Assessing occupational erionite and respirable crystalline silica exposure among outdoor workers in Wyoming, South Dakota, and Montana

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.

Investigating the deposition of fibrous zeolite particles on leaf surfaces: A novel low-cost method for detecting the presence of airborne hazardous mineral fibers

Naturally occurring fibrous minerals, such as erionite, can pose a significant threat to human health when disturbed and subsequently respired. Understanding the spatial abundance and characteristics of these hazardous fibrous minerals in ambient air is crucial for minimizing human exposure and assessing risk. Conventional detection methods for airborne hazardous mineral fibers, such as those developed for asbestos, are of limited utility in environmental settings where fiber concentrations are low and different fiber types may be present and can be costly especially when monitoring large areas over long periods of time. This study presents an innovative methodology for detecting and identifying the presence of airborne naturally occurring fibrous zeolites, using leaf surface deposition sampling, SEM-EDX analysis for the detection and assessment of elemental composition, and TEM-SAED with continuous rotation diffraction (MicroED) to determine their crystallographic unit cell parameters. In total, 309 fibrous zeolite particles (FZPs) were identified on a range of tree leaf surfaces across 80 % of the sampling sites located close to both active and disused zeolite quarries in the Taupo Volcanic Region, New Zealand. The FZPs displayed various morphologies including aggregates, bundles, and fibril-like structures. Of the FZPs detected, 92.2 % were < 5 µm in length. Tetrahedral Si:(Si+Al) ratio results indicated that 40 % of the FZPs were in the reference range for zeolite mordenite. TEM-SAED plus MicroED analysis resulted in 61 % of tested FZPs indexed to unit cell parameters that matched with mordenite. This research demonstrates the potential of leaf sampling as a cost-effective method for detecting airborne FZPs while the MicroED data can be utilized for distinguishing between different types of airborne fibrous zeolites in ambient air.

Fundamental properties and sustainable applications of the natural zeolite clinoptilolite

This review explores a set of sustainable applications of clinoptilolite, a natural zeolite abundant around the world in different localities. Thanks to its physico-chemical properties this material is extremely versatile for several applications, ranging from environmental catalysis and CO2 removal to industrial and agricultural wastewater purification, aquaculture, animal feeding, and food industry but also medical applications and energy storage systems. Due to the presence of cations in its framework, it is possible to tune the material's features making it suitable for adsorbing specific compounds. Thus, this review aims to provide insight into developing new technologies based on the use of this material that is sustainable, not harmful for humans and animals, naturally abundant, and above all cost-effective. Furthermore, it is intended to promote the use of natural materials in various areas with a view to sustainability and to reduce as far as possible the use of chemicals or other materials whose synthesis process can have a polluting effect on the environment.

Evaluation of workplace exposure to respirable crystalline silica in road construction industries in Alberta

Occupational exposure to respirable crystalline silica (RCS) is common for several occupations in construction, not only because of its presence in many handling materials but also in processes such as grinding and sawing. This study investigated workplace exposure to RCS as quartz in industries and occupations within road construction in Alberta through the RCS monitoring database provided by the Alberta Roadbuilders and Heavy Construction Association (ARHCA) between 2007 and 2016. Descriptive statistics were calculated for exposure-related variables, and mixed model analysis was performed to determine factors affecting the exposure levels. Results showed that the highest exposed workers were in the sand and gravel industry (GM = 45 μg/m³). For worker occupations, geometric means ranged from 78 μg/m³ for crusher operators to 10 μg/m³ for concrete truck operators. The maximum exposure severity was 33.3 times the occupational exposure limit (OEL) for the sand and gravel and 31 times the OEL for tower operators. The results also showed the effect of seasonal variability on RCS exposure levels. The heterogeneous exposure results indicated significant room for improvement and that controls should focus more on the activity performed than the occupation to lower exposure to RCS levels in industries.

