Mesothelioma and asbestos

An AI based smart-phone system for asbestos identification

Asbestos identification is a complex environmental and economic challenge. Typical commercial identification of asbestos involves sending samples to a laboratory where someone learned in the field uses light microscopy and specialized mounting to identify the morphologically distinct signatures of Asbestos. In this work we investigate the use of a portable (30x) microscope which works with a smart phone camera to develop an image recognition system. 7328 images from over 1000 distinct samples of cement sheet from Melbourne, Australia were used to train a phone-based image recognition system for Asbestos identification. Three common CNN's were tested ResNet101, InceptionV3 and VGG_16 with ResNet101 achieving the best result. The distinctiveness of Asbestos was found to be identified correctly 90% of the time using a phone-based system and no specialized mounting. The image recognition system was trained with ResNet101 a convolutional neural network deep learning model which weights layers with a residual function. Resulting in an accuracy of 98.46% and loss of 3.8% ResNet101 was found to produce a more accurate model for this use-case than other deep learning neural networks.

Mesothelin methylation, soluble mesothelin related protein levels and inflammation profiling in workers chronically exposed to naturally occurring asbestos fibers

Exposure to asbestiform fibers, including chrysotile and amphibole, is carcinogenic, causing malignant pleural mesothelioma (MPM) when inhaled. Some populations globally face Naturally Occurring Asbestos (NOA) exposure, leading to MPM cases like in Biancavilla, Italy, from Fluoro-edenite (FE) contamination. Studies show NOA exposure causes epigenetic changes, focusing on mesothelin methylation, an MPM marker, and altered inflammation, emphasizing the health risks of FE and asbestos. This research, conducted from February 2022 to October 2022, studied 125 construction workers from Biancavilla and 125 controls from 40 km away without Biancavilla work history. With at least ten years in construction and no respiratory conditions, participants underwent medical assessments and gave blood samples for analysis, including inflammation markers, mesothelin methylation, and soluble mesothelin-related protein levels. The results showed similar demographics but differing inflammation and methylation levels in exposed workers, suggesting long-term cellular changes. Pearson correlation showed intricate biomarker relationships. Significant inflammatory differences were found between FE exposed and non-exposed workers, indicating potential health impacts from FE. This raises concerns for communities like Biancavilla, emphasizing the importance of extensive epigenetic research for public health.

Assessment protocol of mesothelioma and relevance of SEM-EDS analysis through a case studies of legal medicine of Brescia (Italy)

INTRODUCTION

This study evaluates the assessment protocol that allows the correlation between the development of mesothelioma to a specific exposure, with particular focus on investigations with Scanning Electron Microscope with Energy Dispersion Spectroscopy.

METHODS

This retrospective study includes 80 subjects who died from mesothelioma in the period 2001-2019. A judicial autopsy was performed for each case to confirm cause of death and correlate the disease with specific asbestos exposure. In 28 cases investigations were carried out to determine the pulmonary load of the asbestos fibres and corpuscles in the lung tissue through microscopic investigations, in order to confirm the suspicion of occupational exposure.

RESULTS

Our data agree with the scientific literature reported, but it is interesting to underline how the present study uses a different systematic approach than others, which are mainly based on epidemiological and environmental studies without considering the lung content of fibres and corpuscles.

CONCLUSION

It would be desirable that the use of the microscopic analysis was introduced in the evaluation protocol: it should always be carried out if the suspicion of asbestos-related disease is raised and not only as a possible integration to the less expensive anamnestic evaluation, even more so if the work or personal history should be suggestive of exposure to asbestos fibres.

Evaluation of Airborne Asbestos Concentrations Associated with the Operation and Maintenance of Brakes and Clutches on Nonautomated Heavy Equipment

This study evaluated the potential for chrysotile asbestos exposure during maintenance and operation of older, nonautomated heavy equipment with chrysotile-containing brake and clutch linings. Recent reports indicate that such equipment may be in current use in the U.S. and other locations, including developing countries, due to its lower cost and ease of maintenance compared to newer equipment. Personal and area airborne fiber concentrations were measured for cranes with draglines during brake and clutch repair, equipment operation, shop cleanup, and clothes handling of the mechanic's coveralls over a period of three days. The range of airborne chrysotile concentrations during the complete friction band replacement process, including band removal from the equipment, friction lining replacement, and reinstallation, ranged from 0.0053 to 0.0273 f/cc (phase contrast microscopy-equivalent or PCME) over 3.3 to 6.2 hours. Additional bench work tasks, including electric wire brushing, hand sanding, riveting, and compressed air use were also performed. Full shift airborne chrysotile concentrations (6.1-8.5 hours) for all combined maintenance activities were 0.0093, 0.0414, and 0.0445 f/cc (PCME), on days 1, 2, and 3, respectively. Personal short-term samples (14-36 minutes) for lining removal, installation, wire brushing, hand sanding, and compressed air use ranged from nondetect (ND) to 0.238 f/cc (PCME), below the U.S. Occupational Safety and Health Administration's (OSHA's) 30-minute excursion limit of 1 f/cc. Short-term samples during crane operation, shop cleanup, and simulated laundry activities with the mechanic's coveralls ranged from ND to 0.01 f/cc (PCME; 15-36 minutes). The results indicated that full-shift measured airborne chrysotile concentrations during the brake and clutch maintenance activities evaluated remained below the U.S. 8-hour time-weighted average (TWA) permissible exposure limit (PEL) for asbestos of 0.1 f/cc. The results are likely to be relevant to farmers, construction workers, and vehicle maintenance workers historically, as well as today for those who choose to continue using and maintaining such equipment.

