Asbestos bodies in bronchoalveolar lavage fluids of brake lining and asbestos cement workers

Asbestos body (AB) concentrations in bronchoalveolar lavage samples of 15 brake lining (BL) workers exposed only to chrysotile have been determined and compared with those from 44 asbestos cement (AC) workers extensively exposed to amphiboles. The mean AB concentrations (263 +/- 802 and 842 +/- 2086 AB/ml respectively) for those groups did not differ significantly but were much higher than those found in control groups. Analytical electron microscopy of asbestos body cores showed that in the BL group 95.6% were chrysotile fibres whereas in the AC group amphiboles accounted for 93.1%. The size characteristics of the central fibres differed for chrysotile and amphibole AB, the former being shorter and thinner. Examination of repeated bronchoalveolar lavage samples showed that the mechanisms of clearance of chrysotile fibres do not affect AB concentration for at least 10 months after cessation of exposure. It thus appears that routine counting of ABs in BAL allows the assessment of current or recent occupational exposures to asbestos. Exposures to chrysotile lead to AB concentrations comparable with those encountered in exposures to amphiboles.     

Cytological analysis of bronchoalveolar lavage fluid in asbestos-exposed workers

Background:Asbestos-related lung diseases are a group of heterogeneous disorders with different pathogenesis and prognosis. Very few studies investigated the BALF cell profile of asbestos exposed workers. The existence of a relationship between bronchoalveolar lavage fluid (BALF) cellular pattern and specific diagnosis and/or asbestos exposure biomarkers would allow the identification of effect biomarkers useful in the follow up of asbestos-exposed workers and in the diagnosis of asbestos-related diseases.Objectives:To assess BALF cell profile in formerly asbestos-exposed workers and its relationship with asbestos fibre (amphibole and chrysotile) and asbestos body (AB) concentrations.Methods:113 male workers formerly exposed to asbestos underwent bronchoscopy with bronchoalveolar lavage and were retrospectively enrolled. 35 of them were affected by pleural plaques and 10 were affected by asbestosis. Pulmonary functional tests (PFT), BALF cellular pattern, BALF mineralogical analysis with asbestos fibres and AB counting were performed in each patient. A statistical analysis with a multivariate linear regression model was adopted.Results:From the statistical analysis of data a direct correlation between pack-years and BALF macrophages was found. Inversely correlation between pack-years and BALF lymphocytes was detected. There was not relationship among BALF cellular pattern, PFT values, specific diagnosis, BALF AB count or BALF asbestos fibre concentration.Discussion:BALF cellular pattern does not seem to be related to asbestos exposure biomarkers like AB and asbestos fibre concentration in BALF. Instead, smoke habit can induce an increase in BALF macrophages and a decrease of BALF lymphocytes count.Key words: Bronchoalveolar lavage, asbestos, asbestosis, neutrophils, lymphocytes, macrophages     

Asbestos bodies in bronchoalveolar lavage fluid in relation to occupational history

Concentrations of asbestos bodies (AB) were assessed by optical microscopy of 10 ml iron-stained samples and compared with the exposure history acquired by personal interview for 156 patients. Concentrations equalling or exceeding 1 AB/ml were found in 85% of patients who had been heavily exposed to asbestos and only 7% of those who were unlikely to have been exposed. Elevated AB concentrations were observed among primary asbestos, shipyard and construction workers. Smoking was not found to affect the AB concentrations. The use of Papanicolaou-stained cytological Millipore preparations during routine screening was a less sensitive method for the assessment of AB concentrations than that involving iron-stained preparations. The expression of AB concentration as AB/ml or AB/million cells were found to be equally useful indicators of exposure. The correlation between AB concentration and exposure history was greater than in earlier studies on workers exposed to chrysotile. Concentrations exceeding 1 AB/ml were indicative of a nontrivial exposure to asbestos. Despite the observed correlation between AB concentration and exposure history, the individual variability of AB counts, methodological differences and laboratory-bound reference values are important in the interpretation of AB concentrations in bronchoalveolar lavage (BAL) fluid at individual level.     