Global geological occurrence and character of the carcinogenic zeolite mineral, erionite: A review

As with the six regulated asbestos minerals (chrysotile, amosite, crocidolite, anthophyllite, tremolite, and actinolite), the zeolite mineral, erionite, can exhibit a fibrous morphology. When fibrous erionite is aerosolized and inhaled, it has been linked to cases of lung cancers, such as malignant mesothelioma. Importantly, fibrous erionite appears to be more carcinogenic than the six regulated asbestos minerals. The first health issues regarding erionite exposure were reported in Cappadocia (Turkey), and more recently, occupational exposure issues have emerged in the United States. Erionite is now classified as a Group 1 carcinogen. Thus, identifying the geological occurrence of erionite is a prudent step in determining possible exposure pathways, but a global review of the geological occurrence of erionite is currently lacking. Here, we provide a review of the >100 global locations where erionite has been reported, including: 1) geological setting of host rocks; 2) paragenetic sequence of erionite formation, including associated zeolite minerals; 3) fiber morphological properties and erionite mineral series (i.e., Ca, K, Na); and 4) a brief overview of the techniques that have been used to identify and characterize erionite. Accordingly, erionite has been found to commonly occur within two major rock types: felsic and mafic. Within felsic rocks (in particular, tuffaceous layers within lacustrine paleoenvironments), erionite is disseminated through the layer as a cementing matrix. In contrast, within mafic (i.e., basaltic) rocks, erionite is typically found within vesicles. Nevertheless, aside from detailed studies in Italy and the United States, there is a paucity of specific information on erionite geological provenance or fiber morphology. The latter issue is a significant drawback given its impact on erionite toxicity. Future erionite studies should aim to provide more detailed information, including variables such as rock type and lithological properties, quantitative geochemistry, and fiber morphology.

Reanalysis of historic elemental speciation filters to investigate the presence of fibrous mineral particles using microscopy techniques

A case is presented for the value of archiving air quality filters to allow for retrospective analysis of emerging contaminants, that is filter constituents not considered to be harmful (and thus not identified or quantified specifically) at the time of collection but subsequently considered to be of interest. As an example, filters from a 20-year historical archive consisting of 16,000 filters from three sites across Auckland are re-examined for the presence of elongated mineral fibres known to be present in rock across the city. Originally collected for the purpose of the source apportionment of particulate matter, 10 filters from each of the three sites were chosen for reanalysis based on their high silica and aluminium content, and thus considered more likely to contain fibre-like particles (FLP). These filters were analysed using various microscopic methods, including phase contrast microscopy (PCM), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The results show that although the commonly used fibrous polytetrafluoroethylene (PTFE) material of the filters may hamper the visual identification of any fibre-like particles under a certain length, their key components are able to be identified using a combination of PCM and SEM when they are of a suitable dimension and have settled in a certain orientation on the filter. In this case, the use of EDS confirmed the silicon content of the fibres and also revealed elemental spectra. Although the exact identification of the mineral fibre is uncertain, the EDS scan is consistent with hazardous zeolites such as erionite, known to be present in the rock found in Auckland. This study highlights the value in maintaining filter archives for the purpose of investigating the historical evolution of emerging atmospheric pollutants.

Another Potentially Hazardous Zeolite from Northern Italy: Fibrous Mordenite

This study explored morphological, mineralogical, and physicochemical features of suspected toxic mordenite fibers from Northern Italy. All the mordenite samples (FAS1, GC1, SP1) show similar structural and chemical character, are Na-rich (Na > Ca > K), and the Al content decrease reflects the unit cell volumes in the series: FAS1 > SP1 > GC1. The aerodynamic diameter (Dae) values of the mordenite fibers are 1.19 μm for the GC1 sample, 2.69 μm for FAS1, and 3.91 μm for SP1. All the studied mordenite samples are characterized by “respirable” fibers despite the size differences, which could reach the deeper parts of the lungs. For this reason, fibrous mordenite could represent a potential health hazard and then need to be handled with attention, but further toxicity studies are needed.

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.

