Journey to the centre of the lung. The perspective of a mineralogist on the carcinogenic effects of mineral fibres in the lungs

Naturally occurring asbestos in Southern Italy: Geological and mineralogical investigation of fibrous antigorite from Calabrian serpentinites in view of its hazard assessment

In the last few decades, non-occupational asbestos-related diseases have been documented in populations living near naturally occurring asbestos (NOA) sites, including regions in Greece, Cyprus, China, New Caledonia, Turkey, and Italy. This highlights the critical need to assess geological and environmental hazards associated with NOA. Fibrous antigorite, among the >400 naturally occurring fibrous minerals, has emerged as a potential health and environmental hazard. This work examines the morphometrical, mineralogical and surface properties of a fibrous antigorite vein from a serpentinite body at San Mango D'Aquino (Calabria, Italy), relevant to assessing its potential toxicity. The geological site, described through field and petrographic analyses, was selected as representative of serpentinites outcropping over a large area in central Calabria. Results on the morphometric variation induced by a standardized mechanical stress, mineral solubility, and surface chemical reactivity indicated that: i) the fibrous morphology, expressed as % of WHO (World Health Organization) fibres, was largely preserved and consistent with asbestos standards; ii) antigorite fibres have a durability higher than chrysotile and close to a previously characterized fibrous antigorite from Val Varenna, Italy; iii) fibres showed a remarkable redox reactivity, even higher than chrysotile, suggesting that they may promote particle-derived radical imbalance in vitro and in vivo. Our findings revealed that the antigorite fibres from San Mango possess several critical properties commonly associated with asbestos toxicity. On this basis, we identify the NOA site of San Mango as a potential emission source of hazardous antigorite fibres, with significant environmental and public health implications for the surrounding communities.

The cytotoxic/genotoxic role of impurities in soluble minerals: The case of natural (fibrous epsomite) versus synthetic (Epsom salt) magnesium sulphate

Epsomite and Epsom salt are very common mineral phases, and many known uses are found in agriculture, and in food and pharmaceutical industries. Natural epsomite can be fibrous and inhalable, potentially reaching the digestive tract after dissolving in mucus and saliva. Epsom salt is a common food additive (E 518) to which humans can be exposed daily, although its health effects are still debated. This study aims to (i) determine if natural epsomite (MP) and Epsom salt (SE) may be toxic to humans and (ii) identify and quantify the impurities in natural epsomite and try to ascertain their role in the toxicity of this mineral. In vitro experiments were performed on human colon epithelial cancer cells (Caco-2), enterocyte-like Caco-2-derived monolayers, human monocytic cell line THP-1, and THP-1-derived M0 macrophages. Generally, MP showed significantly higher toxicity in terms of oxidative stress, DNA damage and inflammation than SE, whose effects can be considered negligible. The higher pathogenicity of MP undoubtedly comes from the toxic elements of impurities, which are absent in pure SE. This research clarifies the role of impurities in the toxicity of natural epsomite, which may be higher than previously supposed. Moreover, considering its extensive use in the food industry, it represents a new step in assessing the safety of ingesting magnesium sulphate.

Fibrous erionite modifications following THP-1 macrophage phagocytosis: An insight into the mechanisms of interaction with biological systems

Erionite is a ubiquitous natural zeolite, often occurring with fibrous habit, whose strong tumorigenic activity to humans has been certified by its inclusion in the Group 1 Human-Carcinogenic list by the International Agency for Research on Cancer. To date, the reason(s) of erionite toxicity are still unclear, albeit several hypotheses have been proposed. The present work, based on the combined analysis of the chemical and structural modifications of erionite fibres following incubation in human THP-1 macrophages and evaluation of cellular response, indicates that, upon macrophage phagocytosis, a large release of cations is counterbalanced by a significant sequestration of hydronium ions from lysosomes provoking a quick pH dysregulation. This would be restored by the hyperactivation of ATP-dependent proton pumps with significant energy expenditure for the cell, ultimately causing mitochondrial suffering, leading to chronic inflammation and eventually cancer development.

