Occupational exposure to trichloroethylene and perchloroethylene and the risk of lymphoma, liver, and kidney cancer in four Nordic countries

Occupational benzene exposure and risk of kidney and bladder cancers: a systematic review and meta-analysis

INTRODUCTION

Benzene is recognized as leukemogenic. However, the association between it and solid cancers has been the subject of less investigation. We aim to conduct a systematic review and meta-analysis to evaluate the association between occupational exposure to benzene and the risk of urinary tract cancer, including kidney and bladder.

METHODS

We included 41 cohort and case-control studies listed in the most recent International Agency for Research on Cancer (IARC) Monograph on benzene exposure and the result of a literature review to identify more recent studies. Forest plots of relative risk (RR) were constructed for kidney, bladder, and urinary tract cancer overall. A random-effects model was used to address heterogeneity between studies. Stratified analyses were conducted to explore effect modification.

RESULTS

Our findings revealed an association between exposure to occupational benzene and kidney and unspecified urinary tract cancers (RR = 1.20, 95% confidence interval = 1.03-1.39), and an association of borderline statistical significance with bladder cancer (RR = 1.07, 95% confidence interval = 0.97-1.18). Publication bias was excluded for both kidney ( P  = 0.809) and bladder cancer ( P  = 0.748). Stratification analysis according to the selected study characteristics showed no difference except regarding the industry for kidney cancer ( P  < 0.000), with a stronger association in the chemical industry. An analysis by exposure level did not reveal any trend for kidney cancer, whereas there was a trend ( P  = 0.01) for bladder cancer.

CONCLUSION

Our study found an association between occupational benzene exposure and kidney cancer and a dose-effect association between benzene exposure and bladder cancer.

A slow-release reduction material of Escherichia sp. F1 coupled with micron iron powder achieves the remediation of trichloroethylene-contaminated soil

Trichloroethylene (TCE) is a prevalent organic pollutant found in soil. The oxide passivation layer on the surface of micron iron powder inhibits the release of its reducing components, leading to ineffective reduction and purification of TCE in soil. To enhance TCE degradation, a slow-release reduction material "Escherichia sp. F1-micron iron powder" was developed. A novel iron-reducing bacterium, Escherichia sp. F1, was isolated from soil contaminated with chlorinated hydrocarbons. This bacterium demonstrated a sustained iron reduction capability, achieving a reduction rate of 38.7% for Fe(Ⅲ) within 15 days. Genome sequencing revealed that strain F1 harbors 53 functional iron reduction genes and 2 dehalogenation genes. Single-factor experiments identified the optimal conditions for TCE degradation in soil using the coupling material: glucose concentration at 40 mmol/kg, soil water content at 50%, and bacterial inoculum at 1% (v:w). Under these optimal conditions, the coupled material achieved 86.86% degradation of TCE in soil within 28 days. Further analysis using X-ray photoelectron spectroscopy of micron iron powder, soil Fe(Ⅱ) concentration, and soil physicochemical properties demonstrated that the addition of strain F1 to the soil could disrupt the passivation layer of iron oxide on the surface of micron iron powder, promoting the exposure of its reactive sites and internal reducing active components. This resulted in an in situ self-actuated activation of passivated micron iron powder, leading to an improved removal rate and complete dechlorination of TCE in the soil. Soil microbial high-throughput sequencing revealed that the addition of strain F1 regulated the soil bacterial community, significantly enriching of Escherichia-Shigella species associated with iron-reducing functions. This enrichment facilitated the degradation of TCE in the soil through coupling materials. The functional material plays a crucial role in achieving green treatment and risk control of sites contaminated with chlorinated organic pollutants.

Trichloroethylene exposure, multi-organ injury, and potential mechanisms: A narrative review

Trichloroethylene (TCE) is a common environmental pollutant and industrial chemical that has been associated with adverse health effects, especially on organ systems. The purpose of this review is to summarize the current findings on organ system damage caused by TCE exposure and the underlying mechanisms involved. Numerous studies have shown that TCE exposure may cause damage to multiple organ systems, mainly the skin, liver, kidney, and circulatory system. The mechanisms leading to TCE-induced organ system damage are complex and diverse. TCE is metabolized in vivo to reactive intermediates, through which TCE can induce oxidative stress, interfere with cell signaling pathways, and promote inflammatory responses. In addition, studies have shown that TCE interferes with DNA repair mechanisms, leading to genotoxicity and potentially carcinogenic effects. This review highlights the importance of understanding the deleterious effects of TCE exposure on organ systems and provides insights into the underlying mechanisms involved. Further research is needed to elucidate the full range of organ system damage caused by TCE and to develop effective prevention and treatment strategies.

