Retention of Asbestos Bodies in the Lungs of Welders

Examination of asbestos bodies (AB) retained in the lungs is a useful way of assessing past occupational exposure to this material. AB retention has been extensively studied in workers directly exposed to asbestos, but less so in those end users, such as welders, who use asbestos-containing products. We therefore retrospectively studied AB retention in 211 welders, for whom biological testing procedures had been requested by a chest physician, between 1988 and 1991. Optical microscopy of AB was performed on samples of sputum (40 subjects), bronchoalveolar lavage fluid (BAL) (147 subjects), and lung tissue obtained after thoracotomy (38 subjects). Information on previous jobs and exposure was obtained using a questionnaire (the mean duration of welding activities was 16.6 years). Eighty-two subjects (38.9%) had elevated lung retention of AB in all the samples studied. Significant AB retention occurred in only 30% of sputum samples, but in 40.1% of BAL samples and 39.5% of lung tissue samples. The duration of welding activities correlated with the density of AB in BAL or lung tissue (r = 0.31, p < 0.01 and r = 0.49, p < 0.05, respectively). On the basis of the questionnaire, only two of the welders with significant AB retention had other occupational exposure to asbestos. Our findings suggest that welding activities may increase lung retention of AB, and consequently might produce higher risks of fibrotic and/or malignant pulmonary diseases. These potential risks need to be brought to the attention of doctors; a longitudinal follow-up may also be warranted in such populations, even after individuals have ceased their welding jobs.     

Asbestos fibres in bronchoalveolar lavage fluid from asbestos workers: examination by electron microscopy

The uncoated and coated fibre load in bronchoalveolar lavage (BAL) fluid was assessed using light microscopy, scanning electron microscopy, and x ray microanalysis in 15 subjects with previous, unprotected exposure to asbestos, including three with clinical and radiological evidence of asbestosis, and in 13 urban dwelling control subjects with no known occupational exposure to asbestos. The mean ferruginous body count per ml BAL fluid in asbestos exposed subjects as determined by light microscopy was 52 (range 0-333). No ferruginous bodies were detected in control subjects. The mean fibre count per ml BAL fluid in asbestos exposed subjects as determined by electron microscopy was 793 (133-3700), significantly greater than 239 (44-544) in controls (p less than 0.05). Electron microscopic counts correlated with duration of previous exposure to asbestos (r = 0.47, p less than 0.05) and with percentage neutrophil counts (r = 0.53, p less than 0.025). There was no relation between electron microscopic fibre counts and light microscopic ferruginous body counts. In 11 asbestos exposed cases x ray microanalysis confirmed the presence of asbestos and in six the asbestos fibre type was clearly identified. Of five subjects showing no asbestos bodies by light microscopy, all showed fibres by electron microscopy, and in three cases the presence of asbestos was confirmed by microanalysis. Among control subjects, fibres were either large organic fibres or smaller particles which microanalysis showed were not asbestos. In only one control case were a few fibres identified which were confirmed as asbestos fibres on microanalysis. Electron microscopic examination of BAL fluid may confirm past exposure to asbestos and probably gives a crude quantitative estimate of asbestos load.     

Asbestos fibres in bronchoalveolar lavage fluid from asbestos workers: examination by electron microscopy.

The uncoated and coated fibre load in bronchoalveolar lavage (BAL) fluid was assessed using light microscopy, scanning electron microscopy, and x ray microanalysis in 15 subjects with previous, unprotected exposure to asbestos, including three with clinical and radiological evidence of asbestosis, and in 13 urban dwelling control subjects with no known occupational exposure to asbestos. The mean ferruginous body count per ml BAL fluid in asbestos exposed subjects as determined by light microscopy was 52 (range 0-333). No ferruginous bodies were detected in control subjects. The mean fibre count per ml BAL fluid in asbestos exposed subjects as determined by electron microscopy was 793 (133-3700), significantly greater than 239 (44-544) in controls (p less than 0.05). Electron microscopic counts correlated with duration of previous exposure to asbestos (r = 0.47, p less than 0.05) and with percentage neutrophil counts (r = 0.53, p less than 0.025). There was no relation between electron microscopic fibre counts and light microscopic ferruginous body counts. In 11 asbestos exposed cases x ray microanalysis confirmed the presence of asbestos and in six the asbestos fibre type was clearly identified. Of five subjects showing no asbestos bodies by light microscopy, all showed fibres by electron microscopy, and in three cases the presence of asbestos was confirmed by microanalysis. Among control subjects, fibres were either large organic fibres or smaller particles which microanalysis showed were not asbestos. In only one control case were a few fibres identified which were confirmed as asbestos fibres on microanalysis. Electron microscopic examination of BAL fluid may confirm past exposure to asbestos and probably gives a crude quantitative estimate of asbestos load.     