Measurement of asbestos fibre concentrations in fluid of repeated bro-choalveolar lavages of exposed workers

OBJECTIVES: The aim of this study was to assess the reliability of asbestos fibre concentration in bronchoalveolar lavage fluid (BALF) by carrying out the mineralogical analysis of BALF at different times in the same patient and comparing the results. METHODS: Twenty two patients underwent diagnostic fibreoptic bronchoscopy twice: the first was to assess the past asbestos exposure and the second for different clinical reasons. Mineralogical analysis of BALF was carried out. RESULTS: In 16 patients (72.7%), a reduction of concentration in BALF of all asbestos fibres was observed. The concentrations of both chrysotile and amphiboles in the first bronchoalveolar lavage (BAL) were related to their concentrations in the second BAL and the observed differences were not statistically significant. A significant decrease in asbestos body concentration between the first and the second BAL was found (Wilcoxon test, P < 0.01). CONCLUSIONS: The reliability of the fibre concentration in BALF as a marker of past asbestos exposure seems quite good. In most cases, it allows us to distinguish workers in different classes of exposure and gives useful information on the pattern of exposure. Uncertainties related in general to lung residues and in particular to mineralogical analysis of BALF (mainly due to the high coefficient of variation (CV) at low fibre concentrations and the results of the statistical analysis on total fibres) suggest that this biomarker is more likely suitable for a qualitative/categorical approach to exposure assessment than a quantitative one.     

Alveolar fiber load in asbestos workers and in subjects with no occupational asbestos exposure: an electron microscopy study

The alveolar fiber load was evaluated by bronchoalveolar lavage and by scanning and transmission electron microscopy (SEM and TEM) in 50 subjects with or without occupational exposure to asbestos. The concentration of asbestos fibers in bronchoalveolar lavage was significantly higher in the groups of people currently and formerly occupationally exposed, compared to the concentration found in people only exposed environmentally, despite wide interindividual variation within the groups. Nonasbestos inorganic fibers were present in all groups, but the concentrations did not differ significantly. Both in people occupationally exposed and in those only environmentally exposed, the alveolar load consisted mainly of ultrashort and ultrathin fibers, which can be studied only with TEM. In fact, the percentage of fibers greater than 5 micron long was only around 15% in the occupationally exposed and was minimal in those only environmentally exposed. The geometric mean diameters of asbestos fibers retained in the alveoli ranged from 0.05 micron for chrysotile to 0.15 micron for amphiboles.     

Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers

Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysotile was the major type of fibre. The differences were most pronounced for the amphibole fibres (62, 4.7, and 0.15 f/g), especially crocidolite (54, 1.8 and less than 0.001 f/g), but were evident also for tremolite (2.9, less than 0.001, and less than 0.001 f/g) and anthophyllite (1.7, less than 0.001, and less than 0.001 f/g). For amosite, there was no statistically significant difference between lungs from workers with and without mesothelioma; the lungs of workers had, however, higher concentrations than the controls. Strong correlations were found between duration of exposure and content of amphibole fibres in the lungs. Asbestos bodies, counted by light microscopy, were significantly correlated with the amphibole but not with the chrysotile contents. Fibrosis was correlated with the tremolite but not the chrysotile content in lungs from both exposed workers and controls. Overall, similar results were obtained using fibre counts and estimates of mass.     

Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers.

Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysotile was the major type of fibre. The differences were most pronounced for the amphibole fibres (62, 4.7, and 0.15 f/g), especially crocidolite (54, 1.8 and less than 0.001 f/g), but were evident also for tremolite (2.9, less than 0.001, and less than 0.001 f/g) and anthophyllite (1.7, less than 0.001, and less than 0.001 f/g). For amosite, there was no statistically significant difference between lungs from workers with and without mesothelioma; the lungs of workers had, however, higher concentrations than the controls. Strong correlations were found between duration of exposure and content of amphibole fibres in the lungs. Asbestos bodies, counted by light microscopy, were significantly correlated with the amphibole but not with the chrysotile contents. Fibrosis was correlated with the tremolite but not the chrysotile content in lungs from both exposed workers and controls. Overall, similar results were obtained using fibre counts and estimates of mass.     

