Human toxicity of cobalt-containing dust and experimental studies on the mechanism of interstitial lung disease (hard metal disease)

Properties, Advantages, and Prospects of Using Cobalt-Free Composites Based on Tungsten Carbide in Industry

This paper reviews recent advances in the synthesis of cobalt-free high-strength tungsten carbide (WC) composites as sustainable alternatives to conventional WC-Co composites. Due to the high cost of cobalt, limited supply, and environmental concerns, researchers are exploring nickel, iron, ceramic binders, and nanocomposites to obtain similar or superior mechanical properties. Various synthesis methods such as powder metallurgy, encapsulation, 3D printing, and spark plasma sintering (SPS) are discussed, with SPS standing out for its effectiveness in densifying and preventing WC grain growth. The results show that cobalt-free composites exhibit high strength, wear and corrosion resistance, and harsh environment stability, making them viable competitors for WC-Co materials. The use of nickel and iron with SPS is shown to enable the development of environmentally friendly, cost-effective materials. It is emphasized that microstructural control and phase management during sintering are critical to improve a material's properties. The application potential of these composites covers mechanical engineering, metallurgy, oil and gas, and aerospace, emphasizing their broad industrial relevance.

Unusual hard metal lung disease: bronchiolocentric interstitial pneumonia

A 38-year-old woman experienced a persistent dry cough and progressively worsening dyspnoea for 2 years. Spirometry testing revealed a moderate-to-severe restrictive abnormality. High-resolution chest computed tomography showed diffuse reticulonodular opacities. A lung biopsy disclosed alveolar parenchymal inflammation and fibrosis with bronchiolocentric features, prompting consideration of interstitial pneumonia. Following a thorough investigation of her occupational history and an on-site inspection, it was discovered that the patient had been grinding drill bits designed for printed circuit boards for 8 years, exposing her to hard metals. Mineralogical analyses confirmed excessive tungsten in urine, serum and hair, leading to a diagnosis of hard metal lung disease due to tungsten carbide-cobalt exposure. After discontinuing exposure and commencing corticosteroid therapy, her symptoms, pulmonary function and imaging showed modest improvement. This case highlights the significance of assessing occupational history in patients with interstitial pneumonia and understanding industrial hazards for accurate diagnosis and care.

Pretreatment of membrane dye wastewater by CoFe-LDH-activated peroxymonosulfate: Performance, degradation pathway, and mechanism

When a membrane is used to treat dye wastewater, dye molecules are continually concentrated at the membrane surface over time, resulting in a dramatic decrease in membrane flux. Aside from routine membrane cleaning, the pretreatment of dye wastewater to degrade organic pollutants into tiny molecules is a facile solution to the problem. In this study, the use of layered double hydroxide (LDH) to activate peroxymonosulfate (PMS) for efficient degradation of organic pollutant has been thoroughly investigated. We utilized a simple two-drop co-precipitation process to prepare CoFe-LDH. The transition metal components in CoFe-LDH effectively activate PMS to create oxidative free radicals, and the layered structure of LDH increases the number of active sites, and thereby considerably enhancing the reaction rate. It was found that the reaction process produced non-free and free radicals, including singlet oxygen (¹O₂), sulfate radicals (SO₄^•-), and hydroxyl radicals (•OH), with ¹O₂ being the dominant reactive species. Under the optimal conditions (pH 6.7, PMS dosage 0.2 g/L, catalyst loading 0.1 g/L), the degradation of Acid Red 27 dye in the CoFe-LDH/PMS system reached 96.7% within 15 min at an initial concentration of 200 mg/L. The CoFe-LDH/PMS system also exhibited strong resistance to inorganic ions and pH during the degradation of organic pollutants. This study presents a novel strategy for the synergistic treatment of dye wastewater with free and non-free radicals produced by LDH-activated PMS in a natural environment.

Analysis of lung function and respiratory symptoms in brass/metal industrial workers of Moradabad, Uttar Pradesh, India

Background

The job demands of some of the industries have been reported to be hazardous to the health and safety of workers. Workplace environmental hazards or occupational hazards are a globally major cause of disability and mortality among the working population. The present study was done to analyze the effect of exposure to metal dust on pulmonary function and respiratory symptoms.

Materials and Methods

The study population selected as cases were 200 male mill workers working for at least 1-year duration (direct exposure) in the age group of 20-50 years, and controls were 200 age- and gender-matched male participants without any history of occupational or environmental exposure. A complete history was taken. Spirometry was done. Spirometric parameters studied were forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), ratio of FEV1 and FVC, and peak expiratory flow rate (PEFR). The spirometry data and baseline characteristics of the participants were compared using unpaired t-test.

Results

The mean age of the participants of the study group and the control group was 42.3 years and 44.1 years, respectively. The majority of the study population belonged to the age group of 41-50 years. The mean FEV1 value among participants of the study group and control group was 2.69 and 2.13, respectively. The mean FVC value among participants of the study group and control group was 3.18 and 3.63, respectively. The mean FEV1/FVC value among participants of the study group and control group was 84.59% and 86.22%, respectively. The mean PEFR value among the study group and control group was 7.78 and 8.67, respectively. While analyzing statistically, mean lung functional tests were significantly lowered among the study group. About 69.5% of the participants of the study group thought it to be essential for making safety measures a necessity.

Conclusion

The present study concluded that mean lung functional tests were significantly lowered among the study group. Despite the use of face mask, lung function abnormality was present in mill workers.