In vitro cyto- and geno-toxicity of asbestiform erionite from New Zealand

This work is an in vitro toxicity study of two asbestiform erionites from Kaipara and Gawler Downs in New Zealand. This study is the first, to the knowledge of the authors, to investigate the mechanisms that trigger adverse effects leading to carcinogenicity from New Zealand erionites. The effects induced by the erionite fibres from New Zealand were compared with those produced by positive (crocidolite) and negative (wollastonite) standards, and other erionite fibres described in the literature. The cytotoxicity/genotoxicity/inflammatory potential was determined by: (i) analysis of the cytotoxic potential by MTT tests on human cell lines mimicking primary cells making direct contact with fibres in the lungs, combined with apoptosis tests and cell membrane damage by fluorescence microscopy analyses; (ii) analysis of the genotoxic potential by quantification of DNA damage measuring double strand break foci by γ-H2AX nuclear staining in confocal microscopy analyses; (iii) analyses of the acute (24-72h) and early-chronic (7d) inflammatory effect by gene expression analyses of several cytokines, as well as of fibrotic and Epithelial to Mesenchymal transition (EMT) markers. The intensity of cell responses to these erionites are comparable to that of standard carcinogenic crocidolite, indicating that the two erionite fibres exhibit a significant acute toxic potential, with a particular alarming effect from the Gawler Downs sample from South Island. Our results confirm that the investigated erionites from New Zealand may represent an environmental hazard. However, further investigation is required to determine potential environmental exposure pathways by which erionite may become airborne and assess any environmental risks that may arise.

Bridging the gap between toxicity and carcinogenicity of mineral fibres by connecting the fibre parameters to the key characteristics of carcinogens: A comprehensive model inspiring asbestos-induced cancer prevention strategies

Background

Today, many research groups in the world are struggling to fully understand the mechanisms leading to the carcinogenesis of hazardous mineral fibres, like asbestos, in view of devising effective cancer prevention strategies and therapies. Along this research line, our work attempts the completion of a model aimed at evaluating how, and to what extent, physical-crystal-chemical and morphological parameters of mineral fibres prompt adverse effects in vivo leading to carcinogenesis.

Methods

In vitro toxicology tests that deliver information on the 10 key characteristics of carcinogens adopted by the International Association for Research on Cancer (IARC) have been systematically collected for a commercial chrysotile, standard UICC crocidolite and wollastonite. The analysis of the in vitro data allowed us to assess the major fibre parameters responsible for alterations in the key characteristics of carcinogens for each investigated fibre and the intensity of their effect.

Results

Crystal habit and density of the fibres affect exposure but are not major parameters contributing to the KCs. For chrysotile, besides length, we found that fibre parameters that greatly contribute to the KCs are the surface area and the dissolution rate with the related velocity of release of metals (namely iron). For crocidolite, they are the fibre length, iron content and related parameters like the ferrous iron content, iron nuclearity, transition metals content and zeta potential.

Conclusions

The results of our study can be a starting point for developing personalized cancer screening and prevention strategies as long as the nature of the fibre of the exposed patient is known. We can speculate on a future personalized prevention therapy targeting the fibres with surface-engineered nanocarriers with active complexes that are selective for the surface charge of the fibres. For chrysotile, a complex with deferasirox that can chelate Fe2+ and deferoxamine that preferentially chelates Fe3+ is proposed with the anchorage to the silica chrysotile surface driven by aspartic acid. For crocidolite, deferiprone chelating both Fe3+ and Fe2+ combined with lysine to attract the silica crocidolite surface is proposed.

Evaluation of asbestos dispersion during laser ablation of rocks containing Naturally Occurring Asbestos (NOA)

Health risks are often overlooked when the short-term consequences are not immediately apparent. During restoration work, cleaning actions can generate particles that pose health risks to workers through inhalation. This is particularly true in the case of asbestos fibres that might be spread out from the laser cleaning of buildings or heritage artifacts made of stone, such as serpentinite and other ultramafic rocks, that have a high probability of containing asbestos (e.g., chrysotile, tremolite asbestos, actinolite asbestos). To show workers the importance of wearing proper protection to prevent health injuries, several serpentinite samples, ascertained to contain asbestos minerals by specific investigations, have been laser ablated using ad hoc modified equipment in order to collocate a HEPA filter prone to collect all dust emitted during ablation. The powder deposited on the surface of these filters after laser ablation was analyzed, by Powder X -ray Diffraction (PXRD), Transmission Electron Microscopy combined with Energy Dispersive Spectroscopy (TEM/EDS), micro-Raman spectroscopy (μ-Raman) and Fourier-transform infrared spectroscopy (FTIR/ATR). The results confirmed the presence of asbestos fibres during the laser ablation of rocks containing Naturally Occurring Asbestos (NOA), emphasizing the importance of wearing appropriate personal protective equipment (PPE) during these procedures. Noteworthy, approximately 33 % of the analyzed fibres met the WHO criteria in size for respirable fibres. Furthermore, through our experiments, we also demonstrated that using tools that integrate filters into working tools would definitively further decrease the risk of fibres inhalation to workers.

