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PubMed1983

Asbestos-induced alterations of human lymphoid cell mitogenic responses.

Using mitogenic assays, we have investigated the short term effects of two asbestos (amosite and chrysotile) fibers on lymphocyte functions in vitro. These oppositely charged fibers produced different alterations in mitogenesis. The blastogenic responses of concanavalin-A (Con-A) and pokeweed mitogen stimulated human peripheral blood mononuclear cells (PBMN) were significantly increased by the inclusion of 6 micrograms of chrysotile to the culture media. Amosite fibers proved to be inhibitory in all tests. When PBMN were depleted of monocytes, asbestos-related alterations of Con-A responsiveness were unchanged among the remaining cells. However, the addition of chrysotile to phytohemagglutinin (PHA) cultures resulted in a significant increase of the mitogenic response. When PBMN were enriched for T lymphocytes, and again cultured with the mitogens and fibers, the Con-A response still displayed impressive enhancement with chrysotile. In contrast to an intact PBMN population, PHA-induced blastogenesis among these T-enriched lymphocytes was significantly elevated. These experiments demonstrate that asbestos can induce significant changes in the functional integrity of PBMN following a relatively short exposure time in culture.

Asbestos↗

PubMed1987

Effects of in vitro asbestos exposure on natural killer and antibody-dependent cellular cytotoxicity.

Human peripheral blood lymphocytes (PBL) were exposed in vitro to asbestos fibers. Antibody-dependent cellular cytotoxicity (ADCC) activity and natural killer (NK) activity were examined by a chromium-51 release assay. There was a statistically significant enhancement of ADCC and NK activity by chrysotile and crocidolite fibers when cultured together with PBL for a period of 42 hr in medium containing a concentration of at least 2.5% fetal calf serum (P less than 0.05). Isolation of large granular lymphocytes to measure NK activity, however, showed the opposite effect when exposed to asbestos fibers (P less than 0.05). Our results indicate that asbestos fibers can directly affect lymphoid cytotoxic responses in vitro and may provide clues to immunopathogenic mechanisms for the occurrence of neoplasms in vivo.

Adult↗

PubMed1995

Phase contrast microscopy asbestos fiber counting performance in the Proficiency Analytical Testing program.

This report evaluates 20 years (1972-1992) of asbestos fiber count reporting for the Proficiency Analytical Testing (PAT) program, which is operated by the American Industrial Hygiene Association (AIHA) in cooperation with the National Institute for Occupational Safety and Health (NIOSH). Estimates were obtained for total, intracounter, and intercounter variability. Results show that total variability of counting chrysotile asbestos fibers improved by approximately 35% in recent years when compared with the variability found during 1975-1977, at the lowest filter fiber densities used in the PAT program. Total, intercounter, and intracounter variability for counting amosite and chrysotile asbestos fibers also were compared over a six-year period starting in 1986. PAT program laboratories achieved about one-quarter lower intracounter variability and about one-third lower total and intercounter variability when counting amosite fibers versus chrysotile fibers. In addition, amosite intercounter variability improved by about one-third, with large improvements occurring in the first year that amosite was included in the program. Factors affecting performance, such as changes in phase contrast microscope fiber counting methods, PAT participation, the AIHA Laboratory Accreditation Program, and PAT sample production, are discussed as possible factors affecting variability.

Asbestos↗

PubMed1994

Fiber burden and patterns of asbestos-related disease in workers with heavy mixed amosite and chrysotile exposure.

To attempt to determine the mineralogic factors that relate to the appearance of specific types of asbestos-related disease in workers with heavy mixed exposure to amphiboles and chrysotile, we analyzed the pulmonary asbestos fiber burden in a series of 144 shipyard workers and insulators from the Pacific Northwest. Amosite was found in all lungs, and tremolite and chrysotile in most lungs, but the vast majority of fibers were amosite. Tremolite and chrysotile concentrations were significantly correlated, indicating that the tremolite originated from chrysotile products, but no correlation was found between tremolite or chrysotile concentration and amosite concentration. Time since last exposure was correlated with decreasing amosite concentration and the calculated clearance half time was about 20 yr. In a multiple regression analysis that accounted for the presence of more than one disease in many subjects, a high concentration of amosite fibers was correlated with the presence of airway fibrosis and asbestosis, whereas subjects with mesothelioma, lung cancer, pleural plaques, or no asbestos-related disease had about the same, much lower, amosite concentration. No relationship was found between the concentration of chrysotile or tremolite and any disease. Analysis of fiber size measures (length, width, aspect ratio, surface, mass) showed that pleural plaques were strongly associated with high aspect ratio amosite fibers and suggested that mesotheliomas were associated with low aspect ratio amosite fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1983

Effect of asbestos on the P388D1 macrophagelike cell line: preliminary ultrastructural observations.

