Evaluation of workers exposed to dust containing hard metals and aluminum oxide

Critical Review on Toxicological Mechanisms Triggered by Inhalation of Alumina Nanoparticles on to the Lungs

Alumina nanoparticles (Al₂O₃ NPs) can be released in occupational environments in different contexts such as industry, defense, and aerospace. Workers can be exposed by inhalation to these NPs, for instance, through welding fumes or aerosolized propellant combustion residues. Several clinical and epidemiological studies have reported that inhalation of Al₂O₃ NPs could trigger aluminosis, inflammation in the lung parenchyma, respiratory symptoms such as cough or shortness of breath, and probably long-term pulmonary fibrosis. The present review is a critical update of the current knowledge on underlying toxicological, molecular, and cellular mechanisms induced by exposure to Al₂O₃ NPs in the lungs. A major part of animal studies also points out inflammatory cells and secreted biomarkers in broncho-alveolar lavage fluid (BALF) and blood serum, while in vitro studies on lung cells indicate contradictory results regarding the toxicity of these NPs.

Mouse pulmonary response to dust from sawing Corian®, a solid-surface composite material

Corian®, a solid-surface composite (SSC), is composed of alumina trihydrate and acrylic polymer. The aim of the present study was to examine the pulmonary toxicity attributed to exposure to SSC sawing dust. Male mice were exposed to either phosphate buffer saline (PBS, control), 62.5, 125, 250, 500, or 1000 µg of SSC dust, or 1000 µg silica (positive control) via oropharyngeal aspiration. Body weights were measured for the duration of the study. Bronchoalveolar lavage fluid (BALF) and tissues were collected for analysis at 1 and 14 days post-exposure. Enhanced-darkfield and histopathologic analysis was performed to assess particle distribution and inflammatory responses. BALF cells and inflammatory cytokines were measured. The geometric mean diameter of SSC sawing dust following suspension in PBS was 1.25 µm. BALF analysis indicated that lactate dehydrogenase (LDH) activity, inflammatory cells, and pro-inflammatory cytokines were significantly elevated in the 500 and 1000 µg SSC exposure groups at days 1 and 14, suggesting that exposure to these concentrations of SSC induced inflammatory responses, in some cases to a greater degree than the silica positive control. Histopathology indicated the presence of acute alveolitis at all doses at day 1, which was largely resolved by day 14. Alveolar particle deposition and granulomatous mass formation were observed in all exposure groups at day 14. The SSC particles were poorly cleared, with 81% remaining at the end of the observation period. These findings demonstrate that SSC sawing dust exposure induces pulmonary inflammation and damage that warrants further investigation. Abbreviations: ANOVA: Analysis of Variance; ATH: Alumina Trihydrate; BALF: Bronchoalveolar Lavage Fluid; D_pg: Geometric Mean Diameter; FE-SEM: Field Emission Scanning Electron Microscopy; IACUC: Institutional Animal Care and Use Committee; IFN-γ: Interferon Gamma; IL-1 Β: Interleukin-1 Beta; IL-10: Interleukin-10; IL-12: Interleukin-12; IL-2: Interleukin-2; IL-4: Interleukin-4; IL-5: Interleukin-5; IL-6: Interleukin-6; KC/GRO: Neutrophil-Activating Protein 3; MMAD: Mass Median Aerodynamic Diameter; PBS: Phosphate-Buffered Saline; PEL: Permissible Exposure Limit; PM: Polymorphonuclear Leukocytes; PNOR: Particles Not Otherwise Regulated; SEM/EDX: Scanning Electron Microscope/Energy-Dispersive X-Ray; SSA: Specific Surface Area; SSC: Solid Surface Composite; TNFα: Tumor Necrosis Factor-Alpha; VOC: Volatile Organic Compounds; σ_g: Geometric Standard Deviation.

Analysis of the activation routes induced by different metal oxide nanoparticles on human lung epithelial cells

Nanoparticles (Nps) can induce toxicity in the lung by accidental or intentional exposure. The main objective of the study reported here was to characterize the effect that four metal oxide Nps (CeO₂, TiO₂, Al₂O₃ and ZnO) had at the cellular level on a human lung epithelial cell line. This goal was achieved by studying the capacity of the Nps to activate the main mitogen-activated protein kinases (MAPKs) and the nuclear factor NFκB. Only ZnO Nps were able to activate all of the MAPKs and the release of Zn²⁺ ions was the main cause of activation. ZnO and Al₂O₃ Nps activated the NFκB pathway and induced the release of inflammatory cytokines. CeO₂ and TiO₂ Nps were found to have safer profiles.

The graphical abstract was obtained using Servier Medical Art.