Occupational exposure to chrysotile asbestos and cancer risk: a review of the amphibole hypothesis.

OBJECTIVES. This article examines the credibility and policy implications of the "amphibole hypothesis," which postulates that (1) the mesotheliomas observed among workers exposed to chrysotile asbestos may be explained by confounding exposures to amphiboles, and (2) chrysotile may have lower carcinogenic potency than amphiboles. METHODS. A critical review was conducted of the lung burden, epidemiologic, toxicologic, and mechanistic studies that provide the basis for the amphibole hypothesis. RESULTS. Mechanistic and lung burden studies do not provide convincing evidence for the amphibole hypothesis. Toxicologic and epidemiologic studies provide strong evidence that chrysotile is associated with an increased risk of lung cancer and mesothelioma. Chrysotile may be less potent than some amphiboles for inducing mesotheliomas, but there is little evidence to indicate lower lung cancer risk. CONCLUSIONS. Given the evidence of a significant lung cancer risk, the lack of conclusive evidence for the amphibole hypothesis, and the fact that workers are generally exposed to a mixture of fibers, we conclude that it is prudent to treat chrysotile with virtually the same level of concern as the amphibole forms of asbestos.     

Occult exposure to asbestos in steel workers revealed by bronchoalveolar lavage

To investigate the asbestos burden in a steelplant environment, we counted asbestos bodies (ABs) in the bronchoalveolar lavage fluid (BALF) of 65 steel workers who had retired during the previous 5 y. They had worked for at least 15 y in the same area of the plant (coke oven or blast furnace) as maintenance or production workers. On the basis of occupational anamnesis, 28 had occasional past professional exposure to asbestos; the remaining 37 workers denied any contact with asbestos. A total of 54 white-collar workers who had no occupational exposure to asbestos were included in the study as controls. An increased prevalence and concentration of ABs was found in the BALF of steel workers. Electron microscopy and EDAX analysis of AB from steel workers revealed that the core fibers were mainly amphiboles. More ABs were found in the BALF of maintenance workers than in production workers. However, the BALF from steel workers who denied any contact with asbestos revealed an increased AB burden v. controls. This demonstrates that steel workers may be subject to an occult exposure to amphiboles in the steelplant environment.     

Urinary fibres in occupational exposure to asbestos

Urine samples from 10 workers from an asbestos cement factory and from a control group of 10 workers from a foundry, were obtained; drastic precautions were taken to avoid contamination. Each urinary mineral fibre was sized and identified by transmission electron microscopy. Results show that contamination problems encountered by other authors have been overcome and that the workers exposed to chrysotile appear to excrete more chrysotile fibres, but that this difference is not statistically significant. Possibly only a few of the exposed workers are significantly exposed to asbestos, the overall exposure level being very low. The degradability of chrysotile fibres in biological fluids or the retention of fibres in some organ could explain the lack of apparent correlation between exposure and urinary concentration. Unexpectedly high concentrations of crocidolite fibres of unknown origin were detected in both groups of workers.     

Assessment of asbestos exposure via mineralogical analysis of bronchoalveolar lavage fluid