Temporal Variation and Industry-Specific Differences of the Use of Volatile Organic Compounds from 2018 to 2023 and Their Health Risks in a Typical Industrially Concentrated Area in South China

The risk of occupational exposure to organic solvents varies across industries due to factors such as processing materials, ventilation conditions, and exposure duration. Given the dynamic nature of organic solvent use and occupational exposures, continuous monitoring and analysis are essential for identifying high-risk hazards and developing targeted prevention strategies. Therefore, this study aims to analyze the use of organic solvents and volatile organic compounds (VOCs) in different industries in Bao'an District, Shenzhen, China, from 2018 to 2023, to understand their temporal variation and industry-specific differences and to identify high-risk occupational hazards. This study includes 1335 organic solvent samples, used by 414 different industry enterprises, and 1554 air samples. The result shows that the usage of organic solvents in various industries decreased with the outbreak of the pandemic and, conversely, increased as the situation improved. The most frequently detected volatile components in organic solvents were alkanes, followed by aromatic hydrocarbons. The ratios of the detection frequency of VOCs to the total number of detected categories increased year by year after 2020, indicating a tendency towards reduction and concentration of the types of organic solvents used in industrial production. Among the 8 high-risk VOCs, toluene (22.5%), n-hexane (22.0%), xylene (16.1%), and ethylbenzene (15.3%) have relatively high detection rates, suggesting that they need to be focused on in occupational health. Through air samples, the results show that trichloroethylene and xylene pose a high risk to human health (HQ > 1). We recommend that industry should strengthen monitoring of these two VOCs.

Declining incidence and improving survival of ocular and orbital lymphomas in the US between 1995 and 2018

This epidemiological study examined ocular and orbital lymphomas in the United States from 1995 to 2018, using data from the North American Association of Central Cancer Registries database of 87,543 patients with ocular and adnexal malignancies. We identified 17,878 patients (20.4%) with ocular and orbital lymphomas, with an age-standardized incidence rate (ASIR) of 2.6 persons per million (ppm). The incidence was the highest in the orbit (ASIR = 1.24), followed by the conjunctiva (ASIR = 0.57). Non-Hodgkin B-cell lymphoma was the most prevalent subtype (85.4%), particularly marginal-zone lymphoma (45.7%). Racial disparities were noted, with Asia-Pacific Islanders showing the highest incidence (orbit, 1.3 ppm). The incidence increased significantly from 1995 to 2003 (Average Percent Change, APC = 2.1%) but declined thereafter until 2018 (APC = - 0.7%). 5-year relative survival (RS) rates varied, with the highest rate for conjunctival lymphoma (100%) and the lowest for intraocular lymphoma (70.6%). Survival rates have generally improved, with an annual increase in the 5-year RS of 0.45%. This study highlights the changing epidemiological landscape, pointing to initial increases and subsequent decreases in incidence until 2003, with survival improvements likely due to advancements in treatment. These findings underscore the need for further research to investigate the root causes of these shifts and the declining incidence of ocular lymphoma.

Oxidative stress and pro-inflammatory cytokines following perchloroethylene exposure in young female dry-cleaning workers

BACKGROUND

The involvement of Perchloroethylene (PCE) in the development of autoimmune diseases has been reported. However, few studies investigated immunotoxicity in PCE-exposed workers.

OBJECTIVE

To study changes in the oxidative stress and cytokine profile of young female dry-cleaning workers exposed to PCE.

METHODS

Thirty-eight exposed workers and 38 unexposed controls were recruited. All the participants were young nonsmoker females. Individual interviews were conducted by a physician. Blood samples were collected and hematological tests were performed by an automated Coulter Counter. Plasma PCE levels were determined using gas chromatography/flame ionization detection. Plasma total antioxidant capacity (TAC), Catalase (CAT), Superoxide dismutase (SOD), and Malondialdehyde (MDA) levels were measured using the colorimetric method. The levels of plasma cytokines interleukin-1β (IL-1β), IL-2, IL-4, IL-6, IL-8, tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were measured by commercially kits.