Significance of bronchoalveolar lavage in demonstrating previous exposure to asbestos

A study was made via a clinical approach in the absence of environmental data with the aim of demonstrating a possible past exposure to asbestos in a working population that had never been examined before nor had ever undergone any specific health checks. It was deemed useful to compare this working population with a control population not exposed to asbestos. The population under study consisted of 126 employees of a single (thermonuclear) department of a metal engineering industry who reported having used asbestos as insulation material in all heat processes up to the beginning of the 1980's. Pleural plaques were observed in 13 workers that were also confirmed by high resolution TC (HRTC) except in one case. The control group consisted of subjects seen at the Clinica del Lavoro of Milan for non-asbestos related diseases in whom a fibrobronchoscopy with broncho-alveolar lavage (BAL) was performed for diagnostic purposes. In each group asbestos bodies were counted in the BAL liquid using a method with a detection limit of 0.1 bodies/ml. The asbestos bodies detected in the alveolar liquid of subjects in the control group were between a maximum of 0.25 and a minimum of 0 bodies/ml of liquid (mean = 0.03; SD = 0.64) whereas in the sample of subjects from the population under study who underwent BAL the results gave a concentration of asbestos bodies in the BAL liquid between a maximum of 9.0 and a minimum of 0.15 bodies/ml of liquid (mean = 2.38; SD = 2.72). In order to obtain a statistically significant difference between the control population, which was certainly not exposed, and the sample of subjects undergoing BAL from the population for which an occupational exposure was assumed, we applied the non-parametric Wilcoxon-Mann-Whitney test for independent samples in view of the asymmetric distribution of the values of asbestos body concentration in the alveolar liquid: the result was a statistically significant difference (p < 0.001) between the two populations. We also calculated the total asbestos bodies recovered in the BAL liquid of subjects from both populations. In the control group total asbestos bodies were between a maximum of 15 and a minimum of 0 (mean = 1.8; SD = 3.9) while in the group under study the concentration of total asbestos bodies recovered in BAL liquid was between a maximum of 990 and a minimum of 12.7 (mean = 206.5; SD = 270). The Wilcoxon-Mann-Whitney test was also applied to these data, the result of which was that the difference in exposure between the two populations was statistically significant (p < 0.001). Concluding, the study demonstrates the importance of asbestos body count in BAL liquid as an objective indicator of past occupational exposure to asbestos, thus providing documented proof that overcomes any doubts arising from case history and any lack of environmental data that could prove exposure.     

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.     

Markers of fibrogenesis in bronchoalveolar lavage and in serum of workers exposed to asbestos]

The N-terminal peptide of type III procollagen (PIIIP) and fibronectin (FBN), two markers possibly implicated in the pathogenesis of pulmonary fibrosis, were determined in bronchoalveolar lavage fluid (BAL) and in serum of 27 subjects with a history of occupational exposure to asbestos, in 10 sarcoidosis patients and in 7 healthy controls. At the same time, the study of the cell populations and asbestos bodies count in BAL were also performed. In BAL of sarcoidosis patients the mean concentration of PI-IIIP was higher compared to that of the other two groups, and the difference was significant compared with the healthy controls. Among the group of asbestos workers, both PIIIP and FBN were significantly higher in subjects with radiological signs of pulmonary asbestosis compared with those with no signs of asbestosis. On the basis of BAL cytology, the asbestos-exposed were divided into two subgroups, with or without signs of alveolitis: the mean concentrations of BAL PIIIP was significantly higher in the subgroup with alveolitis. Moreover, in this subgroup there was a positive correlation between total number of cells and PIIIP, and between the number of asbestos bodies and PIIIP in BAL. Serum PIIIP values did not differ significantly among the various groups, with the exception of higher values in sarcoidosis patients. The results of this study seem to confirm the usefulness of PIIIP and FBN determinations in BAL, as indicators of the activity of the fibrotic process which, in particular cases, might also assume a prognostic significance.     

