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PubMed1989

[Comparative carcinogenic properties of basalt fiber and chrysotile-asbestos].

In order to eliminate asbestos adverse effect on workers' health it was necessary to use mineral rayon, primarily basalt fibre, instead of asbestos. During a chronic experiment on animals the oncogenicity of 2 kinds of basalt fibre was studied compared to chrysotile asbestos. The dust dose of 25 mg was twice administered by intraperitonial route. All types of dust induced the onset of intraperitonial mesotheliomas but neoplasm rates were significantly lower in the groups exposed to basalt fibre. There was no credible data on the differences between the groups exposed to various types of basalt fibre. Since the latter produced some oncogenic effect, it was necessary to develop a complex of antidust measures, fully corresponding to the measures adopted for carcinogenic dusts.

Animals↗

PubMedDate not supplied

Egestion of asbestos fibers in Tetrahymena results in early morphological abnormalities. A step in the induction of heterogeneous cell lines?

In Tetrahymena populations exposed to crocidolite asbestos fibers, many cells develop morphological abnormalities within 1-2 hours. The abnormalities are mainly large or small protrusions or indentations, or flattened parts of the cell surface and most often located in the posterior part of the cell. They are formed repeatedly in all cells but are also continuously repaired so that the fraction of cells affected represents an equilibrium between these two processes. Their formation is connected with egestion of the large bundles of fibers formed by phagocytosis. Such effects of egestion of fibers do not seem to have been reported previously. Egestion of a bundle of fibers is much slower than for other types of undigestible residues. In contrast to normal exocytosis occurring invariably at the cytoproct, egestion of asbestos often occurs in the posterior part of the cell outside the cytoproct. To my knowledge this is the first reported case of either very slow or extra-cytoproctal egestion in Tetrahymena. Cells with large abnormalities have a greater tendency to develop into "early heterogeneous" cells than the average abnormal cell. Some of these give rise to hereditarily stable heterogeneous cell lines of Tetrahymena. The morphological abnormalities are probably caused by mechanical action of the crocidolite fibers resulting in local damage of the cytoskeletal elements responsible for normal cell shape. The heterogenous cell lines may arise when cellular structures carrying non-genic cytotactically inherited information are modified. The relevance of these ideas to the induction of cancer by asbestos is briefly discussed.

Animals↗

PubMed1988

Ingestion, cytotoxicity, and early morphological effects of asbestos on Tetrahymena.

Crocidolite asbestos fibers are rapidly ingested in large amounts by Tetrahymena. This varies little with incubation time of fibers in the culture medium or with dilution of the medium. The ingested fibers form large, oblong bundles in the cell rather than the normal spherical food vacuoles. In addition, crocidolite results in a rapid dose dependent induction of various minor morphological abnormalities. At 0.1-3 mg/ml these are observed in approximately one third of the population. Crocidolite is, however, not cytotoxic to Tetrahymena even in these high concentrations as measured by cell death and population doubling time. Phagocytosis and cytotoxicity are thus not related in this cell. Preliminary studies indicate that all the U.I.C.C. standard reference asbestos samples have largely similar effects but that their ability to induce abnormalities depends on the species of Tetrahymena used. For studies of the effects of asbestos Tetrahymena should be a suitable model system because the massive ingestion of fibers and its short generation time should facilitate rapid detection of adverse effects. Among such effects is the induction of heterogenous cell lines. This may involve modification of non-nucleic acid carried hereditary (cytotactic) information.

Animals↗

PubMed1986

Inhalation and injection studies in rats using dust samples from chrysotile asbestos prepared by a wet dispersion process.