Risk of asbestosis, mesothelioma, other lung disease or death among motor vehicle mechanics: a 45-year Danish cohort study

INTRODUCTION

The risk of asbestosis, malignant mesothelioma and lung cancer among motor vehicle mechanics is of concern because of potential exposure to chrysotile asbestos during brake, clutch and gasket repair and maintenance. Asbestos has also been used in insulation and exhaust systems.

METHODS

We examined the long-term risk of incident mesothelioma, lung cancer, asbestosis and other lung diseases and mortality due to mesothelioma, lung cancer, asbestosis and other lung diseases in a nationwide cohort of all men registered as motor vehicle mechanics since 1970 in Denmark. This was compared with the corresponding risk in a cohort of male workers matched 10:1 by age and calendar year, with similar socioeconomic status (instrument makers, dairymen, upholsterers, glaziers, butchers, bakers, drivers, farmers and workers in the food industry, trade or public services).

RESULTS

Our study included 138 559 motor vehicle mechanics (median age 24 years; median follow-up 20 years (maximum 45 years)) and 1 385 590 comparison workers (median age 25 years; median follow-up 19 years (maximum 45 years)). Compared with other workers, vehicle mechanics had a lower risk of morbidity due to mesothelioma/pleural cancer (n=47 cases) (age-adjusted and calendar-year-adjusted HR=0.74 (95% CI 0.55 to 0.99)), a slightly increased risk of lung cancer (HR=1.09 (95% CI 1.03 to 1.14)), increased risk of asbestosis (HR=1.50 (95% CI 1.10 to 2.03)) and a chronic obstructive pulmonary disease risk close to unity (HR=1.02 (95% CI 0.99 to 1.05)). Corresponding HRs for mortality were 0.86 (95% CI 0.64 to 1.15) for mesothelioma/pleural cancer, 1.06 (95% CI 1.01 to 1.12) for lung cancer, 1.79 (95% CI 1.10 to 2.92) for asbestosis, 1.06 (95% CI 0.86 to 1.30) for other lung diseases caused by external agents and 1.00 (95% CI 0.98 to 1.01) for death due to all causes.

CONCLUSIONS

We found that the risk of asbestosis was increased among vehicle mechanics. The risk of malignant mesothelioma/pleural cancers was not increased among vehicle mechanics.

Inorganic Fiber Lung Burden in Subjects with Occupational and/or Anthropogenic Environmental Asbestos Exposure in Broni (Pavia, Northern Italy): An SEM-EDS Study on Autoptic Samples

Increased mortality due to malignant mesothelioma has been demonstrated by several epidemiologic studies in the area around Broni (a small town in Lombardy, northern Italy), where a factory producing asbestos cement was active between 1932 and 1993. Until now, the inorganic fiber burden in lungs has not been investigated in this population. The aim of this study is to assess the lung fiber burden in 72 individuals with previous occupational and/or anthropogenic environmental exposure to asbestos during the activity of an important asbestos cement factory. Inorganic fiber lung burden was assessed in autoptic samples taken from individuals deceased from asbestos-related diseases using a scanning electron microscope equipped with an energy-dispersive spectrometer. Significant differences in the detected amount of asbestos were pointed out among the three types of exposure. In most lung samples taken from patients who died of mesothelioma, very little asbestos (or, in some cases, no fibers) was found. Such subjects showed a significantly lower median amount of asbestos as compared to asbestosis. Almost no chrysotile was detected in the examined samples. Overall, crocidolite was the most represented asbestos, followed by amosite, tremolite/actinolite asbestos, and anthophyllite asbestos. There were significant differences in the amount of crocidolite and amosite fibers according to the kind of exposure. Overall, these findings provide novel insights into the link between asbestos exposure and mesothelioma, as well as the different impacts of the various types of asbestos on human health in relation to their different biopersistences in the lung microenvironment.

Obtaining of oil blocks as a way to manage hazardous asbestos

In the second half of the 20th century, asbestos extraction was up to 4 Mt/year. Due to its high strength and insulation properties, this mineral was used as an additive in building materials. Over time these materials were destroyed by the process of weathering and leaching. Asbestos fibers in dust form penetrate the respiratory system causing diseases. This article proposes the binding of hazardous asbestos fibers in a polymer matrix formed from waste cooking oil. Compact materials were produced by heating catalyzed waste cooking oil and asbestos waste, and the process of obtaining these materials was optimized and their physicochemical and strength properties were determined. Oil-asbestos blocks contained sulfuric acid in a mass ratio of 0.05-0.30, being the mass of waste cooking oil, invariable mass of filling and 20% of waste cooking oil to the mass of the whole mixture. The materials were characterized by a compact structure and high hardness. The best mechanical strength above 140 N/mm was obtained for blocks with low acid to oil mass ratio ranging from 0.05 to 0.1125.

