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PubMed1975

The epidermiologic relationship between pleural mesothelioma and asbestos exposure.

This paper describes an investigation of 85 notifications of either probable or possible mesothelioma to the Finnish Cancer Registry from 1953 through 1969. The investigation covers characteristic epidemiologic features and the possibility of the mesothelioma being connected with occupational or other exposure to asbestos. The incidence rate of pleural mesothelioma was estimated at 1.1 per million per year. The male/female ratio was 1.3:1, which greatly differed fsrom that for malignant neoplasms of the bronchus or lung in Finland in 1960. The mean age at dealth from mesothelioma was over 7 years lower than that for bronchial carcinoma. The ratio of the crude incidence rates for the urban and rural populations was 4.2; the corresponding ratio for cases of carcinoma oopulations was 4.2; the corresponding ratio for cases of carcinoma of the bronchus or lung was 1.2 in Finland in 1960. THE LAST OCCUPATIONS OF THE 82 DECEASED PERSONS, OBTAINED FROM THE DEATH CERTIFICATES, WERE DIVIDIED INTO THREE CATEGORIES ACCORDING TO POSSIBLE ASBESTOS EXPOSURE. Exposure was present or probable in 9 (11.0) cases, 28 (34.2 %) had a possible exposure, and in 33 (40.2 %) cases exposure was absent or unlikely. The occupation of 12 (14.6) persons was unknown. Additional information of possible exposure history was obtained by interviewing the relatives of 10 mesothelioma patients. For half of the persons a definite, although in some cases trivial, exposure to asbestos could be ascertained. For the other five persons no exposure, either occupational, neighborhood or domestic, to asbestos could be traced. The residental distribution of the 85 persons with mesothelioma revealed no clustering of cases.

Adult↗

PubMed2004

Factors associated with early-stage pulmonary fibrosis as determined by high-resolution computed tomography among persons occupationally exposed to asbestos.

OBJECTIVES: Asbestosis remains difficult to diagnose, particularly in its early stages. The aim of this study was to determine criteria for independently associated features of pulmonary fibrosis in high-resolution computed tomograms among persons occupationally exposed to asbestos. METHODS: Retired persons with documented occupational asbestos exposure and no known asbestos-related diseases were assessed for occupational, clinical, functional respiratory, and chest X-ray criteria. In addition, they all underwent high-resolution computed tomography (HRCT) in the prone position. RESULTS: Altogether 51 (7.2%) of the 706 enrolled participants had features of pulmonary fibrosis consistent with asbestosis in the HRCT. Among those with small irregular opacities of <1/0 according to the 1980 International Labour Office Classification (ILO-C) in their X-rays, 5% had asbestosis in the HRCT. In a multivariate analysis, only age [odds ratio (OR) per year 1.08, 95% confidence interval (95% CI) 1.02-1.14], cumulative-exposure index (CEI) for asbestos (OR 6.4, 95% CI 1.5-28.4 for a CEI of > or =100 fibers/ml x years), and the presence of small irregular X-ray opacities of > or =1/0 ILO-C (OR 3.0, 95% CI 1.6-6.0) were independently associated with HRCT asbestosis. No combinations of these criteria simultaneously yielded high sensitivity and specificity for the diagnosis of early-stage HRCT asbestosis. Moreover, only 2% of the persons with a CEI of <25 fibers/ml x years had HRCT asbestosis, the finding confirming the low incidence of asbestosis for such low exposure, as previously reported on the basis of X-ray data. CONCLUSIONS: Additional research is needed to better identify the persons most likely to benefit from HRCT screening for asbestosis.

Aged↗

PubMed1999

Asbestos-related pleural disease in Western Australian gold-miners.

Three retired gold-mine workers from Western Australia (WA) were diagnose with asbestos-related pleural disease (two with pleural plaques and one with mesothelioma). Asbestos fibres have been found in air samples from WA gold-mines, and all three patients had worked in these mines (for five to 17 years) and had no other significant known asbestos exposure. To our knowledge, this is the first report of asbestos-related disease in gold-mine workers.

Aged↗

PubMed2005

Effects of asbestos and smoking on gas diffusion in people exposed to crocidolite.