Long term inhalation studies and intraperitoneal injection studies in rats were undertaken with a series of chrysotile asbestos dusts. Three dust samples were generated from chrysotile modified by the wet dispersion process (WDC) and one was from unmodified chrysotile. Following a 1 year inhalation period, all the chrysotile samples proved extremely fibrogenic and carcinogenic and there were no significant differences between the WDC dusts and normal chrysotile. In all experimental groups approximately 25% of animals developed pulmonary carcinomas and in the oldest rats advanced interstitial fibrosis occupied on average 10% of all lung tissue. In the injection studies all the dust samples produced mesotheliomas in over 90% of animals. Very little chrysotile remained in the lungs of the animals that survived longest following dust inhalation and what there was was present as individual chrysotile fibrils. It is suggested that chrysotile is potentially the most harmful variety of asbestos as shown in these and other animal studies but that it is removed from lung tissue quite rapidly. In the long lived human species this may mean that except where exposure levels are very high and of long duration, chrysotile should be less hazardous than other asbestos types.

Animals↗

PubMedDate not supplied

Cytology of experimental mesotheliomas induced with crocidolite asbestos.

The cellular features of 12 pleural and 5 peritoneal effusions, derived from experimental mesotheliomas induced with crocidolite asbestos in white rats, are described. The fluids were obtained 11 to 18 months after the introduction of asbestos into the body cavity. The morphologic characteristics of the cytoplasm, nuclei and nucleoli in the neoplastic mesothelial cells were studied using the Pappenheim, periodic acid-Schiff and Smetana stains. Nearly all effusions examined contained numerous normal and abnormal mitoses. Cell configurations suggestive of amitotic divisions were also observed. The study of the morphologic features of mesothelial cells in effusions in experimental asbestos-induced mesotheliomas may contribute to the understanding of the neoplastic transformation of the mesothelium.

Animals↗

PubMed1996

[Relationship between the physiochemical properties of asbestos and pulmonary fibrosis].

The work presents a review of the literature on the effect of physiochemical properties on the intensity of pulmonary fibrosis. Exposure to asbestos fibres induces inflammatory processes which contribute to collagen deposition in the lung tissue. The toxicity of asbestos fibres depends on physiochemical properties of asbestos. Owing to their advantageous aerodynamics, straight needle-like amphiboles can penetrate much easier into the pulmonary tissue than curly serpentine fibres. With magnesium as its main cation, chrysotile has an unstable structure and tends towards the fragmentation into smaller particles. Therefore, its phagocytosis by macrophages and its clearance from the lung tissue are more effective than those of amphiboles. On the other hand, chrysotile undergoes longitudinal fragmentation into thin elementary particles, thus, it proliferates easier respirable fibres in the pulmonary tissue. Fibrosis induced by long fibres (L < 5 microns) is more extensive than that produced by short fibres (L < 5 microns) because of incomplete phagocytosis by macrophages which releases a stimulus to the synthesis of fibronectin and collagen.

Animals↗

PubMed1998

Asbestos in the lungs of persons exposed in the USA.

Tissues obtained at autopsy or biopsy from 81 workers and 2 household persons, were chemically digested. The asbestos fibres recovered were characterized by analytical transmission electron microscopy. Among the 83 causes of death were 33 mesotheliomas, 35 lung cancers, 12 asbestosis and 3 from other cancers. Of the three major commercial asbestos fibre types, amosite was found to be the most prevalent fibre, occurring in approximately 76% of the cases, followed by chrysotile in approximately 60% and crocidolite in approximately 24%. Amosite and chrysotile were observed as the single commercial fibre in approximately 22 and approximately 17% of the cases respectively, whereas crocidolite and tremolite were found as the single fibre type in only approximately 2.5% of the cases. Among the fifteen cases where chrysotile and tremolite occurred together, the amount of chrysotile fibre always exceeded tremolite. However, tremolite was also found in ten additional cases where chrysotile was not detected. Amosite was present in four, amosite plus crocidolite in three, and crocidolite alone in one. Amosite was present in all of the insulation workers' lungs studied and was found in the highest concentration in this exposure category. The highest chrysotile concentration was found among workers in general trades. Although most prevalent in shipyard workers lungs, crocidolite concentration is not statistically different among the exposure groups studied. Although crocidolite was found in twenty cases, amosite accompanied it in eighteen of these. Eleven of the 20 cases were from shipyard workers. Of the 8 mesothelioma cases, 7 also contained amosite. Crocidolite alone only occurred in 1 of the 33 mesothelioma cases analysed. We concluded the following: crocidolite exposure occurred among USA insulators and a large percentage of other workers as well; insulation workers are primarily exposed to amosite; mixed fibre exposures are associated with more mesotheliomas than single fibre exposures; chrysotile only exposure is associated with approximately 12% of the mesothelioma cases studied; and if tremolite exposure is associated with chrysotile exposure, the chrysotile amount exceeds that for the associated tremolite.