Homogeneous catalytic activation of peroxymonosulfate and heterogeneous reductive regeneration of Co2+ by MoS2: The pivotal role of pH

The application of MoS₂ to enhance Co(II)/peroxymonosulfate (Co(II)/PMS) system for organic pollutants degradation was developed, and the mechanism for pH dependent catalytic activity in the MoS₂ co-catalyzed Co(II)/PMS processes was systematically investigated. It was found that MoS₂ presented enhancement effect for Co(II)/PMS system in the tested pH range from 4.0 to 7.0, especially at pH 5.5 and 6.0. The pseudo first order reaction rates for Rhodamine B (RhB) degradation in MoS₂-Co²⁺/PMS system at pH 5.5 and 6.0 were 3.2 and 1.8 times that in Co²⁺/PMS system (Co²⁺ 2 μmol L^-1, PMS 0.2 mmol L^-1, MoS₂ 0.5 g L^-1). The redox recycle of Co³⁺/Co²⁺ was promoted by Mo(IV) and S(-II) on MoS₂ surface and regenerated Co²⁺ induced homogeneous activation of PMS for the robust production of free radical with the major of hydroxyl radicals. Increasing MoS₂ dosage, Co²⁺ and PMS concentration can linearly raise RhB degradation rate in MoS₂-Co(II)/PMS system. Moreover, MoS₂ exhibited excellent catalytic and chemical stability in recyclability and reuse for catalytic decontamination in MoS₂-Co(II)/PMS system. This work gains new insight into the enhancement effect of MoS₂ in the meal ions/PMS system, and provides a high performance wastewater treatment process of Co(II)/PMS at low concentrated Co²⁺.

Accumulation of essential and non-essential trace elements in rice grain: Possible health impacts on rice consumers in West Bengal, India

Rice is the major staple food to the population in rural West Bengal, India and Bangladesh. Depletion and excess accumulation of different trace elements, which are essential and non-essential to the human body, in rice can have a detrimental impact on the rice consumer. Therefore, this study has investigated the accumulation of different trace elements in rice consumed in rural households in West Bengal. The mean concentration (mg kg^-1) of essential elements in rice follows the order of Fe (39.4) > Zn (9.79) > Mn (4.40) > Cu (3.26) > Se (0.28) > Co (0.03), while this order for non-essential elements is Pb (1.70) > As (0.34) > Ni (0.22) > Cd (0.04). In general, accumulation in rice is higher for elements that show higher mobility under reducing conditions (e.g. Fe, Mn, As, etc.) compared to elements with lower mobility under such conditions (e.g. Se, Cd, etc.). These orders of accumulation can be attributed to the irrigation practice of continuous flooding of the soil during rice cultivation and the abundance of these elements in the paddy soil itself. By combining these analytical results to the data obtained from questionnaire survey it is estimated that rice consumption can be either enough or a major source to fulfill the daily requirement of Fe, Cu, Se, Mn, and Zn necessary for different physiological functions in the human body for the population in rural Bengal. At the same time, it can be a potential route of As, Cd, Ni, and Pb exposure to develop their non-carcinogenic and carcinogenic health effects among the population. This study highlights that attempts should be made to reduce the accumulation of other non-essential elements together with As in rice grain to ensure the health safety of the people who rarely get a balanced diet and relay on rice consumption to meet the daily calorific intake in rural Bengal.

Cobalt nanoparticles trigger ferroptosis-like cell death (oxytosis) in neuronal cells: Potential implications for neurodegenerative disease

The neurotoxicity of hard metal-based nanoparticles (NPs) remains poorly understood. Here, we deployed the human neuroblastoma cell line SH-SY5Y differentiated or not into dopaminergic- and cholinergic-like neurons to study the impact of tungsten carbide (WC) NPs, WC NPs sintered with cobalt (Co), or Co NPs versus soluble CoCl₂ . Co NPs and Co salt triggered a dose-dependent cytotoxicity with an increase in cytosolic calcium, lipid peroxidation, and depletion of glutathione (GSH). Co NPs and Co salt also suppressed glutathione peroxidase 4 (GPX4) mRNA and protein expression. Co-exposed cells were rescued by N-acetylcysteine (NAC), a precursor of GSH, and partially by liproxstatin-1, an inhibitor of lipid peroxidation. Furthermore, in silico analyses predicted a significant correlation, based on similarities in gene expression profiles, between Co-containing NPs and Parkinson's disease, and changes in the expression of selected genes were validated by RT-PCR. Finally, experiments using primary human dopaminergic neurons demonstrated cytotoxicity and GSH depletion in response to Co NPs and CoCl₂ with loss of axonal integrity. Overall, these data point to a marked neurotoxic potential of Co-based but not WC NPs and show that neuronal cell death may occur through a ferroptosis-like mechanism.

Occupational low-level exposure to hard metals: cobalt and tungsten biomonitoring as an effective tool to evaluate the effectiveness of industrial hygiene interventions for risk management

Purpose: The aim of the study was to assess the exposure to Cobalt (Co) and Tungsten (W) in a group of hard metal tool sharpeners through a combined approach of air and biological monitoring, and to evaluate the effectiveness of a control and improvement intervention carried out in collaboration with the medical officers of the local Health Protection Agency, by biomonitoring.Methods: We enrolled 132 workers from 17 companies of the province of Brescia, northern Italy. The study was performed in two phases: (1) an environmental and biomonitoring survey to assess the workers' exposure to Co and W at their usual working conditions; (2) a further biomonitoring survey 3 months after the enforcement of a control and improvement intervention, to assess its effectiveness.Results: Workers were found to be exposed to low concentration of airborne dust containing Co and W but after the intervention we recorded a significant decrease of the urinary concentrations of both Co and W. The extent of the decrease was correlated to the number of preventive industrial hygiene interventions that were carried out.Conclusions: Biological monitoring of Co and W in the hard metal tools manufacturing industry is a sensitive and effective method to evaluate the effectiveness of prevention practices.

Urinary metals and metal mixtures and oxidative stress biomarkers in an adult population from Spain: The Hortega Study

INTRODUCTION

Few studies have investigated the role of exposure to metals and metal mixtures on oxidative stress in the general population.

OBJECTIVES

We evaluated the cross-sectional association of urinary metal and metal mixtures with urinary oxidative stress biomarkers, including oxidized to reduced glutathione ratio (GSSG/GSH), malondialdehyde (MDA), and 8‑oxo‑7,8‑dihydroguanine (8-oxo-dG), in a representative sample of a general population from Spain (Hortega Study).

