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PubMed1984

Fiber localization and its relationship to lung reaction in rats after chronic inhalation of chrysotile asbestos.

Inhalation of chrysotile asbestos fibers causes interstitial lung disease in animals and man. For examination of the anatomic localization of inhaled asbestos and its relationship to alveolar tissue responses of the lung during and after chronic exposure, male and female Fischer 344 rats were exposed to aerosolized chrysotile for 7 hours/day, 5 days/week for 3 or 12 months. A number of exposed animals were kept in filtered air for an additional 12 months. Lung tissue from randomly selected animals in each group was studied by morphometric analysis of electron micrographs. Our findings show that during exposure to asbestos fibers, macrophages and alveolar epithelial cells contain statistically significant amounts of asbestos and are associated with histologic changes indicating marked epithelial injury. Increased amounts of fibers are also localized in the lung interstitium with continued exposure to asbestos and are associated with a progressive interstitial fibrotic reaction. Following cessation of exposure, macrophages and epithelial cells are cleared of fibers and resolve toward normal proportions. However, significant clearance of fibers from the lung interstitium does not occur after cessation of exposure, and there is a continuing process of fibrogenesis. These data provide new insights related to the pathogenesis of diffuse lung disease and the role each alveolar tissue compartment plays in the early and late phases of the disease.

Animals↗

PubMed1984

Chemiluminescence of asbestos-activated macrophages.

Chemiluminescence, a measure of reactive oxygen release by phagocytes, was compared in peritoneal exudate macrophages elicited with chrysotile asbestos, Corynebacterium parvum and saline. Chrysotile asbestos- and C. parvum-activated macrophages produced significantly more chemiluminescence than saline-elicited macrophages. In a second series of experiments the ability of opsonized chrysotile asbestos to act as a trigger for the release of chemiluminescence was tested. Opsonized chrysotile asbestos produced a dose-related release of chemiluminescence from activated macrophages except at the highest dose where chemiluminescence was reduced due, possibly, to a toxic effect of chrysotile during the assay. Opsonized latex also triggered a dose-related chemiluminescent response from activated macrophages. The potential role of toxic reactive oxygen species, released from macrophages, in the development of asbestos-related pulmonary inflammation and fibrosis are discussed.

Animals↗

PubMed1984

Asbestos content in lungs of occupationally and nonoccupationally exposed individuals.

Previous reports have indicated that a majority of the population has asbestos bodies within their lungs. These studies generally have been carried out using cohorts from urban environments. The present study compares the asbestos body levels from three unique cohorts: (1) a nonoccupationally exposed group from a large urban environment having a relatively low asbestos content, (2) patients with lung cancer from a nonurban setting, and (3) amosite asbestos workers, who worked and lived in a rural setting. The number of asbestos bodies in both the urban nonoccupationally exposed group and the patients with lung cancer was generally found to be low or below limits of detectability, with the exceptions being those persons in whom an occupational exposure was eventually found. The ferruginous body content of the occupationally exposed group varied considerably between individuals as well as between sites within the same individual.

Adult↗

PubMed1984

The early pathogenesis of asbestos-induced lung disease.

This paper presents new findings obtained using animal models on the basic mechanisms of asbestos-induced lung disease. Recent, highly visible reviews on the subject have clearly pointed out that little is known about the cellular mechanisms through which inhaled asbestos fibers cause the well known, debilitating lung disease - asbestosis (i.e. interstitial pulmonary fibrosis). During the past five years, my colleagues and I have published a series of papers in which we have attempted to elucidate, in a rat model of asbestosis, the initial events of 1) asbestos fiber deposition, 2) translocation of fibers to the lung interstitium, 3) the response of pulmonary macrophages and the mechanisms through which these cells are attracted to sites of initial asbestos deposition, and 4) the developmental pathogenesis of the earliest anatomic lesion consequent to asbestos exposure.

Animals↗

PubMedDate not supplied

Chrysotile and crocidolite asbestos in Israel: uses, exposures and risks.

Importation of raw asbestos (90% chrysotile; 10% crocidolite) for manufacture of cement products and other uses, including friction materials and spraying, had dropped to under 3000 tons by 1993 from a peak of 10,000 tons per annum in the late 1970s. Drops in use, manufacture, persons exposed in manufacture and measured exposure levels followed heightened public concern over the carcinogenic effects of asbestos products, despite a relatively high worker exposure standard of 400,000 f/m3. The atypically low ratio of reported deaths from lung cancer compared to mesothelioma in asbestos cement workers up to 1992 (1:2.5) is suggested to be a consequence of low baseline risks for lung cancer mortality in Israel and dropping smoking levels. Exposure to asbestos use and asbestos in place remain, but total risk should drop after 2010 if imports continue to drop. These projections may be altered by trade between Israel and its neighbors following peace agreements. Reductions in risk will have resulted from reduction in exposure brought about by reductions in manufacture and use.