RESULTS

The levels of plasma PCE averaged 561±96 ng/ml in the exposed group compared with 1.3±0.5 ng/ml in the controls. The hematological tests failed to find abnormalities in the exposed workers. Exposed workers presented significantly increased plasma levels of MDA, SOD and CAT. There were no significant differences between the two groups for level of plasma TAC. Significantly increased plasma IL-1β and TNF-α and decreased IL-2 and IL-8 levels were seen in the exposed workers. There were no significant differences between the two groups for IL-4, IL-6, and IFN-γ.

CONCLUSION

PCE exposure resulted in changed cytokine profile in dry-cleaning workers, suggesting the potential immunotoxicity of PCE at low exposure levels.

Occupational exposures and cancer risk in commercial laundry and dry cleaning industries: a scoping review

BACKGROUND

The laundry and dry cleaning industries are critical for maintaining cleanliness and hygiene in our daily lives. However, they have also been identified as sources of hazardous chemical exposure for workers, leading to potentially severe health implications. Despite mounting evidence that solvents like perchloroethylene and trichloroethylene are carcinogenic, they remain commonly used in the industry. Additionally, while alternative solvents are increasingly being utilized in response to indications of adverse health and environmental effects, there remains a significant gap in our understanding of the potential risks associated with exposure to these new agents.

METHODS

This study aims to identify gaps in the literature concerning worker exposure to contemporary toxic chemicals in the laundry and dry cleaning industry and their associated carcinogenic risks. A scoping review of peer-reviewed publications from 2012 to 2022 was conducted to achieve this objective, focusing on studies that detailed chemical exposures, sampling methods, and workers within the laundry and dry cleaning sector.

RESULTS

In this scoping review, 12 relevant papers were assessed. A majority (66%) examined perchloroethylene exposure, with one notable finding revealing that biomarkers from dry cleaners had significant micronuclei frequency and DNA damage, even when exposed to PCE at levels below occupational exposure limits. Similarly, another study supported these results, finding an increase in early DNA damage among exposed workers. Separate studies on TCE and benzene presented varied exposure levels and health risks, raising concern due to their IARC Group 1 carcinogen classification. Information on alternative solvents was limited, highlighting gaps in health outcome data, exposure guidelines, and carcinogenic classifications.

CONCLUSION

Research on health outcomes, specifically carcinogenicity from solvent exposure in dry cleaning, is limited, with 66% of studies not monitoring health implications, particularly for emerging solvents. Further, findings indicated potential DNA damage from perchloroethylene, even below set occupational limits, emphasizing the need to reevaluate safety limits. As alternative solvents like butylal and high-flashpoint hydrocarbons become more prevalent, investigations into the effects of their exposure are necessary to safeguard workers' health. This scoping review is registered with the Open Science Framework, registration DOI: https://doi.org/10.17605/OSF.IO/Q8FR3 .

Exposome and unhealthy aging: environmental drivers from air pollution to occupational exposures

The aging population worldwide is facing a significant increase in age-related non-communicable diseases, including cardiovascular and brain pathologies. This comprehensive review paper delves into the impact of the exposome, which encompasses the totality of environmental exposures, on unhealthy aging. It explores how environmental factors contribute to the acceleration of aging processes, increase biological age, and facilitate the development and progression of a wide range of age-associated diseases. The impact of environmental factors on cognitive health and the development of chronic age-related diseases affecting the cardiovascular system and central nervous system is discussed, with a specific focus on Alzheimer's disease, Parkinson's disease, stroke, small vessel disease, and vascular cognitive impairment (VCI). Aging is a major risk factor for these diseases. Their pathogenesis involves cellular and molecular mechanisms of aging such as increased oxidative stress, impaired mitochondrial function, DNA damage, and inflammation and is influenced by environmental factors. Environmental toxicants, including ambient particulate matter, pesticides, heavy metals, and organic solvents, have been identified as significant contributors to cardiovascular and brain aging disorders. These toxicants can inflict both macro- and microvascular damage and many of them can also cross the blood-brain barrier, inducing neurotoxic effects, neuroinflammation, and neuronal dysfunction. In conclusion, environmental factors play a critical role in modulating cardiovascular and brain aging. A deeper understanding of how environmental toxicants exacerbate aging processes and contribute to the pathogenesis of neurodegenerative diseases, VCI, and dementia is crucial for the development of preventive strategies and interventions to promote cardiovascular, cerebrovascular, and brain health. By mitigating exposure to harmful environmental factors and promoting healthy aging, we can strive to reduce the burden of age-related cardiovascular and brain pathologies in the aging population.