METHODS

Urine antimony (Sb), barium (Ba), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), molybdenum (Mo), vanadium (V) and zinc (Zn) were measured by ICPMS in 1440 Hortega Study participants.

RESULTS

The geometric mean ratios (GMRs) of GSSG/GSH comparing the 80th to the 20th percentiles of metal distributions were 1.15 (95% confidence intervals [95% CI]: 1.03-1.27) for Mo, 1.17 (1.05-1.31) for Ba, 1.23 (1.04-1.46) for Cr and 1.18 (1.00-1.40) for V. For MDA, the corresponding GMRs (95% CI) were 1.13 (1.03-1.24) for Zn and 1.12 (1.02-1.23) for Cd. In 8-oxo-dG models, the corresponding GMR (95% CI) were 1.12 (1.01-1.23) for Zn and 1.09 (0.99-1.20) for Cd. Cr for GSSG/GSH and Zn for MDA and 8-oxo-dG drove most of the observed associations. Principal component (PC) 1 (largely reflecting non-essential metals) was positively associated with GSSG/GSH. The association of PC2 (largely reflecting essential metals) was positive for GSSG/GSH but inverse for MDA.

CONCLUSIONS

Urine Ba, Cd, Cr, Mo, V and Zn were positively associated with oxidative stress measures at metal exposure levels relevant for the general population. The potential health consequences of environmental, including nutritional, exposure to these metals warrants further investigation.

Comparative Assessment of Tungsten Toxicity in the Absence or Presence of Other Metals

Tungsten is a refractory metal that is used in a wide range of applications. It was initially perceived that tungsten was immobile in the environment, supporting tungsten as an alternative for lead and uranium in munition and military applications. Recent studies report movement and detection of tungsten in soil and potable water sources, increasing the risk of human exposure. In addition, experimental research studies observed adverse health effects associated with exposure to tungsten alloys, raising concerns on tungsten toxicity with questions surrounding the safety of exposure to tungsten alone or in mixtures with other metals. Tungsten is commonly used as an alloy with nickel and cobalt in many applications to adjust hardness and thermal and electrical conductivity. This review addresses the current state of knowledge in regard to the mechanisms of toxicity of tungsten in the absence or presence of other metals with a specific focus on mixtures containing nickel and cobalt, the most common components of tungsten alloy.

Potentially toxic elements in soil of the Khyber Pakhtunkhwa province and Tribal areas, Pakistan: evaluation for human and ecological risk assessment

Potentially toxic elements (PTEs) contaminations in the soil ecosystem are considered as extremely hazardous due to toxicity, persistence and bioaccumulative nature. Therefore, this study was aimed to summarize the results of published PTEs in soil of Khyber Pakhtunkhwa and Tribal areas, Pakistan. Results were evaluated for the pollution quantification factors, including contamination factor (CF), pollution load index (PLI), ecological risk index (ERI) and human health risk assessment. The highest CF (797) and PLI (7.35) values were observed for Fe and ERI (857) values for Cd. Soil PTEs concentrations were used to calculate the human exposure for the risk assessment, including chronic or non-carcinogenic risks such as the hazard quotient (HQ) and carcinogenic or cancer risk (CR). The values of HQ were > 1 for the Cd, Co and Cr in Khyber Pakhtunkhwa and Tribal areas. Tribal areas showed higher values of ERI, HQ, and CR as compared to the Khyber Pakhtunkhwa that were attributed to the mining activities, weathering and erosion of mafic and ultramafic bedrocks hosting ophiolites. This study strongly recommends that best control measures need to be taken for soil PTEs with the intent to alleviate any continuing potential threat to the human health, property and environment, which otherwise could enter ecosystem and ultimately the living beings. Further studies are recommended to combat the soil PTEs concentrations and toxicity in the Tribal areas for a best picture of understanding the element effects on human, and environment can be achieved that will lead to a sustainable ecological harmony.

Urinary tungsten and incident cardiovascular disease in the Strong Heart Study: An interaction with urinary molybdenum

BACKGROUND

Tungsten (W) interferes with molybdenum (Mo) binding sites and has been associated with prevalent cardiovascular disease (CVD). We evaluated if (1) W exposure is prospectively associated with incident CVD and (2) the association between urinary W levels and incident CVD is modified by urinary Mo levels.

METHODS

We estimated multi-adjusted hazard ratios (HRs) for incident CVD outcomes by increasing W levels for 2726 American Indian participants in the Strong Heart Study with urinary metal levels measured at baseline (1989-1991) and CVD events ascertained through 2008.

RESULTS

Increasing levels of baseline urinary W were not associated with incident CVD. Fully-adjusted HRs (95% CIs) of incident CVD comparing a change in the IQR of W levels for those in the lowest and highest tertile of urinary Mo were 1.05 (0.90, 1.22) and 0.80 (0.70, 0.92), respectively (p-interaction = 0.02); for CVD mortality, the corresponding HRs were 1.05 (0.82, 1.33) and 0.73 (0.58, 0.93), respectively (p-interaction = 0.03).

CONCLUSIONS

The association between W and CVD incidence and mortality was positive although non-significant at lower urinary Mo levels and significant and inverse at higher urinary Mo levels. Although prior cross-sectional epidemiologic studies in the general US population found positive associations between urinary tungsten and prevalent cardiovascular disease, our prospective analysis in the Strong Heart Study indicates this association may be modified by molybdenum exposure.