Assessment of Naturally Occurring Asbestos in the Area of Episcopia (Lucania, Southern Italy)

Over the last few years, the risk to human health related to asbestos fiber exposure has been widely demonstrated by many studies. Serpentinites are the main rocks associated with naturally occurring asbestos (NOA). In order to investigate the presence of NOA, a mineralogical study was conducted on eleven serpentinite samples collected nearby the village of Episcopia (Lucania, Southern Italy). Various analytical techniques such as X-ray powder diffraction (XRPD), scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS) and derivative thermogravimetry (DTG) were used to determine the occurrence of asbestos minerals and to make morphological observations. Results pointed out that all of the samples contain asbestos minerals (e.g., tremolite, actinolite and chrysotile). Moreover, it was observed that both natural processes and human activity may disturb NOA-bearing outcrops and provoke the formation of potentially inhalable airborne dust causing the release of asbestos fibers into the environment, thereby increasing the risk to human health. For this reason, our study aims to highlight the requirement of a natural asbestos survey and periodic update in the area.

Impact of asbestos on public health: a retrospective study on a series of subjects with occupational and non-occupational exposure to asbestos during the activity of Fibronit plant (Broni, Italy)

The goal of this study is to understand more about the role of asbestos in causing human diseases, first of all mesothelioma, by investigating a large series of deaths due to asbestos-related diseases (ARDs). The main aim is to clarify if even very low amounts of asbestos can cause mesothelioma and other ARDs, as well as to find out if a different individual vulnerability can be important. This retrospective study included 188 subjects who died from asbestos related diseases in 2000-2017 in the area around Broni, Italy, where an important asbestos cement factory had been active from 1932 until 1993. In each case, a forensic autopsy has been performed. In order to perform the present study, the records were retrieved, including the clinical files, the autopsy, and the histological report. The statistical analysis performed showed that there was a significant relation between the cause of death (mesothelioma, lung cancer or asbestosis) and the kind of exposure (occupational, neighborhood or household), showing that all the subjects not exposed occupationally (and, therefore, exposed to lower amounts of asbestos) died from mesothelioma, whereas the individuals who used to work at the plant died also from other caused (asbestosis, lung cancer). Significant differences were highlighted examining the distribution of the causes of death according to the smoking habits. Moreover, among the mesothelioma patients, the survival time was shorter in the subjects with a neighborhood or household exposure than in the occupationally exposed individuals. The study provided meaningful data about the role of asbestos in causing human pathologies. In particular, the present data appear to support the hypothesis that even an exposure to a very little amount of asbestos can cause mesothelioma in hypersusceptible subjects (probably, on a genetic basis).

The genetic susceptibility in the development of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a cancer of the pleural cavity whose main risk factor is exposure to asbestos. However, it has been shown that only a minority of exposed people develops MPM. In fact, the incidence among professionally exposed workers was shown to vary between 0.5% and 18.0%. Various hints suggested that other important cofactors could play a role, in particular the genetic susceptibility. Impressive is the case of Cappadocians families exposed to erionite and affected by an "epidemic" of MPM with about half of the inhabitants dying for the disease. However, no results for a "Cappadocia" gene of susceptibility to MPM have been obtained yet and more studies are needed. Among asbestos-exposed workers, several studies reported familial cases of MPM, suggesting that heredity could be important in the tumor development. However, large studies on familial clusters showed only weak increased risks that could be attributable also to indirect exposures in a contaminated household. Moreover, the risk of developing MPM is increased of a limited extent among people exposed to asbestos with a positive history of familial cancers. A particular is represented by carriers of germline mutations within BAP1 gene. In families and in animal models, mutations within BAP1 are strongly predisposing to develop MPM. However, also other types of cancer (such as uveal melanoma) are present, thus BAP1 mutations are considered as responsible for a hereditary form of a multi-cancer syndrome. In any case, among sporadic MPM, the prevalence of germline BAP1 mutations is negligible. Finally, genetic studies highlighted the presence of low-risk susceptibility alleles, such as those within XRCC3, NAT2 or GSTM1. Two different genome-wide association studies could not find positive associations reaching the genome-wide statistical significance threshold, however, both were concordant in showing a weak signal within the SDK1 gene region. Overall, it could be concluded that, as for other types of sporadic cancers, the susceptibility to develop MPM following asbestos exposure is modulated moderately by the individual genetic background. Further studies on larger series could help in a better characterization of more genes predisposing to MPM, being this tumor a rare disease.

A review of mortality associated with elongate mineral particle (EMP) exposure in occupational epidemiology studies of gold, talc, and taconite mining

BACKGROUND

Mining of gold, taconite, and talc may involve exposure to elongate mineral particles (EMP). The involved EMPs are typically non-asbestiform, include dimensions that regulatory definitions exclude, and have been less studied.