Lay abstract: When cells are exposed to a stimulus, they can activate different signaling pathways and these lead to different responses such as proliferation, differentiation, migration or inflammation. The objective of the work described here was to characterize the effects of several metal oxide nanoparticles at the cellular level by studying their capacity to activate the main mitogen-activated protein kinases (MAPKs) and the expression of the transcription factor NFκB on a human lung epithelial cell line. These signaling proteins play a relevant role in the vast majority of the cellular events that are triggered in eukaryotic cells after any stimulus.

ATSDR evaluation of potential for human exposure to tungsten

As part of its mandate, the Agency for Toxic Substances and Disease Registry prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation and Liability Act, National Priorities List sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Tungsten. The primary purpose of this article is to provide interested individuals with environmental information on tungsten that includes production data, environmental fate, potential for human exposure, analytical methods and a listing of regulations and advisories.

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.

Inhalation of inorganic particles as a risk factor for idiopathic pulmonary fibrosis--elemental microanalysis of pulmonary lymph nodes obtained at autopsy cases

Exposure to inorganic particles may induce fibrosis in the lung. However, the association between exposure to inorganic particles and the pathogenesis of idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia (UIP) is obscure. We examined inorganic particles in the pulmonary hilar lymph nodes affected by IPF/UIP to investigate whether inhaled elements are involved in the etiology, and whether there is an increasing risk of developing IPF/UIP. Twenty-three IPF/UIP cases and 23 controls without IPF/UIP were investigated. Pulmonary hilar lymph nodes constituted the study material. The elemental analysis was performed using scanning electron microscopy with an energy dispersive X-ray spectroscope, and we analyzed particles quantitatively and qualitatively. The results showed that the cases contained silicon and aluminum as compared with the control in lymph nodes, and these deposits were statistically significantly associated with an increased risk of IPF/UIP (adjusted odds were 2.99, 95% CI: 1.29-6.85 and 57.84, 95% CI: 1.45-2306.19, respectively). In addition, higher nickel levels in lymph nodes were associated with lung cancer. This study shows that inorganic particles, such as Si and Al, have higher concentrations in the hilar lymph nodes in IPF/UIP, and may play a role in one of the risk factors in the pathogenesis of IPF/UIP.

Serum Clara Cell Protein as an Indicator of Pulmonary Impairment in Occupational Exposure at Aluminum Foundry

OBJECTIVES

Although some of the exposures in aluminum (Al) smelting have been well characterized, and respiratory disorders in aluminum production workers are well known, the relationship between internal aluminum loads and appropriate lung biomarkers have not been elucidated. The aim of our work was to carry out a comprehensive investigation in workers employed in the Aluminum Foundry Casting Department with special reference to currently existing hygiene standards, known as threshold limit values (TLV) based on aluminum effects on the respiratory system. The measurement of serum anti-inflammatory Clara cell protein (CC16) was employed as a peripheral marker of the lung epithelium function.

MATERIALS AND METHODS

A group of 50 casting smelters, 5 locksmiths, 11 sawyers and auxiliary workers exposed to dust containing 14% of aluminum, and a group of 42 controls were examined. Respiratory function tests were performed and forced volume capacity (FVC), forced expiratory volume in 1 s (FEV1), forced expiratory volume in the first percent (FEV1%), forced expiratory flows in 50% VC (FEV50), and markers of foundry workers' exposure and body burden, Al concentration in the breathing zone, blood and urine, biomarkers of the effects of exposure, concentration of CC16 and hyaluronic acid (HA) in serum were determined in all examined workers. Additional measurements comprised determinations of serum iron (Fe) levels, myeloperoxidase (MPO), eosinophil cationic protein (ECP), immunoglobulin E (IgE), glutathione S-transferase (GST), and superoxide dismutase (SOD) activity in erythrocytes.

RESULTS

The group of casting smelters was characterized by the highest levels of aluminum in urine (Al-U) (43.7 microg L(-1)), high levels of MPO, ECP and IgE, high SOD activity, low CC16 levels, and low activity of GST. Lower Al-U excretion was observed in locksmiths (35.2 microg L(-1)) and sawyers (21.7 microg L(-1)). Serum CC16 proved to be the most sensitive biomarker, showing high inverse relationship with serum Al (Al-S) concentrations in casting smelters (p = 0.006).

CONCLUSIONS

The study showed that in conditions of occupational exposure, dusts containing Al2O3 < 1 mg m(-3) cause changes in the respiratory system and biomarkers in serum, especially in CC16, connected with altered functioning of this system. Changes in concentrations of the examined biomarkers and also in respiratory parameters of the study subjects were observed when Al-U concentration was > 40 microg L (-1).