Highly selective apo-arginase based method for sensitive enzymatic assay of manganese (II) and cobalt (II) ions

A novel enzymatic method of manganese (II) and cobalt (II) ions assay, based on using apo-enzyme of Mn²⁺-dependent recombinant arginase I (arginase) and 2,3-butanedione monoxime (DMO) as a chemical reagent is proposed. The principle of the method is the evaluation of the activity of L-arginine-hydrolyzing of arginase holoenzyme after the specific binding of Mn²⁺ or Co²⁺ with apo-arginase. Urea, which is the product of enzymatic hydrolysis of L-arginine (Arg), reacts with DMO and the resulted compound is detected by both fluorometry and visual spectrophotometry. Thus, the content of metal ions in the tested samples can be determined by measuring the level of urea generated after enzymatic hydrolysis of Arg by reconstructed arginase holoenzyme in the presence of tested metal ions. The linearity range of the fluorometric apo-arginase-DMO method in the case of Mn²⁺ assay is from 4pM to 1.10nM with a limit of detection of 1pM Mn²⁺, whereas the linearity range of the present method in the case of Co²⁺ assay is from 8pM to 45nM with a limit of detection of 2.5pM Co²⁺. The proposed method being highly sensitive, selective, valid and low-cost, may be useful to monitor Mn²⁺ and Co²⁺ content in clinical laboratories, food industry and environmental control service.

Environmental Metals and Cardiovascular Disease in Adults: A Systematic Review Beyond Lead and Cadmium

Published systematic reviews concluded that there is moderate to strong evidence to infer a potential role of lead and cadmium, widespread environmental metals, as cardiovascular risk factors. For other non-essential metals, the evidence has not been appraised systematically. Our objective was to systematically review epidemiologic studies on the association between cardiovascular disease in adults and the environmental metals antimony, barium, chromium, nickel, tungsten, uranium, and vanadium. We identified a total of 4 articles on antimony, 1 on barium, 5 on chromium, 1 on nickel, 4 on tungsten, 1 on uranium, and 0 on vanadium. We concluded that the current evidence is not sufficient to inform on the cardiovascular role of these metals because of the small number of studies. Few experimental studies have also evaluated the role of these metals in cardiovascular outcomes. Additional epidemiologic and experimental studies, including prospective cohort studies, are needed to understand the role of metals, including exposure to metal mixtures, in cardiovascular disease development.

Toxicity and oxidative stress responses induced by nano- and micro-CoCrMo particles

Particles on the nano- and micro-meter scales present unique cell-specific cellular effects (i.e.cytotoxicity and oxidative stress).

Cobalt Cardiomyopathy

Cobalt can cause a distinctive, rapidly progressive and reversible depression of cardiac systolic function, which is readily distinguished from other causes of cardiomyopathy. Patients present with the subacute onset of severe heart failure, which is accompanied by hypotension and cyanosis, pericardial effusion, low voltage on the electrocardiogram, marked elevation of serum enzymes, and lactic acidosis. They typically have a history of lethargy, anorexia, and weight loss in the months preceding the illness and exhibit other evidence of cobalt’s effects on the body (eg, polycythemia and goiter). The course of cobalt-related cardiomyopathy may be progressive and fatal, but those who survive and cease exposure generally demonstrate complete resolution of symptoms and recovery of cardiac function. Patients presenting with rapid onset of cardiomyopathy, who also exhibit polycythemia, pericardial effusion, or goiter should be evaluated for cobalt exposure. Exposure can be confirmed by the measurement of cobalt in the serum, but serum levels of the ion are not reliably predictive of clinical cardiotoxicity. The clinical emergence of cobalt cardiomyopathy seems to require the coexistence of one or more cofactors, particularly a low-protein diet, thiamine deficiency, alcoholism, and hypothyroidism. As the medicinal use of cobalt has waned and measures to reduce industrial exposure have been implemented, subacute cobalt-related cardiomyopathy had become rare. However, reports describing classical features of the disease have recently surged among patients with a malfunctioning cobalt-alloy hip prosthesis.

In vitro inflammatory effects of hard metal (WC-Co) nanoparticle exposure

Identifying the toxicity of nanoparticles (NPs) is an important area of research as the number of nanomaterial-based consumer and industrial products continually rises. In addition, the potential inflammatory effects resulting from pulmonary NP exposure are emerging as an important aspect of nanotoxicity. In this study, the toxicity and inflammatory state resulting from tungsten carbide–cobalt (WC–Co) NP exposure in macrophages and a coculture (CC) of lung epithelial cells (BEAS-2B) and macrophages (THP-1) at a 3:1 ratio were examined. It was found that the toxicity of nano-WC–Co was cell dependent; significantly less toxicity was observed in THP-1 cells compared to BEAS-2B cells. It was demonstrated that nano-WC–Co caused reduced toxicity in the CC model compared to lung epithelial cell monoculture, which suggested that macrophages may play a protective role against nano-WC–Co-mediated toxicity in CCs. Nano-WC–Co exposure in macrophages resulted in increased levels of interleukin (IL)-1β and IL-12 secretion and decreased levels of tumor necrosis factor alpha (TNFα). In addition, the polarizing effects of nano-WC–Co exposure toward the M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophage phenotypes were investigated. The results of this study indicated that nano-WC–Co exposure stimulated the M1 phenotype, marked by high expression of CD40 M1 macrophage surface markers.

Efficient degradation of carbamazepine by easily recyclable microscaled CuFeO2 mediated heterogeneous activation of peroxymonosulfate

Microscaled CuFeO2 particles (micro-CuFeO2) were rapidly prepared via a microwave-assisted hydrothermal method and characterized by scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. It was found that the micro-CuFeO2 was of pure phase and a rhombohedral structure with size in the range of 2.8±0.6μm. The micro-CuFeO2 efficiently catalyzed the activation of peroxymonosulfate (PMS) to generate sulfate radicals (SO4-), causing the fast degradation of carbamazepine (CBZ). The catalytic activity of micro-CuFeO2 was observed to be 6.9 and 25.3 times that of micro-Cu2O and micro-Fe2O3, respectively. The enhanced activity of micro-CuFeO2 for the activation of PMS was confirmed to be attributed to synergistic effect of surface bonded Cu(I) and Fe(III). Sulfate radical was the primary radical species responsible for the CBZ degradation. As a microscaled catalyst, micro-CuFeO2 can be easily recovered by gravity settlement and exhibited improved catalytic stability compared with micro-Cu2O during five successive degradation cycles. Oxidative degradation of CBZ by the couple of PMS/CuFeO2 was effective in the studied actual aqueous environmental systems.

