Abnormal liver function associated with occupational exposure to dimethylformamide and hepatitis B virus

The potential health risks of N,N-dimethylformamide: An updated review

N,N-dimethylformamide (DMF) is a universally used industrial material with exponential growth in production and consumption worldwide. The frequently reported occupational DMF poisoning cases in some countries and the gradually recognized unavoidable health risks to the general population highlight that DMF should still be a matter of concern. Previous studies have demonstrated that the liver is the primary target organ of DMF exposure and multiple mechanisms have been revealed. However, most of these studies investigate the detrimental effects of acute and subacute DMF exposure, while the effects of chronic DMF exposure are rarely studied. Furthermore, the key mechanism for the acute hepatotoxicity of DMF remains to be elucidated. Future research may focus on the identification of efficient preventive measures against the toxicity of DMF to occupational workers, the investigation of the detrimental effects of DMF at environmentally relevant doses, and the studies on the elimination and recycling of DMF in industrial wastes. Herein, we present an updated review of the metabolism of DMF, the biomarker of DMF exposure, underlying molecular mechanisms of DMF-induced hepatotoxicity, and the toxicity of DMF to both occupational workers and general populations and discuss the possible directions in future studies.

Effects of toxicants on endoplasmic reticulum stress and hepatic cell fate determination

Toxicant-induced injury is a significant global health issue. However, the mechanisms through which toxicants such as carbon tetrachloride, acetaminophen, dimethylformamide, cocaine, and morphine induce the death of multiple cell types and contribute to liver toxicity are highly complex. This phenomenon involves intricate signaling pathways in association with oxidative stress, inflammation, and activation of death receptors, which are closely linked to endoplasmic reticulum (ER) stress. ER stress initially triggers the unfolded protein response, which either promotes cell survival or causes cell death at later times, depending on the severity and duration of the stress. Thus, comprehending the molecular basis governing cell fate determination in the context of ER stress may provide key insights into the prevention and treatment of toxicant-induced injury. This review summarizes our current understanding of agents that trigger different forms of ER stress-mediated cell death, necroptosis, ferroptosis, pyroptosis, and apoptosis, and covers the underlying molecular basis of toxicant-induced ER stress, as well as potential target molecules.

Pathological characteristics of liver injury induced by N,N-dimethylformamide: From humans to animal models

N,N-Dimethylformamide (DMF) is widely used in chemical industries because of its excellent solvent properties. Poisoning accidents caused by DMF have been frequently reported, particularly hepatotoxicity; however, the hepatic pathological changes have rarely been described. This study aimed to summarise the pathological characteristics of the hepatotoxicity associated with DMF in clinical cases and to verify in animal models. Liver pathologies of two patients with liver failure due to DMF were retrospectively analysed. Thirty-six rats were categorised into the DMF group (intraperitoneally injected with 4 g/kg DMF once a week), carbon tetrachloride (CCl₄) group (intraperitoneally injected with 0.5 g/kg CCl₄ twice a week) and control group (intraperitoneally injected with normal saline once a week). The general condition and changes in hepatic pathology at 48 h and 8 weeks were observed. Liver tissues of patients exhibited multiple unevenly distributed inflammatory and fibrotic lesions. The DMF-induced liver injury animal model was successfully established. Inflammation and fibrosis were heterogeneously observed throughout the liver in the DMF group, contrast to entirely homogeneous lesions in the CCl₄ group. Specific hepatic pathological findings (heterogeneous lesions) caused by DMF detected for the first time in humans and animal model, may be significant in the clinical diagnosis of DMF poisoning.

The effects of dimethylformamide exposure on liver and kidney function in the elderly population: A cross-sectional study

Dimethylformamide (DMF) is widely used as a solvent in the production of synthetic leather. Previous studies have focused on workers exposed to DMF in leather factories; however, little attention has been paid to the general population. This study was conducted to examine the effects of DMF exposure on elderly residents living near synthetic leather factories. A total of 962 subjects over 60 years of age in proximity to these factories (monitoring points) were enrolled as the exposure group, and 1924 permanent residents living distant from the factories were enrolled as the control group. The exposure group was divided into 3 groups according to their distance from the monitoring points. Physical examination, routine blood tests, and liver and renal function data were collected, and the DMF concentration in the air was analyzed by gas chromatography-mass spectroscopy. The prevalence of abnormal heart rhythm, electrocardiogram and B-mode ultrasound results in the exposure group was significantly greater than in the control group. Aspartate transaminase (AST), alanine transaminase (ALT), and blood urea nitrogen (BUN) levels in the exposure group also were higher than those in the control group (P < .01). There was an effect of distance from leather factories on liver and kidney dysfunction in the 3 exposure groups. Compared with the exposure group at >3 km distance from the source, the prevalence of increased AST, ALT, and BUN in the exposure group at <1 km was significantly greater (P < .001). It was concluded that DMF exposure was related to an increased risk of a cardiac injury and liver and kidney dysfunction.