Adolescent↗

PubMed1995

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 microns, 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 > or = 5 microns were in the following decreasing order: tremolite > crocidolite > chrysotile > other fibers > talc-anthophyllite > amosite. For total fibers < 5 microns, 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 microns 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.

Aged↗

PubMedDate not supplied

Effect of two particle surface-modifying agents, polyvinylpyridine-N-oxide and carboxymethylcellulose, on the quartz and asbestos mineral fiber-induced production of reactive oxygen metabolites by human polymorphonuclear leukocytes.

We studied the capacity of quartz and asbestos fibers to induce the generation of reactive oxygen metabolites in human polymorphonuclear leukocytes (PMNs) with a chemiluminescence (CL) assay. On an equal weight basis, the particulates induced CL in the following order of magnitude: chrysotile, quartz greater than amosite, crocidolite, greater than anthophyllite, wollastonite. The intensity of CL correlated positively with the Alcian blue (a cationic dye) binding capacity of the particles. Polyvinylpyridine-N-oxide (0.5 microgram/ml) inhibited completely the CL induced by quartz but had little effect on the CL induced by asbestos fibers. Carboxymethylcellulose (1.0 microgram/ml), however, reduced the CL caused by chrysotile asbestos but had no effect on the CL induced by the other particulates. Our results suggest that in addition to length and diameter, the effect of quartz and asbestos fibers on inflammatory cells will depend on surface characteristics, including the charge of the particles.

Adult↗

PubMed1982

In vitro effect of asbestos fibers on polymorphonuclear leukocyte function.

Incubation of chrysotile and amphibole asbestos fibers with normal human peripheral blood polymorphonuclear leukocytes (PMN) resulted in a significant stimulation of PMN metabolic activity and generation of toxic oxygen by-products as measured by chemiluminescence (CL). Although all asbestos fibers tested were cytotoxic to PMN, cytotoxicity and CL varied disproportionately with fiber type. Anthophyllite asbestos produced the greatest PMN cytotoxicity. It also depressed PMN phagocytosis of latex beads the most and induced the greatest PMN CL response of the fiber types examined. We postulate that asbestos-induced release of toxic oxygen by-products from PMN which have infiltrated into the pulmonary alveoli may contribute to disease pathogenesis in asbestosis.

Asbestos↗

PubMed1992

Tumor incidence was not related to the thickness of visceral pleural in female Syrian hamsters intratracheally administered amphibole asbestos or manmade fibers.

Histological observations were performed on female Syrian hamsters 2 years after the intratracheal administration of amphibole asbestos, amosite, and crocidolite to evaluate the tumorigenicity of six types of fine manmade fibers (reported previously). A mesothelioma and a lung tumor were induced in 20 animals administered amosite, but no tumors were found in the crocidolite group. Because this incidence is not higher than that of manmade fibers, such as basic magnesium sulfate fiber [9 tumor-bearing hamsters in 20 hamsters (9/20)], metaphosphate fiber (5/20), calcium sulfate fiber (3/20), and fiberglass (2/20), it is suggested that some types of manmade fibers have a greater ability than asbestos to induce tumors. Moreover, as a specific observation in manmade fiber groups, tumors were induced at intracelial organs rather than at the pleural cavity. On the other hand, the average thickness of visceral pleura was higher in all asbestos and manmade fiber groups than in the control (2.9 microns), for instance, 36.95 microns in potassium titanate fiber group, 15.90 microns crocidolite group, 13.00 microns basic magnesium sulfate fiber group, and 10.45 microns in the rockwool group. Although both pleural thickening and mesothelioma are known as peculiar lesions in asbestos-exposed people, it might also be suggested that these lesions could be induced by different mechanisms from the result that there was no relation between the pleural thickening and mesothelioma incidence in hamsters.

Adenoma↗

PubMed1994

Asbestos use and carcinogenicity in Germany and a comparison with animal studies.

