asbestos--crocidolite and Pleural-Diseases

Scattered patches of crocidolite, one form of asbestos, were found in the surface soil in the rural county of Da-yao in southwestern China. In 1983, researchers from the West China University of Medical Sciences (WCUMS) discovered that residents of two villages in Da-yao had hyperendemic pleural plaques and excessive numbers of pleural mesotheliomas.. To review and summarise epidemiological studies, along with other relevant data, and to discuss the potential contribution to environmental risk assessment.. This report is based on a review of several clinical/epidemiological studies conducted by WCUMS researchers since 1984, which included one cross sectional medical examination survey, one clinical/pathological analysis of 46 cases of mesothelioma, and three retrospective cohort mortality studies. Additional information acquired from reviewing original data first hand during a personal visit along with an interview of medical specialists from Da-yao County Hospital was also incorporated.. The prevalence of pleural plaque was 20% among peasants in Da-yao over 40 years of age in the cross sectional survey. The average number of mesothelioma cases was 6.6 per year in the 1984-95 period and 22 per year in the 1996-99 period, in a population of 68 000. For those mesothelioma cases that were histology confirmed, there were 3.8 cases/year in the first period and 9 cases/year in the second. Of the 2175 peasants in this survey, 16 had asbestosis. Lung cancer deaths were significantly increased in all three cohort studies. The annual mortality rate for mesothelioma was 85 per million, 178 per million, and 365 per million for the three cohort studies, respectively. The higher exposed peasants had a fivefold increased mesothelioma mortality compared to their lower exposed counterparts. There were no cases of mesothelioma in the comparison groups where no crocidolite was known to exist in the environment. In the third cohort study, almost one of five cancer deaths (22%) was from mesothelioma. The ratio of lung cancer to mesothelioma deaths was low for all three studies (1.3, 3.0, and 1.2, respectively).. The observation of numerous mesothelioma cases at Da-yao was a unique finding, due mainly to their lifetime exposure to crocidolite asbestos. The finding of cases dying at a younger age and the relatively high ratio of mesothelioma cases to lung cancer could also be another unique result of lifetime environmental exposure to crocidolite asbestos. Although the commercial use of crocidolite has been officially banned since 1984, the incidence of mesothelioma has continued to show a steady increase, particularly among peasants. Since the latency of mesothelioma is approximately 30-40 years, the ban had little effect in the 1990s. The increased awareness and changes in diagnosis over time may also contribute to the increase. Furthermore, exposure to asbestos stoves and walls continued. The government implemented reduction of these exposures. However, from a public health standpoint, the most important issue is the complete avoidance of further exposure to asbestos.

Topics: Asbestos, Crocidolite; China; Cohort Studies; Environmental Exposure; Humans; Lung Diseases; Mesothelioma; Pleural Diseases; Residence Characteristics; Retrospective Studies; Risk Assessment; Soil

To further study the pathogenic mechanism of crocidolite, the imperceptible changes of crocidolite surface in rat were observed.. The animal model was established and the changes in the rat infected with dust were observed by use of microscopy, SEM, differential thermal analysis and IR spectroscopy.. In the course of interaction between organism protein and crocidolite, the protein symmetry decreased and structure loosened. The silicon of crocidolite was bonded with the alkyl, amido- of protein. New absorption bands of Si-O-C(N), Si-R clearly appeared. The organism cleared the dust by means of dissolution, enwrapping, winding or in the way of biochemical dissolution, and the fibre became shortened, broken, bifurcated, ends-rounded, and also it could dissolve, transfer and chemically react on surface.. The results showed that the surface radicals of asbestos fibre reacted with some albumen in tissue and hence formed new surface mediator. It is a new form of dissolution and reaction of fibre in vivo that fibres in alveoli transform to carbonate. The residual substances of crocidolite are mainly Si-O. Tissue membrane is the retardation cingulum of dust transference in vivo.

