Possibility of lung cancer risk in indium-exposed workers: An 11-year multicenter cohort study

Subchronic toxicity study of indium-tin oxide nanoparticles following intratracheal administration into the lungs of rats

OBJECTIVES

We aimed to analyze the subchronic toxicity and tissue distribution of indium after the intratracheal administration of indium-tin oxide nanoparticles (ITO NPs) to the lungs of rats.

METHODS

Male Wistar rats were administered a single intratracheal dose of 10 or 20 mg In/kg body weight (BW) of ITO NPs. The control rats received only an intratracheal dose of distilled water. A subset of rats was periodically euthanized throughout the study from 1 to 20 weeks after administration. Indium concentrations in the serum, lungs, mediastinal lymph nodes, kidneys, liver, and spleen as well as pathological changes in the lungs and kidneys were determined. Additionally, the distribution of ionic indium and indium NPs in the kidneys was analyzed using laser ablation-inductively coupled plasma mass spectrometry.

RESULTS

Indium concentrations in the lungs of the 2 ITO NP groups gradually decreased over the 20-week observation period. Conversely, the indium concentrations in the mediastinal lymph nodes of the 2 ITO groups increased and were several hundred times higher than those in the kidneys, spleen, and liver. Pulmonary and renal toxicities were observed histopathologically in both the ITO groups. Both indium NPs and ionic indium were detected in the kidneys, and their distributions were similar to the strong indium signals detected at the sites of inflammatory cell infiltration and tubular epithelial cells.

CONCLUSIONS

Our results demonstrate that intratracheal administration of 10 or 20 mg In/kg BW of ITO NPs in male rats produces pulmonary and renal toxicities.

The quantity and quality of scientific evidence about the health of working women in occupational health of Japan: A scoping review

OBJECTIVE

We aim to investigate the quantity and quality of scientific evidence dealing with comprehensive health issues of working women in occupational health.

METHODS

This scoping review of original articles that investigated comprehensive health issues of working women aged 19-64 years in Japan was published in PubMed (1967-2022) and Igaku Chuo Zasshi (or Ichu-shi, 1982-2022). Using identical broad search terms, we first identified 17 122 English and 6154 Japanese articles. We excluded those with clinically relevant topics, or ethnicity other than Japanese and included 853 English and 855 Japanese articles for review and classified them into nine research areas considered to be critical factors for women in the workforce and five study design groups to investigate the quality of the evidence accumulated.

RESULTS

Among 853 English-language articles in PubMed, "Mental health" was the most frequent area studied, followed by "Work-related disease" and "Lifestyle-related disease." Among 855 Japanese-language articles from Ichu-shi, "Mental health" was the most frequently studied area followed by "Work and balance," and "Work-related disease." "Infertility, pregnancy, and childbirth" and "Menstruation, menopause, and genital disease" were well studied in Ichu-shi but scarcely published in PubMed. "Harassment and discrimination" were sparsely reported in both databases. As for research designs, many articles in both PubMed and Ichu-shi employed descriptive or cross-sectional study designs. However, a few studies employed cohort/longitudinal or interventional studies.

CONCLUSION

The results underscored the need for higher-quality study designs with more scientific evidence on working women's health in the field of occupational health.

Pulmonary effects of exposure to indium and its compounds: cross-sectional survey of exposed workers and experimental findings in rodents

BACKGROUND

Many studies have shown that occupational exposure to indium and its compounds could induce lung disease. Although animal toxicological studies and human epidemiological studies suggest indium exposure may cause lung injury, inflammation, pulmonary fibrosis, emphysema, pulmonary alveolar proteinosis, and even lung cancer, related data collected from humans is currently limited and confined to single workplaces, and the early effects of exposure on the lungs are not well understood.

OBJECTIVES

This study combined population studies and animal experiments to examine the links of indium with pulmonary injury, as well as its mechanism of action. A cross-sectional epidemiological study of indium-exposed workers from China was conducted to evaluate associations between occupational indium exposure and serum biomarkers of early effect. This study also compares and analyzes the causal perspectives of changes in human serum biomarkers induced by indium compound exposure and indium exposure-related rat lung pathobiology, and discusses possible avenues for their recognition and prevention.

