Carbon nanotube pathogenicity conforms to a unified theory for mesothelioma causation by elongate materials and fibers

Habit of elongate amphibole particles as a predictor of mesothelial carcinogenicity

Introduction

Amphiboles are a class of minerals that are abundantly present in the environment. Amphiboles may exist in several habits, with asbestiform particles behaving like typical amphibole asbestos and non-asbestiform (or massive) reported to be less biologically active.

Materials and methods

The available dimensional information for 16 testing sets (8 asbestiform and 8 non-asbestiform types of tremolite) was combined. In addition, three validation sets (an asbestiform sample from Eastern New York and non-asbestiform samples from Quebec and Falls Village, Connecticut) were tested by Transmission Electron Microscopy (TEM) to determine dimensional distribution. Mathematical modeling was utilized to determine the classification method for amphiboles with various habits.

Results

The decision boundary method was developed to distinguish asbestiform vs. non-asbestiform samples (with error rate of 0 % for single-sourced tremolite and 3 % for potentially mixed samples). All validation datasets were correctly classified. A new empirical dimensional coefficient of carcinogenicity (DCC) was proposed, with DCC = 1 - exp(-0.11 Surface Area /(1000width3 + 1)). For several mineral types (crocidolite, amosite, Libby amphiboles, anthophyllite, chrysotile, and erionite), it was demonstrated that mesothelioma potency factors can be predicted based on DCC and biosolubility with a high level of accuracy (R=0.98, R2=0.96, p < 0.006). It was demonstrated that modeled mesothelioma potency correlates with relative potency for pleural instillation in Wistar rats, and correlates inversely with membranolytic toxicity index HC50. Mesothelioma potency was demonstrated to be negligible in all non-asbestiform sets.

Conclusions

The habit of amphibole particles is predictive of biological behavior that can be estimated from the dimensional data for the particles.

Evaluation of inflammatory and mesothelioma-related responses in mice following the intraperitoneal administration of cellulose nanofibers

Mesothelioma can develop from long-term exposure to fine fibrous materials including asbestos and carbon nanotubes, and chronic inflammation is critical for its development. Inflammatory responses and key related markers associated with the development of mesothelioma were evaluated over time in relation to cellulose nanofibers (CNFs), which are being developed as new plant-derived materials, for the purpose of risk management Three types of CNFs, mechanically fibrillated CNFs, TEMPO-oxidized CNFs, and phosphorylated CNFs, were administered intraperitoneally to mice at doses of 0.1 and 1.0 mg per animal, and progress was observed for up to 2 years. In the group receiving mechanically fibrillated CNFs, white substances were observed adhering to the liver surface throughout the observation period. This white substance was presumed to be cellulose. Some CNFs have been shown to persist in the body. During this period, inflammation markers and mesothelioma-related markers were evaluated at 1, 2, and 6 months, and 1, and 2 years after administration. No significant symptoms were observed in animals administered one of the three types of CNFs intraperitoneally during the observation period. Inflammatory markers in the peritoneal lavage fluid remained below the detection limit throughout the entire observation period. Additionally, no significant increase in blood levels of mesothelioma or the major related markers mesothelin, osteopontin, or HMGB1 was observed. In this study, although some CNFs remained in the body, no inflammatory response was observed in vivo under the concentration conditions and observation periods used. Furthermore, no evidence of long-term effects, such as cancer, was found.

The empirical metric of mesothelial carcinogenicity for carbon nanotubes and elongate mineral particles

INTRODUCTION

Carcinogenic potential of elongate particles depends on many characteristics, with dimensional parameters playing an important role at all stages of disease origination and progression. It is important to develop quantitative metrics of mesothelial carcinogenicity for particles in order to predict their behavior within biological systems. It would be especially valuable if such metrics could be developed for both carbon nanotubes (CNTs) and elongate mineral particles (EMPs) to demonstrate similarities and differences in the estimations of mesothelioma risk.

METHODS

The database is organized with dimensional characteristics of EMPs, containing 570,950 records for 246 asbestiform, non-asbestiform, and mixed datasets. A database on carbon nanotubes (CNTs) with various toxicological outcomes of animal experiments, including mesothelioma, was also created. Mathematical modeling was used to determine the best metric of mesotheliomagenicity that would work for CNTs and EMPs.

RESULTS

The dimensional coefficient of carcinogenicity (DCC) was introduced with the formula DCC = 1-exp(-AxSA/(BxWidth3+C)), where SA - surface area of the elongate particle, Width - particle width, A, B, C - coefficients. It was demonstrated that DCC can efficiently determine mesotheliomagenic varieties of CNTs and EMPs, with a threshold for carcinogenic potential of 0.05 with A = 0.11, B = 1000, C = 1.

