Occupational Exposure to Metals and Solvents: Allergy and Airway Diseases

A Critical Review of the Hydrometallurgy and Pyrometallurgical Recovery Processes of Platinum Group Metals from End-of-Life Fuel Cells

Recently, the recovery of metals extracted from the spent membrane electrode assemblies (MEAs) of fuel cells has attracted significant scientific attention due to its detrimental environmental impacts. Two major approaches, i.e., pyrometallurgical and hydrometallurgical, have been explored to recover platinum group metals (PMGs) from used proton exchange membrane fuel cells (PEMFCs). However, the efficacy of these methods has been limited by the low concentrations of the metals and the high costs involved. Essentially, pyrometallurgical processes result in the evolution of harmful gases. Thus, the hydrometallurgical process is preferred as a suitable alternative. In this review, an overview of the application of pyrometallurgical and hydrometallurgical methods in the recovery of PGMs is presented. The health risks, benefits, and limitations of these processes are highlighted. Finally, the hurdles faced by, opportunities for, and future directions of these approaches are identified. It is envisaged that this review will shed light on the current status of processes for the recovery of spent PGMs and propel their advancement for effective recycling strategies.

Advancing analytical and graphical methods for binary and ternary mixtures: The toxic interactions of divalent metal ions in human lung cells

Humans are exposed to various environmental chemicals, particles, and pathogens that can cause adverse health outcomes. These exposures are rarely homogenous but rather complex mixtures in which the components may interact, such as through synergism or antagonism. Toxicologists have conducted preliminary investigations into binary mixtures of two components, but little work has been done to understand mixtures of three or more components. We investigated mixtures of divalent metal ions, quantifying the toxic interactions in a human lung model. Eight metals were chosen: heavy metals cadmium, copper, lead, and tin, as well as transition metals iron, manganese, nickel, and zinc. Human alveolar epithelial cells (A549) were exposed to individual metals and sixteen binary and six ternary combinations. The dose-response was modeled using logistic regression in R to extract LC50 values. Among the individual metals, the highest and lowest toxicity were observed with copper at an LC50 of 102 μM and lead at an LC50 of 5639 μM, respectively. First and second-order interaction coefficients were obtained using machine learning-based linear regression in Python. The resulting second-degree polynomial model formed either a hyperbolic or elliptical conic section, and the positive quadrant was used to produce isobolograms and contour plots. The strongest synergism and antagonism were observed in cadmium-copper and iron-zinc, respectively. A three-way interaction term was added to produce full ternary isobologram surfaces, which, to our knowledge, are a significant first in the toxicology literature.

Occupational agents-mediated asthma: From the perspective of autophagy

Occupational asthma (OA) is a common occupational pulmonary disease that is frequently underdiagnosed and underreported. The complexity of diagnosing and treating OA creates a significant social and economic burden, making it an important public health issue. In addition to avoiding allergens, patients with OA require pharmacotherapy; however, new therapeutic targets and strategies need further investigation. Autophagy may be a promising intervention target, but there is a lack of relevant studies summarizing the role of autophagy in OA. In this review consolidates the current understanding of OA, detailing principal and novel agents responsible for its onset. Additionally, we summarize the mechanisms of autophagy in HMW and LMW agents induced OA, revealing that occupational allergens can induce autophagy disorders in lung epithelial cells, smooth muscle cells, and dendritic cells, ultimately leading to OA through involving inflammatory responses, oxidative stress, and cell death. Finally, we discuss the prospects of targeting autophagy as an effective strategy for managing OA and even steroid-resistant asthma, encompassing autophagy interventions focused on organoids, organ-on-a-chip systems, nanomaterials vehicle, and nanobubbles; developing combined exposure models, and the role of non-classical autophagy in occupational asthma. In briefly, this review summarizes the role of autophagy in occupational asthma, offers a theoretical foundation for OA interventions based on autophagy, and identifies directions and challenges for future research.

Occupational exposure to organic solvents and risk of bladder cancer

BACKGROUND

Bladder cancer has been linked to several occupations that involve the use of solvents, including those used in the dry-cleaning industry.

OBJECTIVES

We evaluated exposure to solvents and risk of bladder cancer in 1182 incident cases and 1408 controls from a population-based study.

METHODS

Exposure to solvents was quantitatively assessed using a job-exposure matrix (CANJEM). Exposure to benzene, toluene and xylene often co-occur. Therefore, we created two additional sets of metrics for combined benzene, toluene and xylene (BTX) exposure: (1) CANJEM-based BTX metrics and (2) hybrid BTX metrics, using an approach that integrates the CANJEM-based BTX metrics together with lifetime occupational histories and exposure-oriented modules that captured within-job, respondent-specific details about tasks and chemicals. Adjusted odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated using logistic regression.