Topics: Animals; Asbestos, Crocidolite; Asbestosis; Dust; Microscopy, Electron, Scanning; Mineral Fibers; Pleural Diseases; Pulmonary Fibrosis; Rats; Silicon

This study was undertaken to determine whether certain criteria could be used to select among asbestos-exposed subjects those who could benefit from computed tomography screening.. Search for criteria enabling the selection of patients who should undergo a CT screening exam after occupational exposure to asbestos was conducted in 150 subjects. All subjects were explored with selected high-resolution CT scans. Studied parameters were age, exposure data, pulmonary function test results.. None of the exposure data or pulmonary function test results suggested with certainty the presence or absence of asbestos-related pleural and parenchymal lung disease. The studied parameters could not be used to select patients who could benefit from CT screening.. None of the studied parameters enabled a selection of asbestos-exposed subjects who should undergo chest CT screening.

Topics: Adult; Age Factors; Aged; Aged, 80 and over; Asbestos; Asbestos, Crocidolite; Asbestos, Serpentine; Asbestosis; Carcinogens; Female; Humans; Male; Mass Screening; Maximal Expiratory Flow-Volume Curves; Middle Aged; Occupational Exposure; Patient Selection; Pleural Diseases; Pulmonary Diffusing Capacity; Residual Volume; Spirometry; Time Factors; Tomography, X-Ray Computed; Vital Capacity

The study aimed to evaluate the risk of pleural plaques according to the degree of past exposure to asbestos, type of amphibole asbestos, and smoking, as well as to estimate the aetiologic fraction of asbestos as a cause of plaques among urban men.. The occurrence and extent of pleural plaques were recorded at necropsies of 288 urban men aged 33 to 69 years. The pulmonary concentration of asbestos and other mineral fibres was analysed with scanning electron microscopy. The probability of past exposure was estimated from the last occupation.. Pleural plaques were detected in 58% of the cases and their frequency increased with age, probability of past occupational exposure to asbestos, pulmonary concentration of asbestos fibres, and smoking. The risk of both moderate and widespread plaques was raised among asbestos exposed cases, and the risk estimates were higher for widespread plaques than for moderate plaques. The age adjusted risk was higher for high concentrations of crocidolite/amosite fibres than for anthophyllite fibres. The aetiologic fraction of pulmonary concentration of asbestos fibres exceeding 0.1 million fibres/g was 43% for widespread plaques and 24% for all plaques. The median pulmonary concentrations of asbestos fibres were about threefold greater among cases with widespread plaques than among those without plaques. No increased risk of pleural plaques was associated with raised total concentrations of non-asbestos fibres.. The occurrence of pleural plaques correlated closely with past exposure to asbestos. The risk was dependent on the intensity of exposure. Due to methodological difficulties in detecting past exposures to chrysotile and such low exposures that may still pose a risk of plaques, the aetiologic fractions calculated in the study probably underestimate the role of asbestos.

Topics: Adult; Age Factors; Aged; Asbestos, Amosite; Asbestos, Amphibole; Asbestos, Crocidolite; Autopsy; Finland; Humans; Male; Middle Aged; Occupational Diseases; Occupational Exposure; Odds Ratio; Pleura; Pleural Diseases; Risk Factors; Smoking; Urban Population

Plain chest radiographs from a one in six random sample of the workforce of the asbestos industry at Wittenoom, Western Australia between 1943 and 1966 have been classified for degree of profusion and pleural thickening by two independent observers according to the 1980 UICC-ILO Classification of Radiographs for the pneumoconioses to clarify the effect of degree of radiological abnormality on survival. A total of 1106 subjects were selected. Each subject's age, cumulative exposure to crocidolite, and time since first exposure were determined from employment records, the results of a survey of airborne concentrations of fibres > 5 mu in length conducted in 1966, and an exposure rating by an industrial hygienist and an ex-manager of the mine and mill at Wittenoom. By the end of 1986 193 subjects had died. Conditional logistic regression was used to model the relative risk of death in five separate case-control analyses in which the outcomes were deaths from: (1) all causes, (2) malignant mesothelioma, (3) lung cancer, (4) asbestosis, and (5) other causes excluding cancer and asbestosis. Up to 20 controls per case were randomly chosen from all men of the same age who were not known to have died before the date of death of the index case. After adjustment for exposure and time since first exposure, there were significant and independent effects of radiographic profusion and pleural thickening on all cause mortality. The effect of profusion was largely a result of the effect on mortality from malignant mesothelioma and asbestosis but not lung cancer. The effect of pleural thickening was greatest on mortality from other causes, mainly ischaemic heart disease. This study has shown that degree of radiographic abnormality has an independent effect on mortality from malignant mesothelioma, asbestosis, and all causes even after allowing for the effects of age, degree of exposure, and time since first exposure.