The influence of airborne N,N-dimethylformamide on liver toxicity measured in industry workers: A systematic review and meta-analysis

Background:

Modern industry is developing and so is the consumption of N, N-dimethylformamide (DMF) and the occupational population exposed to DMF. However, chronic occupational and experimental exposure to DMF has been especially linked to liver and gastrointestinal disturbances.

Aims:

This study aims to systematically review and evaluate with a meta-analysis the influence of DMF exposure on human liver toxicity.

Methods:

The PubMed/Medline, the ECHA restriction dossier and the Web of Science were searched. Midpoint DMF exposure levels were calculated, and the association between DMF exposure and liver toxicity was investigated. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

Results:

Of 92 screened articles, 19 articles were included in the review and of them, 10 articles were included in the meta-analysis. No association was observed when the midpoint DMF exposure was less than 20 mg/m3 (OR: 1.58, 95% CIs: 0.68–3.65). A positive association between DMF exposure and liver toxicity was observed when the midpoint DMF exposure was between 21 mg/m3 and 25 mg/m3 (OR: 3.26, 95% CIs: 1.38–7.73).

Conclusions:

Higher exposure DMF levels are associated with liver toxicity. However, these results tend to overestimate potential risks because the use of midpoint exposures includes and gives weight to populations at the upper end of the exposure distributions and because liver toxicity was defined as a statistical significant difference in liver enzyme levels compared to control groups, which is not identical to biologically relevant effects and adverse health effects.

Making Solid-Phase Peptide Synthesis Greener: A Review of the Literature

To date, the synthesis of peptides is concurrent with the production of enormous amounts of toxic waste. DMF, CH₂ Cl₂ , and NMP are three of the most toxic organic solvents used in chemical synthesis and are the most common solvents used for peptide synthesis. Additionally, concerns about the hepatotoxicity caused by exposure to DMF and from the toxic and allergenic nature of additives used in peptide synthesis necessitates the need for a green, environmentally friendly, and safer protocol for peptide synthesis. This review summarizes the current literature on green solid-phase peptide synthesis successes and challenges encountered. The review concludes with suggestions for future research towards a simple and efficient green peptide synthesis protocol.

Clinical outcomes of occupational exposure to n,n-dimethylformamide: perspectives from experimental toxicology

N,N-Dimethylformamide (DMF) is globally used as an organic solvent in the production of synthetic leather and resins because of its low volatility, making it an attractive industrial material. Despite its excellent property as a chemical solvent, utilization of DMF is somewhat controversial nowadays due to its hazardous effects on exposed workers in work places. Many toxification cases are being reported globally and the number of cases of liver damage is still increasing in developing countries. On account of this, a series of epidemiologic surveys are being conducted to understand the degrees of liver damage caused by DMF exposure. Furthermore, many investigations have been performed to clarify the mechanism of DMF-induced liver toxicity using both human and experimental animal models. This review summarizes the current occupational cases reported on liver damage from workers exposed to DMF in industrial work places and the research results that account for DMF-induced liver failure and possible carcinogenesis. The findings reviewed here show the synergistic toxicity of DMF exposure with other toxicants, which might occur through complicated but distinct mechanisms, which may extend our knowledge for establishing risk assessments of DMF exposure in industrial work places.

Liver and heart toxicity due to 90-day oral exposure of ICR mice to N,N-dimethylformamide

N,N-dimethylformamide (DMF) is a colorless liquid with a faint amine odor, which is widely used in the world. DMF exposure may induce adverse effects on liver, but few studies showed damage to heart after exposure to DMF. In the present study, DMF was administered to ICR mice with the doses of 0.32, 0.63 and 1.26 g/kg of body weight by gavage for 90 days. The increase in the relative liver weight is accompanied with the presence of the centrilobular hepatocellular hypertrophy as well as increased serum levels of aspartate transaminase (AST) and alanine transaminase (ALT). An increase of malondialdehyde (MDA) level was shown in liver homogenate, while superoxide dismutase (SOD) and glutathione (GSH) activities decreased. Heart damage was also shown in mice exposed to DMF for 90 days, although pathological examination showed only slight inflammatory cell infiltration. Increased levels of serum lactate dehydrogenase (LDH), isoenzymes of creatine kinase (CK-MB) and cardiac troponin I (cTnI) were shown. Increased level of MDA was also shown in heart homogenate, in contrast with the decreased activity of SOD. These data suggested that the administration of DMF could induce liver and heart injuries and oxidative stress was involved in the toxic effects.