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.     

Analysis of asbestos bodies in BAL from subjects with particular exposures

Four patients with asbestos-related diseases and with unusual exposures underwent bronchoalveolar lavage (BAL) for mineralogical analysis. Asbestos bodies (AB) were counted by light microscopy and analyzed by transmission electron microscopy and X-ray energy spectrometry. AB's were found in all cases, after a mean delay from the end of exposure of 27.7 years. Analysis of the core fibers indicated the type of alveolar asbestos burden and was compared with the previous exposures: —Pleural plaques due to household exposure to amosite and crocidolite. —Pleural plaques due to occult occupational exposure to crocidolite in a coal miner. —Asbestosis due to environmental exposure to tremolite in Turkey. —Asbestosis, pleural plaques, and peritoneal mesothelioma due to a short, intense exposure to crocidolite. AB counting in BAL and identification of the central fibers by analytical electron microscopy is a useful, non-invasive and reliable method to evaluate the alveolar retention of bio-persistent fibers and to relate them to specific exposures. Am. J. Ind. Med. 31:699–704, 1997. © 1997 Wiley-Liss, Inc.     

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.     

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.     

Analysis of ferruginous bodies in bronchoalveolar lavage from foundry workers.

Classical ferruginous bodies in tissue samples are considered to be markers of past exposure to asbestos. Recent studies have shown that the presence of ferruginous bodies in bronchoalveolar lavage (BAL) fluid correlates with past exposure to asbestos and offers a more sensitive reference than occupational history. Lavage samples from five subjects who had worked in foundries were evaluated by light microscopy for the presence of ferruginous bodies and by transmission electron microscopy for both characterisation of the uncoated fibre burden and analysis of the cores of the ferruginous bodies. All samples at lower magnification (light microscopy (200 x)) contained ferruginous bodies that were externally consistent with asbestos bodies. At higher magnification (400 x), a separate population from this group could be identified by the presence of a thin black ribbon. Transmission electron microscopy of the core materials of ferruginous bodies and comparable uncoated particulates supported the reliability of higher magnification light microscopy for distinguishing most of those non-asbestos cores; however, a population of transparent non-asbestos cored ferruginous bodies were also shown to exist.     

Pleural mesothelioma and exposure to asbestos: evaluation from work histories and analysis of asbestos bodies in bronchoalveolar lavage fluid or lung tissue in 131 patients.

Exposure to asbestos was evaluated in 131 patients with pleural malignant mesothelioma in the Paris area between 1986 and 1992 using data from a detailed specific questionnaire and light microscopy analysis of the retention of asbestos bodies in bronchoalveolar lavage fluid or lung tissue. Probable or definite exposure to significant levels of asbestos dust was identified in only 48 (36.6%) subjects, and significant asbestos body counts (above 1 asbestos body/ml in bronchoalveolar lavage fluid or 1000 asbestos bodies/g of dry lung tissue) were found in only 45 (34.3%) subjects. Overall 50 subjects had experienced exposure to only low levels of asbestos or no exposure at all and showed no significant retention of asbestos bodies in the biological sample analysed. Previous studies have shown that light microscopy may be useful in the identification of subjects with previous exposure to asbestos. In this study, apart from cases with obvious exposure to asbestos, a large group of subjects seemed to have a history of exposure or lung retention of asbestos bodies suggestive of very low levels of cumulative exposure, similar to those described in the general population.     

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.     