RESULTS

Bladder cancer risks were increased among those ever exposed to benzene (OR = 1.63, 95% CI: 1.14-2.32), toluene (OR = 1.60, 95% CI: 1.06-2.43), and xylene (OR = 1.67, 95% CI: 1.13-2.48) individually. We further observed a statistically significant exposure-response relationship for cumulative BTX exposure, with a stronger association using the hybrid BTX metrics (ORQ1vsUnexposed = 1.26, 95% CI: 0.83-1.90; ORQ2vsUnexposed = 1.52, 95% CI: 1.00-2.31; ORQ3vsUnexposed = 1.88, 95% CI: 1.24-2.85; and ORQ4vsUnexposed = 2.23, 95% CI: 1.35-3.69) (p-trend=0.001) than using CANJEM-based metrics (p-trend=0.02).

IMPACT

There is limited evidence about the role of exposure to specific organic solvents, alone or in combination on the risk of developing bladder cancer. In this study, workers with increasing exposure to benzene, toluene, and xylene as a group (BTX) had a statistically significant exposure-response relationship with bladder cancer. Future evaluation of the carcinogenicity of BTX and other organic solvents, particularly concurrent exposure, on bladder cancer development is needed.

[Unmet Needs in Severe Allergic Asthma]

Severe asthma affects 3%-10% of the world's population, according to estimates by the Global Initiative for ASTHMA (GINA). Allergic asthma is one of the most common phenotypes of severe asthma and it is characterized by allergen-induced type 2 inflammation in which immunoglobulin E (IgE) is a key mediator, making it an important therapeutic target. The introduction of targeted biological therapies or treatments has entered the management for severe asthma in the era of precision medicine, and the goal of treatment is clinical remission of the disease. There is a significant percentage of patients with severe allergic asthma who do not respond to treatments and whose symptoms are not controlled. In this paper, a group of experts in the management of severe allergic asthma reviewed and evaluated the most relevant evidence regarding the pathophysiology and phenotypes of severe allergic asthma, the role of IgE in allergic inflammation, allergen identification, techniques, biomarkers and diagnostic challenges, available treatments and strategies for disease management, with a special focus on biological treatments. From this review, recommendations were developed and validated through a Delphi consensus process with the aim of offering improvements in the management of severe allergic asthma to the professionals involved and identifying the unmet needs in the management of this pathology.

Adverse Human Health Effects of Chromium by Exposure Route: A Comprehensive Review Based on Toxicogenomic Approach

Heavy metals are defined as metals with relatively high density and atomic weight, and their various applications have raised serious concerns about the environmental impacts and potential human health effects. Chromium is an important heavy metal that is involved in biological metabolism, but Cr exposure can induce a severe impact on occupational workers or public health. In this study, we explore the toxic effects of Cr exposure through three exposure routes: dermal contact, inhalation, and ingestion. We propose the underlying toxicity mechanisms of Cr exposure based on transcriptomic data and various bioinformatic tools. Our study provides a comprehensive understanding of the toxicity mechanisms of different Cr exposure routes by diverse bioinformatics analyses.

Occupational Asthma Caused by Low-Molecular-Weight Chemicals Associated With Contact Dermatitis: A Retrospective Study

BACKGROUND

Occupational asthma (OA) may have different etiologies, but it is not clear whether the etiologic agents influence the clinical presentation, especially the co-occurrence of skin lesions.

OBJECTIVE

To determine the impact of different asthmagens on the characteristics of OA, with a focus on the occurrence of prior or concomitant skin disorders.

METHODS

In a retrospective analysis of patients who visited the Occupational and Environmental Disease Clinic of a tertiary referral hospital from 2009 to 2019, we classified patients into definite, probable, or possible OA according to prespecified diagnostic guidelines. In multivariate logistic regression with sensitivity analysis, we examined the relation of high- and low-molecular-weight (HMW and LMW) agents with the clinical presentation.

RESULTS

Of 209 cases of OA, 66 were caused by HMW agents and 143 by LMW agents. Patients with OA exposed to LMW agents had higher odds of having (had) allergic contact dermatitis (odds ratio, 5.45 [1.80-23.70]; P < .01), compared with patients exposed to HMW agents. Conversely, HMW agents were associated with higher odds of rhinitis symptoms (odds ratio of LMW/HMW, 0.33 [0.17-0.63]; P < .001) and high total IgE (odds ratio of LMW/HMW, 0.35 [0.17-0.70]; P < .01). Risk factors for having coexisting contact dermatitis included construction work, hairdressing, and exposure to metals or epoxy resins.

CONCLUSIONS

Among patients with OA, exposure to specific LMW agents was associated with a high frequency of contact dermatitis. Different types of asthmagens within HMW or LMW agents appear to determine the phenotype and comorbidity of OA.