METHODS

A review of the literature was undertaken for this exposure and occupational epidemiological studies that occur in gold, talc, and taconite mining.

RESULTS

Quantitative EMP exposure information in these industries is incomplete. However, there are consistent findings of pneumoconiosis in each of these types of mining. A recent case-control study suggests a possible association between this exposure and mesothelioma. Lung cancer is inconsistently reported in these industries and is an unlikely outcome of non-asbestiform EMP exposure. There is evidence of cardiovascular mortality excess across all of these types of mining.

CONCLUSIONS

Non-malignant respiratory disease and cardiovascular mortality have been consistently increased in these industries. Further investigation, including additional insights for the role of non-asbestiform EMP, is warranted. Am. J. Ind. Med. 59:1047-1060, 2016. © 2016 Wiley Periodicals, Inc.

Anthophyllite asbestos: state of the science review

Anthophyllite is an amphibole form of asbestos historically used in only a limited number of products. No published resource currently exists that offers a complete overview of anthophyllite toxicity or of its effects on exposed human populations. We performed a review focusing on how anthophyllite toxicity was understood over time by conducting a comprehensive search of publicly available documents that discussed the use, mining, properties, toxicity, exposure and potential health effects of anthophyllite. Over 200 documents were identified; 114 contained relevant and useful information which we present chronologically in this assessment. Our analysis confirms that anthophyllite toxicity has not been well studied compared to other asbestos types. We found that toxicology studies in animals from the 1970s onward have indicated that, at sufficient doses, anthophyllite can cause asbestosis, lung cancer and mesothelioma. Studies of Finnish anthophyllite miners, conducted in the 1970s, found an increased incidence of asbestosis and lung cancer, but not mesothelioma. Not until the mid-1990s was an epidemiological link with mesothelioma in humans observed. Its presence in talc has been of recent significance in relation to potential asbestos exposure through the use of talc-containing products. Characterizing the health risks of anthophyllite is difficult, and distinguishing between its asbestiform and non-asbestiform mineral form is essential from both a toxicological and regulatory perspective. Anthophyllite toxicity has generally been assumed to be similar to other amphiboles from a regulatory standpoint, but some notable exceptions exist. In order to reach a more clear understanding of anthophyllite toxicity, significant additional study is needed. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of Chrysotile Exposure in Human Bronchial Epithelial Cells: Insights into the Pathogenic Mechanisms of Asbestos-Related Diseases

BACKGROUND

Chrysotile asbestos accounts for > 90% of the asbestos used worldwide, and exposure is associated with asbestosis (asbestos-related fibrosis) and other malignancies; however, the molecular mechanisms involved are not fully understood. A common pathogenic mechanism for these malignancies is represented by epithelial-mesenchymal transition (EMT), through which epithelial cells undergo a morphological transformation to assume a mesenchymal phenotype. In the present work, we propose that chrysotile asbestos induces EMT through a mechanism involving a signaling pathway mediated by tranforming growth factor beta (TGF-β).

OBJECTIVES

We investigated the role of chrysotile asbestos in inducing EMT in order to elucidate the molecular mechanisms involved in this event.

METHODS

Human bronchial epithelial cells (BEAS-2B) were incubated with 1 μg/cm2 chrysotile asbestos for ≤ 72 hr, and several markers of EMT were investigated. Experiments with specific inhibitors for TGF-β, glycogen synthase kinase-3β (GSK-3β), and Akt were performed to confirm their involvement in asbestos-induced EMT. Real-time polymerase chain reaction (PCR), Western blotting, and gelatin zymography were performed to detect mRNA and protein level changes for these markers.

RESULTS

Chrysotile asbestos activated a TGF-β-mediated signaling pathway, implicating the contributions of Akt, GSK-3β, and SNAIL-1. The activation of this pathway in BEAS-2B cells was associated with a decrease in epithelial markers (E-cadherin and β-catenin) and an increase in mesenchymal markers (α-smooth muscle actin, vimentin, metalloproteinases, and fibronectin).

CONCLUSIONS

Our findings suggest that chrysotile asbestos induces EMT, a common event in asbestos-related diseases, at least in part by eliciting the TGF-β-mediated Akt/GSK-3β/SNAIL-1 pathway.

CITATION

Gulino GR, Polimeni M, Prato M, Gazzano E, Kopecka J, Colombatto S, Ghigo D, Aldieri E. 2016. Effects of chrysotile exposure in human bronchial epithelial cells: insights into the pathogenic mechanisms of asbestos-related diseases. Environ Health Perspect 124:776-784; http://dx.doi.org/10.1289/ehp.1409627.

