Exposure to naturally occurring mineral fibers due to off-road vehicle use: A review

Asbestos and Other Hazardous Fibrous Minerals: Potential Exposure Pathways and Associated Health Risks

There are six elongate mineral particles (EMPs) corresponding to specific dimensional and morphological criteria, known as asbestos. Responsible for health issues including asbestosis, and malignant mesothelioma, asbestos has been well researched. Despite this, significant exposure continues to occur throughout the world, potentially affecting 125 million people in the workplace and causing thousands of deaths annually from exposure in homes. However, there are other EMPS, such as fibrous/asbestiform erionite, that are classified as carcinogens and have been linked to cancers in areas where it has been incorporated into local building materials or released into the environment through earthmoving activities. Erionite is a more potent carcinogen than asbestos but as it is seldom used for commercial purposes, exposure pathways have been less well studied. Despite the apparent similarities between asbestos and fibrous erionite, their health risks and exposure pathways are quite different. This article examines the hazards presented by EMPs with a particular focus on fibrous erionite. It includes a discussion of the global locations of erionite and similar hazardous minerals, a comparison of the multiple exposure pathways for asbestos and fibrous erionite, a brief discussion of the confusing nomenclature associated with EMPs, and considerations of increasing global mesothelioma cases.

Non-Malignant Respiratory Illnesses in Association with Occupational Exposure to Asbestos and Other Insulating Materials: Findings from the Alberta Insulator Cohort

Many insulating materials are used in construction, although few have been reported to cause non-malignant respiratory illnesses. We aimed to investigate associations between exposures to insulating materials and non-malignant respiratory illnesses in insulators. In this cross-sectional study, 990 insulators (45 ± 14 years) were screened from 2011-2017 in Alberta. All participants underwent pulmonary function tests and chest radiography. Demographics, work history, and history of chest infections were obtained through questionnaires. Chronic obstructive pulmonary disease (COPD) was diagnosed according to established guidelines. Associations between exposures and respiratory illnesses were assessed by modified Poisson regression. Of those screened, 875 (88%) were males. 457 (46%) participants reported having ≥ 1 chest infection in the past 3 years, while 156 (16%) were diagnosed with COPD. In multivariate models, all materials (asbestos, calcium silicate, carbon fibers, fiberglass, and refractory ceramic fibers) except aerogels and mineral fibers were associated with recurrent chest infections (prevalence ratio [PR] range: 1.18-1.42). Only asbestos was associated with COPD (PR: 1.44; 95% confidence interval [CI]: 1.01, 2.05). Therefore, occupational exposure to insulating materials was associated with non-malignant respiratory illnesses, specifically, recurrent chest infections and COPD. Longitudinal studies are urgently needed to assess the risk of exposure to these newly implemented insulation materials.

Autoimmune markers for progression of Libby amphibole lamellar pleural thickening

Exposure to Libby Asbestiform Amphibole (LAA) is associated with asbestos-related diseases, including mesothelioma, pulmonary carcinoma, pleural fibrosis, and systemic autoimmune diseases. The pleural fibrosis can manifest as a rapidly progressing lamellar pleural thickening (LPT), which causes thoracic pain, dyspnea, and worsening pulmonary function tests (PFT). It is refractory to treatment and frequently fatal.Objective: Because of the immune dysfunction that has been described in the LAA-exposed population and the association of pleural manifestations with the presence of autoantibodies, this study tested whether specific immunological factors were associated with progressive LPT and whether they could be used as markers of progressive disease.Methods: Subjects were placed into three study groups defined as (1) progressive LPT, (2) stable LPT, (3) no LPT. Serum samples were tested for antinuclear autoantibodies, mesothelial cell autoantibodies, anti-plasminogen antibodies, IL1 beta, and IL17; which have all been shown to be elevated in mice and/or humans exposed to LAA.Results: Group 1 had significantly higher mean values for all of the autoantibodies, but not IL1 or IL-17, compared to the control Group 3. All three autoantibody tests had high specificity but low sensitivity, but ROC area-under-the-curve values for all three antibodies were over 0.7, statistically higher than a test with no value. When all LPT subjects were combined (Progressive plus Stable), no marker had predictive value for disease.Conclusion: The data support the hypothesis that progressive LPT is associated with immunological findings that may serve as an initial screen for progressive LPT.