The centralized structure of economic affairs in the former German Democratic Republic (East Germany) and the isolation from the free market led to the situation that imported asbestos was almost exclusively chrysotile. More than 90% came from the Kiembay mining area in the Ural Mountains, and about 7% was long-fibre chrysotile from Canada. Sturm and co-workers detected 1082 mesothelioma cases from 1960 to 1990 in the counties of Magdeburg and Halle. In 843 of these cases an exposure to asbestos was evident. Seventy-two cases were exposed to chrysotile only. Suspected exposure to amphiboles imported before World War II or to fibre contained in talc could not be substantiated. Up to now, there have been no analyses of lung fibre burdens from such cases. Reviewing the carcinogenicity studies in rats performed by inhalation or intra-cavitary injection of chrysotile, amosite and crocidolite fibres, the results give no clear indication of a lower carcinogenic potency per chrysotile fibre than per amphibole fibre if equal fibre numbers and fibre sizes are applied, although the chrysotile content of the lungs is relatively low. Also the mesothelioma rates after inhalation exposure to extremely high concentrations of the different asbestos fibre types are similar for chrysotile and the amphiboles and in the region of 5%. Compared with the asbestos-related cancer rates in chrysotile textile workers, rats have to be exposed to a more than 100-fold higher fibre concentration than humans to induce the same lung tumour incidence.

Animals↗

PubMed1986

Comparison of the results of asbestos fibre dust counts in lung tissue obtained by analytical electron microscopy and light microscopy.

The efficiency of the light microscope with that of the electron microscope in detecting asbestos fibres in human lung tissue was computed. Necropsy material from 55 patients who had died from asbestos related diseases was analysed independently by phase contrast microscopy and electron microscopy. As expected the number of fibres identified using electron microscopy was higher than that identified by light microscopy. By adjusting the electron allow for the limited resolving power of the light microscope, however, a significant correlation of the number of fibres identified using the two methods was obtained. The best correlation was found with specimens containing crocidolite (correlation coefficient 0.79) and amosite (correlation coefficient 0.74), while chrysotile gave a much lower correlation (correlation coefficient 0.15). The cumulated fibre diameter distribution obtained using the electron microscope suggests that the light microscope is able to visualise only 5% of crocidolite, 26.5% of amosite, and 0.14% of chrysotile present in lung tissue. Therefore, although it is possible, using the electron microscope, to predict the asbestos fibre count that would be obtained by light microscopy, the reserve prediction cannot be made: it is impossible to determine the proportion of the various asbestos mineral types using the light microscope.

Asbestos↗

PubMed1985

Effects of asbestos on the random migration of rabbit alveolar macrophages.

The toxicity of sized and characterized chrysotile, crocidolite, and amosite preparations obtained from Dr. K. R. Spurny have been evaluated using alveolar macrophage (AM) migration inhibition assays and viability tests. These results have been compared with asbestos samples obtained from the National Institute of Environmental Health Sciences (NIEHS). These latter samples are designated chrysotile A (RT), crocidolite (RT), and amosite (RT). In addition, filter-isolated preparations of chrysotile A (RT) that consisted mainly of large nonphagocytosable fibers were also tested. Chrysotile (Spurny) and sonicated chrysotile A (RT) produced 50% migration inhibition at about 115 micrograms/mL. Spurny crocidolite produced 50% migration inhibition at about 340 micrograms/mL, whereas RT crocidolite produced 50% migration inhibition at about 230 micrograms/mL. RT amosite caused 50% migration inhibition at about 180 micrograms/mL, whereas Spurny amosite was inactive up to 500 micrograms/mL. The large nonphagocytosable chrysotile A (RT) fibers produced 50% migration inhibition at about 66 micrograms/mL. This indicates that fibers can be toxic for AM through extracellular membrane contact. In general the results from the viability studies paralleled the migration inhibition observations. None of the asbestos preparations induced a burst in the hexose monophosphate shunt of BCG-immune AM at 1 mg/mL. BCG-immune AM were more susceptible to cell death than normal AM when incubated with chrysotile A (RT), amosite (RT) and zymosan. Migration inhibition induced by asbestos fibers probably reflects toxicity of the asbestos preparations and could play an important role in blocking normal alveolar clearance of inhaled particles.

Animals↗

PubMed1984

Proliferation stimulating effects of chrysotile and crocidolite asbestos fibres on B lymphocyte cell lines.

Asbestos fibres of chrysotile, crocidolite and amosite were incubated with eight types of human cell lines in vitro. These asbestos fibre were cytotoxic to fibroblasts and monocyte like cells, as is already known. On the other hand, immature B lymphocyte lines (B1 2) were stimulated significantly by chrysotile and crocidolite, while a mature B cell line (B3) was not affected. Cell proliferation of a T cell line and an erythromyeloid cell line also was not affected by asbestos. For the stimulation of lymphocytes, the binding of the mitogen to the reactive sites on the lymphocyte surface is thought to be indispensable. It seems that chrysotile and crocidolite asbestos can bind to immature B lymphocytes, but not to mature B cells.