The role of interleukin-6 in malignant mesothelioma

Malignant mesothelioma (MM) still remains a dismal disease with a median overall survival between 9-12 months. During the past decade since the introduction of the multi-folate antagonist, pemetrexed, there have been no significant advances in its systemic treatment, particularly with novel therapeutics that have exhibited varying degrees of success in other solid tumours. In recent years, the pleiotropic proinflammatory cytokine, interleukin-6 (IL-6) has emerged as a mediator of pivotal processes such as cell proliferation and chemoresistance within the mesothelioma tumour microenvironment in addition to clinical symptoms commonly witnessed in this disease. This manuscript provides a brief summary on the pathophysiology and clinical management of MM, followed by the role of IL-6 in its tumourigenesis and the rationale for utilising anti-IL-6 therapeutics alongside standard chemotherapy and targeted agents in an attempt to prolong survival.

Occupational asbestos exposure and risk of pleural mesothelioma, lung cancer, and laryngeal cancer in the prospective Netherlands cohort study

OBJECTIVE

To study the association between occupational asbestos exposure and pleural mesothelioma, lung cancer, and laryngeal cancer, specifically addressing risk associated with the lower end of the exposure distribution, risk of cancer subtypes, and the interaction between asbestos and smoking.

METHODS

Using the Netherlands Cohort Study (n = 58,279 men, aged 55 to 69 years), asbestos exposure was estimated by linkage to job-exposure matrices. After 17.3 years of follow-up, 132 pleural mesothelioma, 2324 lung cancer, and 166 laryngeal cancer cases were available.

RESULTS

The multivariable-adjusted model showed overall positive associations between all levels of asbestos exposure and mesothelioma, lung cancer, and laryngeal cancer. Lung adenocarcinoma and glottis cancer showed only a positive association after prolonged higher asbestos exposure (hazard ratio per 10 years increment, 1.43 [95% confidence interval, 1.06 to 1.93] and 1.95 [95% confidence interval, 1.36 to 2.80], respectively). There was no statistically significant interaction between asbestos and smoking.

CONCLUSIONS

Asbestos levels encountered at the lower end of the exposure distribution may be associated with an increased risk of pleural mesothelioma, lung cancer, and laryngeal cancer.

Evaluation of take-home exposure and risk associated with the handling of clothing contaminated with chrysotile asbestos

The potential for para-occupational (or take-home) exposures from contaminated clothing has been recognized for the past 60 years. To better characterize the take-home asbestos exposure pathway, a study was performed to measure the relationship between airborne chrysotile concentrations in the workplace, the contamination of work clothing, and take-home exposures and risks. The study included air sampling during two activities: (1) contamination of work clothing by airborne chrysotile (i.e., loading the clothing), and (2) handling and shaking out of the clothes. The clothes were contaminated at three different target airborne chrysotile concentrations (0-0.1 fibers per cubic centimeter [f/cc], 1-2 f/cc, and 2-4 f/cc; two events each for 31-43 minutes; six events total). Arithmetic mean concentrations for the three target loading levels were 0.01 f/cc, 1.65 f/cc, and 2.84 f/cc (National Institute of Occupational Health and Safety [NIOSH] 7402). Following the loading events, six matched 30-minute clothes-handling and shake-out events were conducted, each including 15 minutes of active handling (15-minute means; 0.014-0.097 f/cc) and 15 additional minutes of no handling (30-minute means; 0.006-0.063 f/cc). Percentages of personal clothes-handling TWAs relative to clothes-loading TWAs were calculated for event pairs to characterize exposure potential during daily versus weekly clothes-handling activity. Airborne concentrations for the clothes handler were 0.2-1.4% (eight-hour TWA or daily ratio) and 0.03-0.27% (40-hour TWA or weekly ratio) of loading TWAs. Cumulative chrysotile doses for clothes handling at airborne concentrations tested were estimated to be consistent with lifetime cumulative chrysotile doses associated with ambient air exposure (range for take-home or ambient doses: 0.00044-0.105 f/cc year).

Tumors that mimic asbestos-related mesothelioma: time to consider a genetics-based tumor registry?

The diagnosis of mesothelioma is not always straightforward, despite known immunohistochemical markers and other diagnostic techniques. One reason for the difficulty is that extrapleural tumors resembling mesothelioma may have several possible etiologies, especially in cases with no meaningful history of amphibole asbestos exposure. When the diagnosis of mesothelioma is based on histologic features alone, primary mesotheliomas may resemble various primary or metastatic cancers that have directly invaded the serosal membranes. Some of these metastatic malignancies, particularly carcinomas and sarcomas of the pleura, pericardium and peritoneum, may undergo desmoplastic reaction in the pleura, thereby mimicking mesothelioma, rather than the primary tumor. Encasement of the lung by direct spread or metastasis, termed pseudomesotheliomatous spread, occurs with several other primary cancer types, including certain late-stage tumors from genetic cancer syndromes exhibiting chromosomal instability. Although immunohistochemical staining patterns differentiate most carcinomas, lymphomas, and mestastatic sarcomas from mesotheliomas, specific genetic markers in tumor or somatic tissues have been recently identified that may also distinguish these tumor types from asbestos-related mesothelioma. A registry for genetic screening of mesothelioma cases would help lead to improvements in diagnostic criteria, prognostic accuracy and treatment efficacy, as well as improved estimates of primary mesothelioma incidence and of background rates of cancers unrelated to asbestos that might be otherwise mistaken for mesothelioma. This information would also help better define the dose-response relationships for mesothelioma and asbestos exposure, as well as other risk factors for mesothelioma and other mesenchymal or advanced metastatic tumors that may be indistinguishable by histology and staining characteristics.