Topics: Asbestos, Crocidolite; Asbestosis; Cause of Death; Cohort Studies; Humans; Male; Mesothelioma; Neoplasms; Occupational Diseases; Occupational Exposure; Pleura; Pleural Diseases; Radiography; Random Allocation; Western Australia

Topics: Asbestos; Asbestos, Crocidolite; Humans; Mining; Occupational Diseases; Occupational Exposure; Pleura; Pleural Diseases; Western Australia

Serial plain chest radiographs of 384 men who worked at the Wittenoom crocidolite mine and mill between 1943 and 1966 and who applied for pneumoconiosis compensation between 1948 and 1982 have been examined independently by two trained observers for pleural disease using the 1980 ILO-UICC classification of radiographs to record width and extent of pleural disease. Radiographs covering follow up periods of from two to 38 years were examined (median number of films per subject was nine). The degree of crocidolite exposure was estimated from employment records and a survey of airborne fibre concentrations performed in 1966. Agreement between the observers on the presence and degree of pleural disease in the final film for each subject was moderately close (Kendall's tau B = 0.62) and was least for subjects with thickening less than 5 mm in width. Diffuse pleural thickening extending for greater than 50% of the lateral chest wall was the most common type recorded by both observers. Minor pleural thickening frequently progressed in extent along the lateral chest wall but progression beyond 5 mm in thickness was less common. Pleural plaques were not seen to progress beyond their initial thickness or extent. The rate of onset of thickening in this population increased continually from the time of first exposure and also increased slightly with age. There was evidence that the level of total cumulative exposure to crocidolite increased the rate of onset of pleural thickening in the period between five and 15 years after first exposure. Rate of progression of established thickening was greatest in subjects who first developed thickening early after first exposure. The relative rate of progression decreased slowly with time from first signs of thickening and there was no evidence of any progression more than 15 years after onset.

Topics: Asbestos; Asbestos, Crocidolite; Humans; Male; Occupational Diseases; Pleura; Pleural Diseases; Risk Factors; Time Factors

The pleura is a main target for various reactions related to asbestos exposure. However there are great radiological and clinical differences between the various reactions, and there is also increasing evidence that they have different prognoses. The main reactions are pleural plaques on the one hand and acute pleurisy and diffuse pleural fibrosis on the other. In a population with a low mesothelioma risk, the anthophyllite-exposed population of Northern Karelia in Finland, there are very few reactions of the second type, while plaques are very common. In Turkey, where the exposure is to erionite, the mesothelioma level is extremely high, and reactions of type two are very common in the exposed population. Thus it seems that careful discrimination of the various pleural changes can have prognostic value. There are also indications that plaques do not have any relation to a disturbed immunologic system, while pleurisy and diffuse pleurisy have.

Topics: Aluminum Silicates; Asbestos; Asbestos, Crocidolite; Asbestosis; Finland; Humans; Mesothelioma; Pleural Diseases; Pleural Neoplasms; Pneumoconiosis; Radiography; Risk; Sweden; Turkey; Zeolites

Standard (UICC) crocidolite was subjected to ball milling to reduce the length of the fibre. These milled materials and the original standard sample were injected into the pleural cavity of rats to determine their ability to induce mesothelioma. Previous in vitro work on the same materials had suggested that biological activity was related to fibres greater than 6.5 microns in length and that the material milled for 4 and 8 h did not contain fibres in this range and was biologically inactive. The results of the animal work, however, did not follow this pattern; mesotheliomas occurred in rats in all treatment groups including the 4 and 8 h milled samples. Examination of the tissues and the dust recovered from them showed the presence of fibres greater than the suggested threshold. Attention is drawn to the problems associated with drawing conclusions from size distributions and in vitro studies without considering in vivo mechanisms.

Topics: Animals; Asbestos; Asbestos, Crocidolite; Female; Granuloma; Male; Mesothelioma; Microscopy, Electron; Particle Size; Pleural Diseases; Pleural Neoplasms; Rats; Rats, Inbred F344; Time Factors