Inhalation cancer risk assessment of cobalt metal

Cobalt compounds (metal, salts, hard metals, oxides, and alloys) are used widely in various industrial, medical and military applications. Chronic inhalation exposure to cobalt metal and cobalt sulfate has caused lung cancer in rats and mice, as well as systemic tumors in rats. Cobalt compounds are listed as probable or possible human carcinogens by some agencies, and there is a need for quantitative cancer toxicity criteria. The U.S. Environmental Protection Agency has derived a provisional inhalation unit risk (IUR) of 0.009 per μg/m(3) based on a chronic inhalation study of soluble cobalt sulfate heptahydrate; however, a recent 2-year cancer bioassay affords the opportunity to derive IURs specifically for cobalt metal. The mechanistic data support that the carcinogenic mode of action (MOA) is likely to involve oxidative stress, and thus, non-linear/threshold mechanisms. However, the lack of a detailed MOA and use of high, toxic exposure concentrations in the bioassay (≥1.25 mg/m(3)) preclude derivation of a reference concentration (RfC) protective of cancer. Several analyses resulted in an IUR of 0.003 per μg/m(3) for cobalt metal, which is ∼3-fold less potent than the provisional IUR. Future research should focus on establishing the exposure-response for key precursor events to improve cobalt metal risk assessment.

A meta-analysis of carbon nanotube pulmonary toxicity studies--how physical dimensions and impurities affect the toxicity of carbon nanotubes

This article presents a regression-tree-based meta-analysis of rodent pulmonary toxicity studies of uncoated, nonfunctionalized carbon nanotube (CNT) exposure. The resulting analysis provides quantitative estimates of the contribution of CNT attributes (impurities, physical dimensions, and aggregation) to pulmonary toxicity indicators in bronchoalveolar lavage fluid: neutrophil and macrophage count, and lactate dehydrogenase and total protein concentrations. The method employs classification and regression tree (CART) models, techniques that are relatively insensitive to data defects that impair other types of regression analysis: high dimensionality, nonlinearity, correlated variables, and significant quantities of missing values. Three types of analysis are presented: the RT, the random forest (RF), and a random-forest-based dose-response model. The RT shows the best single model supported by all the data and typically contains a small number of variables. The RF shows how much variance reduction is associated with every variable in the data set. The dose-response model is used to isolate the effects of CNT attributes from the CNT dose, showing the shift in the dose-response caused by the attribute across the measured range of CNT doses. It was found that the CNT attributes that contribute the most to pulmonary toxicity were metallic impurities (cobalt significantly increased observed toxicity, while other impurities had mixed effects), CNT length (negatively correlated with most toxicity indicators), CNT diameter (significantly positively associated with toxicity), and aggregate size (negatively correlated with cell damage indicators and positively correlated with immune response indicators). Increasing CNT N2 -BET-specific surface area decreased toxicity indicators.

Loss of hypoxia-inducible factor 2 alpha in the lung alveolar epithelium of mice leads to enhanced eosinophilic inflammation in cobalt-induced lung injury

Hard metal lung disease (HMLD) is an occupational lung disease specific to inhalation of cobalt-containing particles whose mechanism is largely unknown. Cobalt is a known hypoxia mimic and stabilizer of the alpha subunits of hypoxia-inducible factors (HIFs). Previous work revealed that though HIF1α contrib utes to cobalt toxicity in vitro, loss of HIF1α in the alveolar epithelial cells does not provide in vivo protection from cobalt-induced lung inflammation. HIF1α and HIF2α show unique tissue expression profiles, and HIF2α is known to be the predominant HIF mRNA isoform in the adult lung. Thus, if HIF2α activation by cobalt contributes to pathophysiology of HMLD, we hypothesized that loss of HIF2α in lung epithelium would provide protection from cobalt-induced inflammation. Mice with HIF2α-deficiency in Club and alveolar type II epithelial cells (ATIIs) (HIF2α(Δ/Δ)) were exposed to cobalt (60 µg/day) or saline using a subacute occupational exposure model. Bronchoalveolar lavage cellularity, cytokines, qRT-PCR, and histopathology were analyzed. Results show that loss of HIF2α leads to enhanced eosinophilic inflammation and increased goblet cell metaplasia. Additionally, control mice demonstrated a mild recovery from cobalt-induced lung injury compared with HIF2α(Δ/Δ) mice, suggesting a role for epithelial HIF2α in repair mechanisms. The expression of important cytokines, such as interleukin (IL)-5 and IL-10, displayed significant differences following cobalt exposure when HIF2α(Δ/Δ) and control mice were compared. In summary, our data suggest that although loss of HIF2α does not afford protection from cobalt-induced lung inflammation, epithelial HIF2α signaling does play an important role in modulating the inflammatory and repair response in the lung.

Intolerability of cobalt salt as erythropoietic agent

Unfair athletes seek ways to stimulate erythropoiesis, because the mass of haemoglobin is a critical factor in aerobic sports. Here, the potential misuse of cobalt deserves special attention. Cobalt ions (Co(2+) ) stabilize the hypoxia-inducible transcription factors (HIFs) that increase the expression of the erythropoietin (Epo) gene. Co(2+) is orally active, easy to obtain, and inexpensive. However, its intake can bear risks to health. To elaborate this issue, a review of the pertinent literature was retrieved by a search with the keywords 'anaemia', 'cobalt', 'cobalt chloride', 'erythropoiesis', 'erythropoietin', 'Epo', 'side-effects' and 'treatment', amongst others. In earlier years, cobalt chloride was administered at daily doses of 25 to 300 mg for use as an anti-anaemic agent. Co(2+) therapy proved effective in stimulating erythropoiesis in both non-renal and renal anaemia, yet there were also serious medical adverse effects. The intake of inorganic cobalt can cause severe organ damage, concerning primarily the gastrointestinal tract, the thyroid, the heart and the sensory systems. These insights should keep athletes off taking Co(2+) to stimulate erythropoiesis.