Synthetic vitreous fibers (SVFs): adverse outcome pathways (AOPs) and considerations for next generation new approach methods (NAMs)

Fiber dimension, durability/dissolution, and biopersistence are critical factors for the risk of fibrogenesis and carcinogenesis. In the modern era, to reduce, refine, and replace animals in toxicology research, the application of in vitro test methods is paramount for hazard evaluation and designing synthetic vitreous fibers (SVFs) for safe use. The objectives of this review are to: (1) summarize the international frameworks and acceptability criteria for implementation of new approach methods (NAMs), (2) evaluate the adverse outcome pathways (AOPs), key events (KEs), and key event relationships (KERs) for fiber-induced fibrogenesis and carcinogenesis in accordance with Organization for Economic Co-operation and Development (OECD) guidelines, (3) consider existing and emerging technologies for in silico and in vitro toxicity testing for the respiratory system and the ability to predict effects in vivo, (4) outline a recommended testing strategy for evaluating the hazard and safety of novel SVFs, and (5) reflect on methods needs for in vitro in vivo correlation (IVIVC) and predictive approaches for safety assessment of new SVFs. AOP frameworks following the conceptual model of the OECD were developed through an evaluation of available molecular and cellular initiating events, which lead to KEs and KERs in the development of fiber-induced fibrogenesis and carcinogenesis. AOP framework development included consideration of fiber physicochemical properties, respiratory deposition and clearance patterns, biosolubility, and biopersistence, as well as cellular, organ, and organism responses. Available data support that fiber AOPs begin with fiber physicochemical characteristics which influence fiber exposure and biosolubility and subsequent key initiating events are dependent on fiber biopersistence and reactivity. Key cellular events of pathogenic fibers include oxidative stress, chronic inflammation, and epithelial/fibroblast proliferation and differentiation, which ultimately lead to hyperplasia, metaplasia, and fibrosis/tumor formation. Available in vitro models (e.g. single-, multi-cellular, organ system) provide promising NAMs tools to evaluate these intermediate KEs. However, data on SVFs demonstrate that in vitro biosolubility is a reasonable predictor for downstream events of in vivo biopersistence and biological effects. In vitro SVF fiber dissolution rates >100 ng/cm2/hr (glass fibers in pH 7 and stone fibers in pH 4.5) and in vivo SVF fiber clearance half-life less than 40 or 50 days were not associated with fibrosis or tumors in animals. Long (fiber lengths >20 µm) biodurable and biopersistent fibers exceeding these fiber dissolution and clearance thresholds may pose a risk of fibrosis and cancer. In vitro fiber dissolution assays provide a promising avenue and potentially powerful tool to predict in vivo SVF fiber biopersistence, hazard, and health risk. NAMs for fibers (including SVFs) may involve a multi-factor in vitro approach leveraging in vitro dissolution data in complement with cellular- and tissue- based in vitro assays to predict health risk.

Toxicity and inflammatory potential of mineral fibres: The contribute of released soluble metals versus cell contact direct effects

Asbestos fibres have been considered an environmental hazard for decades. However, little is known about the attempts of circulating immune cells to counteract their toxicity. We addressed the early effects of fibre-released soluble factors (i.e. heavy metals) in naïve immune cells, circulating immediately below the alveolar/endothelial cell layer. By comparison, the direct fibre effects on endotheliocytes were also studied since these cells are known to sustain inflammatory processes. The three mineral fibres analysed showed that mainly chrysotile (CHR) and erionite (ERI) were able to release toxic metals in extracellular media respect to crocidolite (CRO), during the first 24 h. Nevertheless, all three fibres were able to induce oxidative stress and genotoxic damage in indirectly challenged naïve THP-1 monocytes (separated by a membrane). Conversely, only CHR-released metal ions induced apoptosis, NF-κB activation, cytokines and CD163 gene overexpression, indicating a differentiation towards the M0 macrophage phenotype. On the other hand, all three mineral fibres in direct contact with HECV endothelial cells showed cytotoxic, genotoxic and apoptotic effects, cytokines and ICAM-I overexpression, indicating the ability of these cells to promote an inflammatory environment in the lung independently from the type of inhaled fibre. Our study highlights the different cellular responses to mineral fibres resulting from both the nature of the cells and their function, but also from the chemical-physical characteristics of the fibres. In conclusion, CHR represented the main pro-inflammatory trigger, able to recruit and activate circulating naïve monocytes, through its released metals, already in the first 24 h after inhalation.