Asbestos lung burden and asbestosis after occupational and environmental exposure in an asbestos cement manufacturing area: a necropsy study

OBJECTIVE: The largest Italian asbestos cement factory had been active in Casale Monferrato until 1986: in previous studies a substantial increase in the incidence of pleural mesothelioma was found among residents without occupational exposure to asbestos. To estimate exposure to asbestos in the population, this study evaluated the presence of histological asbestosis and the lung burden of asbestos fibres (AFs) and asbestos bodies (ABs). METHODS: The study comprises the consecutive series of necropsies performed at the Hospital of Casale Monferrato between 1985 and 1988. A sample of lung parenchima was collected and stored for 48 out of 55 necropsies. The AF concentration was measured with a TEM electron microscope with x ray mineralogical analysis. The ABs were counted and fibrosis evaluated by optical microscopy. The nearest relative of each subject was interviewed on occupational and residential history. Mineralogical and histological analyses and interviews were conducted in 1993-4. RESULTS: Statistical analyses included 41 subjects with AF, AB count, and interview. Subjects without occupational exposure who ever lived in Casale Monferrato had an average concentration of 1500 AB/g dried weight (gdw); Seven of 18 presented with asbestosis or small airway lung disease (SAL). G2 asbestosis was diagnosed in two women with no occupational asbestos exposure. One of them had been teaching at a school close to the factory for 12 years. Ten subjects had experienced occupational asbestos exposure, seven in asbestos cement production: mean concentrations were 1.032 x 10(6) AF/gdw and 96,280 AB/gdw. Eight of the 10 had asbestosis or SAL. CONCLUSION: The high concentration of ABs and the new finding of environmental asbestosis confirm that high asbestos concentration was common in the proximity of the factory. Subjects not occupationally exposed and ever living in Casale Monferrato tended to have higher AB concentration than subjects never living in the town (difference not significant). The concentrations of ABs and AFs were higher than those found in other studies on nonoccupationally exposed subjects.

 

     

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.     

Clinical research in the field of occupational diseases (pneumonology aspects)

In the second half of the seventies, at the same time as the control of silicosis was achieved thanks to pathogenetic and preventive developments, the major efforts of the Clinica del Lavoro in the pneumological field were focused on studying dose-response relationship in asbestos-exposed subjects. Thus for the first time biological indicators (and not radiological ones) were mentioned for asbestos diseases. Bronchoalveolar lavage (BAL) allowed to compare an internal dose indicator (number of bodies/ml) and schlerogenous effect indicators (dose-response). Our experience over nearly 20 years for exposure assessment in asbestos-related diseases, based on over 500 cases has produced the following results: parenchymial asbestosis is dose-dependent while pleural plaques are dose-independent; epidemiologic data on existence of asbestos resistant subjects were confirmed; asbestos bodies proved to persist in alveolar cavities for several decades. At present, with the ban of asbestos and the increase in forensic medicine cases regarding past asbestos exposures, our Department demonstrated the importance of asbestos body counting in BAL as an objective indicator of asbestos exposure. Besides the asbestos issue, two less frequent work-related diseases were studied and in this regard bronchoalveolar lavage proved to be a substantial diagnostic tool, sometimes even decisive: these were hard metal disease and hypersensitive pneumonitis. In subjects exposed to hard metals, our experience showed the presence of a large lymphocytic alveolitis with CD4+/CD8+ reverse ratio for bronchial asthma and macrophagic-eosinophylic alveolitis characterized by several "bizarre" giant cells in the case of interstitial disease. In extrinsic allergic alveolitis, we noted the presence of a large lymphocytic alveolitis mostly with CD4+/CD8+ reverse ratio, persisting also during clinical remission of the disease.     

The usefulness of bronchoalveolar lavage in identifying past occupational exposure to asbestos: a light and electron microscopy study.

Fiberoptic bronchoscopy has permitted the development of lavage procedures for the collection of lung washes. In certain disease states this material may contain large numbers of phagocytic cells (macrophages and neutrophils). Since these phagocytes are the predominant "dust scavenger cells" in the lung, the assessment of their particulate burden as well as that of the overall lavage material has been suggested as a potentially important diagnostic tool. The studies to date have shown that the presence of ferruginous bodies is an indication of past occupational exposure. In the present study, a digestion procedure was carried out on bronchoalveolar lavage material collected from individuals who were occupationally exposed to asbestos and from samples obtained from the general population. The parameters used for distinguishing the source of these samples included both light microscopy assessment of the filters for the presence of ferruginous bodies and electron microscopic screening for the presence of uncoated fibers.     