A comprehensive summary of disease variants implicated in metal allergy

Allergic disease represents one of the most prominent global public health crises of the 21^st century. Although many different substances are known to produce hypersensitivity responses, metals constitute one of the major classes of allergens responsible for a disproportionately large segment of the total burden of disease associated with allergy. Some of the most prevalent forms of metal allergy - including allergic contact dermatitis - are well-recognized; however, to our knowledge, a comprehensive review of the many unique disease variants implicated in human cases of metal allergy is not available within the current scientific literature. Consequently, the main goal in composing this review was to (1) generate an up-to-date reference document containing this information to assist in the efforts of lab researchers, clinicians, regulatory toxicologists, industrial hygienists, and other scientists concerned with metal allergy and (2) identify knowledge gaps related to disease. Accordingly, an extensive review of the scientific literature was performed - from which, hundreds of publications describing cases of metal-specific allergic responses in human patients were identified, collected, and analyzed. The information obtained from these articles was then used to compile an exhaustive list of distinctive dermal/ocular, respiratory, gastrointestinal, and systemic hypersensitivity responses associated with metal allergy. Each of these disease variants is discussed briefly within this review, wherein specific metals implicated in each response type are identified, underlying immunological mechanisms are summarized, and major clinical presentations of each reaction are described.Abbreviations: ACD: allergic contact dermatitis, AHR: airway hyperreactivity, ASIA: autoimmune/ autoinflammatory syndrome induced by adjuvants, BAL: bronchoalveolar lavage, CBD: chronic beryllium disease, CTCL: cutaneous T-cell lymphoma, CTL: cytotoxic T-Lymphocyte, DRESS: drug reaction with eosinophilia and systemic symptoms, GERD: gastro-esophageal reflux disease, GI: gastrointestinal, GIP: giant cell interstitial pneumonia, GM-CSF: granulocyte macrophage-colony stimulating factor, HMLD: hard metal lung disease, HMW: high molecular weight, IBS: irritable bowel syndrome, Ig: immunoglobulin, IL: interleukin, LMW: low molecular weight, PAP: pulmonary alveolar proteinosis, PPE: personal protective equipment, PRR: pathogen recognition receptor, SLE: systemic lupus erythematosus, SNAS: systemic nickel allergy syndrome, Th: helper T-cell, UC: ulcerative colitis, UV: ultraviolet.

Metal biomonitoring using fractioned dust to investigate urinary and oxidative stress biomarkers among occupationally exposed chromite mine workers

Exposure to heavy metals has been associated with the generation of reactive oxygen species (ROS) among exposed individuals in occupational and environmental settings. Dust is considered a significant contributor to airborne metal exposure, and previous data suggest that their levels in dust may vary based on its particle sizes. However, no biomonitoring study has been reported so far to address the metal-induced oxidative stress using different dust fractions, particularly in occupational settings. We designed a systematic cross-sectional study involving 110 chromite mine workers stratified into loaders (n = 28), extractors (n = 47) and operators (n = 35), and controls (n = 30) to find out the association between dust-bound metal exposure and oxidative stress using urinary creatinine-adjusted metal level as a biomarker of metal exposure. Results suggested elevated urinary levels of Cr 51.34 ± 8.6 along with Pb 34.29 ± 4.39, Cd 21.1 ± 2.6, and Ni 18.98 ± 3.01 µg/g creatinine in exposed (extractor group) workers. Correlating metal levels with oxidative stress revealed elevated malondialdehyde (MDA) levels of 62.28 ± 5.52 nM/dl among the extractors showing high levels of lipid peroxidation. Furthermore, blood superoxide dismutase (SOD) was also found significantly correlated (P = 0.000) with urinary toxic metal levels among exposed workers. We report the association between metal exposure and oxidative stress in exposed mining workers that may give rise to workers' susceptibility towards genetic and non-genetic health implications. The current study emphasized on the need for exposure control measures in the chromite ore mining activity areas.

Release of Interleukin-1β evaluation among mineral oil mist–exposed workers

Exposure to aerosols has been found to be linked to respiratory impairment. Although the effects of both indoor and outdoor exposures to particulates have been extensively reported, exposures to mists are less studied. Herein, we reported a survey of mineral oil mist toxicity in an occupational exposure scenario. For the purpose of this study, 65 lathe workers of the metal processing industry, as mineral oil mist–exposed population, were studied. Thereafter, the participants’ age, smoking habits and work experience were matched with those of the control workers ( n = 65) who were not occupationally exposed to mist. Thereafter, air samples were evaluated from the breathing zone of the workers using NIOSH method 5026. Plasma Interleukin-1β as a pro-inflammatory indicator was assessed in all the studied subjects. Mean ± standard deviation of mineral oil mist time-weighted average exposure in lathe workers was 7.10± 3.49 mg/m3. IL-1β cytokine levels were significantly higher in the lathe groups compared to the control group. The mean level of Interleukin-1β in the control subjects (2922 pg/L) was selected as the cut-off point of the inflammation effect. Based on this pro-inflammatory point, the results of monitoring showed that 60% of the exposed were affected. A Spearman correlation was also found between mineral oil mist exposure and inflammation in the affected subjects. Our findings highlighted the immunological potential of mineral oil mist in occupational exposure. Overall, the results of this study suggested that Interleukin-1β evaluation in mineral oil mist exposure could be considered as both an acute and chronic inflammation marker.