The in vitro cytotoxic effects of natural (fibrous epsomite crystals) and synthetic (Epsom salt) magnesium sulfate

Exposure to mineral fibers represents an occupational and environmental hazard since particulate inhalation leads to several health disorders. However, few data are available on the effect of fibers with high solubility like natural epsomite, a water-soluble fiber with an inhalable size that allows it to penetrate biological systems, with regard to the respiratory tract. This study evaluated the natural (fibrous epsomite) and synthetic (Epsom salt) magnesium sulfate pathogenicity. Investigations have been performed through morpho-functional and biochemical analyses, in an in vitro cell model that usually grows as monocytes, but that under appropriate conditions differentiates into macrophages. These latter, known as alveolar macrophages, if referred to lungs, represent the first line of defense against harmful inhaled stimuli. Morphological observations reveal that, if Epsom salt induces osmotic stress on cell culture, natural epsomite fibers lead to cellular alterations including thickening of the nuclear envelope and degenerated mitochondria. Moreover, the insoluble fraction (impurities) internalized by cells induces diffuse damage characterized at the highest dosage and exposure time by secondary necrosis or necrotic cell death features. Biochemical analyses confirm this mineral behavior that involves MAPK pathway activation, resulting in many different cellular responses ranging from proliferation control to cell death. Epsom salt leads to MAPK/ERK activation, a marker predictive of overall survival. Unlike, natural epsomite induces upregulation of MAPK/p38 protein involved in the phosphorylation of downstream targets driving necrotic cell death. These findings demonstrate natural epsomite toxicity on U937 cell culture, making the inhalation of these fibers potentially hazardous for human health. RESEARCH HIGHLIGHTS: Natural epsomite and synthetic Epsom salt effects have been evaluated in U937 cell model. Epsom salt induces an osmotic cellular stress. Natural epsomite fibers lead to cellular damage and can be considered potentially dangerous for human health.

Mechanisms of action of mineral fibres in a placental syncytiotrophoblast model: An in vitro toxicology study

Asbestos has been widely used due to its unique characteristics. It is known that exposure to asbestos causes serious damage to health but one species, chrysolite, is still used because it is considered less toxic and not biopersistent in some countries. The aim of our study was to investigate if cellular process underlying the proliferation, differentiation and cell death of placental tissues could be modify in presence of asbestos fibres (50 μg/ml final concentration), long chrysolite fibres (CHR-L) and short chrysolite fibres (CHR-S), using BeWo cell line, an in vitro model that mimics the syncytiotrophoblast (STB), the outer layer of placental villi. Our data demonstrated that none of the fibres analysed alter syncytiotrophoblast formation but all of them induce ROS formation and reduced cell proliferation. Moreover, we showed that only CHR-L fibre induced was able to induce irreversible DNA alterations that carried cells to apoptosis. In fact, BeWo cells exposed to CHR-L fibre showed a significant increase in cleaved CASP3 protein, a marker of apoptosis. These data suggest that CHR-L may induce death of the placental villi leading to impaired placental development. The impairment of placental development is the basis of many gestational pathologies such as preeclampsia and intrauterine growth retardation. Since these pathologies are very dangerous for foetal and maternal life, we suggest to the gynaecologists to carefully evaluate the area of maternal residence, the working environment, the food used, and the materials used daily to avoid contact with these fibres as much as possible.

