The distribution and characteristics of asbestos fibers in the lungs of Finnish anthophyllite mine-workers

Asbestos: Mineralogical features and fiber analysis in biological materials

Asbestos is a mineral with unique physical and chemical properties that make it highly resistant to heat, fire, and corrosion. Nevertheless, exposure to asbestos fibers has been linked to serious health problems, including lung cancer, mesothelioma, and asbestosis. Despite the ban on asbestos usage, asbestos-related diseases are still a major cause of morbidity and mortality worldwide. Analyzing the mineralogical features and fiber analysis of asbestos in biological materials is critical for scenarios where an asbestos exposure history cannot be obtained, a clinical diagnosis cannot be made, or legal aspects necessitate further investigation. This review outlines the mineralogical features and fiber analysis techniques of asbestos in biological materials.

High frequency and severity of pleural changes in former workers exposed to anthophyllite associated with other contaminating amphibole asbestos in Brazil

OBJECTIVE

To evaluate the frequency and severity of pleuropulmonary alterations in anthophyllite-exposed former workers in Itapira, São Paulo, Brazil. The amphibole anthophyllite, a magnesium-iron silicate, had its mining, marketing, and use forbidden in Brazil in 1995.

METHODS

Former workers were followed from 1999 to 2011. All completed chest X-ray interpreted using the International Labour Office (ILO) classification. High-resolution computed tomography was used at the final evaluation. Spirometry assessed forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and FEV1/FVC throughout the follow-up period. Samples from the mined ore were analyzed by X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS).

RESULTS

XRD and SEM-EDS confirmed the presence in ore of anthophyllite at a concentration of 75%, in addition to tremolite and other amphiboles in lower concentrations. Twenty-eight subjects were evaluated. Median time of exposure was 3 years (minimum = 1; maximum  = 18; interquartile interval = 1-4). Twenty cases of pleural abnormalities were diagnosed in 26 evaluated (77%). The average latency time was 25.6 ± 7.4 years. Two individuals (7.7%) showed progressive worsening of diffuse pleural thickening (DPT) and exhibited an annual FVC decrease of 85 mL and 150 mL, respectively.

CONCLUSION

This small sample showed a very high index of nonmalignant pleural abnormalities in anthophyllite-exposed workers compared with workers exposed to other kinds of fibers. Rapidly progressive DPT, defined by the severity of pleural compromise, was possibly secondary to the presence of other amphibole types in the inhaled dust. No significant loss of FVC was found in the studied group as a whole. No cases of asbestosis, lung carcinoma, and mesothelioma were diagnosed in this cohort.

Cumulative Retrospective Exposure Assessment (REA) as a predictor of amphibole asbestos lung burden: validation procedures and results for industrial hygiene and pathology estimates

CONTEXT

A detailed evaluation of the correlation and linearity of industrial hygiene retrospective exposure assessment (REA) for cumulative asbestos exposure with asbestos lung burden analysis (LBA) has not been previously performed, but both methods are utilized for case-control and cohort studies and other applications such as setting occupational exposure limits.

OBJECTIVE

(a) To correlate REA with asbestos LBA for a large number of cases from varied industries and exposure scenarios; (b) to evaluate the linearity, precision, and applicability of both industrial hygiene exposure reconstruction and LBA; and (c) to demonstrate validation methods for REA.

METHODS

A panel of four experienced industrial hygiene raters independently estimated the cumulative asbestos exposure for 363 cases with limited exposure details in which asbestos LBA had been independently determined. LBA for asbestos bodies was performed by a pathologist by both light microscopy and scanning electron microscopy (SEM) and free asbestos fibers by SEM. Precision, reliability, correlation and linearity were evaluated via intraclass correlation, regression analysis and analysis of covariance. Plaintiff's answers to interrogatories, work history sheets, work summaries or plaintiff's discovery depositions that were obtained in court cases involving asbestos were utilized by the pathologist to provide a summarized brief asbestos exposure and work history for each of the 363 cases.