Occupational Exposures to Organic Solvents and Asthma Symptoms in the CONSTANCES Cohort

Solvents are used in many workplaces and may be airway irritants but few studies have examined their association with asthma. We studied this question in CONSTANCES (cohort of ‘CONSulTANts des Centres d’Examens de Santé’), a large French cohort. Current asthma and asthma symptom scores were defined by participant-reported respiratory symptoms, asthma medication or attacks, and the sum of 5 symptoms, in the past 12 months, respectively. Lifetime exposures to 5 organic solvents, paints and inks were assessed by questionnaire and a population-based Job-Exposure Matrix (JEM). Cross-sectional associations between exposures and outcomes were evaluated by gender using logistic and negative binomial regressions adjusted for age, smoking habits and body mass index. Analyses included 115,757 adults (54% women, mean age 47 years, 9% current asthma). Self-reported exposure to ≥1 solvent was significantly associated with current asthma in men and women, whereas using the JEM, a significant association was observed only in women. Significant associations between exposures to ≥1 solvent and asthma symptom score were observed for both self-report (mean score ratio, 95%CI, women: 1.36, 1.31–1.42; men: 1.34, 1.30–1.40) and JEM (women: 1.10, 1.07–1.15; men: 1.14, 1.09–1.18). Exposure to specific solvents was significantly associated with higher asthma symptom score. Occupational exposure to solvents should be systematically sought when caring for asthma.

Work-related asthma

Work-related asthma (WRA) is highly prevalent in the adult population. WRA includes occupational asthma (OA), which is asthma caused by workplace exposures, and work-exacerbated asthma (WEA), also known as work-aggravated asthma, which is preexisting or concurrent asthma worsened by workplace conditions. In adults, the estimated prevalence of OA is 16.0%, whereas that of WEA is 21.5%. An increasing number of chemicals used in industrial production, households, and services are associated with the incidence of adult-onset asthma attributable to exposure to chemicals. This review article summarizes the different types of WRA and describes diagnostic procedures, treatment, prevention, and approaches to patient management. It is not always easy to distinguish between OA and WEA. It is important to establish a diagnosis (of sensitizer-/irritant-induced OA or WEA) in order to prevent worsening of symptoms, as well as to prevent other workers from being exposed, by providing early treatment and counseling on social security and work-related issues.

Molecular Insights of Nickel Binding to Therapeutic Antibodies as a Possible New Antibody Superantigen

The binding of nickel by immune proteins can manifest as Type IV contact dermatitis (Ni-specific T cells mediated) and less frequently as Type I hypersensitivity with both mechanisms remaining unknown to date. Since there are reports of patients co-manifesting the two hypersensitivities, a common mechanism may underlie both the TCR and IgE nickel binding. Focusing on Trastuzumab and Pertuzumab IgE variants as serendipitous investigation models, we found Ni-NTA interactions independent of Her2 binding to be due to glutamine stretches. These stretches are both Ni-inducible and in fixed pockets at the antibody complementarity-determining regions (CDRs) and framework regions (FWRs) of both the antibody heavy and light chains with influence from the heavy chain constant region. Comparisons with TCRs structures revealed similar interactions, demonstrating the possible underlying mechanism in selecting for Ni-binding IgEs and TCRs respectively. With the elucidation of the interaction, future therapeutic antibodies could also be sagaciously engineered to utilize such nickel binding for biotechnological purposes.

Contact dermatitis

Contact dermatitis (CD) is among the most common inflammatory dermatological conditions and includes allergic CD, photoallergic CD, irritant CD, photoirritant CD (also called phototoxic CD) and protein CD. Occupational CD can be of any type and is the most prevalent occupational skin disease. Each CD type is characterized by different immunological mechanisms and/or requisite exposures. Clinical manifestations of CD vary widely and multiple subtypes may occur simultaneously. The diagnosis relies on clinical presentation, thorough exposure assessment and evaluation with techniques such as patch testing and skin-prick testing. Management is based on patient education, avoidance strategies of specific substances, and topical treatments; in severe or recalcitrant cases, which can negatively affect the quality of life of patients, systemic medications may be needed.