Aged↗

PubMed1988

Asbestos exposure-cigarette smoking interactions among shipyard workers.

We studied the roentgenograms, pulmonary function tests, and physical findings of 294 shipyard workers to evaluate asbestos exposure-cigarette smoking interactions. Roentgenographic parenchymal opacities, decreased pulmonary diffusing capacity for carbon monoxide, decreased flow at low lung volume, rales, and clubbing were each significantly related to the number of years elapsed since first exposure to asbestos and cigarette smoking status when analyzed by logistic regression. A dose-dependent cigarette smoking response that was consistent with synergism was present only for parenchymal opacities and decreased flow at low lung volume. These findings suggest that decreased flow at low lung volume, possibly reflecting peribronchiolar fibrosis, may be a functional corollary to smoking-associated parenchymal roentgenographic opacities among some asbestos-exposed individuals.

Asbestos↗

PubMed1996

Unrecognized asbestos-induced disease.

It is being slowly recognized that there is serious under-reporting of cancers that are occupationally related, in the sense that they would not have occurred without the occupational exposure. Data from the Workers' Compensation Boards of New South Wales in Australia and British Columbia in Canada relating to disease attributable to asbestos exposure indicate that in both jurisdictions the ratio of lung cancer cases to mesothelioma cases is much lower than epidemiological studies indicate must be occurring. Over the period from 1980 to 1994, if both jurisdictions are considered together, about 1,207 cases of lung cancer that would not have occurred without asbestos exposure went unrecognized as occupationally related. The data also suggest that it is unlikely that radiological asbestosis should be regarded as a necessary condition for there to be an increased risk of lung cancer following asbestos exposure.

Asbestos↗

PubMed1997

Analysis of asbestos bodies in BAL from subjects with particular exposures.

Four patients with asbestos-related diseases and with unusual exposures underwent bronchoalveolar lavage (BAL) for mineralogical analysis. Asbestos bodies (AB) were counted by light microscopy and analyzed by transmission electron microscopy and X-ray energy spectrometry. AB's were found in all cases, after a mean delay from the end of exposure of 27.7 years. Analysis of the core fibers indicated the type of alveolar asbestos burden and was compared with the previous exposures: Pleural plaques due to household exposure to amosite and crocidolite. Pleural plaques due to occult occupational exposure to crocidolite in a coal miner. Asbestosis due to environmental exposure to tremolite in Turkey. Asbestosis, pleural plaques, and peritoneal mesothelioma due to a short, intense exposure to crocidolite. AB counting in BAL and identification of the central fibers by analytical electron microscopy is a useful, non-invasive and reliable method to evaluate the alveolar retention of bio-persistent fibers and to relate them to specific exposures.

Aged↗

PubMed1997

Smoking intervention in subjects at risk of asbestos-related lung cancer.

A smoking intervention counseling program was applied among asbestos-exposed male smokers younger than 65 years of age to examine the effect of an intervention based on risk communication. Intervention subjects (n = 431) were invited to a health status checkup combined with physician-delivered smoking intervention counseling. Control subjects (n = 141) received no intervention. After 1 year, 5% of the responders in the intervention group, versus 3.4% in the control group, had stopped smoking. Corresponding conservative estimates were 3.5% and 2.6%, respectively. The quitters had been exposed to a higher "dose" of asbestos but had smoked less, and for a shorter period, than had the continuing smokers. Counseling by a general physician increased successful quitting threefold, compared to counseling by a physician in a specialized institution. These results suggest a potential for smoking cessation among subjects at high risk of lung cancer due to asbestos exposure. General practice care may be an appropriate setting both for identification of such subjects and for intervention.

Asbestos↗

PubMed1999

Cancer in ex-asbestos cement workers in Israel, 1953-1992.