Spirometric function in non-smoking workers exposed to aluminum

BACKGROUND

Exposure to aluminum (Al) causes the onset of respiratory disorders. This study is aimed at providing further information on how occupational exposure to Al affects the respiratory apparatus in healthy non-smokers, with particular attention to respiratory function.

METHODS

A group of 50 male shipyard workers who were exposed to Al underwent medical examination, standard chest X-rays and spirometry in accordance with the C.E.C.A. protocol. The data were compared with those of a homogeneous group of controls, all with blood aluminum (AlB) levels below 7.5 ng/ml. Statistical analysis was performed on the following spirometric parameters: vital capacity (VC), forced vital capacity (FVC), maximum forced expiratory volume in 1 s (FEV1), and mean forced expiratory flow during mid-half of FVC (FEF(25-75%)). Environmental Al levels were also measured at the various workstations.

RESULTS

Fifty male workers with an average age 31.82 +/- 5.05 years, occupational exposure of 11.81 +/- 3.71 years, presented with average AlB levels of 32.64 +/- 8.69 ng/ml. Environmental monitoring displayed Al levels higher than TLV TWA for all the workstations studied. None of the sample displayed significant pathological conditions. Statistical comparison of the spirometric parameters showed a decrease in the examined values in exposed workers. This decrease was found to be directly proportional to the AlB level.

CONCLUSION

The authors conclude that Al affects respiratory function and that limit values should be reassessed.

Pro-inflammatory effects of aluminum in human glioblastoma cells

Inflammatory events have been associated with senile plaques, one of the pathological hallmarks of Alzheimer's disease (AD). It is believed that aggregated beta-amyloid (betaA) proteins, which form the core of these plaques, may be responsible for triggering the inflammatory reaction. In the present study, the ability of aluminum (Al) to initiate similar inflammatory events was investigated in a human glioblastoma cell line. A 6-day exposure to either lipopolysaccharide (LPS) or aluminum sulfate caused a significant increase in the rate of proliferation of the glioblastoma cells. Both treatments also caused activation of the immune-responsive transcription factor NF-kappaB although there were time-related differences. The levels of secreted cytokines, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) were both increased by the LPS treatment although exposure to Al decreased the secretion of the former while elevating the levels of the latter. These events may be due to the activation of glial cells and subsequent stress response to either Al complexes or LPS. Although exposure to either stress factor caused a stimulation of inflammatory markers, there were time-dependent differences in the response. This may reflect the ability of the cells to discern different stress factors and thus orchestrate an innate immune response profile distinct to each immunogen.

Microdermabrasion: a clinical and histopathologic study

BACKGROUND

Microdermabrasion is a widely performed skin rejuvenation procedure. Few studies have examined its efficacy.

OBJECTIVE

To evaluate the clinical and histopathologic effects of microdermabrasion.

METHODS

Fourteen patients underwent microdermabrasion treatments over 12-14 weeks. Self-rated questionnaires were given before and after the treatment series and were evaluated by a paired t-test. Three of the 14 patients were treated for moderate to severe acne scarring. Acute histologic effects were assessed ex vivo on human abdominal skin. Chronic histopathologic effects were examined in three volunteers who underwent skin biopsies before and after a treatment series on the dorsal forearms.

RESULTS

By patient assessment, there was statistically significant improvement in roughness, mottled pigmentation, and overall improvement of skin appearance, but not in rhytides. Acne scarring sometimes improved, but required deeper ablation. Acutely the stratum corneum was homogenized and focally compacted. Chronically there was epidermal hyperplasia, decreased melanization, and some increase in elastin.

CONCLUSION

Microdermabrasion improves some aspects of photoaging and select cases of acne scarring.

Clearance and translocation of aluminum oxide (alumina) from the lungs

Significant respiratory-tract exposure to insoluble aluminum compounds, such as alumina (aluminum oxide, Al(2)O(3)), can occur in occupational settings, yet little is known about the temporal pattern of pulmonary clearance of these materials from the lungs with repeated exposures, and potential subsequent translocation to other organs. This study evaluated the clearance pattern of alumina from the lungs of rats, and burdens in selected extrapulmonary organs (brain, bone, liver, spleen, kidney). Rats were instilled with alumina once weekly for 20 wk. Quantification of retention was performed by measuring aluminum burdens in the lungs and extrapulmonary organs during the exposure period, and then weekly for an additional 19 wk after the exposures ended. Lung burdens of aluminum were found to steadily increase during exposure. Clearance of the material following the end of the exposure regime was extremely slow; only approximately 9% of the amount in the lungs following the 20 weekly exposures was cleared by the end of the postexposure period. This study supports the concept of gradual accumulation and long-term retention of aluminum within the respiratory tract of individuals repeatedly exposed to alumina in occupational settings.