The ultrastructural effects of mineral dusts on a macrophagelike cell line (P388D1) were studied by transmission electron microscopy. The cells were found to contain virus particles which probably did not exert a cytopathic effect toward the cells. During mitosis the asbestos fibers appeared to be pushed to the periphery of the cell. The distribution of the asbestos in the P388D1 cells was similar to that seen previously in cultured peritoneal macrophages, and it was concluded that the cytotoxic effect of asbestos towards the cells was due to mechanical effects, e.g., by penetrating structures such as the nucleus or phagosomes, by preventing the ordered movement of organelles with the cell or by disrupting the cytoskeletal framework of the cell.

Animals↗

PubMed1983

Characterization of cytotoxic effect of asbestos on normal human fibroblasts.

Using viable cell counting and the incorporation of radioactive thymidine in cell TCA precipitate, we have attempted to separate the effects of asbestos on cell growth inhibition (reproductive failure) vs. cell killing. NIEHS crocidolite and NIEHS intermediate-sized chrysotile at a concentration of 10 micrograms/mL were studied. Cytotoxic effects were demonstrated with both types of asbestos. Thymidine incorporation expressed as cpm/viable cell was enhanced in the presence of either form of asbestos. It is concluded that both negatively charged crocidolite and positively charged chrysotile are toxic to human fibroblast cells in culture and exert their cell killing but not growth inhibition effect concurrently with a stimulation of DNA synthesis.

Asbestos↗

PubMed1989

Asbestos fibre content of lungs with mesotheliomas in Osaka, Japan: a preliminary report.

That crocidolite and amosite are both associated with the development of mesothelioma is now well established, but earlier studies have failed to find an excess of chrysotile in lungs with mesotheliomas as compared with the amounts in lungs of unaffected controls. In an attempt to clarify the importance of fibre type in tissue, an examination of a series of mesotheliomas is being undertaken in Osaka, Japan. A total of 23 mesotheliomas and 5 rejected cases reviewed by the Osaka Mesothelioma Panel were examined for the types of asbestos and semiquantitative fibre content by means of a transmission electron microscope equipped with energy-dispersive X-ray analyser. Asbestos fibres were detected in 19 of the 23 mesotheliomas (21 pleura, 1 pericardium, 1 peritoneum; 19 males, 4 females). Amphibole fibres were found in 13 cases. Five pleural and one peritoneal mesothelioma were found to have only chrysotile fibres. One female pleural mesothelioma with neighbourhood exposure had short chrysotile fibres. Among the 5 rejected cases, only one case with occupational exposure had both chrysotile and amosite fibres. A group of 17 controls were also examined and asbestos fibres were found in 5. Our data, while not definitive, suggest that mesotheliomas can be induced in humans, not only by crocidolite and amosite, but also by chrysotile, though possibly to a lesser extent.

Asbestos↗

PubMed1984

Chemotactic factor generation by asbestos. Fibre type differences and the effects of leaching.

The generation of chemotactic factors in normal human serum by treatment with chrysotile and crocidolite asbestos was investigated using the Boyden chamber method. Both types of asbestos produced chemotactic activity but not to the same extent. The two fibre types also produced different levels of complement activation as measured by C3 conversion using two dimensional immunoelectrophoresis. While there was a simple correlation between fibre concentration and C3 conversion the production of chemotactic activity declined at high doses of chrysotile. Phosphate buffer treatment reduced the differences between fibre types. The possible role of these phenomena in asbestos-associated disease is discussed.

Asbestos↗

PubMedDate not supplied

Asbestos mineralogic analysis as indicator of carcinogenic risk.

Asbestos fibers can be found in several tissues and fluids, by different techniques, but up to now there is not a standardised approach. Chrysotile seems to be removed from the lung with greater ease than the amphiboles, but it is more frequently found in pleural tissues. Human and animal studies agree in documenting that chrysotile and amphiboles produce mesotheliomas, even if these studies rarely add much to the understanding of mechanisms of asbestos-related diseases. Further of asbestos-related diseases. Further studies are needed with standardized materials and techniques to better understand these mechanisms and to determine which individuals may be at highest risk for the development of disease.

Asbestos↗

PubMed1997

Cancer incidence and mortality among Finnish asbestos sprayers and in asbestosis and silicosis patients.