RESULTS

Linear relationships between REA and LBA were found when adjustment was made for asbestos fiber-type exposure differences. Significant correlation between REA and LBA was found with amphibole asbestos lung burden and mixed fiber-types, but not with chrysotile. The intraclass correlation coefficients (ICC) for the precision of the industrial hygiene rater cumulative asbestos exposure estimates and the precision of repeated laboratory analysis were found to be in the excellent range. The ICC estimates were performed independent of specific asbestos fiber-type.

CONCLUSIONS

Both REA and pathology assessment are reliable and complementary predictive methods to characterize asbestos exposures. Correlation analysis between the two methods effectively validates both REA methodology and LBA procedures within the determined precision, particularly for cumulative amphibole asbestos exposures since chrysotile fibers, for the most part, are not retained in the lung for an extended period of time.

Medicolegal Aspects of Asbestos II — Benign Pleural and Lung Diseases

A variety of benign lesions affecting the pleura and/or lung can result from inhaling asbestos fibers. Establishing the presence or absence of these entities often plays an important role in the evaluation, presentation and ultimate resolution of asbestos disease litigation. Forensic pathologists may become involved in these cases to address issues of diagnosis, exposure and/or disease attribution. This article reviews medicolegal issues pertaining to benign asbestos-induced diseases of the pleura and lung.

Peroxidase-like activity of ferruginous bodies isolated by exploiting their magnetic property

Ferruginous bodies (FB) are polymorphic structures whose formation is macrophage dependent, and are composed of a core, which may consist of an asbestos fiber coated with proteins, among which ferritin is the main component. Within ferritin, the ferric and ferrous ions are coordinated as ferrihydrite, which is the main iron (Fe) storage compound. However, when ferritin accumulates in some tissues following Fe overload it also contains magnetite along with ferrihydrite, which endows it with magnetic properties. Recently studies showed that magnetite exerts peroxidase-like activity, and since ferruginous bodies display magnetic properties, it was postulated that these particular structures may also contain magnetite within the ferritin coating, and thus may also exert peroxidase-like activity. Histochemical analysis for peroxidase of isolated FB smears demonstrated positive staining. Samples isolated from 4 different autopsy lung fragments were also able to oxidize 3,3',5,5'-tetramethyl-benzidine to a blue colored compound that absorbs at 655 nm. This activity was (1) azide and heat insensitive with optimal pH from 5 to 6, and (2) highly variable, changing more than 25-fold from one sample to another. These findings, together with evidence that the peroxidase-like activity of ferruginous bodies has a hydrogen peroxide and substrate requirement different from that of human myeloperoxidase, can exclude that this enzyme gives a significant contribution to the formation of FB. Standard Fe-rich asbestos fibers also express a peroxidase-like activity, but this appears negligible compared to that of ferruginous bodies. Strong acidification of standard Fe-containing asbestos fibers or magnetically isolated ferruginous bodies liberates a high amount of peroxidase-like activity, which is probably accounted for by the release of Fe ions. Further, FB also damage mesothelial cells in vitro. Data suggest that FB exert peroxidase-like activity and cytotoxic activity against mesothelial cells, and hence may be an important factor in pathogenesis of asbestos-related diseases.

Reproducibility of asbestos body counts in digestions of autopsy and surgical lung tissue

BACKGROUND

Asbestos body (AB) counting by a single observer is the most commonly used objective technique to demonstrate asbestos deposition in the lung. In this study, the accuracy and reliability of this procedure is analyzed by evaluating the degree of agreement between two experienced readers.

METHODS

Lung tissue specimens from 66 individuals, most of whom had not been exposed to asbestos, were studied: 35 were obtained in postmortem studies (upper, middle, and lower lung) and 31 were from patients who underwent surgery for lung cancer. Overall, 167 samples were analyzed. Lung tissue sections weighing 0.5 g were obtained prospectively and processed, and the inorganic residue was analyzed by light microscopy at 400× magnification by two experienced readers. Results were expressed as AB/g of dry lung tissue. Interobserver variability was analyzed using the Spearman correlation coefficient and agreement was evaluated by the Bland-Altman method and the kappa index.

