SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Since the early reports of the deleterious health effects of asbestos first appeared in the British literature, the paucity of information on dust levels has been decried. Research into archival material reporting various methods of assessing asbestos dust levels in British factories during the 1930s indicates that these levels were high indeed.
Ambient air concentrations of asbestos fibers were measured during the period June 20 to August 12, 1980, at three locations; Danville, Asbestos, and Wottenville in the eastern townships of Quebec. Measurements were done with low-volume samplers and measurement periods extended from 3 to 13 days. Fiber counts were done by means of electron microscopy. Results indicate that overall fiber concentrations are related to atmospheric stability and to the direction of the prevailing wind with respect to the source of emission.
It is well established that many different types of fibre, both organic and inorganic, can become coated with ferritin in lung to give ferruginous bodies. The presence of such bodies is one factor which is taken into account in assessing cases with asbestos-related disease for the purpose of compensation, although their presence is only an indication of past exposure and not proof of the causative role of asbestos. In this paper, evidence relating to the formation of ferruginous bodies in human lung is reviewed, to identify factors which predispose certain types and dimensions of fibre to become coated. Work with experimental animals is also summarised to give some indication of the time course of body formation.
Asbestos concentrations were measured within powered respirators used by workers involved in the removal of asbestos-containing insulation. Fibre concentrations within the protective gear appeared to be above the Dutch threshold limit value for crocidolite (0.2 f cm-3). Possible sources of exposure were analysed and measures were taken to improve the situation. After this, the fibre concentrations in the breathing area were reduced and were below the Dutch concentration limit.
In an attempt to determine whether there exists a threshold asbestos dose below which asbestosis does not occur, data on 807 men who had worked on amphibole asbestos mines and undergone autopsy were analysed. When exposure was expressed as fibre-years no asbestosis was found at autopsy when exposure was up to 2 fibre-years, even after 31-45 years of residence time. In the group exposed to greater than 2-5 fibre-years asbestosis was found. When exposure was expressed as average fibre concentration asbestosis occurred below 2 fibres per ml (f ml-1) and the prevalence increased with residence time. In conclusion, if a threshold dose for asbestosis does exist it is at approximately 2 fibre-years if off-shift exposure is ignored.
The mortality from ischaemic heart disease was studied in a prospective cohort of 1725 shipyard workers exposed to asbestos. The analyses were stratified for age and smoking habits and restricted to men. In agreement with other findings, men with impaired lung function had a significantly higher risk (relative risk (RR) = 3.5) of dying from ischaemic heart disease than men with normal lung function. Men with asbestosis or suspected asbestosis had a significantly higher risk (RR = 3.1) of dying from ischaemic heart disease than men without asbestosis. Thus asbestosis or suspected asbestosis also seemed to be a risk factor for ischaemic heart disease. This finding was independent of respiratory function. There was no increased risk for ischaemic heart disease in men with compared with men without pleural plaques. Men with production of phlegm or sputum and wheezing or whistling had no increased risk for ischaemic heart disease compared with men without these symptoms. In the group with normal lung function men with dyspnoea had a significantly higher risk of dying from ischaemic heart disease than men without dyspnoea. The findings for men with asbestosis or suspected asbestosis indicated a further risk factor besides impaired lung function, in persons exposed to asbestos. Perhaps this risk factor is due to lesions of the pericardium with consequences for heart function.
A specimen preparation technique is described which yields uniformly dispersed particles on transmission electron microscope (TEM) grids. It is relatively rapid and probably incurs no fiber loss. This technique was used to test the hypothesis that orally administered chrysotile asbestos may pass through the wall of the gastrointestinal tract (GI) of the neonate baboon. A test neonate baboon was bottle-fed chrysotile asbestos which was suspended in a milk formula. Control and test baboons were sacrificed at the end of a 9-day feeding period, and several tissues were removed and preserved. Kidney, liver, and spleen tissues were prepared for TEM analysis. Tissues from the control animal showed no fibers. The number of chrysotile fibers recovered from the test kidney cortex was significantly higher than the level found in the control kidney cortex (p less than 0.005). The frequency distribution of fibers lengths in the kidney cortex was very similar to that of the feeding suspension. This study suggests that a wide range of fiber sizes can penetrate the GI tract and migrate.