The role of genotoxicity in asbestos-induced mesothelioma: an explanation for the differences in carcinogenic potential among fiber types

The mechanism(s) underlying asbestos toxicity associated with the pathogenesis of mesothelioma has been a challenge to unravel for more than 60 years. A significant amount of research has focused on the characteristics of different fiber types and their potential to induce mesothelioma. These mechanistic studies of fiber toxicity have proceeded along two lines: those demonstrating biochemical mechanisms by which fibers induce disease and those investigating human susceptibility. Most recent studies focused on in vitro genotoxic effects induced by asbestos as the mechanism responsible for asbestos-induced disease. Although asbestos exerts a genotoxic effect at certain concentrations in vitro, a positive response in these tests does not indicate that the chemical is likely to produce an increased risk of carcinogenesis in exposed human populations. Thus far, findings from studies on the effects of fiber type in mesothelial cells are seriously flawed by a lack of a dose response relationship. The common limitation of these in vitro experiments is the lack of attention paid to the complexities of the human anatomy, biochemistry and physiology, which make the observed effects in these experimental systems difficult to extrapolate to persons in the workplace. Mechanistic differences between carcinogenic and genotoxic processes indicate why tests for genotoxicity do not provide much insight regarding the ability to predict carcinogenic potential in workers exposed to asbestos doses in the post-Occupational Safety and Health Administration era. This review discusses the existing literature on asbestos-induced genotoxicity and explains why these studies may or may not likely help characterize the dose-response curve at low dose.

Medicolegal Aspects of Asbestos I — Malignant Mesothelioma and Lung Cancer

Inhalation of asbestos fibers can cause a variety of conditions, benign and malignant, of the lungs and pleura. Illnesses and deaths in which asbestos may have had a causal or contributory role are often the subject of litigation. Forensic pathologists (FP) can become involved in some of these cases in their capacity of a medical examiner or coroner, autopsy pathologist or as an expert retained by one or more parties involved in litigation. FP input may be sought to address issues such as diagnosis, assessment of exposure, and attribution. This review will discuss medicolegal issues that surround lung and mesothelial tumors that can be caused by the inhalation of asbestos fibers.

Mesothelioma associated with use of drywall joint compound: a case series and review of literature

BACKGROUND

Drywall joint compound contained asbestos fibers, primarily chrysotile, in the 1950s through the 1970s. Workers in a variety of construction trades and homeowners were exposed to respirable asbestos from the use of these products, including during handling, mixing, sanding, and sweeping. Disturbance of in-place asbesto-containing joint compound continues to be a potential source of exposure during demolition or repair of wallboard. Studies from the 1970s and 1980s report air fiber measurements above current and historic regulatory limits during intended usage, and typical asbestos-related disease in drywall construction workers.

OBJECTIVES

We present three cases of mesothelioma in which the only known exposure to asbestos was from joint compound and review the literature on exposure circumstances, dose and fiber types.

CONCLUSIONS

Physicians treating mesothelioma patients should obtain a history of exposure to these products during work or home remodeling.

Impacts of land use on spatial distribution of mortality rates of cancers caused by naturally occurring asbestos

This study investigated the spatial distributions of mortality rates of six cancers: mesothelioma, lung cancer, intestinal cancer, nasopharyngeal and laryngeal cancer, liver cancer, and stomach cancer in Dayao using Geographic Information Systems. Relationships between the mortality rates of the six cancers and land use patterns were investigated by Pearson Correlation Coefficients. The results indicated that the mortality rates of nasopharyngeal and laryngeal cancer, lung cancer, intestinal cancer, and mesothelioma were significantly associated with outcropped asbestos. Both the proportions of farmland and urban area were positively related to the mortality rates of nasopharyngeal and laryngeal cancer, lung cancer, intestinal cancer, and mesothelioma, and significant negative correlations were found between the proportion of forestland and nasopharyngeal and laryngeal cancer and intestinal cancer. It can be concluded that naturally occurring asbestos may significantly elevate the mortality rates of nasopharyngeal and laryngeal cancer, intestinal cancer, lung cancer, and mesothelioma. Moreover, higher proportions of farmland, urban area, and lower proportions of forested land may elevate the mortality rate of the four cancers.