RESULTS

The interobserver correlation was 0.8975: 0.8029 for autopsy samples and 0.9592 for biopsy samples. Bland-Altman plots showed that most values were grouped around the 95% limits of agreement. The kappa index was 0.87 for all samples, and 0.79, 0.65, and 0.54 for upper, middle, and lower lung specimens, respectively.

CONCLUSIONS

Asbestos body counting by a single reader is a reliable method, especially at low concentrations of asbestos bodies in lung tissue. Double reading may be indicated in borderline cases with asbestos body levels close to levels of 1 000 AB/g.

Mesothelioma and analysis of tissue fiber content

The strong relationship between mesothelioma and asbestos exposure is well established. The analysis of lung asbestos burden by light and electron microscopy assisted to understand the increased incidence of mesothelioma in asbestos mining and consuming nations.The data on the occupational exposure to asbestos are important information for the purpose of compensation of occupational disease No. 4105 (asbestos-associated mesothelioma) in Germany.However, in many cases the patients have forgotten conditions of asbestos exposure or had no knowledge about the used materials with components of asbestos. Mineral fiber analysis can provide valuable information for the research of asbestos-associated diseases and for the assessment of exposure. Because of the variability of asbestos exposure and long latency periods, the analysis of asbestos lung content is a relevant method for identification of asbestos-associated diseases. Also, sources of secondary exposure, so called "bystander exposition" or environmental exposure can be examined by mineral fiber analysis.Household contacts to asbestos are known for ten patients (1987-2009) in the German mesothelioma register; these patients lived together with family members working in the asbestos manufacturing industry.Analysis of lung tissue for asbestos burden offers information on the past exposure. The predominant fiber-type identified by electron microscopy in patients with mesothelioma is amphibole asbestos (crocidolite or amosite). Latency times (mean 42.5 years) and mean age at the time of diagnose in patients with mesothelioma are increasing (65.5 years). The decrease of median asbestos burden of the lung in mesothelioma patients results in disease manifestation at a higher age.Lung dust analyses are a relevant method for the determination of causation in mesothelioma. Analysis of asbestos burden of the lung and of fiber type provides insights into the pathogenesis of malignant mesothelioma. The most important causal factor for the development of mesothelioma is still asbestos exposure.

Simple quantitative analysis of asbestos body using the sediment of formalin injected into surgically resected lung cancers

A simple screening method for quantitatively analyzing asbestos bodies that can be carried out even in community hospitals, is needed in order for laborers and neighborhoods in the vicinity of asbestos factories to apply for compensation for asbestos-related injury. Eighty-eight consecutive cases of surgically resected primary lung cancer were analyzed for asbestos bodies using two methods, and the correlation between them was statistically examined. The first was the conventional technique using lung tissue digestion and phase-contrast scanning, and the second was the authors' method using light microscopy to scan the sediment of formalin-injected lung specimens. The overall correlation coefficient of the concentration of asbestos bodies between the authors' method (C(AB/SED)) and the conventional method (C(AB/DLT)) was 0.4576, a weak statistically significant correlation; in patients with occupational asbestos exposure, however, the correlation coefficient was 0.7341. Despite the cost, it may be prudent to use the conventional method under the present law for patients with C(AB/SED)>or=3.5/mL. C(AB/DLT) >3000/g dry lung tissue when C(AB/SED) is >or=3.5/mL suggests the potential for the accumulation of asbestos absorption by lung tissue.

[Prevalence and distribution of asbestos lung residue in a Spanish urban population]

INTRODUCTION

The purpose of the present study is to analyse the prevalence and distribution of asbestos lung residue in the Barcelona urban population.