Occupational liver injury due to N,N-dimethylformamide in the synthetics industry

N,N-dimethylformamide (DMF) is a solvent used extensively in the chemical industry. The main toxic effect reported after exposure to DMF is hepatotoxicity. We encountered four patients with liver injury due to DMF exposure; the severity of the liver injury was related to the exposure levels. After removal of exposure, all patients recovered without specific treatment. A careful evaluation of occupational history is necessary when liver dysfunction develops in industrial workers.

Abnormal liver function and central obesity associate with work-related fatigue among the Taiwanese workers

AIM: To examine the associations between objective health indicators and high need for recovery (NFR) after work, one of the subjective presentations of work related-fatigue, among apparently healthy workers in modern workplaces.

METHODS: From October to December, 2007, an annual health examination was performed for the workers from an electronics manufacturing factory in Taiwan. Health records of 1216 workers with a relatively homogeneous socioeconomic status were used for analysis. The health checkups included personal and NFR scale questionnaires, physical examinations, blood tests for biochemistry and hematology. The workers within the top tertile NFR score were defined as high-NFR workers.

RESULTS: After adjusted for potential confounders, the workers with elevated alanine aminotransferase (ALT) and central obesity had a significantly higher NFR after work, with increased risks of 1.4-fold [95% confidence interval (CI) = 1.01-2.0] and 1.8-fold (95% CI = 1.2-2.7), respectively. Shiftworkers had a 2.0-fold (95% CI = 1.5-2.6) increased risk for high-NFR. The associations between high-NFR and lipid profiles, blood sugar, hematology indexes or blood pressure were insignificant after controlling for confounders.

CONCLUSION: For apparently healthy workers, high NFR after work is not simply a subjective experience. Objective health measures, such as elevated ALT and increased waist circumference, should be carefully evaluated for the apparently healthy workers having a higher NFR after work.

Abnormal liver function associated with occupational exposure to dimethylformamide and glutathioneS-transferase polymorphisms

Dimethylformaide (DMF) is a major solvent predominately used in synthetic leather and resin production. Many human and animal studies have linked the cause of hepatoxicity to DMF. Previously, the authors demonstrated the significant dose-response relationship between abnormal liver function tests and DMF exposure and the interaction with hepatitis B virus (HBV) infection in Taiwanese workers. Because the toxic effect of various chemicals can be modified by metabolic traits, the study also investigated the influence of the glutathione S-transferases (GSTM1 and GSTT1) on the toxic effect of DMF. The average DMF exposure concentration was 23.87 ppm (range 5.2-86.6 ppm) in the high-exposure (>/=5 ppm) group and 2.41 ppm (range 0.9-4.3 ppm) in the low-exposure (<5 ppm) group. There were 13 of 44 (29.6%) abnormal liver function tests (elevations of either glutamate oxaloacetate transaminase (GOT) or glutamate pyruvate transaminase (GPT)) among the high DMF exposure workers, two of 22 (9.1%) abnormal liver function tests among the low DMF exposure workers. Chronic liver disease as determined by ultrasonography was present in seven of 44 (15.9%) high DMF exposure workers, and 0 of 22 (0%) low DMF exposure workers. There were 11 of 34 (32.4%) abnormal liver function tests among the GSTT1 null genotype workers, and four of 32 (12.5%) abnormal liver function tests among the GSTT1-positive genotype workers. Compared with the low DMF exposure workers, the adjusted odds ratio and 95% confidence intervals for abnormal liver function tests was 6.78 (0.94-48.7) for the high DMF exposure workers. Compared with the GSTT1-positive genotype workers, the adjusted odds ratio and 95% confidence intervals for abnormal liver function tests was 4.41 (1.15-16.9) for the GSTT1 null genotype workers. Compared with the low DMF group with GSTT1-positive genotype workers, the odds ratio (adjusted for HBV status) of abnormal liver function test was 12.38, 95% CI=(1.04-146.9) for the high DMF group with GSTT1 null genotype workers. This study indicates that abnormal liver function and chronic liver disease are associated with DMF exposure, and there are more than multiplicative interaction effects on abnormal liver function tests between the DMF exposure and the GSTT1 genotype.