BACKGROUND: Mineralogical analysis of bronchoalveolar lavage fluid (BALF) by electron microscopy could be the most suitable method for assessing asbestos exposure. However, it has been claimed that there is not a standardized or systematic approach to the subject of mineralogical analysis. OBJECTIVES: The aim of the study was to evaluate mineralogical analysis of BALF by transmission electron microscopy (TEM) as biomarker of asbestos fibre load. METHODS: BALF was examined in 193 exposed workers (189 men and 4 women) and in 84 patients (65 men and 19 women) who underwent diagnostic fibreoptic bronchoscopy for various clinical purposes. Asbestos bodies (AB) in BALF were counted with a phase contrast microscope, while fibres were counted and analysed by TEM. RESULTS: Fibre counting by TEM showed a significant difference in the two populations (two tailed Mann-Whitney U test, p=0.0044), since it was positive in all exposed subjects. Only 75.1% of the exposed population was positive for asbestos bodies (AB). Subjects who had been exposed over a long time period had higher concentrations of fibres than subjects who had been exposed more recently probably because of higher exposure in the past. CONCLUSIONS: The study confirms the results of a previous study on a limited number of subjects. Fibre concentrations in BALF can be considered as a reliable biomarker of past asbestos exposure even after many years after cessation of exposure.     

Airborne fibre concentrations and lung burden compared to the tumour response in rats and humans exposed to asbestos

The excess risk of tumours exposed to asbestos were previously compared with the results of rat inhalation experiments. It could be demonstrated that humans at the workplace suffer from a tumour risk at fibre concentrations which are 300 times lower than those needed in the rat inhalation model to produce the same risk. However, the estimation of human risk was based on the study of workers at a chrysotile textile factory, whereas animal experimental results were related to exposure to amphiboles. Since for this comparison the risk of cancer due to exposure to amosite or crocidolite fibres at the workplace is of interest, quantitative exposure-response relationships for lung cancer and mesothelioma for the white workforce of South African amosite and crocidolite mines were discussed. On comparing the risk of lung cancer in this study with the risk of lung cancer for chrysotile textile workers, it can be concluded, that the risk of lung cancer and mesothelioma from crocidolite and amosite was higher than in the chrysotile textile factory.It could be also demonstrated, on the basis of a study of the lung burden of mesothelioma cases and of controls, that a significantly increased odds ratio of about 5 was established at amphibole concentrations of between 0.1 and 0.2 f μg⁻¹ dry lung (WHO fibres longer than 5 μm from TEM analysis). On the other hand, carcinogenic response was observed at a fibre concentration 6000 times higher in animal inhalation experiments with crocidolite asbestos (SEM analysis of WHO fibres). As a result of these findings, it has been concluded that inhalation studies in rats are not sufficiently sensitive for the detection of hazards and risks to humans exposed to man-made fibres.     

Exposure and mineralogical correlates of pulmonary fibrosis in chrysotile asbestos workers.

OBJECTIVES: The relation between lifetime cumulative exposure to asbestos, pathological grade of pulmonary fibrosis, and lung burden of asbestos at death, was explored in a necropsy population of former workers in a chrysotile asbestos textile plant in South Carolina. METHODS: Estimates of cumulative, mean, and peak exposures to asbestos were available for 54 workers. Necropsy records and lung tissue samples were obtained from hospital files. Matched control cases were selected from consecutive necropsies performed at the same hospitals. The extent and severity of pulmonary fibrosis was graded on tissue sections. Mineral fibres in lung tissue were characterised by transmission electron microscopy combined with x ray spectroscopy. RESULTS: A significant positive correlation (r = 0.67, P < 0.0001) was found between lifetime cumulative exposure to asbestos and total lung burden of asbestos fibres. This relation was also found for the individual types of asbestos associated with the exposure: chrysotile and tremolite. Pulmonary fibrosis was correlated with both cumulative exposure to asbestos (r = 0.60, P < 0.01) and the concentration of asbestos fibres in the lung (r = 0.62, P < 0.0001). The concentration of tremolite fibres in the lung provided a better estimate of lung fibrosis than did the concentration of chrysotile. Asbestosis was usually present in asbestos textile workers with more than 20 fibre-years cumulative exposure. The lengths and aspect ratios of chrysotile asbestos, but not amphibole asbestos, were greater in the lungs of asbestos fibre workers than in the control population. Textile workers with lung cancer had significantly greater cumulative exposures and fibrosis scores than workers without lung cancer. CONCLUSIONS: Both cumulative exposure to asbestos and lung fibre burden are strongly correlated with severity of asbestosis. The data also support the hypothesis that the high prevalence of asbestosis and lung cancer in this population resulted from exposure to long fibres of chrysotile asbestos in the workplace.     