OBJECTIVE: To examine the effects of asbestos exposure and tobacco smoking on the level and rate of change of the diffusing capacity of the lung for carbon monoxide (DLCO). DESIGN AND PARTICIPANTS: A cohort study of 934 people (including both mine workers and town residents) exposed to crocidolite (blue asbestos) at the asbestos mines and in the town of Wittenoom, Western Australia, between 1943 and 1966. DLCO measurements were taken during a follow-up period from 1992 to 2002. MAIN OUTCOME MEASURES: Baseline levels of DLCO and change in levels over time. RESULTS: 2980 DLCO measurements were done on 934 people (of whom 818 were men and 724 were workers) who underwent a median of 2 (range, 1-17) measurements during the follow-up period. Radiographic asbestosis at baseline and asbestos exposure at a younger age were associated with lower DLCO values. The average rate of decline in DLCO was 0.33 (95% CI, 0.31-0.35) units per year, plus an additional decrement of 0.22 (95% CI, 0.12-0.32) units per year if the participant had radiographic asbestosis at the beginning of the follow-up period. Compared with never-smokers, current smokers and ex-smokers had lower DLCO at baseline, but smoking status did not affect the change in DLCO during the follow-up period. CONCLUSIONS: Our results confirm a continuous deleterious effect of crocidolite on DLCO, especially on people with asbestosis. Smoking was associated with lower DLCO levels, but was not a significant predictor of rate of change in DLCO. Smoking status did not affect the relationships between crocidolite exposure and the level or rate of change of DLCO in this population.

Age Distribution↗

PubMed1999

DNA single strand breaks induced by asbestos fibers in human pleural mesothelial cells in vitro.

The mechanisms of the cellular effects and DNA damage caused by asbestos fibers in human mesothelial cells are not well understood. We exposed transformed human pleural mesothelial cells to 1-4 microg/cm2 crocidolite and to 10-100 ng/ml tumor necrosis factor alpha for up to 48 hr and studied the induction of DNA damage using the Comet assay. As a positive control, 100 microM H2O2 was used. The DNA single strand breaks were assessed as the mean tail moments and as distributions of the tail DNA in the cell. The Comet assay showed significant but reversible increases in the mean tail moments, but not in the distribution of Comet tails in the histograms in cells exposed to 1 microg/cm2 crocidolite for 6 hr. At higher concentrations of asbestos fibers all the indices in the Comet assay showed significant and irreversible change. All the doses of TNF-alpha caused marginal increase in the mean tail moments. The mean tail moments were highest in the cells with concurrent treatment to TNF-alpha and crocidolite. In the cells pretreated with inhibitors of antioxidant enzymes (aminotriazole for catalase and buthionine sulfoximine for gamma-glutamylcysteine synthetase) asbestos fibers slightly increased oxidant-related fluorescence of dichlorofluorescein (DCFH) but did not cause any further increases in the mean tail moments. This study shows that asbestos fibers cause DNA single strand breaks in human mesothelial cells. Since the inhibition of antioxidant enzymes did not have an effect on the DNA damage caused by the fibers, other mechanisms than free radicals seem to be involved in the induction of DNA damage by mineral fibers.

Asbestos, Crocidolite↗

PubMed1999

[Occupational problems of serpentine asbestos in industry (history and trends)].

The article presents summarized data of long-standing research of work conditions, asbestosis occurrence, and epidemiology of malignancies in "URALASBEST" enterprises extracting and utilizing asbestos. The research served as a base to elaborate and put into practice a complex of sanitary, technical, medical and biologic measures in various asbestos enterprises. Those measures lowered occupational morbidity due to asbestos. Considering the experience accumulated, the authors set prospects for further studies on "Asbestos and Health" problem.

Asbestos, Serpentine↗

PubMedDate not supplied

[Separate and combined mutagenic effect of radiation and asbestos on the micronucleus test in experiments].

We investigated the isolated and combined mutagenic effect (ME) of radiation (gamma-irradiation, 0.5 or 2 Gy) and asbestos (i.p. 10 mg/mice) in mice CBA. We studied also the antioxidant activity and malonic dialdehyde concentration in blood serum as possible mechanism of ME and its possible modification. For the ME the micro-nuclei incidence in polychromatic bone marrow erythrocytes was scored. The reciprocal modification (potentiation) of both radiation and asbestos ME was established for combination "radiation, 2 Gy + asbestos", the additivity--for combination "radiation, 0.5 Gy + asbestos".

Animals↗

PubMed1999

[Apical pleural fibrosis related to inhalation of asbestos fibers].

The involvement of the apical pleura is infrequent in diffuse pleural thickening secondary to asbestos exposure. Most often diffuse pleural thickening is accompanied by an obliteration of the costophrenic angle and the posterior and paraspinous pleural surfaces of the pleura are involved to the greatest extent. Unlike this typical form, we observed in five patients exposed to asbestos an apical pleural fibrosis, uni or bilateral, accompanied with lung retraction, hilar ascension and tracheal attraction. Apical pleural thickening with upper lobe changes in asbestos-exposed persons should be regarded as due to the asbestos exposure, after exclusion of other causes like tuberculosis and the apex tumors. Usually the evolution of the lesions is slowly progressive over several years or even decade, and results in mild restrictive defect.