Asbestos↗

PubMed1996

Mortality among maintenance employees potentially exposed to asbestos in a refinery and petrochemical plant.

This paper reports the mortality experience from 1948 to 1989 of 2,504 maintenance employees who had a minimum of one year of employment in jobs with potential exposure to asbestos at a Texas refinery and petrochemical plant. For the purposes of this study, "potential exposure" is equated with those jobs or crafts having the greatest direct potential proximity to, or which worked directly with, asbestos-containing materials, especially asbestos-containing thermal insulation. Approximately one-half of the study population had 10 years or longer potential exposure, and 80% had their first potential exposure before 1970. The total population exhibited significantly lower mortality for all causes, the standardized mortality ratio (SMR = 77); and for all cancer (SMR = 85), as compared to residents in the surrounding communities. Statistically significant deficits in mortality were also observed in a number of noncancerous diseases such as heart disease (SMR = 78; 95% CI = 69-88), nonmalignant respiratory disease (SMR = 70; 95% CI = 50-95), and cirrhosis of the liver (SMR = 44; 95% CI = 22-79). Mortality among employees who had 20 years or longer since their first potential exposure was also examined; the pattern of mortality was similar to that exhibited by the total cohort, with a slight increase in the SMR for most of the causes. The only statistically significant excess of mortality found was a fourfold increase in mesothelioma (5 observed and 1.2 expected deaths) the SMR was 428 (95% CI = 139-996) for the total cohort and was 469 (95% CI = 152-1093) for those who had 20 years or more since first potential exposure. In contrast to asbestos industry worker studies, mortality for lung cancer was substantially lower than the general population (SMR = 81; 95% CI = 63-103). The observed number of deaths for cancer of the larynx was virtually the same as expected (3 observed vs. 2.8 expected). This study also showed decreased mortality for cancers of gastrointestinal organs such as the esophagus (SMR = 78), stomach (SMR = 63), large intestine (SMR = 91), rectum (SMR = 55), or pancreas (SMR = 90)--cancers that have been reported to be elevated in studies of various industry workers directly exposed to asbestos.

Adult↗

PubMed1996

Comparison of measures of exposure to asbestos in former crocidolite workers from Wittenoom Gorge, W. Australia.

Determinations of exposure-response relationships between crocidolite and the major asbestos-related diseases in the Wittenoom cohort have previously depended on the validity of estimates of airborne exposure to asbestos. This work aims to validate the airborne exposure measurements by obtaining measurements of the concentrations of uncoated crocidolite fibers and asbestos bodies retained in the lungs of individual workers, and to estimate the half-life of crocidolite fibers in the lungs. Samples of lung tissue, excluding tumor, of all former Wittenoom workers known to have died in Western Australia (WA) were sought from teaching hospitals, pathology departments, and the Coroner's pathologist. The lung specimens were processed using Pooley's method with TEM for counts of fibers of all types and using Smith and Naylor's method with conventional light microscopy for asbestos bodies (AB). Multiple linear regression was utilized to examine the associations between crocidolite concentrations in the lung and duration of employment at Wittenoom, time since last employed at Wittenoom, nature of job, estimated average fiber concentration at the worksite, and estimated cumulative crocidolite exposure (CCE) in fiber-years/ml for each subject. Lung tissue from 90 cases was processed and there was good agreement between counts of crocidolite fibers, asbestos bodies, and CCE. Correlations were 0.77 for AB and fibers, 0.54 for AB and CCE, and 0.58 for CCE and fibers, after log transformation. The half-life of crocidolite fibers in the lung was estimated at 92 months (95% CI 55-277 months). Previous estimates of airborne exposure to Wittenoom crocidolite have been reasonably reliable. The relatively simple technique of light microscopy for counting ABs in lung tissue also provides a useful and reliable indication of the level of past occupational exposure to crocidolite in subjects whose exposure has been only to crocidolite. The half-life of crocidolite fibers in the lungs of former Wittenoom workers is about 7-8 years.

Adult↗

PubMed1996

Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos.