Molecular and Cellular Mechanism of Action of Chrysotile Asbestos in MRC5 Cell Line

Asbestos is a known carcinogen; however, the influence of chrysotile asbestos on the development of tumor-related diseases remains a subject of intense debate within the scientific community. To analyze the effect of asbestos, we conducted a study using the MRC5 cell line. We were able to demonstrate that chrysotile asbestos stimulated the production of reactive oxygen species (ROS), leading to cell death and DNA damage in the MRC5 cell line, using various techniques such as ROS measurement, comet assay, MTT assay, and qPCR. In addition, we found that chrysotile asbestos treatment significantly increased extracellular mitochondrial DNA levels in the culture medium and induced significant changes in the expression profile of several miRNAs, which was the first of its kind. Thus, our research highlights the importance of studying the effects of chrysotile asbestos on human health and reveals multiple adverse effects of chrysotile asbestos.

There is plenty of asbestos at the bottom. The case of magnesite raw material contaminated with asbestos fibres

Although all six asbestos minerals (the layer silicate chrysotile and five chain silicate species actinolite asbestos, amosite, anthophyllite asbestos, crocidolite and tremolite asbestos) are classified as carcinogenic, chrysotile is still mined and used in many countries worldwide. Other countries, like Italy, impose zero tolerance for all asbestos species, but conflicting views repress the development of globally uniform treaties controlling international trade of asbestos-containing materials. Hence, countries with more severe legislations against the use of these hazardous materials lack of an international safety net against importation of non-compliant products. This research reports the first discovery of commercial magnesite raw materials contaminated with white asbestos (chrysotile). X-ray powder diffraction and thermogravimetric/thermodifferential measurements showed the presence of serpentine group minerals in both the semi-processed (powder) and quarried material. The univocal identification of chrysotile in the powders was confirmed by its peculiar Raman bands of the OH stretching vibrations between 3500 and 3800 cm-1, with an intense peak at ∼3695 cm-1 and a weak contribution at ∼3647 cm-1. Transmission electron microscope showed that chrysotile forms fibres up to a few microns long and up to 80 nm thick with a nanotube structure characterized by inner channels as large as 30-40 nm. Fibres size analysis obtained by scanning electron microscopy indicates mean length and diameter of 5.95 and 0.109 μm with medians of 2.62 and 0.096 μm, respectively; some among the fibres analysed exhibit the so-called "Stanton size" (i.e., asbestos fibres longer than 8 μm and thinner than 0.25 μm that are strongly carcinogenic). Quantitative analysis showed a chrysotile content around 0.01 wt% not allowed by current regulations in Italy and many other countries. More generally, our findings demonstrate that without shared policies aimed at regulating asbestos circulation on the global market, "asbestos-free" national policies will inevitably fail.

Quantitative assessment of asbestos fibers in some normal and pathological extra-abdominal tissues-a scoping review

BACKGROUND

Asbestos is a mineral present in nature and it has been used for years in numerous settings. Asbestos enters the bloodstream and lymphatic system mainly through breathing.

OBJECTIVES

Studies with asbestos fiber's quantification in human tissues are scarce except for the lung. This article summarizes asbestos studies in some extra-abdominal tissues.

METHODS

A scoping review of articles that quantified asbestos fibers in extra-abdominal tissues (lymph nodes, pharynx, larynx, trachea, heart) by electron microscopy (Scanning-SEM or Transmission-TEM) was performed.

RESULTS

The 10 studies selected comprised 52 cases, out of whom 108 samples were analyzed. Mostly samples were lymph node tissues (102), followed by larynx (3) and myocardium (3). No studies were found that determined the presence of asbestos in the pharynx or trachea. The concentration of asbestos fibers detected in the lymph nodes was from 0.003 million fibers per gram of dry tissue (mfgdt) up to 7400 mfgdt, in the larynx the range was from 0.5 mfgdt up to 3.6 mfgdt, in myocardium no asbestos fibers were detected.

DISCUSSION

The studies included were heterogeneous in terms of case and sample characteristics and analytical techniques. As subjects exposed to asbestos are often positive for fibers in thoracic lymph nodes, we suggest that whenever a human tissue sample is analyzed for asbestos presence, the relevant draining lymph node should be concomitantly studied.