Aged↗

PubMed1999

[An experimental quality assurance program for asbestos measurements performed with x-ray diffractometry in bulk samples].

A quality assurance program for the diffractometric determinations of asbestos in bulk samples is presented. The program, developed upon request of the Italian Health Ministry, includes two tests: the qualitative determination of the asbestos forms present in three samples and their quantitative measurements. The samples to be analyzed, the asbestos standards and the criteria for results evaluation are described in detail. The program will start in the year 2000. Compliance with the tests minimum requirements will be considered mandatory for a public or private laboratory be legally allowed to work in the field of asbestos determinations by X-ray diffractometry. The description of the program is preceded by an in-depth discussion on the definition of the terms "quality control" and "quality assurance", which are often confused, and on their operational meaning when they are applied to laboratory measurements. The analytical difficulties involved with the measurement procedures currently used are also discussed. Moreover, the results of a preliminary intercalibration test among fifteen Italian laboratories of proven experience are reported since they provided important information for the arrangement of the present quality assurance program.

Asbestos↗

PubMed2000

Asbestos exposure and laryngeal cancer.

OBJECTIVE: To carry out a systematic review of the evidence relating asbestos exposure to the risk of laryngeal cancer. METHOD: All identified studies of asbestos workers providing data on laryngeal disease were reviewed, together with studies of laryngeal cancers giving epidemiological or experimental evidence of associated exposures. RESULTS: Confounding due to smoking and alcohol intake, and to a lesser extent diet and socio-economic factors, creates a major difficulty over the identification of any asbestos or other occupational effect. Not only are smoking and alcohol independently associated with large increases in relative risk (RR) of laryngeal cancer, but also have a synergistic effect with each other. Few of the studies provide details of either habit. Among 24 prospective studies for which a standardized mortality ratio (SMR) was available, nine had an SMR at or below unity, and among a further 11 without an SMR for comparison, in only one was there a clear excess risk. In 17 retrospective studies, only two showed a significantly increased RR. Evidence from animal experiments, studies of associations with pleural plaques, and autopsy findings also appear negative or inconclusive. CONCLUSION: The evidence does not indicate that asbestos exposure increases the RR of laryngeal cancer.

Asbestos↗

PubMed2001

Performance of asbestos fibre counting laboratories by transmission electron microscopy.

In France, the owners of buildings have been obliged since February 1996 to ascertain whether asbestos has been incorporated into surfacing materials, insulation products or false ceilings. In certain circumstances, there is also a requirement to measure the airborne asbestos fibre concentration. Three years (1996-1998) of asbestos fibre count reporting are evaluated for the proficiency testing scheme organized in France to evaluate the performance of laboratories using an indirect-transfer transmission electron microscopy procedure to measure the airborne asbestos fibre concentration. Each year eight filters are distributed to each participating laboratory. These filters are obtained by filtering a suspension containing chrysotile or amphibole fibres. In 1996, 36% of the laboratories were rated 1 (the best performers; i.e. those providing counts close to the reference value). Performance improved appreciably in the last round where 85% of the laboratories were rated 1.

Air Pollution, Indoor↗

PubMedDate not supplied

[Malignant mesothelioma: clinical and radiological description of 45 cases with and without asbestos exposure].

OBJECTIVE: Our aim was to identify and describe the main symptoms, clinical presentation, and radiographic changes in malignant mesothelioma (MM) patients. MATERIAL AND METHODS: We reviewed the medical and X-ray records of all patients diagnosed with MM, admitted between 1991 and 1998 to the National Institute of Respiratory Diseases (INER), which is a governmental institution specialized in chest disease in Mexico City. The following data were collected: Age, occupation, asbestos exposure, latency, family history of cancer, clinical symptoms, and X-ray changes. Data are presented as percentages by sex and age group. RESULTS: We found 45 cases of MM; in 80% of them a history of asbestos exposure could not be documented. The 51-60 years age group had the highest frequency of MM. Dispnea and chest pain were the presenting symptoms in most patients. Pleural effusion and pleural thickening were the X-ray abnormalities observed in 75% of the patients. CONCLUSIONS: The clinical and radiographic findings among patients with MM without asbestos exposure were similar to those with a history of asbestos exposure.