METHODS

This is a study of 57 exposed (at least 6 h per day for one year) workers from an indium ingot production plant, and 63 controls. Indium concentration in serum, urine, and airborne as exposure indices were measured by inductively coupled plasma-mass spectrometry. Sixteen serum biomarkers of pulmonary injury, inflammation, and oxidative stress were measured using ELISA. The associations between serum indium and 16 serum biomarkers were analyzed to explore the mechanism of action of indium on pulmonary injury in indium-exposed workers. Animal experiments were conducted to measure inflammatory factors levels in bronchoalveolar lavage fluid (BALF) and lung tissue protein expressions in rats. Four different forms of indium compound-exposed rat models were established (intratracheal instillation twice per week, 8 week exposure, 8 week recovery). Model I: 0, 1.2, 3, and 6 mg/kg bw indium tin oxide group; Model II: 0, 1.2, 3, and 6 mg/kg bw indium oxide (In₂O₃) group; Model III: 0, 0.523, 1.046, and 2.614 mg/kg bw indium sulfate (In₂(SO₄)₃) group; Model IV: 0, 0.065, 0.65, and 1.3 mg/kg bw indium trichloride (InCl₃) group. Lung pathological changes were assessed by hematoxylin & eosin, periodic acid Schiff, and Masson's staining, transmission electron microscopy, and the protein changes were determined by immunohistochemistry.

RESULTS

In the production workshop, the airborne indium concentration was 78.4 μg/m³. The levels of serum indium and urine indium in indium-exposed workers were 39.3 μg/L and 11.0 ng/g creatinine. Increased lung damage markers, oxidative stress markers, and inflammation markers were found in indium-exposed workers. Serum indium levels were statistically and positively associated with the serum levels of SP-A, IL-1β, IL-6 in indium-exposed workers. Among them, SP-A showed a duration-response pattern. The results of animal experiments showed that, with an increase in dosage, indium exposure significantly increased the levels of serum indium and lung indium, as well as the BALF levels of IL‑1β, IL‑6, IL‑10, and TNF‑α and up-regulated the protein expression of SP-A, SP-D, KL-6, GM-CSF, NF-κB p65, and HO-1 in all rat models groups. TEM revealed that In₂(SO₄)₃ and InCl₃ are soluble and that no particles were found in lung tissue, in contrast to the non-soluble compounds (ITO and In₂O₃). No PAS-staining positive substance was found in the lung tissue of In₂(SO₄)₃ and InCl₃ exposure groups, whereas ITO and In₂O₃ rat models supported findings of pulmonary alveolar proteinosis and interstitial fibrosis seen in human indium lung disease. ITO and InCl₃ can accelerate interstitial fibrosis. Findings from our in vivo studies demonstrated that intra-alveolar accumulation of surfactant (immunohistochemistry) and characteristic cholesterol clefts granulomas of indium lung disease (PAS staining) were triggered by a specific form of indium (ITO and In₂O₃).

CONCLUSIONS

In indium-exposed workers, biomarker findings indicated lung damage, oxidative stress and an inflammatory response. In rat models of the four forms of indium encountered in a workplace, the biomarkers response to all compounds overall corresponded to that in humans. In addition, pulmonary alveolar proteinosis was found following exposure to indium tin oxide and indium oxide in the rat models, and interstitial fibrosis was found following exposure to indium tin oxide and indium trichloride, supporting previous report of human disease. Serum SP-A levels were positively associated with indium exposure and may be considered a potential biomarker of exposure and effect in exposed workers.

Two-year follow-up of exposure, engineering controls, respiratory protection and respiratory health among workers at an indium-tin oxide (ITO) production and reclamation facility

OBJECTIVES

To determine whether engineering controls and respiratory protection had measurable short-term impact on indium exposure and respiratory health among current indium-tin oxide production and reclamation facility workers.

METHODS

We documented engineering controls implemented following our 2012 evaluation and recorded respirator use in 2012 and 2014. We measured respirable indium (Inresp) and plasma indium (InP) in 2012 and 2014, and calculated change in Inresp (∆Inresp) and InP (∆InP) by the 13 departments. We assessed symptoms, lung function, serum biomarkers of interstitial lung disease (Krebs von den Lungen (KL)-6 and surfactant protein (SP)-D) and chest high-resolution CT at both time points and evaluated workers who participated in both 2012 and 2014 for changes in health outcomes (new, worsened or improved).