Methods and rationale for keeping records of hepatitis virus testing in Japanese workplaces

In Japan, the Ministry of Health, Labour and Welfare issued corporate guidance that employers should recommend their employees to have tests for hepatitis B virus and hepatitis C virus (HV) at least once in their lifetime. However, employers should treat this information as confidential, even though the testing is carried out along with the health examination designated by the Industrial Safety and Health Law. Therefore, the records of HV tests should not be kept by employers, even though records of medical examinations designated by the law must be. This study aimed to clarify the present method for keeping records of HV infection and the rationale in Japanese workplaces. Questionnaires about viral hepatitis were sent to 118 occupational health physicians, and 81 physicians from 100 workplaces responded. The HV test for employees was conducted in 58 workplaces (75.8% of large, 60.4% of bigger medium-sized and 16.7% of smaller medium-sized enterprises). These workplaces were the types of industries where the risk of infecting other persons was low. Subjects of the HV tests were workers who were suspected to have hepatitis virus, and workers who were applicants. Occupational health physicians from most workplaces answered that records of medical examinations designated by law and records of HV tests were not kept separately and shouldn't be. The opinion that the two types of records should not be kept separately appeared to be more from the workplaces where employers or health insurance covered the cost of the HV test. In these cases, the purpose of conducting HV tests at the workplaces was thought to be both promoting welfare of employees and occupational considerations for workers. Occupational health physicians from about 60% of workplaces had misgivings about employees who had hepatitis virus being discriminated against at the workplace if the HV test was included with the required medical examination. Among occupational health physicians from workplaces where occupational health professionals were in charge of the records, there was no standardized rationale for keeping records. However, most workplaces took into consideration the workers' privacy by getting employees' consent before divulging information to their employers. This relied not only on the occupational health professional's or health/safety officer's ethics, but also the necessity of reviewing the purpose and methods of keeping records of HV testing of employees, based on official notices or the Act on the Protection of Personal Information.

HBV‐ and HCV‐ Infected Workers in the Japanese Workplace

Around three million Japanese are persistently infected with HBV or HCV. Though most of them work in various industries, little is known about the actual conditions in their workplaces. To clarify the workplace conditions of workers with hepatitis, three kinds of questionnaire surveys, answered by occupational health physicians and workers with hepatitis, were carried out. The rates of workers recognized as workers with hepatitis B or C by occupational health physicians were 0.82% and 0.48% of 130,092 workers, respectively. About 30% of workers with hepatitis were engaged in "hazardous work". The percentage of workers engaged in various types of hazardous work among workers with hepatitis was nearly the same as that among all Japanese workers. About 30% of occupational health physicians witnessed exacerbation of hepatitis in the workers at their workplaces, and 22% of workers with hepatitis experienced exacerbation of hepatitis. The rate of workers with hepatitis who had experienced exacerbation was not significantly different between workers with and without hazardous work. Workers with hepatitis have strong concerns about the relationship between work and exacerbation. As causes of exacerbation, occupational health physicians cited "unknown", "drinking" and "quit treatment" while workers with hepatitis answered "work-related causes", besides "unknown" and "drinking."

Synergistic effect of hepatitis virus infection and occupational exposures to vinyl chloride monomer and ethylene dichloride on serum aminotransferase activity

AIMS

To study the synergistic effect of occupational chemical exposure and hepatitis virus infection on serum aminotransferase activity.

METHODS

A total of 568 male workers who were employed in five polyvinyl chloride (PVC) or four vinyl chloride monomer (VCM) manufacturing factories were studied. Information relating to current job title, alcohol consumption, and cigarette smoking was obtained. Exposure level of chemical mixtures was classified by hygienic effect (a summation of personal time weighted average/reference permissible exposure level of each chemical) into high, moderate, and low exposure groups. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and anti-hepatitis C antibody were assayed.

RESULTS

Hepatitis virus infection and increased body mass index were associated with abnormal serum aminotransferase activity. In workers with hepatitis virus infection, those with high exposure had a higher prevalence of abnormal AST and ALT compared to low exposure; among those without hepatitis virus infection, the differences of prevalence of abnormal AST and ALT were not significant between different chemical exposure groups. There was a significant trend of increasing risks of increased AST and ALT in moderate and high exposure groups with hepatitis virus infection. Such a synergistic effect was more prominent among HBeAg-positive workers.

CONCLUSIONS

Mixed exposures to 1,2-ethylene dichloride and VCM have a positive synergistic effect with hepatitis virus infection on liver damage. Assessment of fitness for work should be considered in workers with hepatitis B and C infection, when they have potential exposure to hepatotoxins in the workplace.