Adult↗

PubMed2000

[Pleural and parenchymal lung diseases from asbestos exposure. CT diagnosis].

INTRODUCTION: We report the CT findings of parenchymal and pleural diseases in a group of patients with a history of asbestos exposure, excluding lung cancer (which is not typical in this subjects) and asbestosis (which is a parenchymal fibrosis). MATERIAL AND METHODS: We retrospectively reviewed a series of CT examinations (conventional, helical and high resolution scans) of 21 patients examined from 1995 to 1999. They had pleural plaques (10), round atelectasis (2) and malignant pleural mesothelioma (9). All patients had a history of direct or indirect asbestos exposure, except one with malignant pleural mesothelioma. We evaluated the following CT findings: nodular, plaque or uniform pleural thickening; pleural calcifications; pleural thickening less or greater than 1 cm; pleural margins (regular, polycyclic, spiculated); localization (uni/bilateral hemithorax); distribution (upper, medium or lower region); pulmonary, mediastinal and diaphragmatic involvement; fissural involvement; pleural effusion; lymph node enlargement; lung mass with the comet-tail sign; lung volume (normal, reduced, increased). RESULTS: Pleural plaques were always bilateral and less than 1 cm thick, with calcifications in 80% of the cases. Margins were always regular, polycyclic in 40% of the patients and never irregular. The pulmonary pleura in the mid-chest was involved in cell cases the diaphragmatic pleura in the 50% of the cases and the upper and lower regions in 60% and 80% of the patients, respectively. Round atelectasis (3 cases in 2 patients) was always shown as a parenchymal mass in the lower lobes, posteriorly or posteromedially, with adjacent pleural thickening; its diameter ranged 4.4-6 cm and there was the comet-tail sign. In malignant pleural mesothelioma we always found pleural effusion, with unilateral pleural effusion being the only sign in 2 patients. Other findings were pleural nodules (77.7%), with spiculated (22.2%) and polycyclic (77.7%) margins, more than 1 cm in diameter. The disease was always unilateral. The parenchymal pleural was involved in 77.7% of the cases while the mediastinal and diaphagmatic pleura were involved in 44.4% of the patients. Fissural involvement was demonstrated in 66.6% of the patients. Lymph nodes were enlarged in 66.6% of the cases. The volume of the affected hemithorax was increased (22.2%), decreased (44.4%) or normal (33.3%). DISCUSSION AND CONCLUSIONS: The presence of pleural plaques is a specific sign of asbestos exposure. Round atelectasis may also indicate asbestos exposure, but it can be found in many diseases with pleural inflammation, such as tuberculous effusion, trauma, pulmonary infarct, congestive heart failure, coronary artery bypass. The CT patterns of these two diseases are typical and no other finding is necessary to confirm the diagnosis. CT-guided needle biopsy is needed only if the round atelectasis has an atypical appearance on CT images, that is without the comet-tail sign. Malignant pleural mesothelioma is strongly associated with previous occupational exposure and presents typical CT findings only in an advanced stage (irregular and nodular pleural thickening, pleural effusion, mediastinal and pulmonary contraction for tumor encasement, parenchymal and lymph node metastases), but the differential diagnosis with pleural metastatic disease can be difficult. CT plays an important role in tumor assessment but biopsy is necessary for lesion characterization.

Adult↗

PubMed2000

[Clinico-roentgenological and occupational correlations as a method of revealing the dose-effect dependence in the development of chrysotile-asbestos fibrosis].

For understanding up-to-date situation with fibrosis caused by chrysotile-asbestos, the authors conducted X-ray and hygienic studies in 2 enterprises extracting and enriching asbestos--"Tuvaasbest" JSC and "Orenbourgasbest" JSC. Authors followed correlation between diffuse pulmonary changes and length of service, dust load and cumulative exposure dose of respirable fibers. The strongest correlation was demonstrated for dust load. Workers engaged into up-to-date industry extracting and enriching asbestos are diagnosed as having indistinct and moderate roentgenologic types of fibrosis. Examples of dose-effect dependence prove dust load to be informative and expedient integral parameter for hygienic regulation and evaluation of asbestos-containing dust and industrial aerosols doses.

Adult↗

PubMed2001

Increased TGF-beta1 in the lungs of asbestos-exposed rats and mice: reduced expression in TNF-alpha receptor knockout mice.