Detection of chrysotile asbestos in workers' urine

Urinary asbestos concentrations were evaluated as an indicator of occupational exposure to chrysotile asbestos via inhalation and ingestion. Detection of asbestos in the urine represents the first step in developing a biological indicator of exposure. Such an indicator could be used to supplement exposure data from workplace air sampling. A biological indicator would be particularly valuable in evaluating workers with intermittent airborne asbestos exposures and in determining if airborne exposure results in penetration of asbestos through the lung or gastro-intestinal tract. Transmission electron microscopy was selected as the most sensitive technique for identification of all sizes of asbestos fibers which might appear in the urine. First morning void urine samples were obtained from six workers (occupationally exposed to chrysotile asbestos in a factory producing roof coatings) and from a control group (six individuals with no occupational exposure). The levels of chrysotile asbestos detected in the urine of five workers were significantly greater than the asbestos concentrations in matched field blanks (both on a number and mass basis). Field blanks were designed to detect asbestos in the urine samples due to contamination which might occur during urine collection. Also, the workers' urinary asbestos levels were significantly greater than the concentrations found in the control group (both on a number and mass basis). Finally, the levels of chrysotile asbestos detected in the urine of two of six controls were significantly greater than those in matched field blanks (both on a number and mass basis). Although the project was not specifically designed to correlate urinary and airborne asbestos concentrations, preliminary data indicated that a correlation did not exist between these factors.     

Malignant mesothelioma of the pleura in a worker with brief atypical exposure to chrysotile asbestos

BACKGROUND: The appearance of malignant mesothelioma in workers exposed to asbestos dusts even for relatively short periods of time is amply demonstrated in the literature. The workers however were usually exposed to amphiboles in jobs well known as involving exposure, that are characterized by high levels of dusts. OBJECTIVES: To describe a clinical case of pleural mesothelioma that occurred in a patient exposed to chrysotile, in a job (driver) that cannot be directly linked to such high exposure, and which moreover he only did for a few months. METHODS: The clinical history was reconstructed by analyzing the clinical files of the hospital admittances from May 2002 to August 2003, during which the patient underwent radiological examinations (chest x-rays, chest and abdomen TC), cytological examination of the pleural fluid, videothoracoscopic surgery with histological examination (including immunohistochemical coloration) of the tissue taken in biopsy. The job history, as well as any possible non-occupational exposures to asbestos, was examined via a standardised questionnaire, which the patient himself answered, as used in the Lombardy Mesothelioma Register, in operation at the "Clinica del Lavoro" in Milan. RESULTS: Examination of all clinical files confirmed the diagnosis of malignant pleural mesothelioma. Analysis of job history was found appropriate for defining as certain an occupational aetiology due to inhalation of asbestos fibres which occurred for few months as a truck driver in a chrysotile mine.     

Retention patterns of asbestos fibres in lung tissue among asbestos cement workers.

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.     

Pulmonary mineral fibers after occupational and environmental exposure to asbestos in the Russian chrysotile industry

BACKGROUND: As an indicator of occupational, domestic, and environmental exposure, the level and type of asbestos fibers were determined from lung tissue samples of workers and residents who resided in the area of the world's largest asbestos mine at Asbest, Russia. METHODS: Electron microscopy was used to analyze and measure the concentration of asbestos fibers in a series of 47 autopsies at the Asbest Town Hospital. Work histories were obtained from pathology reports and employment records. RESULTS: In 24 chrysotile miners, millers, and product manufacturers, the pulmonary concentrations of retained fibers (over 1 microm in length) were 0. 8-50.6 million f/g for chrysotile, and < 0.1-1.9 million f/g for amphiboles (tremolite and anthophyllite). The concentrations were lower in 23 persons without any known occupational contact with asbestos; 0.1-14.6 million f/g for chrysotile, and < 0.1-0.7 million f/g for amphiboles. On average, 90% of all inorganic fibers were chrysotile, and 5% tremolite/anthophyllite. No amosite or crocidolite fibers were detected in any of the samples. CONCLUSIONS: The mean and range of pulmonary chrysotile concentrations were about the same as reported previously from the Canadian mining and milling industry. In the Russian samples, the mean concentration of tremolite fibers were less by at least one order of magnitude. Occupational contact was the most important source of asbestos exposure.     