A cohort of 3,057 male workers employed in an asbestos-cement plant using 90% chrysotile-10% crocidolite, located in Northern Israel, was followed from 1953-1992 for incidence and mortality from cancer. In the years 1978-1992, the cohort had an elevated risk for all malignant neoplasms combined (n = 153, SIR = 117, ns), lung cancer (n = 28, SIR = 135, ns), mesothelioma (n = 21; SIR > 5000, p < .0001), unspecified pleural cancer (n = 5; SIR = 278, P < .0001), and liver cancer (n = 7, SIR 290, ns). Risks for colo-rectal (n = 19; SIR = 79, ns), bladder (n = 12, SIR 69) and renal cancers (n = 5, SIR 104) were less than expected. Risk for mesothelioma showed a sharp risk gradient with duration of exposure, increasing from 1 per 625 for those employed less than 2 years to 1 per 4.5 workers employed over 30 years. The ratio of mesothelioma to excess lung cancer cases was 2.9 to 1, or 3.6 to 1, if pleural cases of unspecified origin were included; the pleura to peritoneum ratio of verified mesothelioma cases was 20 to 1. This atypically high ratio of mesothelioma to excess lung cancer cases is suggested to be the combined result of high past asbestos exposures in the workers and their low prior risk for lung cancer, and possibly, relatively early smoking cessation in relation to asbestos exposure.

Aged↗

PubMed1999

Asbestos, chromosomal deletions, and tumor suppressor gene alterations in human malignant mesothelioma.

Exposure to the carcinogen asbestos is considered to be a major factor contributing to the development of most malignant mesotheliomas (MMs). We highlight the role of asbestos in MM and summarize cytogenetic and molecular genetic findings in this malignancy. The accumulation of numerous clonal chromosomal deletions in most MMs suggests a multistep process of tumorigenesis, characterized by the loss and/or inactivation of multiple tumor suppressor genes (TSGs). Cytogenetic and loss of heterozygosity (LOH) analyses of MMs have demonstrated frequent deletions of specific sites within chromosome arms 1p, 3p, 6q, 9p, 13q, 15q, and 22q. Furthermore, TSGs within two of these regions, i.e., p16/CDKN2A-p14ARF at 9p21 and NF2 at 22q12, are frequently altered in MMs. Homozygous deletion appears to be the major mechanism affecting p16/CDKN2A-p14ARF, whereas inactivating mutations coupled with allelic loss occur at the NF2 locus. Finally, recent studies have demonstrated the presence and expression of simian virus 40 (SV40) in many MMs. SV40 large T antigen has been shown to inactivate the TSG products Rb and p53, suggesting the possibility that asbestos and SV40 could act as cocarcinogens in MM. The frequent occurrence of homozygous deletions of p16/CDKN2A-p14ARF and the ability of SV40 Tag to bind TSG products suggest that perturbations of both Rb- and p53-dependent growth-regulatory pathways are critically involved in the pathogenesis of MM.

Asbestos↗

PubMed1980

Latency of asbestos disease among insulation workers in the United States and Canada.

Two thousand two hundred seventy-one deaths were recorded among 17,800 asbestos insulation workers observed from January 1, 1967-December 31, 1976. There was little increase in cancer deaths or of asbestosis in less than 15-19 years from onset of employment. In general, though, the period of clinical latency was 2-4 decades or more and there were important differences among the several asbestos-associated diseases. Lung cancer peaked at about 30-35 years from onset and asbestosis at 40-45 years. Each tended to decline in incidence afterwards. Pleural and peritoneal mesothelioma reached their highest incidence later than lung cancer, but the incidence did not decline. In studies of effects of asbestos exposure, it appears advantageous to observe for at least 35-40 years or more from onset of exposure and to analyze the experience in duration-from-onset categories. If this is not possible, only the very limited early effects will be identified and the full import of the exposure may not be appreciated.

Adolescent↗

PubMed2004

Concentration of hydroxyproline in blood: a biological marker in occupational exposure to asbestos and its relationship with PiZ and PiS polymorphism in the alpha-1 antitrypsin gene.