DISCUSSION

The new quantitative metric of carcinogenicity can be used for the purposes of mineralogical evaluation and toxicological analysis. It was confirmed that DCC-based models predict negligible mesothelioma potency for non-asbestiform amphiboles.

Critical values for dimensional parameters of mesotheliomagenic mineral fibers: evidence from the dimensions and rigidity of MWCNT

MWCNT (multi-walled carbon nanotubes) used in 72 animal instillation or inhalation studies were classified by average length, average width, Young's modulus, Rigidity Index (RI), and potency for mesothelioma in animals. The RI is based on the Euler buckling theory. MWCNT that induce mesothelioma have average lengths >2 µm and widths >37 nm, and average RI > 0.05 (µm2 x GPa x 104). Many noncarcinogenic MWCNT materials have RI < 0.05 and lack biological rigidity. In comparison, Elongate Mineral Particle (EMP) populations with one exception have RI > 0.05. Mineral particles likely to have RI < 0.05 include chrysotile fibrils with lengths >5 μm, amosite and crocidolite fibers with widths <60 nm, and sheet silicate fibers with widths <200 nm. The product of percent EMPA, average RI, and biosolubility among silicates correlates with known mesothelioma potency. The derived models reproduce published values of RM with high statistical significance (P < 0.05). Average RI, length, and width are critical parameters for mesotheliomagenicity for both MWCNT and EMPA mineral fiber.

Characterizing applications, exposure risks, and hazard communication for engineered nanomaterials in construction

BACKGROUND

Engineered nanomaterials (ENMs) may pose health risks to workers. Objectives were to characterize ENM applications in construction, identify exposure scenarios, and evaluate the quality of safety data sheets (SDSs) for nano-enabled construction products.

METHODS

SDSs and product data were obtained from a public database of nano-enabled construction products. Descriptive statistics were calculated for affected trades, product categories, and types of ENMs. A sample of SDSs (n = 33) was evaluated using modified criteria developed by NIOSH researchers. Bulk analysis via transmission electron microscopy characterized nanoparticles in a subset of products.

RESULTS

Companies report using >50 ENMs in construction products. ENM composition could not be determined via SDSs for 38.1% of the 907 products examined. Polymers and metal oxides tied for most frequently reported ENMs (n = 87, 9.6%). Nano silica, graphene, carbon nanotubes, and silver nanoparticles were also frequently reported. Most of the products were paints and coatings (n = 483, 53.3%), followed by pre-market additives, cementitious materials, insulation, and lubricants. Workers in twenty construction trades are likely to handle nano-enabled products, these particularly encompass cement and brick masons, painters, laborers, carpenters, glaziers, and insulators. A wide range of exposure scenarios were identified. SDSs were classified as satisfactory (18%), in need of improvement (12%), or in need of significant improvement (70%). Bulk analyses revealed discrepancies between actual ENM composition and those in SDSs.

DISCUSSION AND CONCLUSION

There has been significant progress investigating risks to construction workers posed by ENMs, but SDSs need major improvements. This study provides new insights on the use of ENMs in construction, exposure risks, and hazard communication.

A risk assessment of mechanics who changed chrysotile asbestos containing brakes and other vehicle components in the 1950s-early 2000s era: an update on the 2004 evaluation

For the past 50 years, there has been an ongoing interest in understanding the potential health hazards, if any, to vehicle mechanics who worked with asbestos-containing brakes in the 1950s-early 2000s era. Two reviews have been published on this topic, one by Langer (2003) ("Reduction of the biological potential of chrysotile asbestos arising from conditions of service on brake pads") and another by Paustenbach, et al. (2004) ("Environmental and occupational health hazards associated with the presence of asbestos in brake linings and pads (1900 to present): a 'state-of-the-art' review"). This analysis is an update on those papers since a considerable amount of research has been published over the past 20 years on this topic. The following important aspects are addressed in this review: new information on the toxicology of chrysotile, toxicology studies of brake dust associated with grinding, additional epidemiology studies and meta-analyses published on auto mechanics of the era, previously unfound data on how brakes (during the era when chrysotile was used) were manufactured, and new work describing the transformation of chrysotile to various degradation products during vehicle braking. This update also addresses questions about the health hazards associated with asbestos in vehicle clutches, transmissions, and gaskets. The exposure data indicate that the airborne concentrations of chrysotile fibers associated with vehicle mechanic work when asbestos was in auto brakes were, on average, less than 0.04 f/cm3 (8-h TWA) and the average lifetime cumulative dose was in the vicinity of 0.5-3 f/cm3-year for mechanics of that era. Although many of these fibers may have no toxicity due to thermal degradation and the conversion to degradation products, 31 epidemiology studies have evaluated the risks of mesothelioma for vehicle mechanics of this era and all but one indicate that there was no increased incidence of this disease in these workers. The weight of evidence continues to indicate that the asbestos-related health risks to vehicle mechanics from asbestos-containing components were de minimis. The risks associated with take-home and bystander exposure of a mechanic were also addressed and they were found to pose a de minimis or zero health risk to those potentially exposed. Based on our evaluation, there is no indication that asbestos from asbestiform tremolite was present at detectable concentrations in bulk samples of brakes or in the air during brake work. The recent U.S. Environmental Protection Agency (EPA) risk assessment of 2024 on chrysotile and their views of the hazards of asbestos-containing brakes were discussed. Their analyses did not alter our views that exposures to mechanics posed no increased risk of asbestos related disease. The latest knowledge about the role of genetic susceptibility on the development of mesothelioma is also addressed.