Inhalation of numerous fibrogenic agents causes interstitial pulmonary fibrosis (IPF) in humans and in a number of animal models. Several of these models provide evidence that certain peptide growth factors (GF) are playing a role in the disease process. Transforming growth factor beta 1 (TGF-beta1) is a potent inducer of extracellular matrix production by mesenchymal cells, and we have shown that this peptide is produced in the lung after asbestos exposure. We used in situ hybridization to demonstrate that the mRNA for TGF-beta1 is rapidly expressed post-exposure at sites of initial asbestos-induced lung injury in both rats and mice. The TGF-beta1 is expressed by bronchiolar-alveolar epithelial cells as well as by mesenchymal cells and lung macrophages in exposed animals. Normal rats and mice express little TGF-beta1, as we have demonstrated previously for PDGF-A and -B, TGF-alpha, and TNF-alpha. TGF-beta1 expression is accompanied by collagen and fibronectin production in asbestos-exposed animals. Most interesting, TGF-beta1 expression is largely absent in the lungs of TNF-alpha receptor knockout mice that fail to develop asbestos-induced IPE We have shown previously that the mRNAs and cognate peptides of PDGF-A and -B and TGF-alpha, but not TNF-alpha, are reduced in the fibrosis-resistant knockout mice. In this article, we show that TGF-beta1 is included in this group of cytokines, supporting the postulate that TNF-alpha is necessary for the expression of other, more downstream growth factors, and the consequent development of idiopathic pulmonary fibrosis (IPF).

Administration, Inhalation↗

PubMed2001

Navy Asbestos Medical Surveillance Program, 1995-1999: demographic characteristics and smoking status.

A descriptive study of the Navy Asbestos Medical Surveillance Program is presented from data provided by the Navy Environmental Health Center in Norfolk, Virginia, with an emphasis on demographic characteristics and smoking. Analysis of 79,598 physical examinations for the period 1995 to 1999 revealed that Navy and Marine Corps civil service employees constituted 90% and Navy active duty personnel constituted 9%. Most personnel reported "no current exposure, have prior exposure" to asbestos (Navy active duty, 77%; civil service employees, 61%). Current smoking rates per year decreased for Navy active duty (from 34.6% to 28.7%) and civil service workers (from 26.0% to 21.6%), both reductions being significant for trend. Logistic regression for current smoking showed higher rates for Navy active duty and those with "direct" asbestos exposure, whereas those 50 years or older and of Asian ethnicity had lower smoking rates. These findings provide programmatic insights for the Asbestos Medical Surveillance Program and suggest areas for further study.

Adult↗

PubMed2002

Distinct spectrum of mutations induced by crocidolite asbestos: clue for 8-hydroxydeoxyguanosine-dependent mutagenesis in vivo.

DNA damage due to reactive oxygen or nitrogen species is proposed to be involved in the molecular mechanism of asbestos-induced carcinogenicity. However, indications for this hypothesis came mainly from in vitro assays using cultured cells or cell-free systems. In the present study, the mutagenicity of crocidolite fibers and the underlying molecular mechanisms were investigated in vivo. Mutation frequencies were determined in DNA of omenta, a relevant target tissue for mesothelioma carcinogenesis, using lacI transgenic rats. The mutagenic effect of 2 and 5 mg of crocidolite asbestos was demonstrated, with a maximal relative increase in mutation frequency of 3.4 compared with the control group. The molecular analysis of the mutations revealed striking differences according to mutation types between asbestos-induced mutations and spontaneous mutations. Therefore, a specific molecular mechanism induced by crocidolite that differs from that induced by the generation of spontaneous mutations can be proposed. G to T transversions, which are known to be induced by the premutagenic DNA adduct 8-hydroxydeoxyguanosine (8-OHdG), were the most prominent mutation type (29%) within crocidolite-induced mutations. In additional experiments, 8-OHdG in DNA of omenta from rats treated with 1 or 2 mg of crocidolite asbestos was determined. Levels of 8-OHdG in animals treated with crocidolite were significantly increased compared with negative controls. These data give strong evidence for the involvement of reactive oxygen or nitrogen species in crocidolite-induced mutagenesis in vivo.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

Fate of the miraculous mineral--ban asbestos worldwide campaign.

Asbestos is a generic term used to describe natural mineral fibers found in the ground in many regions of the world. This cheap material with special chemical and physical properties that make it virtually indestructible was widely used in the 20th century. Within twenty years of the first industrial production, the public health hazards associated with asbestos started to come to light. Asbestos has become one of the most worrying industrial pollutants, since it poses a health hazard of asbestosis, lung cancer, mesotheliomas, and benign changes in the pleura. In spite of the WHO recommendations, environmental health criteria and their revision, asbestos is still around.

Asbestos↗