Mesothelioma: Scientific clues for prevention, diagnosis, and therapy

Mesothelioma affects mostly older individuals who have been occupationally exposed to asbestos. The global mesothelioma incidence and mortality rates are unknown, because data are not available from developing countries that continue to use large amounts of asbestos. The incidence rate of mesothelioma has decreased in Australia, the United States, and Western Europe, where the use of asbestos was banned or strictly regulated in the 1970s and 1980s, demonstrating the value of these preventive measures. However, in these same countries, the overall number of deaths from mesothelioma has not decreased as the size of the population and the percentage of old people have increased. Moreover, hotspots of mesothelioma may occur when carcinogenic fibers that are present in the environment are disturbed as rural areas are being developed. Novel immunohistochemical and molecular markers have improved the accuracy of diagnosis; however, about 14% (high-resource countries) to 50% (developing countries) of mesothelioma diagnoses are incorrect, resulting in inadequate treatment and complicating epidemiological studies. The discovery that germline BRCA1-asssociated protein 1 (BAP1) mutations cause mesothelioma and other cancers (BAP1 cancer syndrome) elucidated some of the key pathogenic mechanisms, and treatments targeting these molecular mechanisms and/or modulating the immune response are being tested. The role of surgery in pleural mesothelioma is controversial as it is difficult to predict who will benefit from aggressive management, even when local therapies are added to existing or novel systemic treatments. Treatment outcomes are improving, however, for peritoneal mesothelioma. Multidisciplinary international collaboration will be necessary to improve prevention, early detection, and treatment.

Four-miRNA Signature to Identify Asbestos-Related Lung Malignancies

BACKGROUND

Altered miRNA expression is an early event upon exposure to occupational/environmental carcinogens; thus, identification of a novel asbestos-related profile of miRNAs able to distinguish asbestos-induced cancer from cancer with different etiology can be useful for diagnosis. We therefore performed a study to identify miRNAs associated with asbestos-induced malignancies.

METHODS

Four groups of patients were included in the study, including patients with asbestos-related (NSCLC^Asb) and asbestos-unrelated non-small cell lung cancer (NSCLC) or with malignant pleural mesothelioma (MPM), and disease-free subjects (CTRL). The selected miRNAs were evaluated in asbestos-exposed population.

RESULTS

Four serum miRNAs, that is miR-126, miR-205, miR-222, and miR-520g, were found to be implicated in asbestos-related malignant diseases. Notably, increased expression of miR-126 and miR-222 were found in asbestos-exposed subjects, and both miRNAs are involved in major pathways linked to cancer development. Epigenetic changes and cancer-stroma cross-talk could induce repression of miR-126 to facilitate tumor formation, angiogenesis, and invasion.

CONCLUSIONS

This study indicates that miRNAs are potentially involved in asbestos-related malignancies, and their expression outlines mechanism(s) whereby miRNAs may be involved in an asbestos-induced pathogenesis.

IMPACT

The discovery of a miRNA panel for asbestos-related malignancies would impact on occupational compensation and may be utilized for screening asbestos-exposed populations.

Case series: rheumatological manifestations attributed to exposure to Libby Asbestiform Amphiboles

An increased risk for Systemic Autoimmune Diseases (SAID) has been reported in Libby, Montana, where extensive exposures to fibrous amphiboles occurred due to mining and use of asbestos-laden vermiculite. In addition, positive antinuclear autoantibody tests are associated with exposure to Libby Asbestiform Amphiboles (LAA) in both humans and mice. Among 6603 subjects who underwent health screening at the Center for Asbestos Related Diseases (CARD, Libby MT), 13.8% were diagnosed with an autoimmune disease, with prevalence values for the most common SAID being significantly higher than expected in the United States. Among the CARD screening population, serological and clinical profiles are diverse, representing symptoms and autoantibodies reflective of systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis, and other rheumatic syndromes, including undifferentiated connective tissue disease (UCTD). Based upon screening of medical records by physicians with rheumatology expertise, the evolving nature of rheumatological disease in these patients is often atypical, with mixed diagnostic criteria and with a 1:1 male-to-female ratio. Through the Libby Epidemiology Research Program, cases were identified that illustrate clinical autoimmune outcomes with LAA exposure. Our goal was to better characterize SAID in Libby, MT in order to improve recognition of autoimmune outcomes associated with this exposure. In view of recent discoveries of widespread exposure to fibrous minerals in several areas of the U.S. and globally, it is critical to evaluate rheumatologic manifestations in other cohorts so that screening, surveillance, and diagnostic procedures are able to detect and recognize potential autoimmune outcomes of asbestos exposure.

ABBREVIATIONS

ANA, antinuclear autoantibody; ARD, Asbestos-Related Diseases; ATSDR, Agency for Toxic Substances & Disease Registry; CARD, Center for Asbestos Related Diseases; CCP, Cyclic citrullinated peptide antibody; CREST, limited cutaneous form of scleroderma; CT, computed tomography; DIP, Distal Interphalangeal Joint; DLCO, Diffusing Capacity of the Lung for CO₂; DMARD, Disease Modifying Anti-Rheumatic Drugs; ENA, Extractable Nuclear Antigen antibodies; FVC, Forced Vital Capacity; LAA, Libby Asbestiform Amphiboles; LERP, Libby Epidemiology Research Program; MCP, Metacarpal Phalangeal Joint; PIP, Proximal Interphalangeal Joint; PIP, rheumatoid arthritis; RV, Residual Volume; SAID, Systemic autoimmune diseases; SLE, systemic lupus erythematosus; SSc, Systemic Sclerosis; TLC, Total Lung Capacity.