Antioxidants prevent the RhoA inhibition evoked by crocidolite asbestos in human mesothelial and mesothelioma cells

Asbestos is a naturally occurring fibrous silicate, whose inhalation is highly related to the risk of developing malignant mesothelioma (MM), and crocidolite is one of its most oncogenic types. The mechanism by which asbestos may cause MM is unclear. We have previously observed that crocidolite in human MM (HMM) cells induces NF-κB activation and stimulates the synthesis of nitric oxide by inhibiting the RhoA signaling pathway. In primary human mesothelial cells (HMCs) and HMM cells exposed to crocidolite asbestos, coincubated or not with antioxidants, we evaluated cytotoxicity and oxidative stress induction (lipid peroxidation) and the effect of asbestos on the RhoA signaling pathway (RhoA GTP binding, Rho kinase activity, RhoA prenylation, hydroxy-3-methylglutharyl-CoA reductase activity). In this paper we show that the reactive oxygen species generated by the incubation of crocidolite with primary HMCs and three HMM cell lines mediate the inhibition of 3-hydroxy-3-methylglutharyl-CoA reductase (HMGCR). The coincubation of HMCs and HMM cells with crocidolite together with antioxidants, such as Tempol, Mn-porphyrin, and the association of superoxide dismutase and catalase, prevented the cytotoxicity and lipoperoxidation caused by crocidolite alone as well as the decrease of HMGCR activity and restored the RhoA/RhoA-dependent kinase activity and the RhoA prenylation. The same effect was observed when the oxidizing agent menadione was administrated to the cells in place of crocidolite. Such a mechanism could at least partly explain the effects exerted by crocidolite fibers in mesothelial cells.

Mineralogy of asbestos

The term asbestos collectively refers to a group of naturally occurring fibrous minerals which have been exploited in numerous commercial and industrial settings and applications dating to antiquity. Its myriad uses as a "miracle mineral" owe to its remarkable properties of extreme resistance to thermal and chemical breakdown, tensile strength, and fibrous habit which allows it to be spun and woven into textiles. Abundant in nature, it has been mined considerably, and in all continents save Antarctica. The nomenclature concerning asbestos and its related species is complex, owing to the interest held therein by scientific disciplines such as geology, mineralogy and medicine, as well as legal and regulatory authorities. As fibrous silicates, asbestos minerals are broadly classified into the serpentine (chrysotile) and amphibole (crocidolite, amosite, tremolite, anthophyllite, actinolite) groups, both of which may also contain allied but nonfibrous forms of similar or even identical chemical composition, nonpathogenic to humans. Recently, fibrous amphiboles, not historically classified or regulated as asbestos (winchite, richterite), have been implicated in the causation of serious disease due to their profusion as natural contaminants of vermiculite, a commercially useful and nonfibrous silicate mineral. Although generally grouped, classified, and regulated collectively as asbestos, the serpentine and amphibole groups have different geologic occurrences and, more importantly, significant differences in crystalline structures and chemical compositions. These in turn impart differences in fiber structure and dimension, as well as biopersistence, leading to marked differences in relative potency for causing disease in humans for the group of minerals known as asbestos.

Malignant pleural mesothelioma in a female lion (Panthera leo)

An 18-year-old female lion (Panthera leo) was referred to the Department of Animal Pathology of the University of Turin (Italy). At necropsy, multiple nodular, 4-20-mm, confluent white firm nodules were scattered throughout the pleural surfaces of the thoracic wall and of the lungs. Histological lesions were represented by proliferations of papillary structures lined by cuboidal basophilic mesothelial cells with large, oval nuclei and abundant granular eosinophilic cytoplasm. Immunohistochemistry revealed immunoreactivity for pancytokeratin and vimentin. None of the cells expressed calretinin antigen. Asbestos fibers and asbestos bodies were not detected respectively by light microscopy and by Scanning Electron Microscope-Energy Dispersive Spectrometer investigations. On the contrary, chrysotile asbestos were identified in samples from shelter material. Histological and immunohistochemical findings were consistent with the diagnosis of an epithelial malignant mesothelioma. To our best knowledge, this is the first report of a pleural mesothelioma in a lion.

Asbestos is still with us: repeat call for a universal ban

All forms of asbestos are proven human carcinogens. All forms of asbestos cause malignant mesothelioma, lung, laryngeal, and ovarian cancers, and may cause gastrointestinal and other cancers. No exposure to asbestos is without risk, and there is no safe threshold of exposure to asbestos. Asbestos cancer victims die painful lingering deaths. These deaths are almost entirely preventable. When evidence of the carcinogenicity of asbestos became incontrovertible, concerned parties, including the Collegium Ramazzini, called for a universal ban on the mining, manufacture and use of asbestos in all countries around the world [1]. Asbestos is now banned in 52 countries [2], and safer products have replaced many materials that once were made with asbestos. Nonetheless, a large number of countries still use, import, and export asbestos and asbestos-containing products. And still today in many countries that have banned other forms of asbestos, the so-called "controlled use" of chrysotile asbestos continues to be permitted, an exemption that has no basis in medical science but rather reflects the political and economic influence of the asbestos mining and manufacturing industry. To protect the health of all people in the world-industrial workers, construction workers, women and children, now and in future generations-the Collegium Ramazzini calls again today on all countries of the world, as we have repeatedly in the past to join in the international endeavor to ban all forms of asbestos. An international ban on asbestos is urgently needed. New Solutions is one of ten international journals that have agreed to publish the Repeat Call in order to bring the message to a wide readership.