Evaluation of metal ion release from Ti6Al4V and Co-Cr-Mo casting alloys: in vivo and in vitro study

PURPOSE

The aim of this study was to evaluate the amount of ions released from Ti6Al4V and Co-Cr-Mo alloys both in vivo and in vitro.

MATERIALS AND METHODS

Twenty-one discs of each alloy were constructed and divided into seven groups. Three specimens from each group were immersed in a buffered saline solution over a period of 1, 3, 5, 7, 14, 21, and 28 days. Twenty-eight participants were also included in the study, where the study group consisted of 14 mandibular partially edentulous patients, and the control group consisted of 14 volunteers. The study group was further divided into two equal groups: the first group received removable partial dentures (RPDs) constructed from Co-Cr-Mo alloy, while the second group received RPDs constructed from Ti6Al4V alloy. Saliva samples were collected from each participant over the same study period. The conditioning media and saliva samples were analyzed using a spectrophotometer. One-way ANOVA and Tukey tests were used for statistical analysis (p < 0.05).

RESULTS

The concentrations of metal ions released from the studied alloys were significantly higher in the in vitro than in the in vivo study group during the follow-up periods. A statistically significant increase in ion concentrations of the different elements for both alloys was found with time (p < 0.05).

CONCLUSION

The amounts of released metallic ions from Co-Cr-Mo and Ti6Al4V alloys were higher in the buffered saline solutions than in the studied saliva samples and control groups; however, these amounts were still within the physiological limit of trace elements in the human body.

Apoptosis induced by tungsten carbide-cobalt nanoparticles in JB6 cells involves ROS generation through both extrinsic and intrinsic apoptosis pathways

In this study, apoptosis and related signaling induced by WC-Co nanoparticles were investigated in JB6 cells and rat lung macrophages. Electron spin resonance (ESR) and fluorescent staining indicated that both WC-Co nanoparticles and fine particles stimulated reactive oxygen species (ROS) generation. Catalase exhibited an inhibitory effect on WC-Co nanoparticle-induced ROS as well as mitochondrial membrane permeability damage. Further study indicated that WC-Co nanoparticles elicited higher cytotoxicity and apoptotic induction than fine particles. Western blot analysis showed activation of proapoptotic factors including Fas, Fas-associated protein with death domain (FADD), caspase 3, 8 and 9, BID and BAX. In addition, both cytochrome c and apoptosis-inducing factor (AIF) were upregulated and released from mitochondria to the cytoplasm. Our findings demonstrate that, on a mass basis, WC-Co nanoparticles exhibit higher cytotoxicity and apoptotic induction than fine particles. Apoptosis induced by WC-Co nanoparticles and fine particles involves both extrinsic and intrinsic apoptosis pathways.

Lung function and respiratory symptoms in hard metal workers exposed to cobalt

OBJECTIVE

To follow-up lung function and airway symptoms in workers exposed to cobalt dust at a hard metal plant.

METHODS

A total of 582 employees underwent spirometry and completed a questionnaire. A historical exposure matrix was created, assigning figures for historical and recent work-related exposure.

RESULTS

At the time of employment, 5% reported symptoms from respiratory tract. At follow-up, 5% suffered from persistent coughing and 7% reported asthma; 20% were daily smokers. Among nonsmokers without asthma, an evident, statistically nonsignificant, dose-response effect was seen between increasing cobalt exposure and decline in FEV1 (forced expiratory volume in the first second). In all exposure categories, the FEV1 in smokers declined 10 mL more per year than for nonsmokers.

CONCLUSIONS

Even low levels of cobalt exposure seem to hamper lung function both in smokers and nonsmokers. This impact is considered low in relation to the effect of aging.

Divergent effect of cobalt and beryllium salts on the fate of peripheral blood monocytes and T lymphocytes

Occupational exposure to metals such as cobalt and beryllium represents a risk factor for respiratory health and can cause immune-mediated diseases. However, the way they act may be different. We show here that the two metals have a divergent effect on peripheral T lymphocytes and monocytes: BeSO(4) induces cell death in monocytes but not in T lymphocytes, which instead respond by producing Interferon gamma (IFN-γ); conversely, CoCl(2) induces apoptosis in T lymphocytes but not in monocytes. Interestingly, both metals induce p53 overexpression but with a dramatic different outcome. This is because the effect of p53 in CoCl(2)-treated monocytes is counteracted by the antiapoptotic activity of cytoplasmic p21(Cip1/WAF1), the activation of nuclear factor κB, and the inflammasome danger signaling pathway leading to the production of proinflammatory cytokines. However, CoCl(2)-treated monocytes do not fully differentiate into macrophage or dendritic cells, as inferred by the lack of expression of CD16 and CD83, respectively. Furthermore, the expression of HLA-class II molecules, as well as the capability of capturing and presenting the antigens, decreased with time. In conclusion, cobalt keeps monocytes in a partially activated, proinflammatory state that can contribute to some of the pathologies associated with the exposure to this metal.

Reactive oxygen species and oxidative DNA damage mediate the cytotoxicity of tungsten-nickel-cobalt alloys in vitro

Tungsten alloys (WA) have been introduced in an attempt to find safer alternatives to depleted uranium and lead munitions. However, it is known that at least one alloy, 91% tungsten-6% nickel-3% cobalt (WNC-91-6-3), causes rhabdomyosarcomas when fragments are implanted in rat muscle. This raises concerns that shrapnel, if not surgically removable, may result in similar tumours in humans. There is therefore a clear need to develop rapid and robust in vitro methods to characterise the toxicity of different WAs in order to identify those that are most likely to be harmful to human health and to guide development of new materials in the future. In the current study we have developed a rapid visual in vitro assay to detect toxicity mediated by individual WA particles in cultured L6-C11 rat muscle cells. Using a variety of techniques (histology, comet assay, caspase-3 activity, oxidation of 2'7'-dichlorofluorescin to measure the production of reactive oxygen species and whole-genome microarrays) we show that, in agreement with the in vivo rat carcinogenicity studies, WNC-91-6-3 was the most toxic of the alloys tested. On dissolution, it produces large amounts of reactive oxygen species, causes significant amounts of DNA damage, inhibits caspase-3, triggers a severe hypoxic response and kills the cells in the immediate vicinity of the alloy particles within 24h. By combining these in vitro data we offer a mechanistic explanation of the effect of this alloy in vivo and show that in vitro tests are a viable alternative for assessing new alloys in the future.