MATERIAL AND METHODS

Lung autopsy samples were obtained from 35 individuals who had lived in Barcelona. The close family were interviewed in order to rule out asbestos exposure. Samples were obtained from three areas of the right lung during the autopsy: upper lobe apex, lower lobe apex, and lower lobe base. The samples were treated to remove organic material. The inorganic residue was analysed using a light microscope. The results were expressed as asbestos bodies (AB) per gram of dry tissue. Levels greater than 1000AB/g of dry tissue were considered as potentially causing disease.

RESULTS

AB were detected in 29(83%) of the subjects, of which 86% had levels less than 300AB/g. Only one individual (3%) had values greater than 1000AB/g dry tissue. The asbestos residue was higher in the lower lung lobe in 17 individuals (48%) than in the rest, although no significant differences were seen as regards AB residue in the three lung areas studied.

CONCLUSIONS

The results of this study show that the urban population of Barcelona have asbestos levels in the lung that vary between 0 and 300AB/g dry tissue. No differences in the asbestos residues were detected in the lung areas studied in this population.

Relationships between ferruginous bodies and uncoated asbestos fibers in lung tissue

Tissue was obtained from two American groups. The tissue was defined by ferruginous body levels of either < or = 1000 or > 1000 ferruginous bodies/g dry weight, and tissue was evaluated by light microscopy and analyzed by analytical transmission electron microscopy. Tissue was bleach digested, and uncoated asbestos fibers were classified with respect to type and size. In addition, some ferruginous body cores were analyzed. There was a wide range of uncoated fibers associated with each ferruginous body. A relationship was found between amosite fibers and ferruginous bodies. Other asbestos types were not associated significantly with the development of ferruginous bodies. Uncoated crocidolite fibers were not detected in these samples; this result further emphasizes the under-appreciated exposure of Americans to amosite. The levels of ferruginous bodies in both groups suggest exposures above those expected in the general population. Uncoated chrysotile levels were below the ranges reported previously for some general populations. The data suggest that there is a wide variation in the ratio of uncoated to coated fibers and that the amphibole in the United States is more likely to be amosite than crocidolite.

Analysis and interpretation of inorganic mineral particles in "lung" tissues

Mineral analysis of tissue specimens has provided very useful information in pathological conditions associated with occupational exposures to mineral particles, particularly when combined with epidemiological information. Most of the data have been related to exposures to fibrous particles such as asbestos. More investigations of this nature are required in diseases associated with exposure to non-fibrous particles. In the future it is likely that these types of investigation will be extended into the effects of pollutants.

Distribution of asbestos bodies in the human lung as determined by bronchoalveolar lavage

Asbestos-related lung diseases tend to have distinct local distributions, for example, asbestosis first appears and tends to be more severe in the peripheral parts of the lower lung zones. The risk for asbestosis is related to the total asbestos burden of the lung. This suggests that the lower lobes in asbestos-exposed individuals may contain more asbestos than the other lobes. To test whether such topographic differences exist, we compared the number of retrieved asbestos bodies (AB) per ml BAL fluid in three groups of occupationally asbestos-exposed subjects who underwent BAL at different sampling sites. In Group 1 (n = 24) we performed BAL at three sites, namely in a segment of the right upper, right middle, and right lower lobe, to evaluate differences in asbestos body burden from lung apex to basis. There was a distinct increase in BAL asbestos body concentrations from the upper (21.2 +/- 9.1 AB/ml BAL fluid) to the middle (30.4 +/- 12.8 AB/ml BAL fluid) and to the lower lobe (56.0 +/- 20.2 AB/ml BAL fluid), all differences being significant (p < 0.01). In Group 2 (n = 40), we found good interlobar correlations for asbestos body counts between the right middle lobe (21.0 +/- 5.8 AB/ml BAL fluid) and the lingula (22.4 +/- 5.9 AB/ml BAL fluid) (r = 0.941, p < 0.001) and, in Group 3 (n = 15), between the ventral basal segment of the right (41.2 +/- 13.6 AB/ml BAL fluid) and left lung (39.0 +/- 13.6 AB/ml BAL fluid) (r = 0.966, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)