BACKGROUND: Hydroxyproline (OHP) is one of the most abundant amino acids in collagen and, in general, it provides a good measure of overall collagen catabolism. METHODS: Asbestos workers suffering from asbestosis (cases n = 85); asbestos exposed workers without asbestosis (exposed controls, EC, n = 86), and non-exposed population (non-exposed controls, NEC, n = 122) were studied. The concentration of free OHP in whole blood was measured following the Pico-Tag procedure. RESULTS: Concentration of OHP in blood was significantly different in the three groups studied (P < 0.001), being higher in cases (19.8 +/- 14.7 micromol/L) than in EC (16 +/- 12.4) and NEC (13.5 +/- 6.7). When all individuals were grouped and stratified by the Pi*S and Pi*Z polymorphisms in the alpha-1-antitrypsin gene, the highest OHP levels were detected in the Pi*S homozygotes, one of the asbestosis-at risk-genotypes (Pi*S homozygotes, x = 24.5 +/- 11.7; Pi*S heterozygotes, x = 16.6 +/- 10.0; wild type, wt, x = 15.9 +/- 11.8). CONCLUSIONS: Blood OHP concentration could be used for monitoring human exposure to asbestos, either as a marker for occupational monitoring or as an additional clinical parameter in diagnostic exploration of asbestosis.

Alleles↗

PubMed2006

Re: Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability.

BACKGROUND: In Atkinson et al. 2004 rinsates of unused brake components were analyzed by transmission electron microscopy (TEM) for the presence of asbestos fibers. RESULTS: We do not believe that the findings of Atkinson et al. are informative and could have been predicted based on the study design and the fact that one would expect to find measurable TEM asbestos fibers on an unused brake component. We also find that the paper did not provide a full or even partial discussion of the published literature with respect to industrial hygiene or epidemiology data. CONCLUSION: The findings of Atkinson et al. do not, in our view, "further raise concerns" about historical asbestos exposures experienced by automotive mechanics because of the vast amount of published literature to the contrary.

Air Pollutants, Occupational↗

PubMed2006

Revising the British Occupational Hygiene Society asbestos standard: 1968-1982.

BACKGROUND: In 1968 the British Occupational Hygiene Society (BOHS) published a chrysotile asbestos hygiene standard. As a consequence of acknowledged inadequacies of the data, it underestimated the risks of exposure, but its influence was international and operated for longer than it merited. Five years later, BOHS reported the standard not to be in need of amending, despite its own doubts and no cognizance having been taken of the cancer hazard. Within months, stung by criticism from Dr. Irving J. Selikoff, industry required it to review the standard, which BOHS continued to do for a number of years before giving up. METHODS: Material obtained for the American Courts by means of legal discovery from an asbestos company's archive, provided information on the membership of the new BOHS committees, and on its operation. RESULTS: Alterations in the composition of the new committees included importantly the introduction of certain independent scientists, whose rigor militated against the ready production of a new hygiene standard acceptable to industry. CONCLUSIONS: There was a time in Britain when a learned society might with impunity omit to consult the views of workers or their representatives when making value judgments about their health and safety, but consider it proper to accede to industry's decision as to what hygiene standard it would accept. Health and Safety at Work legislation in 1974, established an organization on which industry and labor were represented, with the onus for recommending hygiene standards. For several years the BOHS Asbestos Sub-Committee continued attempting to reconcile the interests of industry, until finally abandoning hygiene standard setting as its mission.

Academies and Institutes↗

PubMed1980

Radiological evidence of asbestos disease among ship repair workers.

Asbestos materials are now infrequently used in new ship construction. However, significant amounts were used in vessels constructed before 1975. As a consequence, for the next 30 or more years, the potential for asbestos exposure in the repair of such vessels will remain. We studied 286 workers who were 30 or more years from onset of employment in ship repair work. Eighty-six percent had radiological evidence of asbestosis, and five instances of previously undiagnosed lung cancer were found. This suggests that unless industrial hygiene precautions are taken in the future repair of vessels that have been built with asbestos, we will add additional decades to the legacy we already face as the result of uncontrolled shipyard exposures of the past.

Adult↗