An unusual exposure to asbestosis risk in a bag manufacturing plant: observations on 22 cases

Although the risks connected with occupational exposure to asbestos and its numerous industrial uses are widely known, it still happens that instances of exposure with high potential risk are discovered. A detailed study of a worker suffering from silicosis and asbestosis who had worked for many years in a firm dealing with the recovery and re-use of used jute sacks also containing asbestos, revealed the existence of a real asbestosis risk in the firm, with the result that other workers in the same firm were studied. A total of 22 subjects were studied, 17 of whom also underwent bronchoalveolar lavage (BAL) and determination of the cellular composition of the recovery liquid in order to establish the presence of asbestous alveolitis. The age of the subjects ranged between 39 and 75 years (x = 56.36), length of service in the firm ranged between 2 and 18 years (x = 9.27), time between start of exposure and clinical examination varied between 29 and 50 years (x = 40.27). The 22 subjects were divided into 3 groups on the basis of the radiological examinations: 1) 8 cases were negative (36.36%); 2) 8 cases had pleural alterations only (36.36%); 3) 6 cases had interstitial lung disease (with and without pleural lesions) (27.27%). Of the 17 subjects who underwent BAL, 7 were in the first group, 7 in the second and 3 in the third. Among these 17 subjects BAL showed absence of alveolitis in all subjects of the first group, diagnosis of alveolitis in only some of the second group, and in all of the third group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fibres and asbestos bodies in bronchoalveolar lavage fluids of asbestos sprayers.

The alveolar content of fibres and asbestos bodies was assessed by bronchoalveolar lavage (BAL) in 21 asbestos sprayers. Transmission and scanning electron microscopy (TEM and SEM) and two light microscopical (LM) methods, cytocentrifugation, and Millipore filtration were used. The subjects had been exposed mainly to crocidolite asbestos for an average of 2.8 (range 0.2-13) years in 1950-75. The mean (median) total fibre count (of asbestos bodies and uncoated fibres) per ml of BAL fluid was 5500 (2800) by TEM and 2900 (1000) by SEM. The mean (median) count of asbestos bodies per ml with LM was 810 (500) with cytocentrifugation and 750 (480) with Millipore filtration, 840 (320) by TEM, and 1750 (420) by SEM. The mean proportion of coated fibres was 35% by TEM and 45% by SEM. The mean length of the coated fibres was 22 (range 4-65) microns by TEM and 34 (range 4.5-170) microns by SEM. The total fibre count exceeded 1000 fibres per ml in 70% of the cases by TEM. Asbestos body counts exceeded 1 per ml in 95% of the cases by LM. The fibre counts by SEM were in good accordance with counts by TEM except in a few cases in which the TEM result was considerably higher. In these cases the proportion of coated fibres was also low. All four counting methods appeared to give consistent results in heavily exposed cases when fibre load in the lungs was high. The counting of asbestos bodies may, however, underestimate the total alveolar fibre load in some cases.     

Fibres and asbestos bodies in bronchoalveolar lavage fluids of asbestos sprayers.

The alveolar content of fibres and asbestos bodies was assessed by bronchoalveolar lavage (BAL) in 21 asbestos sprayers. Transmission and scanning electron microscopy (TEM and SEM) and two light microscopical (LM) methods, cytocentrifugation, and Millipore filtration were used. The subjects had been exposed mainly to crocidolite asbestos for an average of 2.8 (range 0.2-13) years in 1950-75. The mean (median) total fibre count (of asbestos bodies and uncoated fibres) per ml of BAL fluid was 5500 (2800) by TEM and 2900 (1000) by SEM. The mean (median) count of asbestos bodies per ml with LM was 810 (500) with cytocentrifugation and 750 (480) with Millipore filtration, 840 (320) by TEM, and 1750 (420) by SEM. The mean proportion of coated fibres was 35% by TEM and 45% by SEM. The mean length of the coated fibres was 22 (range 4-65) microns by TEM and 34 (range 4.5-170) microns by SEM. The total fibre count exceeded 1000 fibres per ml in 70% of the cases by TEM. Asbestos body counts exceeded 1 per ml in 95% of the cases by LM. The fibre counts by SEM were in good accordance with counts by TEM except in a few cases in which the TEM result was considerably higher. In these cases the proportion of coated fibres was also low. All four counting methods appeared to give consistent results in heavily exposed cases when fibre load in the lungs was high. The counting of asbestos bodies may, however, underestimate the total alveolar fibre load in some cases.