Cohorts of Finnish asbestos sprayers and of asbestosis and silicosis patients were followed for cancer with the aid of the Finnish Cancer Registry in the period 1967-1994. Compared with the cancer incidence of the total Finnish population, asbestos sprayers had an increased risk for total cancer (standardized incidence ratio [SIR] 6.7, 95% confidence interval [95% CI] 4.2-10); lung cancer (SIR 17.95% CI 8.2-31); and mesothelioma (SIR 263, 95% CI 85-614). The SIR of the asbestosis patients was 3.7 (95% CI 2.8-5.0) for all sites, 10 (95% CI 6.9-14) for lung cancer, and 65 (95% CI 13-188) for mesothelioma. The silicosis patients also had significantly high SIR values for all sites (1.5, 95% CI 1.0-2.1) and lung cancer (2.7, 95% CI 1.5-4.5). The values for the SIR and the standardized mortality ratio for all sites and lung cancer were very similar, and therefore it seems that both are reliable indicators of the occurrence of occupational cancer. It was concluded that pneumoconioses patients and asbestos-exposed workers have a markedly elevated risk for cancer. Asbestos-induced occupational cancers are not only diseases of the elderly, since the relative risk is high also for middle-aged people.

Adult↗

PubMed2002

Study of smoking behavior in asbestos workers.

BACKGROUND: Asbestos exposure and concomitant cigarette smoking markedly increase the risk of lung cancer and contribute to the prevalence and severity of pulmonary interstitial fibrosis. METHODS: A cross-sectional survey of 214 asbestos workers was initiated to determine the prevalence of smoking and their readiness to quit smoking using the stage of change theory. RESULTS: The study was comprised of 61 never smokers (28.5%), 118 ex-smokers (55.1%), and 35 current smokers (16.4%). Reasons for smoking cessation in ex-smokers included perception of ill-health (51%) and knowledge of smoking-asbestos hazards (3.4%). Stage of change of current smokers revealed: precontemplation (26.5%), contemplation (35%), preparation (29%), and action (8.8%). Current smokers had the highest prevalence of small airway obstruction on spirometry. CONCLUSIONS: A detailed smoking history during medical surveillance activities will enable the occupational physician to identify asbestos workers who have difficulty quitting and to develop a system in which such individuals can be referred to comprehensive smoking cessation programs.

Adult↗

PubMed1981

Asbestos-related diseases in the Federal Republic of Germany.

Until recently, in the Federal Republic of Germany there has been a lack of epidemiological data on asbestos-related tumors. Only the numbers of occupational diseases accepted for compensation by the German industrial injuries insurance institutes (Berufsgenossenschaften) can be stated. These show, for 1979, 94 cases of asbestosis, 21 cases of asbestosis associated with lung cancer, and 34 cases of mesothelioma. Since 1972 employees exposed to asbestos dust have been included in a central register by the industrial injuries insurance institutes and are medically examined periodically. By December 31, 1979, 28,476 persons were registered. Of those, 6,582 were still being followed medically, although they were no longer working with asbestos dust exposure. In January 1, 1977, a prospective epidemiological study was started with these people who were formerly exposed to asbestos dust. Up to December 31, 1980, altogether 2,944 people were enrolled in the study. Besides several other enrollment criteria, the individual's permission was required to evaluate his personal data. Of the people enrolled, 85 had died by December 31, 1980. Even if five questionable cases of lung cancer are excluded (n = 80), the observed rates of about 43% tumours of all sites, with 15% lung cancer and 6% mesothelioma, seem to be comparable to the international epidemiological mortality pattern.

Adult↗

PubMed1987

Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study.

The prevalence of respiratory symptoms and lung function impairment was studied in a sample of men from a population screening of asbestos-related disorders. When the rates were adjusted for age and smoking habits, 83 subjects with lung fibrosis had an increased prevalence of respiratory symptoms, in particular, phlegm when coughing and breathlessness grades 1-3. Among 200 subjects under 70 years of age who had pleural plaques only, a statistically significant increase was observed in the prevalence of breathlessness grade 1 compared to an external reference population. Among 98 asbestos-exposed subjects who had normal chest X-rays, there was an increase in the prevalence of breathlessness grade 2, cough during the day, and phlegm when coughing. There was a higher proportion of subjects with lung fibrosis who were below 80% of the predicted values for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than in the other groups. There was also a higher proportion of subjects with pleural plaques only who were below 90% of the predicted value for FVC than in a group of 90 subjects without asbestos exposure. In accordance with previous studies, these results indicate that pleural plaques in asbestos workers may be of greater importance as a clinical feature than has been recognized in the past.

Adult↗

PubMed1988

Railroad workers with pleural plaques: II. Small airway dysfunction among asbestos-exposed workers.

Increased volume of trapped gas (VTG) was found in 87 asbestos-exposed railroad repair shop workers, divided into three subgroups according to smoking habits. All the examined subjects had pleural plaques. Determination of VTG was used to study function of small airways. Increased VTG was found among asbestos-exposed smokers as well as nonsmokers. In both groups the VTG:TLC ratio was elevated compared with controls. Increased VTG is a sign of small airways dysfunction. In asbestos-exposed subjects, it might be caused by an early peribronchial reaction to inhaled asbestos fibers.

