Fibers in lung tissues of mesothelioma cases among miners and millers of the township of Asbestos, Quebec

Short, fine and WHO asbestos fibers in the lungs of quebec workers with an asbestos-related disease

BACKGROUND

The possible role of short asbestos fibers in the development of asbestos-related diseases and availability of lung fiber burden data prompted this study on the relationships between fiber characteristics and asbestos-related diseases among compensated workers.

METHODS

Data collected between 1988 and 2007 for compensation purposes were used; lung asbestos fibers content of 123 Quebec workers are described according to socio-demographic characteristics, job histories and diseases (asbestosis, mesothelioma, lung cancer).

RESULTS

Most workers (85%) presented chrysotile fibers in their lungs, and respectively 76%, 64%, and 43% had tremolite, amosite, and crocidolite. Half of the total fibers were short, 30% were thin fibers and 20% corresponded to the World Health Organization definition of fibers (length ≥ 5 μm, diameter ≥ 0.2 and <3 μm). Chrysotile fibers were still observed in the lungs of workers 30 years or more after last exposure.

CONCLUSION

Our findings stress the relevance of considering several dimensional criteria to characterize health risks associated with asbestos inhalation.

Quantitative Analysis of Asbestos Burden in a Series of Individuals with Lung Cancer and a History of Exposure to 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.

Exposing the "myth" of ABC, "anything but chrysotile": a critique of the Canadian asbestos mining industry and McGill University chrysotile studies

BACKGROUND

Beginning in the 1930s, the Canadian asbestos industry created and advanced the idea that chrysotile asbestos is safer than asbestos of other fiber types.

METHODS

We critically evaluate published and unpublished studies funded by the Quebec Asbestos Mining Association (QAMA) and performed by researchers at McGill University.

RESULTS

QAMA-funded researchers put forth several myths purporting that Quebec-mined chrysotile was harmless, and contended that the contamination of chrysotile with oils, tremolite, or crocidolite was the source of occupational health risk. In addition, QAMA-funded researchers manipulated data and used unsound sampling and analysis techniques to back up their contention that chrysotile was "essentially innocuous."

CONCLUSIONS

These studies were used to promote the marketing and sales of asbestos, and have had a substantial effect on policy and occupational health litigation. Asbestos manufacturing companies and the Canadian government continue to use them to promote the use of asbestos in Europe and in developing countries. Am. J. Ind. Med. 44:540-557, 2003.

An asbestos job exposure matrix to characterize fiber type, length, and relative exposure intensity

The relationship between asbestos exposure and disease has been well documented, although questions persist as to variation in risk by the type and length of fiber. For a series of jobs with potential asbestos exposure, the primary fiber type (e.g., amosite, anthophylite, chrysotile, crocidolite, or tremolite) and fiber length were identified and the relative exposure intensity was estimated. The resulting job exposure matrix may be useful in epidemiological studies where asbestos is an exposure of interest.

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.

Lung mineral fibers of former miners and millers from Thetford-Mines and asbestos regions: a comparative study of fiber concentration and dimension

Fiber dimension and concentration may vary substantially between two necropsy populations of former chrysotile miners and millers of Thetford-Mines and Asbestos regions. This possibility could explain, at least in part, the higher incidence of respiratory diseases among workers from Thetford-Mines than among workers from the Asbestos region. The authors used a transmission electron microscope, equipped with an x-ray energy-dispersive spectrometer, to analyze lung mineral fibers of 86 subjects from the two mining regions and to classify fiber sizes into three categories. The most consistent difference was the higher concentration of tremolite in lung tissues of workers from Thetford-Mines, compared with workers from the Asbestos region. Amosite and crocidolite were also detected in lung tissues of several workers from the Asbestos region. No consistent and biologically important difference was found for fiber dimension; therefore, fiber dimension does not seem to be a factor that accounts for the difference in incidence of respiratory diseases between the two groups. The greater incidence of respiratory diseases among workers of Thetford-Mines can be explained by the fact that they had greater exposure to fibers than did workers at the Asbestos region. Among the mineral fibers studied, retention of tremolite fibers was most apparent.

Pulmonary mineral fibers after occupational and environmental exposure to asbestos in the Russian chrysotile industry

BACKGROUND

As an indicator of occupational, domestic, and environmental exposure, the level and type of asbestos fibers were determined from lung tissue samples of workers and residents who resided in the area of the world's largest asbestos mine at Asbest, Russia.

METHODS

Electron microscopy was used to analyze and measure the concentration of asbestos fibers in a series of 47 autopsies at the Asbest Town Hospital. Work histories were obtained from pathology reports and employment records.

RESULTS

In 24 chrysotile miners, millers, and product manufacturers, the pulmonary concentrations of retained fibers (over 1 microm in length) were 0. 8-50.6 million f/g for chrysotile, and < 0.1-1.9 million f/g for amphiboles (tremolite and anthophyllite). The concentrations were lower in 23 persons without any known occupational contact with asbestos; 0.1-14.6 million f/g for chrysotile, and < 0.1-0.7 million f/g for amphiboles. On average, 90% of all inorganic fibers were chrysotile, and 5% tremolite/anthophyllite. No amosite or crocidolite fibers were detected in any of the samples.