Distinct Pro-Inflammatory Mechanisms Elicited by Short and Long Amosite Asbestos Fibers in Macrophages

While exposure to long amphibolic asbestos fibers (L > 10 µm) results in the development of severe diseases including inflammation, fibrosis, and mesothelioma, the pathogenic activity associated with short fibers (L < 5 µm) is less clear. By exposing murine macrophages to short (SFA) or long (LFA) fibers of amosite asbestos different in size and surface chemistry, we observed that SFA internalization resulted in pyroptotic-related immunogenic cell death (ICD) characterized by the release of the pro-inflammatory damage signal (DAMP) IL-1α after inflammasome activation and gasdermin D (GSDMD)-pore formation. In contrast, macrophage responses to non-internalizable LFA were associated with tumor necrosis factor alpha (TNF-α) release, caspase-3 and -7 activation, and apoptosis. SFA effects exclusively resulted from Toll-like receptor 4 (TLR4), a pattern-recognition receptor (PRR) recognized for its ability to sense particles, while the response to LFA was elicited by a multifactorial ignition system involving the macrophage receptor with collagenous structure (SR-A6 or MARCO), reactive oxygen species (ROS) cascade, and TLR4. Our findings indicate that asbestos fiber size and surface features play major roles in modulating ICD and inflammatory pathways. They also suggest that SFA are biologically reactive in vitro and, therefore, their inflammatory and toxic effects in vivo should not be underestimated.

Exposure of Rats to Multi-Walled Carbon Nanotubes: Correlation of Inhalation Exposure to Lung Burden, Bronchoalveolar Lavage Fluid Findings, and Lung Morphology

To evaluate lung toxicity due to inhalation of multi-walled carbon nanotubes (MWCNTs) in rats, we developed a unique MWCNT aerosol generator based on dry aerosolization using the aerodynamic cyclone principle. Rats were exposed to MWNT-7 (also known as Mutsui-7 and MWCNT-7) aerosolized using this device. We report here an analysis of previously published data and additional unpublished data obtained in 1-day, 2-week, 13-week, and 2-year inhalation exposure studies. In one-day studies, it was found that approximately 50% of the deposited MWNT-7 fibers were cleared the day after the end of exposure, but that clearance of the remaining fibers was markedly reduced. This is in agreement with the premise that the rapidly cleared fibers were deposited in the ciliated airways while the slowly cleared fibers were deposited beyond the ciliated airways in the respiratory zone. Macrophage clearance of MWNT-7 fibers from the alveoli was limited. Instead of macrophage clearance from the alveoli, containment of MWNT-7 fibers within induced granulomatous lesions was observed. The earliest changes indicative of pulmonary toxicity were seen in the bronchoalveolar lavage fluid. Macrophage-associated inflammation persisted from the one-day exposure to MWNT-7 to the end of the two-year exposure period. Correlation of lung tumor development with MWNT-7 lung burden required incorporating the concept of area under the curve for the duration of the study; the development of lung tumors induced by MWNT-7 correlated with lung burden and the duration of MWNT-7 residence in the lung.

Malignant mesothelioma tumours: molecular pathogenesis, diagnosis, and therapies accompanying clinical studies

The pathetic malignant mesothelioma (MM) is a extremely uncommon and confrontational tumor that evolves in the mesothelium layer of the pleural cavities (inner lining- visceral pleura and outer lining- parietal pleura), peritoneum, pericardium, and tunica vaginalis and is highly resistant to standard treatments. In mesothelioma, the predominant pattern of lesions is a loss of genes that limit tumour growth. Despite the worldwide ban on the manufacture and supply of asbestos, the prevalence of mesothelioma continues to increase. Mesothelioma presents and behaves in a variety of ways, making diagnosis challenging. Most treatments available today for MM are ineffective, and the median life expectancy is between 10 and 12 months. However, in recent years, considerable progress has already been made in understanding the genetics and molecular pathophysiology of mesothelioma by addressing hippo signaling pathway. The development and progression of MM are related to many important genetic alterations. This is related to NF2 and/or LATS2 mutations that activate the transcriptional coactivator YAP. The X-rays, CT scans, MRIs, and PET scans are used to diagnose the MM. The MM are treated with surgery, chemotherapy, first-line combination chemotherapy, second-line treatment, radiation therapy, adoptive T-cell treatment, targeted therapy, and cancer vaccines. Recent clinical trials investigating the function of surgery have led to the development of innovative approaches to the treatment of associated pleural effusions as well as the introduction of targeted medications. An interdisciplinary collaborative approach is needed for the effective care of persons who have mesothelioma because of the rising intricacy of mesothelioma treatment. This article highlights the key findings in the molecular pathogenesis of mesothelioma, diagnosis with special emphasis on the management of mesothelioma.