The case for a global ban on asbestos

BACKGROUND

All forms of asbestos are now banned in 52 countries. Safer products have replaced many materials that once were made with it. Nonetheless, many countries still use, import, and export asbestos and asbestos-containing products, and in those that have banned other forms of asbestos, the so-called "controlled use" of chrysotile asbestos is often exempted from the ban. In fact, chrysotile has accounted for > 95% of all the asbestos used globally.

OBJECTIVE

We examined and evaluated the literature used to support the exemption of chrysotile asbestos from the ban and how its exemption reflects the political and economic influence of the asbestos mining and manufacturing industry.

DISCUSSION

All forms of asbestos, including chrysotile, are proven human carcinogens. All forms cause malignant mesothelioma and lung and laryngeal cancers, and may cause ovarian, gastrointestinal, and other cancers. No exposure to asbestos is without risk. Illnesses and deaths from asbestos exposure are entirely preventable.

CONCLUSIONS

All countries of the world have an obligation to their citizens to join in the international endeavor to ban the mining, manufacture, and use of all forms of asbestos. An international ban is urgently needed. There is no medical or scientific basis to exempt chrysotile from the worldwide ban of asbestos.

Asbestos is still with us: repeat call for a universal ban

All forms of asbestos are proven human carcinogens. All forms of asbestos cause malignant mesothelioma, lung, laryngeal, and ovarian cancers, and may cause gastrointestinal and other cancers. No exposure to asbestos is without risk. Asbestos cancer victims die painful lingering deaths. These deaths are almost entirely preventable. When evidence of the carcinogenicity of asbestos became incontrovertible, concerned parties, including the Collegium Ramazzini, called for a universal ban on the mining, manufacture, and use of asbestos in all countries around the world (J Occup Environ Med. 1999;41:830-832). Asbestos is now banned in 52 countries, and safer products have replaced many materials that once were made with asbestos. Nonetheless, a large number of countries still use, import, and export asbestos and asbestos-containing products. And in many countries that have banned other forms of asbestos, the so-called "controlled use" of chrysotile asbestos is exempted from the ban, an exemption that has no basis in medical science but rather reflects the political and economic influence of the asbestos mining and manufacturing industry. All countries of the world have an obligation to their citizens to join in the international endeavor to ban all forms of asbestos. An international ban on asbestos is urgently needed.

Risk Factors and Clinicopathological Study of Prognostic Factors in the Peritoneal Mesothelioma

This study evaluates the clinical and treatment related prognostic indicators for survival of patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for peritoneal mesothelioma. We did an observational study of the risk factors and clinicopathological factors of 20 patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for peritoneal mesothelioma at the St George Hospital, Sydney. Survival analysis was performed using the Kaplan-Meier method and prognostic factors were correlated with survival using the Log Rank test. There were six females. The mean age was 55 years. The overall median survival was 30 (0.5-87) months with 1- and 3-year survival of 78 per cent and 46 per cent, respectively. The overall median disease-free survival was 8 months. Factors influencing a longer disease-free survival included age ≥ 55 ( P = 0.006), not smoking ( P = 0.04), female ( P = 0.03), and epithelioid tumors ( P = 0.002). Overall survival was influenced by not consuming alcohol ( P = 0.003), complete cytoreduction ( P = 0.02), and epithelioid tumors ( P = 0.01). Risk factors identified to be prognostic for survival include the female gender, not smoking, not consuming alcohol, and an epithelioid tumor type. Treatment factor associated with an improved survival was a complete cytoreduction.

Malignant mesothelioma

Malignant mesothelioma is a fatal asbestos-associated malignancy originating from the lining cells (mesothelium) of the pleural and peritoneal cavities, as well as the pericardium and the tunica vaginalis. The exact prevalence is unknown but it is estimated that mesotheliomas represent less than 1% of all cancers. Its incidence is increasing, with an expected peak in the next 10–20 years. Pleural malignant mesothelioma is the most common form of mesothelioma. Typical presenting features are those of chest pain and dyspnoea. Breathlessness due to a pleural effusion without chest pain is reported in about 30% of patients. A chest wall mass, weight loss, sweating, abdominal pain and ascites (due to peritoneal involvement) are less common presentations. Mesothelioma is directly attributable to occupational asbestos exposure with a history of exposure in over 90% of cases. There is also evidence that mesothelioma may result from both para-occupational exposure and non-occupational "environmental" exposure. Idiopathic or spontaneous mesothelioma can also occur in the absence of any exposure to asbestos, with a spontaneous rate in humans of around one per million. A combination of accurate exposure history, along with examination radiology and pathology are essential to make the diagnosis. Distinguishing malignant from benign pleural disease can be challenging. The most helpful CT findings suggesting malignant pleural disease are 1) a circumferential pleural rind, 2) nodular pleural thickening, 3) pleural thickening of > 1 cm and 4) mediastinal pleural involvement. Involvement of a multidisciplinary team is recommended to ensure prompt and appropriate management, using a framework of radiotherapy, chemotherapy, surgery and symptom palliation with end of life care. Compensation issues must also be considered. Life expectancy in malignant mesothelioma is poor, with a median survival of about one year following diagnosis.