Asbestos body (AB) countings on both bronchoalveolar lavage (BAL) fluids and digested lung tissue samples were performed in one hundred consecutive subjects submitted to a thoracotomy procedure, mostly for lung carcinoma. A good correlation (r = 0.73) was found between the two groups of values for the total group of subjects. When restrictive selection criteria were taken into account, such as lavage homolateral to the analysed lung, performed by the same trained physician, this correlation improved (r = 0.82). Absence of AB's or low AB counts (less than 1 AB/ml) in BAL corresponded in about 70% of cases to concentrations of less than 1,000 AB/gm and in 100% of cases to concentrations less than 10,000 AB/gm. In subjects with BAL containing more than 1 AB/ml, the lung tissues of 85% contained more than 1,000 AB/gm and the tissues of 44% contained more than 10,000 AB/gm. Above 10 AB/ml BAL, all lung tissues contained more than 10,000 AB/gm. Since lung tissue is not readily available in patients undergoing assessment of their asbestos exposure, BAL fluid analysis seems to be a useful tool to evaluate lung AB concentrations. This technique cannot be performed, however, in patients with severe lung impairment which does not allow sufficient recovery of BAL fluid.
Humoral immunological profile including immunoglobulins IgG, IgA, IgM, C-reactive protein, rheumatoid factor, antinuclear antibodies and circulating immune complexes were studied in a representative sample of 36 workers suffering from asbestosis (group A), 35 workers who are exposed to asbestos but not having evidence of asbestosis (group B) and 28 control workers (group C). Mean IgG and IgA levels were found to be significantly higher in the two exposed groups than in the controls. Circulating immune complexes of IgG, IgA and IgM class were detected in a significant percentage of cases in exposed groups than in controls. In groups A and B, the percentage of positive ANF cases was much higher than in the controls. The results suggest that immunological changes are associated with exposure to asbestos and these may play an important role in the pathogenesis of the disease process.
Retention patterns in lung tissue (determined by transmission electron microscopy and energy dispersive spectrometry) of chrysotile, tremolite, and crocidolite fibres were analysed in 69 dead asbestos cement workers and 96 referents. There was an accumulation of tremolite with time of employment. Among workers who died within three years of the end of exposure, the 13 with high tremolite concentrations had a significantly longer duration of exposure than seven in a low to intermediate category (medians 32 v 20 years; p = 0.018, one sided). Crocidolite showed similar patterns of accumulation. In workers who died more than three years after the end of exposure, there were no correlations between concentrations of amphibole fibres and time between the end of exposure and death. Chrysotile concentrations among workers who died shortly after the end of exposure were higher than among the referents (median difference in concentrations 13 million fibres (f)/g dry weight; p = 0.033, one sided). No quantitative differences in exposure (duration or intensity) could be shown between workers with high and low to intermediate concentrations. Interestingly, all seven workers who had had a high intensity at the end of exposure (> 2.5 f/ml), had low to intermediate chrysotile concentrations at death, whereas those with low exposure were evenly distributed (31 subjects in both concentration categories); hence, there was a dependence between last intensity of exposure and chrysotile concentration (p = 0.014). Among 14 workers with a high average intensity of exposure, both those (n = 5) with high tissue concentrations of chrysotile and those (n = 10) with high tissue concentrations of tremolite fibres had more pronounced fibrosis than those with low to intermediate concentrations (median fibrosis grades for chrysotile: 2 v 1, p = 0.021; for tremolite: 2 v 0.5, p = 0.012). Additionally, workers who died shortly after the end of exposure with high concentrations of chrysotile and crocidolite had smoked more than those with low intermediate concentrations (medians for chrysotile 35 v 15 pack-years, p = 0.030; for crocidolite 37 v 15 pack-years, p = 0.012). The present data indicate that chrysotile has a relatively rapid turnover in human lungs, whereas the amphiboles, tremolite and crocidolite, have a slower turnover. Further, chrysotile retention may be dependent on dose rate. Chrysotile and crocidolite deposition and retention may be increased by tobacco smoking; chrysotile and tremolite by fibrosis.
