The dependence of particle size on cell toxicity for modern mining dust

Assessment of Sub-micrometer-Sized Particles with Practical Activities in an Underground Coal Mine

This assessment was designed to explore and characterize the airborne particles, especially for the sub-micrometer sizes, in an underground coal mine. Airborne particles present in the breathing zone were evaluated by using both (1) direct reading real-time instruments (RTIs) to measure real-time particle number concentrations in the workplaces and (2) gravimetric samplers to collect airborne particles to obtain mass concentrations and conduct further characterizations. Airborne coal mine particles were collected via three samplers: inhalable particle sampler (37 mm cassette with polyvinyl chloride (PVC) filter), respirable dust cyclone (10 mm nylon cyclone with 37 mm Zefon cassette and PVC filter), and a Tsai diffusion sampler (TDS). The TDS, a newly designed sampler, is for collecting particles in the nanometer and respirable size range with a polycarbonate filter and grid. The morphology and compositions of collected particles on the filters were characterized using electron microscopy (EM). RTIs reading showed that the belt entry had a greatly nine-times higher total particle number concentration in average (~ 34,700 particles/cm3) than those measured at both the underground entry and office building (~ 4630 particles/cm3). The belt entry exhibited not only the highest total particle number concentration, but it also had different particle size fractions, particularly in the submicron and smaller sizes. A high level of submicron and nanoparticles was found in the belt conveyor drift area (with concentrations ranging from 0.54 to 1.55 mg/m3 among three samplers). The data support that small particles less than 300 nm are present in the underground coal mine associated with dust generated from practical mining activities. The chemical composition of the air particles has been detected in the presence of Ca, Cu, Si, Al, Fe, and Co which were all found to be harmful to miners when inhaled.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42461-024-01140-w.

Factors influencing airway smooth muscle tone: a comprehensive review with a special emphasis on pulmonary surfactant

A thin film of pulmonary surfactant lines the surface of the airways and alveoli, where it lowers the surface tension in the peripheral lungs, preventing collapse of the bronchioles and alveoli and reducing the work of breathing. It also possesses a barrier function for maintaining the blood-gas interface of the lungs and plays an important role in innate immunity. The surfactant film covers the epithelium lining both large and small airways, forming the first line of defense between toxic airborne particles/pathogens and the lungs. Furthermore, surfactant has been shown to relax airway smooth muscle (ASM) after exposure to ASM agonists, suggesting a more subtle function. Whether surfactant masks irritant sensory receptors or interacts with one of them is not known. The relaxant effect of surfactant on ASM is absent in bronchial tissues denuded of an epithelial layer. Blocking of prostanoid synthesis inhibits the relaxant function of surfactant, indicating that prostanoids might be involved. Another possibility for surfactant to be active, namely through ATP-dependent potassium channels and the cAMP-regulated epithelial chloride channels [cystic fibrosis transmembrane conductance regulators (CFTRs)], was tested but could not be confirmed. Hence, this review discusses the mechanisms of known and potential relaxant effects of pulmonary surfactant on ASM. This review summarizes what is known about the role of surfactant in smooth muscle physiology and explores the scientific questions and studies needed to fully understand how surfactant helps maintain the delicate balance between relaxant and constrictor needs.

Evidence of soil particle-induced ecotoxicity in old abandoned mining area

Ecotoxicity of heavy metals in soil is primarily associated with their bioaccessibility and bioavailability in the soil media. However, in some exceptional cases, soil ecotoxicity has been observed despite high total metal concentrations and low extractable metal concentrations in contaminated field sites; therefore, other exposure pathways must be considered. Therefore, the aim of this study was to evaluate the soil-particle induced ecotoxicity in an old mining area. We hypothesized that heavy metals, strongly adsorbed onto soil particles of consumable size for soil organisms, exhibit ecotoxicity, especially on soil particles ∼1 µm to 300 µm in size. A plant seedling assay, in vivo cytotoxicity assay using earthworm immune cells, and a metal bioconcentration assessment were performed. The results of soil particle toxicity revealed that the soil from the study area (A1-A4) had a low contribution to the soil ecotoxicity of extractable metals. For instance, the concentration of extractable arsenic was only 1.9 mg/kg soil, despite the total arsenic concentration reaching 36,982 mg/kg soil at the A1 site. The qualitative and quantitative analyses using SEM-EDX and ICP-OES, as well as principal component analyses, supported the hypothesis of the present study. Overall, the study results emphasize the importance of soil particle-induced ecotoxicity in long-term contaminated field soils. Our study results can inform on effective site-specific soil ecological risk assessment as they suggest the inclusion of soil particle-induced ecotoxicity as an important criterion in old, contaminated field sites, even when the extractable metal fraction in the field soil is low. ENVIRONMENTAL IMPLICATION: Bioaccessibility and bioavailability are primary factors contributing to the soil ecotoxicity of heavy metals. However, in some cases, such as long-term contaminated field sites, soil ecotoxicity has been confirmed even when low extractable metal concentrations were detected alongside high total metal concentrations. The findings of this study reveal that soil particles of edible size could be sources of soil ecotoxicity in the case of long-term contaminated fields with low extractable metal concentrations. The results of this study would contribute to the area of site-specific soil ecological risk assessment.

Tissue-specific toxic effects of nano-copper on zebrafish

Understanding the behavior and potential toxicity of copper nanoparticles (nano-Cu) in the aquatic environment is a primary way to assess their environmental risks. In this study, RNA-seq was performed on three different tissues (gills, intestines, and muscles) of zebrafish exposed to nano-Cu, to explore the potential toxic mechanism of nano-Cu on zebrafish. The results indicated that the toxic mechanism of nano-Cu on zebrafish was tissue-specific. Nano-Cu enables the CB1 receptor of the presynaptic membrane of gill cells to affect short-term synaptic plasticity or long-term synaptic changes (ECB-LTD) through DSI and DSE, causing dysfunction of intercellular signal transmission. Imbalance of de novo synthesis of UMP in intestinal cells and its transformation to UDP, UTP, uridine, and uracil, resulted in many functions involved in the pyrimidine metabolic pathway being blocked. Meanwhile, the toxicity of nano-Cu caused abnormal expression of RAD51 gene in muscle cells, which affects the repair of damaged DNA through Fanconi anemia and homologous recombination pathway, thus causing cell cycle disorder. These results provide insights for us to better understand the differences in toxicity of nano-Cu on zebrafish tissues and are helpful for a comprehensive assessment of nano-Cu's effects on aquatic organisms.