To evaluate the presence of asbestos-related pleural and parenchymal abnormalities and their correlation with pulmonary function and smoking habits, 119 asbestos-exposed asymptomatic workers (mean age, 46.2 years; mean duration of asbestos exposure, 8.6 years; mean latency time, 21.6 years) with normal standard P.A chest radiographs were submitted to HRCT, CO-diffusing capacity and pulmonary function tests. HRCT scans were normal only in 31 (26%) examined workers; 31 (26%) subjects showed both pleural and parenchymal involvement, and 50 (42%) and seven (6%) had exclusively pleural and parenchymal abnormalities, respectively. Based on CO-diffusing capacity and pulmonary function tests, no significant difference was demonstrated between workers with pleural lesions and subjects with normal pleura; however, lower values of FVC were observed in the nonsmoking workers with parenchymal abnormalities in comparison with nonsmoking subjects with normal parenchyma (78.2 vs. 89.7% of predicted values; p = 0.03 by student's two-tailed t test), and lower values of FEV1/FVC in the smokers with parenchymal lesions with respect to smokers with normal parenchyma (93.7 vs. 100.2% of predicted values; p = 0.005 by students' two-tailed t test). In conclusion, our results demonstrate that HRCT may detect early parenchymal abnormalities which correlate with exposure to asbestos and respiratory function impairment, including a reduction in obstructive indices in smokers occupationally exposed to asbestos, without any clinically evident disease.

Adult↗

PubMed1996

Asbestos plaques in a typical Veteran's hospital population.

Previous authors have described several pleural abnormalities on chest radiology as being pathognomonic for asbestos exposure. We sought to determine the percentage of admissions and outpatients at a typical Veteran's Affairs hospital with these findings, and researched medical records to verify the frequency at which patients having positive radiographs were suspected either by clinical/occupational history or radiologically to have had prior significant exposure to asbestos. Radiographs of 1,212 consecutive patients were evaluated by a certified B reader, and the medical records as well as previous radiology reports of all positive patients were reviewed. Twenty-eight (2.3%t) of the radiographs had pleural abnormalities consistent with asbestos exposure, with the patients, all male, ranging in age from 50 to 98 years (mean 75.6). Radiology reports described pleural plaques in only 12 of the 21 (57%) cases with prior exams available; in only seven (33%) was an asbestos etiology considered by the interpreting radiologist. The plaques were misdiagnosed in four instances as being indicative of other, unrelated pathology. A history of known dust exposure was expressed by only five patients (18%). Eleven described working in occupations now known to have a high incidence of exposure, but neither patient nor examining physician expressed consideration of dust inhalation. In conclusion, we have found that a significant percentage of patients in certain subpopulations show radiographic evidence of asbestos exposure that may be a harbinger of related pathology. Unfortunately, because of a low index of suspicion, thorough environmental histories are often deferred, many radiographic changes are either not recognized or are misdiagnosed, and these patients are not followed with the stringent protocols they deserve.

Aged↗

PubMed1999

Peritoneal cancer and occupational exposure to asbestos: results from the application of a job-exposure matrix.

BACKGROUND: Because of the rarity of peritoneal mesothelioma, occupational risks associated with it have seldom been studied, particularly among women. In this respect, death certificates databases may provide numbers large enough for analysis, although the International Classification of Diseases, 9th revision (ICD-9) does not single out mesothelioma from the rest of peritoneal cancers. The aim of this paper is twofold: to explore occupational risks of peritoneal cancer among men and women, and to test the performance of a job-exposure matrix in detecting its association with asbestos exposure using the occupation and industry reported in the death certificate. METHODS: From a large database containing information on the 1984-1992 death certificates of 24 U.S. states, we identified 657 deaths from peritoneal cancer and 6,570 controls who died from non-malignant diseases, 1:10 matched by region, gender, race, and 5-year age group. RESULTS: Occupations at risk included insulators among men, and machine operators among women. Among men, we found a significant increase in risk associated with employment in manufacturing industries, such as industrial and miscellaneous chemicals; miscellaneous non-metallic mineral and stone products; construction and material handling machines; and electrical machinery, equipment, and supplies; as well as in services to dwellings and other buildings. Industries at increased risk among women included elementary and secondary schools; miscellaneous retail stores; and publishing and printing. Our job-exposure matrix classified 17 male cases and 3 controls in the high probability category of exposure to asbestos (OR = 61.6). Among men, risk of peritoneal cancer increased significantly by probability and intensity of exposure to asbestos. No such pattern was observed among women. The job-exposure matrix did not classify any female subjects in the high probability or intensity of asbestos exposure. DISCUSSION: This study provides evidence that death certificate data and job-exposure matrices are useful tools to observe well-established associations, such as the one existing between peritoneal cancer and asbestos exposure among men, in spite of crude information, disease misclassification, and occupational misclassification. These factors are more likely to preclude meaningful results among women.

Aged↗