Acute cobalt-induced lung injury and the role of hypoxia-inducible factor 1alpha in modulating inflammation

Air pollution is a critical factor in the development and exacerbation of pulmonary diseases. Ozone, automobile exhaust, cigarette smoke, and metallic dust are among the potentially harmful pollution components that are linked to disease progression. Transition metals, such as cobalt, have been identified at significant levels in air pollution. Cobalt exerts numerous biological effects, including mimicking hypoxia. Similar to hypoxia, cobalt exposure results in the stabilization of hypoxia-inducible factors (HIFs), a family of proteins that regulate the cellular response to oxygen deficit. HIFs also play an important role in innate immunity and inflammatory processes. To characterize the role of HIF1alpha, the most ubiquitously expressed HIF, in the early events during cobalt-induced lung inflammation, an inducible lung-specific HIF1alpha deletion model was employed. Control mice showed classical signs of metal-induced injury following cobalt exposure, including neutrophilic infiltration and induction of Th1 cytokines. In contrast, HIF1alpha-deficient mice exhibited pronounced eosinophil counts in bronchoalveolar lavage fluid and lung tissue complemented with Th2 cytokine induction. The timing of these results suggests that the loss of epithelial-derived HIF1alpha alters the lung's innate immune response and biases the tissue toward a Th2-mediated inflammation.

Toxicity of tungsten carbide and cobalt-doped tungsten carbide nanoparticles in mammalian cells in vitro

BACKGROUND

Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration.

OBJECTIVE

We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobalt-doped tungsten carbide (WC-Co) nanoparticle suspensions in an array of mammalian cells.

METHODS

We examined acute toxicity of WC and of WC-Co (10% weight content Co) nanoparticles in different human cell lines (lung, skin, and colon) as well as in rat neuronal and glial cells (i.e., primary neuronal and astroglial cultures and the oligodendrocyte precursor cell line OLN-93). Furthermore, using electron microscopy, we assessed whether nanoparticles can be taken up by living cells. We chose these in vitro systems in order to evaluate for potential toxicity of the nanoparticles in different mammalian organs (i.e., lung, skin, intestine, and brain).

RESULTS

Chemical-physical characterization confirmed that WC as well as WC-Co nanoparticles with a mean particle size of 145 nm form stable suspensions in serum-containing cell culture media. WC nanoparticles were not acutely toxic to the studied cell lines. However, cytotoxicity became apparent when particles were doped with Co. The most sensitive were astrocytes and colon epithelial cells. Cytotoxicity of WC-Co nanoparticles was higher than expected based on the ionic Co content of the particles. Analysis by electron microscopy demonstrated presence of WC nanoparticles within mammalian cells.

CONCLUSIONS

Our findings demonstrate that doping of WC nanoparticles with Co markedly increases their cytotoxic effect and that the presence of WC-Co in particulate form is essential to elicit this combinatorial effect.

Comparison between exhaled breath condensate analysis as a marker for cobalt and tungsten exposure and biomonitoring in workers of a hard metal alloy processing plant

OBJECTIVE

Cobalt (Co), Tungsten (W) and Tungsten Carbides (WC) are major constituents of hard metal alloys. Whereas little is known about potential health hazards due to tungsten carbide exposure, occupational exposure to cobalt has been shown to induce a variety of respiratory diseases. Since the concentration of a potentially hazardous substance in the target organ is the most meaningful risk indicator in occupational medicine, the detection of hard metals in exhaled breath condensate (EBC) has been proposed to be a valuable instrument. The present study examines the correlation of Co and W concentrations in EBC and urine with one another and various spirometrical and clinical parameters to scrutinize this potential.

METHODS

A total of 62 subjects (90.3% males, age 40.6 +/- 9.2 years) were recruited from a hard metal processing plant in Germany. Examinations included the airborne workplace exposure, a complete spirometry, measurements of Co and W concentrations in EBC and urine with high resolution inductive coupled plasma mass spectrometry (HR ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS).

RESULTS

Air concentrations ranged between 0.0019 mg/m(3) and 0.074 mg/m(3) for Co and 0.012 mg/m(3) and 0.021 mg/m(3) for W. Median urine concentrations and interquartile ranges of the exposed subjects ranged from 0.81 (0.0-1.46) microg/l for Co and 30.5 (14.5-57.7) microg/l for W. Median breath condensate metal concentrations and interquartile ranges ranged from 8.4 (5.0-13.9) microg/l for Co and 8.8 (4.4-18.5) microg/l for W. Urine concentrations of Co and W were closely related to the airborne workplace exposure that had been assessed by air monitoring. EBC concentrations of Co and W showed no correlations to urinary W and Co concentrations and the ambient monitoring results of the individual workplace, respectively. Cobalt EBC concentration was elevated in subjects who reported to have suffered from respiratory disease; both Co and W concentrations in EBC, however, decreased with increasing spirometrical signs of obstruction.

CONCLUSION

According to our study, urinary concentrations of Co and W seem to be more reliable indicators of current workplace exposure than EBC concentrations. As far as new methods and exposure matrices for valid concentration measurements in respiratory organs and possible hazardous effects--especially of cobalt--in the lung are concerned, the present results are less clear-cut, and further research is required.