Adult↗

PubMed1988

Asbestos-related pleural plaques and lung function.

The present study examines the association between asbestos-related pleural plaques and lung function in a group of workers with occupational exposure to asbestos. Exposure, smoking, and respiratory histories, chest radiographs, flow-volume loops, and single breath DLCOs were obtained on 383 railroad workers. A score based on the ILO-1980 classification system was used to quantify the extent of plaquelike thickening. In order to eliminate potential confounders, we excluded from final analysis subjects with diffuse pleural thickening (n = 10) or small irregular opacities classified as profusion 0/1 or greater (n = 6) on chest radiograph. Definite pleural plaques were observed in 22.6%. The single breath DLCO was similar in the groups with and without plaques (p = 0.0550). Decrement in FVC and the occurrence of pulmonary restriction were associated with the presence of definite plaques (p = 0.0306 and 0.0431, respectively) and with quantitative pleural score (p = 0.0135 and 0.0126), controlling for duration of asbestos exposure and smoking. A test for trend revealed an association between level of diagnostic certainty (none, suspect, definite) for pleural plaques and these measures of lung function (p less than 0.02). Our findings reveal an association between asbestos-related pleural plaques and decrement in lung function as measured by FVC and criteria for pulmonary restriction.

Asbestosis↗

PubMed1994

The National Sheet Metal Worker Asbestos Disease Screening Program: radiologic findings. National Sheet Metal Examination Group.

This report presents data gathered from a series of asbestos disease screening examinations of 9,605 United States sheet metal workers who were first employed in the trade at least 20 years before the examination. The overall prevalence of asbestos-related radiographic changes was 31.1%: 18.8% had pleural abnormalities alone, 6.6% had parenchymal abnormalities (International Labour Office (ILO) score of 1/0 or higher) alone, and 5.7% had both. Among those with 40 years or more since entering the trade, 41.5% had radiographic signs of asbestos-related disease, 24.2% pleural alone, 7.7% parenchymal alone, and 9.6% both pleural and parenchymal abnormalities. After controlling for several surrogates for asbestos exposure level, cigarette smoking was found to increase risk of parenchymal, and more modestly, pleural abnormalities. Each pack-year was associated with a 1% increased prevalence odds ratios for parenchymal abnormalities (ILO category 1 compared to category 0), and 0.4% increased prevalence odds ratios for pleural abnormalities. A history of shipyard employment also produced significantly increased prevalence odds ratios for each radiographic category. More that 90% of chest radiographs were classified by A or B readers; after adjustment for other risk factors, A readers were more likely to report parenchymal abnormalities of category 1, but not more likely to report category 2 or pleural abnormalities, than B readers.

Adult↗

PubMed1986

Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis.

The study of 3,472 chest x-rays from four populations with different levels of exposure to asbestos and with different cigarette smoking histories shows that smoking in the general population does not produce pulmonary fibrosis recognizable on chest radiography. In the general population of Michigan, the prevalence of a radiographic pattern of fibrosis was 0.5 percent in men and 0.0 percent in women. In a Long Beach, California census tract population, the prevalences were 3.7 percent for men and 0.6 percent for women. Similarly, cigarette smoking does not enhance fibrosis when the exposure to asbestos has been as light as that in households of shipyard workers. Asbestosis was recognized in 6.6 percent of 137 shipyard workers' wives who have never smoked and 7.6 percent of 132 who had ever smoked. Cigarette smoking and asbestos appear to be synergistic in those occupationally exposed to asbestos (as insulators), since 7.2 percent of 97 nonsmokers and 20.5 percent of 316 ever-smokers showed fibrosis. This apparent synergy was also found in shipyard workers up to age 70 with 31 percent of nonsmokers and 43.3 percent of ever-smokers having fibrosis. There were increases of approximately 10 percent in the prevalence of fibrosis in cigarette smokers and nonsmokers for each decade after age 40.

Adult↗

PubMed1981

Crackles in asbestos workers: auscultation and lung sound analysis.

We surveyed 270 asbestos factory workers and 222 control subjects matched for age to assess the usefulness of listening for fine discontinuous adventitious lung sound (fine crackles) in detection of the early stages of interstitial fibrosis of asbestosis. Fine crackles at both bases were heard more frequently in asbestos workers (32.2%) than in controls (4.5%) (P less than 0.01). The presence of bilateral basal crackles was related to the duration of asbestos exposure and occurred before abnormalities could be detected by chest radiography. Two observers examined 74 workers randomly chosen from among 270 asbestos workers and found inter-observer agreement to be high (91.9%). There was close agreement between findings on chest auscultation and sound recordings.

Adolescent↗