The incidence and characteristics of cement-asbestos pneumoconiosis were compared with those of asbestosis and cement pneumoconiosis in three homogeneous samples of cases. The clinical, functional, and radiological features of cement-asbestos pneumoconiosis are similar to those of classical asbestosis, but the observed changes are less common and occur after a longer exposure.
This article presents an evaluation model of the mortality attributed to asbestos occupational exposure. French workers exposed at least ten years between 1950 and 1979 constitute the population studied. Exposure-risk relations are used to estimate mortality from lung cancer, mesothelioma, or asbestosis, and the associated reduction of life expectancy among 76 groups (about 18,500 workers) defined by their level of asbestos exposure. The most important results are presented and discussed as are the main hypotheses regarding historical exposure parameters.
From sputum samples collected from nine former asbestos workers, one portion not needed for cytopathologic screening was fixed, embedded and sectioned for transmission electron microscopy (TEM) while a second portion was digested and collected on a Nuclepore filter for scanning electron microscopy (SEM). Energy-dispersion analysis was used in assessing inorganic matter in both preparations. The ultrastructural relationships between the ferruginous bodies and related macrophages as well as the presence of other particulate matter in the preparations were studied. Our results are the first to confirm the presence of uncoated asbestos fibers, diatomaceous earth and aluminosilicates in sputum. Our data indicate that it would be reasonable to use this analytical technique as an initial test before using invasive procedures in the diagnosis of many pneumoconioses and other lung diseases.
Hamster tracheal explants were maintained in culture in the presence or absence of benzo[a]pyrene (BP), crocidolite asbestos, or BP-coated crocidolite. Dose-dependent squamous metaplasia was observed in the treated samples. L-Ascorbic acid and DL-alpha-tocopherol were able to partially protect the tracheal explants from the metaplastic response induced by crocidolite. Furthermore, ascorbic acid reduced the extent of metaplasia observed in hamster tracheal explants that were exposed to BP-crocidolite.
A mathematical model for predicting the concentration (Nv) of asbestos bodies (AB) in human tissue from the count (No) of these bodies in planar tissue sections is presented. The result is the equation Nv = No/[0.54 X A X (La + t)], giving the concentration of AB in numbers per gram of wet lung tissue. La, the average length (in microns) of the AB, is specific for each case; A is the area (square millimeters) of the tissue counted, and t is the thickness of the section (in microns). This equation fits experimental digestion results to a multiplicative error factor of less than 3. When an estimate of La, such as 51.6 microns, is used, the equation is less accurate but probably sufficiently accurate for the screening of lung specimens.
Taking advantage of the spontaneous polymerisation of eugenol to lignin-like species catalysed by the surface of crocidolite fibres, a procedure is proposed, possibly useful in asbestos removal and disposal, where the polymer avoids the release of airborne fibres and also scavenges ROS (reactive oxygen species).
A method is descirbed for isolating chrysotile fibers from feces and counting them with an electron microscope. The detection limit was 150,000 fibers per gram feces; average recovery was 85.5%. When the method was used to check the asbestos in feces of people subjected to industrial exposure vs. controls, the means were significantly different (p less than 0.02). Duplicate fecal samples were found to check within an average of +/- 31.1% of their means.
In order to compare methods of counting asbestos fibers in lung tissue, seven laboratories participated in an interlaboratory trial in which tissue samples from five human lungs were analyzed. In some laboratories, fiber concentrations were assessed with the light microscope and, in others, with either scanning or transmission electron microscopes. Within each laboratory the ranking of the results was similar, but there were marked differences in the absolute values obtained by the different laboratories. It is concluded that the laboratories participating in this trial appear to produce internally consistent results, but there is difficulty in directly comparing results from one laboratory to the next.