RESULTS

Engineering controls included installation of local exhaust ventilation in both grinding departments (Rotary and Planar) and isolation of the Reclaim department. Respiratory protection increased in most (77%) departments. ∆InP and ∆Inresp often changed in parallel by department. Among 62 workers participating in both 2012 and 2014, 18 (29%) had new or worsening chest symptoms and 2 (3%) had functional decline in lung function or radiographic progression, but average KL-6 and SP-D concentrations decreased, and no cases of clinical indium lung disease were recognised.

CONCLUSIONS

Increased engineering controls and respiratory protection can lead to decreased Inresp, InP and biomarkers of interstitial lung disease among workers in 2 years. Ongoing medical monitoring of indium-exposed workers to confirm the longer-term effectiveness of preventive measures is warranted.

Toxicokinetics and systematic responses of differently sized indium tin oxide (ITO) particles in mice via oropharyngeal aspiration exposure

Indium tin oxide (ITO) is an important semiconductor material, because of increasing commercial products consumption and potentially exposed workers worldwide. So, urgently we need to assess and manage potential health risks of ITO. Although the Occupational Exposure Limit (OEL) has been established for ITO exposure, there is still a lack of distinguishing the risks of exposure to particles of different sizes. Therefore, obtaining toxicological data of small-sized particles will help to improve its risk assessment data. Important questions raised in quantitative risk assessments for ITO particles are whether biodistribution of ITO particles is affected by particle size and to what extent systematic adverse responses is subsequently initiated. In order to determine whether this toxicological paradigm for size is relevant in ITO toxic effect, we performed comparative studies on the toxicokinetics and sub-acute toxicity test of ITO in mice. The results indicate both sized-ITO resided in the lung tissue and slowly excreted from the mice, and the smaller size of ITO being cleared more slowly. Only a little ITO was transferred to other organs, especially with higher blood flow. Two type of ITO which deposit in the lung mainly impacts respiratory system and may injure liver or kidney. After sub-acute exposure to ITO, inflammation featured by neutrophils infiltration and fibrosis with both dose and size effects have been observed. Our findings revealed toxicokinetics and dose-dependent pulmonary toxicity in mice via oropharyngeal aspiration exposure, also replenish in vivo risk assessment of ITO. Collectively, these data indicate that under the current OEL, there are potential toxic effects after exposure to the ITO particles. The observed size-dependent biodistribution patterns and toxic effect might be important for approaching the hazard potential of small-sized ITO in an occupational environment.

Indium kinetics in an indium exposed worker before and after bilateral lung transplantation

Background

A male worker with indium‐tin oxide (ITO)‐induced pneumoconiosis underwent bilateral lung transplantation (LT).

Methods

Post‐LT histopathological investigations of the isolated lungs and hilar lymph nodes were performed and indium concentration in serum (In‐S) and serum Krebs von den Lungen‐6 (KL‐6) were tracked for 122 weeks.

Results

He has attained the ultimate treatment goal of > 2‐year survival. The main histopathological characteristics were pan‐lobular emphysematous change, interstitial fibrosis, and lymphocytic infiltration in the peribronchiolar/perivascular portions, and numerous cholesterol clefts and giant cells containing brown particles. These findings support the conclusion that the lung injury was caused by the inhalation of ITO. Metal element mapping and indium in the isolated lungs revealed that inhaled ITO particles in humans migrate to the lymph nodes. In‐S remained at remarkably high levels (≥30 ng/mL) and showed wide fluctuation with bimodality until 46 weeks after LT, but KL‐6 remained in the normal range for almost the entire period. The indium concentration in the donor's resection lung at 10 weeks after LT was 143.5 ng/g wet‐weight, which was only one one‐thousandth of the recipient's lung (161 µg/g wet‐weight). After 48 weeks of LT, the recipient's In‐S had gradually decreased; the biological half‐life was 1.2 years. These results clearly suggest that indium remaining in the recipient's tissues did not adversely influence the transplant donor's lungs.

Conclusions

The transplanted donor's lungs were not influenced by indium in the recipient's organs. Bilateral LT is thus an effective treatment option in severe indium lung disease cases.

