risk of death compared to patients with a moderate fiber burden [95% confidence interval (CI), 0.95-9.5; p=0.06], and patients with a high asbestos burden had a 4.8-fold elevated risk of death (95% CI, 1.5-15.0; p<0.01) versus those with moderate exposure. CONCLUSION: Our data suggest that patient survival is associated with asbestos fiber burden in MPM and is perhaps modified by susceptibility.     

Fibers in lung tissues of mesothelioma cases among miners and millers of the township of asbestos,quebec

Twenty cases of mesothelioma among miners of the township of Asbestos, Quebec, Canada, have been reported. To further explore the mineral characteristics of various fibrous material, we studied the fibrous inorganic content of postmortem lung tissues of 12 of 20 available cases. In each case, we measured concentrations of chrysotile, amosite, crocidolite, tremolite, talc-anthophyllite, and other fibrous minerals. The average diameter, length, and length-to-diameter ratio of each type of fiber were also calculated. For total fibers > 5 μm, we found > 1,000 asbestos fibers per mg tissue (f/mg) in all cases; tremolite was above 1,000 f/mg in 8 cases, chrysotile in 6 cases, crocidolite in 4 cases, and talc anthophyllite in 5 cases. Among cases with asbestos fibers, the tremolite count was highest in 7 cases, chrysotile in 3 cases, and crocidolite in 2 cases. The geometric mean concentrations of fibers ? 5 μm were in the following decreasing order: tremolite > crocidolite > chrysotile > other fibers > talc-anthophyllite > amosite. For total fibers < 5 μm, we found > 1,000 fibers per mg tissue (f/mg) in all cases; tremolite was above 1,000 f/mg in 12 cases, chrysotile in 8 cases, crocidolite in 7 cases, and talc-anthophyllite in 6 cases. Tremolite was highest in 8 cases, chrysotile in 2 cases, and crocidolite and amosite in 2 cases. The geometric mean concentrations of fibers < 5 μm were in the following decreasing order: tremolite > other fibers > chrysotile > crocidolite > talc-anthophyllite > amosite. We conclude, on the basis of the lung burden analyses of 12 mesothelioma cases from the Asbestos township of Quebec, that the imported amphibole (crocidolite and amosite) were the dominant fibers retained in the lung tissue in 2/12 cases. In 10/12 cases, fibers from the mine site (chrysotile and tremolite) were found at highest counts; tremolite was clearly the highest in 6, chrysotile in 2, and 2 cases had about the same counts for tremolite and chrysotile. If a relation of fiber burden-causality of mesothelioma is accepted, mesothelioma would be likely caused by amphibole contamination of the plant in 2/12 cases and by the mineral fibers (tremolite and chrysotile) from the mine site in the 10 other cases.     

Quantitative analysis of asbestos burden in women with mesothelioma

BACKGROUND: Lung tissue from 15 women who died from mesothelioma was evaluated for tissue burden of ferruginous bodies and uncoated asbestos fibers. The group contained individuals who had occupational exposure to asbestos and others had family members whose work history included vocations where contact with asbestos containing materials occurred. METHODS: Tissue samples from tumor free lung were digested and filtered and then investigated for ferruginous bodies by light microscopy and asbestos and non-asbestos fibers by analytical transmission electron microscopy (ATEM). Size and type of fibers were also analyzed. RESULTS: Asbestos bodies were found in 13 of the 15 samples and asbestos fibers were found in all cases. The most commonly found uncoated asbestos fiber in these individuals was amosite whereas tremolite was the second most commonly found form. The asbestos fiber burden in these females was often of mixed types. CONCLUSIONS: 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.     

Pleural plaques as risk indicators for malignant pleural mesothelioma: A necropsy-based study

Pleural plaque is recognized as a reliable marker of previous exposure to asbestos. However, it is controversial whether pleural plaque is a risk indicator for asbestos-related malignancies. In the present study, the thoracic cavities were examined for pleural plaques in 3,005 necropsies performed at the Monfalcone Hospital in people aged 15 years or older. Plaques were classified into three classes: 1, small (plaques measuring 1–4 cm in major diameter); 3, large (plaques involving a major part of a hemithorax); and 2, moderate (intermediate conditions). The prevalences of pleural plaques were 70.9% among men, and 24.0% among women. The prevalences of plaques (total plaques, various classes) among subjects with pleural mesothelioma were compared with those observed in the remaining cases. The series included 92 subjects with malignant pleural mesothelioma (82 men and 10 women). Mesothelioma cases showed higher prevalences of total plaques as well as higher prevalences of classes 1, 2, and 3, when compared with controls. These differences reached the statistical significance for total plaques, and classes 2,3. The present data are consistent with the idea that pleural plaque is a risk indicator for pleural mesothelioma. Am. J. Ind. Med. 32:445–449, 1997. © 1997 Wiley-Liss, Inc.     

Accumulation of long asbestos fibers in the peripheral upper lobe in cases of malignant mesothelioma

Animal studies suggest that mesothelioma is most effectively induced by fibers longer than 8 mu. However, studies of asbestos fibers recovered from human lungs in cases of mesothelioma indicate that, at least in large-scale samples, relatively few fibers meet this size criterion, perhaps implying that the animal data do not apply to man. Since asbestos concentration in lung is known to be extremely inhomogeneous, it is also possible that long fibers may selectively accumulate in specific sites, such as under the pleura. To examine this possibility, we selected ten cases of mesothelioma that contained relatively large amounts of amosite asbestos and extracted fibers from an 0.5-cm-thick strip of subpleural tissue and an area 3-cm deep to the subpleural sample for upper and lower lobes. Amosite fibers were identified and sized by electron microscopic techniques. Fibers in the peripheral upper lobe were significantly longer, broader, and of higher aspect ratio than those in the central upper lobe. The lower lobe showed a reverse pattern, with longer fibers and broader fibers in the central sample. These data indicate that the two lobes behave differently in regard to fiber size, with selective accumulation of long fibers in the peripheral upper lobe, but not in the peripheral lower lobe. Whether these differences reflect differences in initial deposition of fibers within the lung, or, more likely, specific redistribution of fibers, is unclear, but in either case, accumulation of long fibers immediately under the upper lobe pleura may be important in the genesis of mesothelioma.