Asbestos bodies and the diagnosis of asbestosis in chrysotile workers

It has been suggested that because chrysotile asbestos forms asbestos bodies poorly, use of the traditional histologic requirements (diffuse interstitial fibrosis plus asbestos bodies) for the diagnosis of asbestosis, may lead to an underdiagnosis of this condition in workers exposed only to chrysotile. We examined lungs from 25 chrysotile miners with diffuse interstitial fibrosis. Asbestos bodies were found easily in histologic section using hematoxylin and eosin stains in all cases. Mineralogic analysis of four cases showed that 46 of 72 (64%) bodies isolated and examined contained chrysotile cores, and 21 of 72 (29%) bodies contained cores of the amphiboles tremolite and actinolite. By contrast, tremolite and actinolite constituted the majority of uncoated fibers in these cases. The mean length for bodies formed on chrysotile was 35 micron, and for bodies formed on tremolite or actinolite, 36 micron. We conclude that (1) the usual histologic criteria for the diagnosis of asbestos are applicable to chrysotile-exposed workers; (2) in workers with occupational chrysotile exposure, bodies form readily on this mineral; and (3) asbestos bodies in these lungs reflect the presence of long asbestos fibers.     

Airborne concentrations of chrysotile asbestos in serpentine quarries and stone processing facilities in Valmalenco, Italy

Asbestos may be naturally present in rocks and soils. In some cases, there is the possibility of releasing asbestos fibres into the atmosphere from the rock or soil, subsequently exposing workers and the general population, which can lead to an increased risk of developing asbestos-related diseases. In the present study, air contaminated with asbestos fibres released from serpentinites was investigated in occupational settings (quarries and processing factories) and in the environment close to working facilities and at urban sites. The only naturally occurrence of asbestos found in Valmalenco area was chrysotile; amphibole fibres were never detected. An experimental cut-off diameter of 0.25 μm was established for distinguishing between Valmalenco chrysotile and antigorite single fibres using selected area electron diffraction analyses. Air contamination from chrysotile fibres in the examined occupational settings was site-dependent as the degree of asbestos contamination of Valmalenco serpentinites is highly variable from place to place. Block cutting of massive serpentinites with multiple blades or discs and drilling at the quarry sites that had the highest levels of asbestos contamination generated the highest exposures to (i.e. over the occupational exposure limits) asbestos. Conversely, working activities on foliated serpentinites produced airborne chrysotile concentrations comparable with ambient levels. Environmental chrysotile concentrations were always below the Italian limit for life environments (0.002 f ml(-1)), except for one sample collected at a quarry property boundary. The present exposure assessment study should encourage the development of an effective and concordant policy for proper use of asbestos-bearing rocks and soils as well as for the protection of public health.     

Fibre type and concentration in the lungs of workers in an asbestos cement factory

The predominant asbestos fibre type used in the production of asbestos cement is chrysotile. The use of asbestos in relation to fibre type in a Norwegian asbestos cement plant during 1942-80 was 91.7% chrysotile, 3.1% amosite, 4.1% crocidolite, and 1.1% anthophyllite respectively. Electron microscopy and x ray microanalysis of lung tissue samples of asbestos cement workers who had died of malignant pleural mesothelioma or bronchogenic carcinoma showed a completely inverse ratio with regard to fibre type. The percentage of chrysotile asbestos in lung tissue varied between 0% and 9% whereas the corresponding numbers for the amphiboles were 76% and 99%. These differences are discussed with respect to the behaviour of different fibre types in the human body and to the occurrence of malignant mesothelioma in this asbestos cement factory.