Response to pembrolizumab in a patient with primary lung adenocarcinoma originated from indium lung

Background

Indium is a metal used as a compound called indium-tin oxide for liquid crystal display. Its inhalation causes lung toxicity, resulting in a new occupational lung disease called indium lung. Although the carcinogenicity of indium has been reported in an animal model, its carcinogenicity in humans is unknown.

Case presentation

This is the first reported case of a primary lung cancer originating from indium lung. In this report, we describe a 46-year-old man with interstitial pneumonia-type indium lung diagnosed 16 years ago. The initial symptom was left chest pain, and computed tomography showed a mass adjacent to the aorta with left pleural effusion. Specimens collected using video-assisted thoracoscopy revealed an adenocarcinoma with a high expression of programmed cell death-ligand 1 (cT4N0M1a stage IVA). Although the lesions showed a remarkable aggressive nature, the patient benefited from pembrolizumab, a monoclonal antibody against programmed cell death 1, which was used as second-line therapy for 2 years.

Conclusions

It is important for clinicians to be aware of lung cancer development in indium-exposed workers or in patients with indium lung, as this could have an aggressive behavior. Treatment with immune checkpoint inhibitors is an option even in patients with interstitial pneumonia-type indium lung.

Biomonitorization of concentrations of 28 elements in serum and urine among workers exposed to indium compounds

Many studies have documented the abnormal concentrations of metals/metalloids in serum or urine of occupational workers, but no works systematically analysed the concentrations of elements in serum or urine of indium-exposed workers. This study was aimed to assess 28 elements in serum and urine from 57 individuals with occupational exposure to indium and its compounds. Control subjects were 63 workers without metal exposure. We collected information on occupation and lifestyle habits by questionnaire. Biological samples were collected to quantify elements by inductive coupled plasma-mass spectrometer. Air in the breathing zones was drawn at flow rates of 1.5-3 L/min for a sampling period of 6 to 8 h, using a Model BFC-35 pump. The average ambient indium level was 0.078 mg/m3. Serum/urine Indium levels were significantly higher in indium-exposed workers than in controls (P < 0.01). Moreover, serum/urine indium concentrations in the group with 6-14 years and ≥15 years of employment were significantly higher than those with ≤5 employment years(P < 0.05). Ten of the other 27 elements/metals measured were higher in serum/urine in indium-exposed workers compared to the controls (aluminum, beryllium, cadmium, cesium, chromium, lithium, manganese, magnesium, molybdenum and vanadium). Zinc levels in serum/urine were significantly decreased in the indium-exposed workers. Additionally, other elements/metals were higher in one specimen (serum or urine) but lower in the other (Selenium was lower in serum but higher in urine in the indium-exposed workers compared with the controls; likewise Thallium and Rubidium were higher in serum but lower in urine). Linear regression analyses, revealed significant correlations between serum and urine for indium, aluminum, arsenic, barium, cadmium, cesium, cobalt, selenium, silver, and zinc (P < 0.05). These data suggest that occupational exposure to indium and its compounds may disturb the homeostasis of trace elements in systemic circulation, indium concentrations in serum or urine appear reflective of workers' exposure to ambient indium and their years of working, respectively. The serum/urine levels of essential metals are modified by exposure to indium in occupationally exposed workers. Further studies including larger sample size and more kinds of biological sample are needed to validate our findings.

Lung disorders induced by respirable organic chemicals

Respirable organic chemicals were originally thought to cause allergic respiratory diseases, such as bronchial asthma and hypersensitivity pneumonitis, and believed not to cause lung disorders derived from inflammatory or fibrotic processes such as pulmonary fibrosis and interstitial pneumonitis. It has recently been reported, however, that exposure to organic chemicals can cause interstitial lung diseases. In this review, we discuss the clinical features of occupational asthma and hypersensitivity pneumonitis, as well as other lung disorders, including interstitial pneumonitis, caused by humidifier disinfectants in Korea and by a cross-linked acrylic acid-based polymer (CL-PAA) in Japan.