Unravelling the toxicity of carbon nanomaterials - From cellular interactions to mechanistic understanding

The application of carbon nanomaterials in diverse fields has substantially increased their demand for commercial usage. Within the earliest decade, the development of functional materials has further increased the significance of this element. Despite the advancements recorded, the potential harmful impacts of embracing carbon nanomaterials for biological applications must be balanced against their advantages. Interestingly, many studies have neglected the intriguing and dynamic cellular interaction of carbon nanomaterials and the mechanistic understanding of their property-driven behaviour, even though common toxicity profiles have been reported. Reiterating the toxicity issue, several researchers conclude that these materials have minimal toxicity and may be safe for contact with biological systems at certain dosages. Here, we aim to provide a report on the significance of some of the properties that influence their toxicity. After that, a description of the implication of nanotoxicology in humans and living systems, revealing piece by piece their exposure routes and possible risks, will be provided. Then, an extensive discussion of the mechanistic puzzle modulating the interface between various human cellular systems and carbon nanomaterials such as carbon nanotubes, carbon dots, graphene, fullerenes, and nanodiamonds will follow. Finally, this review also sheds light on the organization that handles the risk associated with nanomaterials.

Pulmonary Toxicity of Boron Nitride Nanomaterials Is Aspect Ratio Dependent

Boron nitride (BN) nanomaterials have drawn a lot of interest in the material science community. However, extensive research is still needed to thoroughly analyze their safety profiles. Herein, we investigated the pulmonary impact and clearance of two-dimensional hexagonal boron nitride (h-BN) nanosheets and boron nitride nanotubes (BNNTs) in mice. Animals were exposed by single oropharyngeal aspiration to h-BN or BNNTs. On days 1, 7, and 28, bronchoalveolar lavage (BAL) fluids and lungs were collected. On one hand, adverse effects on lungs were evaluated using various approaches (e.g., immune response, histopathology, tissue remodeling, and genotoxicity). On the other hand, material deposition and clearance from the lungs were assessed. Two-dimensional h-BN did not cause any significant immune response or lung damage, although the presence of materials was confirmed by Raman spectroscopy. In addition, the low aspect ratio h-BN nanosheets were internalized rapidly by phagocytic cells present in alveoli, resulting in efficient clearance from the lungs. In contrast, high aspect ratio BNNTs caused a strong and long-lasting inflammatory response, characterized by sustained inflammation up to 28 days after exposure and the activation of both innate and adaptive immunity. Moreover, the presence of granulomatous structures and an indication of ongoing fibrosis as well as DNA damage in the lung parenchyma were evidenced with these materials. Concurrently, BNNTs were identified in lung sections for up to 28 days, suggesting long-term biopersistence, as previously demonstrated for other high aspect ratio nanomaterials with poor lung clearance such as multiwalled carbon nanotubes (MWCNTs). Overall, we reveal the safer toxicological profile of BN-based two-dimensional nanosheets in comparison to their nanotube counterparts. We also report strong similarities between BNNTs and MWCNTs in lung response, emphasizing their high aspect ratio as a major driver of their toxicity.

Advanced Theranostic Strategies for Viral Hepatitis Using Carbon Nanostructures

There are several treatment protocols for acute viral hepatitis, and it is critical to recognize acute hepatitis in its earliest stages. Public health measures to control these infections also rely on rapid and accurate diagnosis. The diagnosis of viral hepatitis remains expensive, and there is no adequate public health infrastructure, while the virus is not well-controlled. New methods for screening and detecting viral hepatitis through nanotechnology are being developed. Nanotechnology significantly reduces the cost of screening. In this review, the potential of three-dimensional-nanostructured carbon substances as promising materials due to fewer side effects, and the contribution of these particles to effective tissue transfer in the treatment and diagnosis of hepatitis due to the importance of rapid diagnosis for successful treatment, were extensively investigated. In recent years, three-dimensional carbon nanomaterials such as graphene oxide and nanotubes with special chemical, electrical, and optical properties have been used for the diagnosis and treatment of hepatitis due to their high potential. We expect that the future position of nanoparticles in the rapid diagnosis and treatment of viral hepatitis can be better determined.