CONCLUSIONS

The mean and range of pulmonary chrysotile concentrations were about the same as reported previously from the Canadian mining and milling industry. In the Russian samples, the mean concentration of tremolite fibers were less by at least one order of magnitude. Occupational contact was the most important source of asbestos exposure.

Inferences on the kinetics of asbestos deposition and clearance among chrysotile miners and millers

BACKGROUND

The health effects of asbestos are intimately related to the fate of inhaled fibers in the lungs. The kinetics of asbestos fibers have been studied primarily in rodents. The objective of this study was to explore the application of these kinetic models to human autopsy data.

METHODS

We analyzed the asbestos fiber content of the lungs of 72 Quebec chrysotile miners and millers and 49 control subjects using analytical transmission electron microscopy. Statistical methods included standard multivariate linear regression and locally weighted regression methods.

RESULTS

The lung burdens of asbestos bodies and chrysotile and tremolite fibers were correlated, as were the concentrations of short, medium, and long fibers of each asbestos variety. There were significant associations between the duration of occupational exposure and the burdens of chrysotile and tremolite. The concentration of chrysotile decreased with the time since last exposure but the concentration of tremolite did not. The clearance rate varied inversely with the length of chrysotile fibers. For fibers greater than 10 mu in length the clearance half-time was estimated to be 8 years.

CONCLUSIONS

The patterns in our data are compatible with both of the hypotheses suggested from rodent experiments; the existence of a long-term sequestration compartment and overload of clearance mechanisms in this compartment.

Analysis of asbestos fiber burden in lung tissue from mesothelioma patients

Mesothelioma is a rare neoplasm that occurs most frequently in individuals with previous asbestos exposure. Differences for risk of development of asbestos-related mesothelioma and lung cancer have been attributed to the various types of asbestos, as well as to the dimension of the inhaled fibers. In the present study, 55 individuals with the pathological diagnosis of mesothelioma were evaluated as to ferruginous body and fiber content in lung tissue. The procedures used in the analysis included tissue digestion and analysis of the collected material for ferruginous bodies by light microscopy and for uncoated fibers by analytical transmission electron microscopy. Forty-six of the samples had ferruginous body concentrations of over 1000/per gram dry weight of lung tissue. The majority of the cores of these ferruginous bodies were amosite. Likewise, the most common uncoated asbestos fiber in the tissue was amosite. Only a small percentage of each type of asbestos would have been visible by light microscopy or even potentially by electron microscopy if the magnification was not sufficient to detect those with thin (< 0.2 micron) diameters. The consistent finding in most of the cases was a considerable presence of asbestos, often of mixed types.

Retention of asbestos fibres in lungs of workers with asbestosis, asbestosis and lung cancer, and mesothelioma in Asbestos township

OBJECTIVE

To conduct a mineralogical study on the particles retained in the necropsied lungs of a homogenous group of asbestos miners and millers from Asbestos township (and a local reference population) and to consider the hypothesis that there is a difference in size between fibres retained in the lungs of patients with asbestosis with and without lung cancer.

METHODS

Samples of lung tissue were obtained from 38 patients with asbestosis without lung cancer, 25 with asbestosis and lung cancer, and 12 with mesothelioma, from necropsied Quebec chrysotile miners and millers from Asbestos township. Fibre concentrations in the lungs of these patients were compared with those in tissue from necropsies carried out on a local reference population: men who had died of either accidental death or acute myocardial infarction between 1990 and 1992. 23 were born before 1940 and 26 after 1940.

RESULTS

Geometric mean (GM) concentrations were higher in cases than in the controls for chrysotile fibres 5 to 10 microns long in patients with asbestosis with or without lung cancer; for tremolite fibres 5 to 10 microns long in all patients; for crocidolite, talc, or anthophyllite fibres 5 to 10 microns long in patients with mesothelioma; for chrysotile and tremolite fibres > or = 10 microns long in patients with asbestosis; and crocidolite, talc, or anthophyllite fibres > or = 10 microns long in patients with mesothelioma. However, median concentrations of each type of fibre in the lungs did not show any significant differences between the three disease groups. Average length to diameter ratios of the fibres were calculated to be larger in patients with asbestosis and lung cancer than in those without lung cancer for crocidolite fibres > or = 10 microns long, for chrysotile, amosite, and tremolite fibres 5 to 10 microns long, and for chrysotile and crocidolite fibres < 5 microns long. However, there was no statistical difference in the median length to diameter ratios for any type of fibres across the disease groups when they were calculated in each patient. Cumulative smoking index (pack-years) was higher in the group with asbestosis and lung cancer but was not statistically different from the two other disease groups.

CONCLUSION

Lung cancers occurred in workers with asbestosis from Asbestos township who had an equal concentration of retained fibres but a tendency to a higher length to diameter ratio of amphiboles. These workers had a 29% higher average cumulative smoking index.