Influence of humic substances on the transport of indium and gallium in porous media

Indium and gallium are used widely in modern industry, mostly for the production of semiconductors. They are considered as Technology-Critical Elements and have therefore received growing attention in the past few years. We investigated the influence of different types of humic substances on the transport of indium and gallium in laboratory-scale, saturated column experiments, to gain understanding of their mobility in natural environments. We evaluated the effect of different humic substances on the transport of indium and gallium in quartz sand: a commercial humic acid (Aldrich Humic Acid, AHA), a fulvic acid (Suwannee River Fulvic Acid, SRFA) and an aquatic natural organic matter (Suwannee River Natural Organic Matter, SRNOM). The impact of the flow rate and the influence of different concentrations of organic matter were also investigated. Indium was shown to be more mobile than gallium in the presence of humic substances. The mobility of indium in sand was highest for SRNOM, followed by SRFA and then AHA, while for gallium the order was SRFA > SRNOM > AHA. These results can be significant in understanding the mobility of indium and gallium in soils with various compositions of organic matter.

Effects of indium exposure on respiratory symptoms: a retrospective cohort study in Japanese workers using health checkup data

BACKGROUND

Indium compounds are known health hazards for lung cancer and interstitial pneumonia. Furthermore, they are related to emphysema, alveolar proteinosis, and cholesterol granuloma. In Japan, laws were revised in 2013 to tighten regulations on indium exposure in workplaces. However, its impact on the health of workers who handle indium has not been evaluated. This study aimed to investigate whether subjective respiratory symptoms in these workers have reduced after the 2013 amendment in the regulations.

METHODS

The subjects were workers from certain areas of Japan who had undergone health checkups between January 1, 2013, and June 30, 2015. Indium-handling and non-handling workers were categorized into the exposed and less-exposed groups, respectively. Based on the findings of health checkups during this period, the hazard ratio of subjective respiratory symptoms (cough, sputum production, shortness of breath, and palpitation) and its 95% confidence intervals (CIs) were calculated with the less-exposed group as the reference. The Prentice-Williams-Peterson model was used for calculation, and a model that adjusted for coarse analysis and potential confounding factors was adopted.

RESULTS

Overall, 2,561 workers (from 22 companies) who underwent 6,033 health checkups were included. The total person-years were 2,562.8 years, and 162 outcome events occurred. The hazard ratios of the exposed group were 1.65 (95% CI [1.14-2.39]: p = 0.008) and 1.61 (95% CI [1.04-2.50]: p = 0.032) in the crude and adjusted models, respectively.

CONCLUSION

Indium-handling workers had a high hazard of the subjective respiratory symptoms than non-indium -handling workers despite stricter regulations on indium exposure in workplaces. This indicates the need for further changes to the legislation to protect the health of workers exposed to harmful substances in workplaces. Further studies including larger diverse cohorts are needed to validate our findings.

Possibility of lung cancer risk in indium-exposed workers: An 11-year multicenter cohort study

Background

We established a causal relationship between indium exposure and lung interstitial and emphysematous effects. Lung cancer has been clearly demonstrated in rats and mice exposed to indium phosphide and in rats exposed to indium tin oxide. However, no information is available on human indium‐related lung cancer.

Methods

The baseline studies were conducted on 381 indium‐exposed and 150 referent workers in 11 factories from 2003 to 2006. Items examined included indium concentration in serum (In‐S), occupational history, Krebs von den Lungen‐6 (KL‐6), chest high‐resolution computed tomography (HRCT), medical history, smoking habits, and subjective symptoms. Subjects received follow‐up health checkups, and a total of 220 indium‐exposed and 26 nonexposed workers were examined at least once with chest HRCT from 2013 to 2018.

Results

Four lung cancer cases were identified only in indium‐exposed workers. Two were prevalent cases and two were incident cases. The averages (range) of age (years), exposure duration (years), In‐S (μg/L), and KL‐6 (U/mL) at the baseline survey were 58 (50‐74), 1.7 (0.3‐4.8), 3.1 (0.3‐9.7), and 663 (414‐942). The mean (range) latency from initial indium exposure was 5.3 (0.4‐11) years. The HRCT findings in two incident cases were mild interstitial/emphysematous change and mild interstitial change. The standardized incidence ratio (SIR) of the incident cases was 1.89 (95%CI 0.52‐6.88).

Conclusions

Although the SIR was not statistically significant, there was an undeniable possibility of indium‐related lung cancer due to the short follow‐up duration being insufficient to disclose lung cancer and the small number of lung cancer cases. Further follow‐up is necessary.