The oxidation of glutathione by cobalt/tungsten carbide contributes to hard metal-induced oxidative stress

The occupational exposure to cobalt/tungsten carbide (Co/WC) dusts causes asthma and interstitial fibrosis. The International Agency for Research on Cancer (IARC) recently classified the mixture Co/WC as probably carcinogenic to humans (group 2A). The mechanism of action of Co/WC involves particle driven generation of Reactive Oxygen Species (ROS) with consequent oxidative damage. The present study evaluates the reactivity of Co/WC dust toward glutathione (GSH) and cysteine (Cys). Co/WC oxidized thiols through a mechanism involving the generation of sulphur-centred radicals. The results are consistent with the oxidation taking place at surface active sites, a part of which is accessible only to Cys S-H groups, but not to GSH ones. Such a reaction, with consequent irreversible depletion of antioxidant defenses of cells, will potentiate the oxidative stress caused by particle and cell generated ROS.

Assessment of aerosol (PM10) and trace elemental interactions by Taguchi experimental design approach

An attempt has been made to assess the trace elemental interactions of atmospheric aerosol through Taguchi orthogonal array (OA) experimental design (DOE) approach. Seven toxic trace metals (Cu, Cd, As, Pb, Cr, Co and Ni) along with aerosol mass (PM(10)) at three different concentration levels were considered for this study. The annual mean concentrations of PM(10) and its trace components observed at Tirupati, southern peninsular India, and 50% lower and 50% higher values to the permissible exposure limit (PEL) of each factor in air were considered for level 1, level 2, and level 3 respectively. Interactions between the factors have been estimated by orthogonal array design of experiments with eighteen sets of experimental trial (L18) and varied combinations of factor levels.

In vitro expression of hard metal dust (WC-Co)--responsive genes in human peripheral blood mononucleated cells

Hard metals consist of tungsten carbide (WC) and metallic cobalt (Co) particles and are important industrial materials produced for their extreme hardness and high wear resistance properties. While occupational exposure to metallic Co alone is apparently not associated with an increased risk of cancer, the WC-Co particle mixture was shown to be carcinogenic in exposed workers. The in vitro mutagenic/apoptogenic potential of WC-Co in human peripheral blood mononucleated cells was previously demonstrated by us. This study aimed at obtaining a broader view of the pathways responsible for WC-Co induced carcinogenicity, and in particular genotoxicity and apoptosis. We analyzed the profile of gene expression induced in vitro by WC-Co versus control (24 h treatment) in human PBMC and monocytes using microarrays. The most significantly up-regulated pathways for WC-Co treated PBMC were apoptosis and stress/defense response; the most down-regulated was immune response. For WC-Co treated monocytes the most significantly up- and down-regulated pathways were nucleosome/chromatin assembly and immune response respectively. Quantitative RT-PCR data for a selection of the most strongly modulated genes (HMOX1, HSPA1A, HSPA1L, BNIP3, BNIP3L, ADORA2B, MT3, PLA2G7, TNFAIP6), and some additionally chosen apoptosis related genes (BCL2, BAX, FAS, FASL, TNFalpha), confirmed the microarray data after WC-Co exposure and demonstrated limited differences between the Co-containing compounds. Overall, this study provides the first analysis of gene expression induced by the WC-Co mixture showing a large profile of gene modulation and giving a preliminary indication for a hypoxia mimicking environment induced by WC-Co exposure.

Two-dimensional Analysis of Elements and Mononuclear Cells in Hard Metal Lung Disease

RATIONALE

Hard metal lung disease is caused by exposure to hard metal, a synthetic compound that combines tungsten carbide with cobalt as well as a number of other metals. Interstitial lung disease caused by hard metal is uniquely characterized by giant cell interstitial pneumonia. The pathogenesis of hard metal lung disease is unclear.

OBJECTIVES

To elucidate the distribution of inhaled hard metal and reactive inflammatory cells in biopsy lung tissue from patients with hard metal lung disease.

METHODS

Seventeen patients with interstitial lung disease in which tungsten was detected and five control subjects were studied. Detection and mapping of elements were performed with an electron probe microanalyzer equipped with a wavelength dispersive spectrometer. We immunohistochemically stained mononuclear cells, in tissue samples available from five patients, with anti-human CD4, CD8, CD20, CD68, and CD163 antibodies, and compared the distribution of positive cells with hard metal elements.

MEASUREMENTS AND MAIN RESULTS

Thirteen of 17 patients were pathologically diagnosed as having giant cell interstitial pneumonia. Tungsten and cobalt were accumulated in the centrilobular fibrotic lesions, but were never found in the control lungs. CD8+ lymphocytes and CD163+ monocyte-macrophages were distributed predominantly in centrilobular fibrotic lesions around the hard metal elements. CD163+ colocalized with tungsten. Small numbers of CD8+ and CD163+ cells were also immunohistochemically shown in peribronchiolar areas and alveolar walls.

CONCLUSIONS

Macrophages may phagocytose inhaled tungsten via CD163 and play an important role in forming the fibrotic lesion of hard metal lung disease with cytotoxic T lymphocytes.

[Interstitial pulmonary diseases]

Interstitial pneumonia is a rare disease, posing a diagnostic challenge to pneumologists, pediatricians, radiologists and pathologists. Only by the combined efforts of the European Respiratory Society (ERS) and the American Thoracic Society (ATS) has has been possible to standardize the formerly different European and Northern American nomenclature of interstitial lung diseases (alveolitis versus interstitial pneumonia) in adults and to clearly and unambiguously define the diagnostic criteria. The ATS/ERS classification of 2002 comprises seven entities: usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), cryptogenic organizing pneumonia (COP), lymphocyte interstitial pneumonia (LIP), and acute interstitial pneumonia (AIP). Using the ATS/ERS classification of interstitial pulmonary diseases in premature infants, infants and children is problematic, since UIP, RB-ILD and AIP do not occur at this age. Although infants with severe respiratory insufficiency may sometimes show morphological features similar to DIP or NSIP, this entity should rather be classified as chronic pneumonitis of infancy (CPI) because of differences in etiology, pathogenesis and prognostic outcome.