From field analysis to nanostructural investigation: A multidisciplinary approach to describe natural occurrence of asbestos in view of hazard assessment

The environmental impact of natural occurrences of asbestos (NOA) and asbestos-like minerals is a growing concern for environmental protection agencies. The lack of shared sampling and analytical procedures hinders effectively addressing this issue. To investigate the hazard posed by NOA, a multidisciplinary approach that encompasses geology, mineralogy, chemistry, and toxicology is proposed and demonstrated here, on a natural occurrence of antigorite from a site in Varenna Valley, Italy. Antigorite is, together with chrysotile asbestos, one of the serpentine polymorphs and its toxicological profile is still under debate. We described field and petrographic analyses required to sample a vein and to evaluate the NOA-hazard. A combination of standardized mechanical stress and automated morphometrical analyses on milled samples allowed to quantify the asbestos-like morphology. The low congruent solubility in acidic simulated body fluid, together with the toxicity-relevant surface reactivity due to iron speciation, signalled a bio-activity similar or even greater to that of chrysotile. Structural information on the genetic mechanism of antigorite asbestos-like fibres in nature were provided. Overall, the NOA site was reported to contain veins of asbestos-like antigorite and should be regarded as source of potentially toxic fibres during hazard assessment procedure.

A critical review of asbestos concentrations in water and air, according to exposure sources

Asbestos, a group of minerals with unique physical and chemical properties, has been widely used in various industries. However, extensive exposure to asbestos fibers, present in the environment, has been linked to several types of cancer, mesothelioma, and asbestosis. Despite worldwide regulations prohibiting or regulating the use of this material, the uncertainty surrounding the concentrations of asbestos fibers in the environment (air and water) from different sources of exposure persists. The objective of this review paper is to identify the levels of asbestos in air and water reported in the literature based on the source of exposure in diverse contexts to assess conformity with the reference limits for this mineral. Initially, the review delineates various forms of exposure and the origin of fiber generation in the environment, whether direct or indirect. Regarding the presence of asbestos in the environment, high concentrations were identified in natural water bodies known as Naturally Occurring Asbestos (NOA), and there is a risk in the process of distributing drinking water due to the presence of asbestos-cement pipes. In the air, studies to determine asbestos concentrations vary based on the sources of exposure in each region or city studied. The presence of asbestos mines around the city and the intensity of vehicular traffic are some of the most relevant sources found to be related to high concentrations of asbestos fibers in the air. The present review paper features a critical review section in each chapter to highlight critical points found in the literature and suggest new methodologies/ideas to standardize future research. It emphasizes the necessity to standardize methods for measuring asbestos concentrations in air and water arising from diverse sources of exposure to enable comparisons between different regions and countries.

Synthesis of Ni-Doped Tremolite Fibers to Help Clarify the Aetiology of the Cytotoxic Outcome of Asbestos

Asbestos fibers act as complex crystal-chemical reservoirs susceptible of releasing potentially toxic elements (such as ions impurities) into the lung cellular environment during permanency and dissolution. To comprehend the exact pathological mechanisms that are triggered upon inhalation of asbestos fibers, in vitro studies on possible interactions between the mineral and the biological system have been carried out mostly by using natural asbestos. However, this latter comprises intrinsic impurities such as Fe²⁺/Fe³⁺ and Ni²⁺ ions, and other eventual traces of metallic pathogens. Furthermore, often, natural asbestos is characterized by the co-presence of several mineral phases, fiber dimensions of which are randomly distributed in width and in length. For these reasons, it is albeit challenging to precisely identify toxicity factors and to define the accurate role of each factor in the overall pathogenesis of asbestos. In this regard, the availability of synthetic asbestos fibers with accurate chemical composition and specific dimensions for in vitro screening tests would represent the perfect tool to correlate asbestos toxicity to its chemico-physical features. Herein, to palliate such drawbacks of natural asbestos, well-defined Ni-doped tremolite fibers were chemically synthesized in order to offer biologists adequate samples for testing the specific role of Ni²⁺ in asbestos toxicity. The experimental conditions (temperature, pressure, reaction time and water amount) were optimized to produce batches of asbestos fibers of the tremolite phase, with uniformly distributed shape and dimensions and a controlled content of Ni²⁺ metal ions.