Characterisation of potentially toxic natural fibrous zeolites by means of electron paramagnetic resonance spectroscopy and morphological-mineralogical studies

This study explored the morphological, mineralogical, and physico-chemical features of carcinogenic erionite and other possibly hazardous zeolites, such as mesolite and thomsonite, while also investigating the interacting capability of the mineral surface at the liquid/solid interface. Extremely fibrous erionite is K⁺ and Ca²⁺-rich and shows the highest Si/Al ratio (3.38) and specific surface area (8.14 m²/g). Fibrous mesolite is Na⁺ and Ca²⁺-rich and displays both a lower Si/Al ratio (1.56) and a smaller specific surface area (1.56 m²/g). The thomsonite composition shows the lowest values of Si/Al ratio (1.23) and specific surface area (0.38 m²/g). Electron paramagnetic resonance data from selected spin probes reveal that erionite has a homogeneous site distribution and interacts well with all spin probes. The surfaces of mesolite and thomsonite are less homogeneous and closer polar sites were found through consequent interaction with the probes. The mesolite surface can also clearly interact but with a lower strength and may represent a potential health hazard for humans, though with a lower degree if compared to erionite. The thomsonite surface is not inert and interacts with the probes with a low-grade capability. We can expect small fragments of thomsonite to interact with the biological environment, though with a low-grade intensity.

Effects of Zeolite as a Drug Delivery System on Cancer Therapy: A Systematic Review

Zeolites and zeolitic imidazolate frameworks (ZIFs) are widely studied as drug carrying nanoplatforms to enhance the specificity and efficacy of traditional anticancer drugs. At present, there is no other systematic review that assesses the potency of zeolites/ZIFs as anticancer drug carriers. Due to the porous nature and inherent pH-sensitive properties of zeolites/ZIFs, the compounds can entrap and selectively release anticancer drugs into the acidic tumor microenvironment. Therefore, it is valuable to provide a comprehensive overview of available evidence on the topic to identify the benefits of the compound as well as potential gaps in knowledge. The purpose of this study was to evaluate the potential therapeutic applications of zeolites/ZIFs as drug delivery systems delivering doxorubicin (DOX), 5-fluorouracil (5-FU), curcumin, cisplatin, and miR-34a. Following PRISMA guidelines, an exhaustive search of PubMed, Scopus, Embase, and Web of Science was conducted. No language or time limitations were used up to 25th August 2021. Only full text articles were selected that pertained to the usage of zeolites/ZIFs in delivering anticancer drugs. Initially, 1279 studies were identified, of which 572 duplicate records were excluded. After screening for the title, abstract, and full texts, 53 articles remained and were included in the qualitative synthesis. An Inter-Rater Reliability (IRR) test, which included a percent user agreement and reliability percent, was conducted for the 53 articles. The included studies suggest that anticancer drug-incorporated zeolites/ZIFs can be used as alternative treatment options to enhance the efficacy of cancer treatment by mitigating the drawbacks of drugs under conventional treatment.

Zeolite Clinoptilolite: Therapeutic Virtues of an Ancient Mineral

Zeolites are porous minerals with high absorbency and ion-exchange capacity. Their molecular structure is a dense network of AlO4 and SiO4 that generates cavities where water and other polar molecules or ions are inserted/exchanged. Even though there are several synthetic or natural occurring species of zeolites, the most widespread and studied is the naturally occurring zeolite clinoptilolite (ZC). ZC is an excellent detoxifying, antioxidant and anti-inflammatory agent. As a result, it is been used in many industrial applications ranging from environmental remediation to oral applications/supplementation in vivo in humans as food supplements or medical devices. Moreover, the modification as micronization of ZC (M-ZC) or tribomechanically activated zeolite clinoptilolite (TMAZ) or furthermore as double tribomechanically activated zeolite clinoptilolite (PMA-ZC) allows improving its benefits in preclinical and clinical models. Despite its extensive use, many underlying action mechanisms of ZC in its natural or modified forms are still unclear, especially in humans. The main aim of this review is to shed light on the geochemical aspects and therapeutic potentials of ZC with a vision of endorsing further preclinical and clinical research on zeolites, in specific on the ZC and its modified forms as a potential agent for promoting human brain health and overall well-being.