Occupational Exposures in Commercial Laundry and Dry Cleaning Industries and their Associative Cancers: A Scoping Review

Background

The laundry and dry cleaning industries are critical for maintaining cleanliness and hygiene in our daily lives. However, these industries have also been identified as sources of hazardous chemical exposure for workers, leading to potentially severe health implications. Despite mounting evidence that solvents like perchloroethylene and trichloroethylene are carcinogenic to humans, they remain the most commonly used solvents in the industry. In addition, while alternative solvents are increasingly being utilized in response to evidence of adverse health and environmental effects, there remains a significant gap in our understanding of the potential risks associated with exposure to these new agents.

Methods

A systematic scoping review was conducted to identify prevalent toxic substances in the commercial laundry and dry cleaning industries that workers are exposed to and, further, to identify gaps in the existing literature regarding those exposures and related cancer development. Reported study exposure values were compared with current occupational exposure limits and biological exposure indices.

Results

Most studies examined perchloroethylene exposure in the dry cleaning industry, with one notable finding being that genotoxic effects were found even below current occupational exposure limits. Separate studies on TCE and benzene presented varied exposure levels and health risks, raising concern due to their IARC Group 1 carcinogen classification. Lastly, data on alternative solvents was limited, with a lack of health outcome data and gaps in their exposure guidelines and carcinogenic classifications.

Conclusion

A gap in research exists regarding health outcomes, particularly cancer development, from solvent exposure in the dry cleaning industry. Most studies (66%) overlooked health implications, especially for emerging solvents. Further, results showed potential DNA damage from the established solvent, perchloroethylene, even below current occupational exposure limits, emphasizing the need to reevaluate safety limits. As alternative solvents like butylal and high-flashpoint hydrocarbons become more prevalent, investigations into the effects of their exposure are necessary to safeguard workers' health. This scoping review is registered with the Open Science Framework, registration DOI: https://doi.org/10.17605/OSF.IO/Q8FR3.

Recent advances and trends of trichloroethylene biodegradation: A critical review

Trichloroethylene (TCE) is a ubiquitous chlorinated aliphatic hydrocarbon (CAH) in the environment, which is a Group 1 carcinogen with negative impacts on human health and ecosystems. Based on a series of recent advances, the environmental behavior and biodegradation process on TCE biodegradation need to be reviewed systematically. Four main biodegradation processes leading to TCE biodegradation by isolated bacteria and mixed cultures are anaerobic reductive dechlorination, anaerobic cometabolic reductive dichlorination, aerobic co-metabolism, and aerobic direct oxidation. More attention has been paid to the aerobic co-metabolism of TCE. Laboratory and field studies have demonstrated that bacterial isolates or mixed cultures containing Dehalococcoides or Dehalogenimonas can catalyze reductive dechlorination of TCE to ethene. The mechanisms, pathways, and enzymes of TCE biodegradation were reviewed, and the factors affecting the biodegradation process were discussed. Besides, the research progress on material-mediated enhanced biodegradation technologies of TCE through the combination of zero-valent iron (ZVI) or biochar with microorganisms was introduced. Furthermore, we reviewed the current research on TCE biodegradation in field applications, and finally provided the development prospects of TCE biodegradation based on the existing challenges. We hope that this review will provide guidance and specific recommendations for future studies on CAHs biodegradation in laboratory and field applications.

Systematic review of perchloroethylene and non-Hodgkin's lymphoma

We conducted a systematic review of epidemiology studies that evaluated the association between perchloroethylene (PCE) and non-Hodgkin's lymphoma (NHL). This included an independent detailed assessment of a few critical aspects of study quality (i.e., study design, exposure measurement, exposure levels, and potential confounding), and a consideration of other aspects of quality less formally. Of the identified 18 cohort studies of 15 unique cohorts, 17 case-control studies of 14 unique population groups, and 3 ecological studies, none was high quality for all four critical quality elements and each study also had other major methodological study limitations. Reported risk estimates were mostly null, ranged widely from below to above 1, and often had extremely wide confidence intervals (CIs), indicating unstable risk estimates. In addition, there was no consistent evidence of dose-response. Overall, given the low quality of the available epidemiology studies, the evidence does not support an association between PCE exposure and NHL.

Epidemiology of Renal Cell Carcinoma: 2022 Update

CONTEXT

International variations in the rates of kidney cancer (KC) are considerable. An understanding of the risk factors for KC development is necessary to generate opportunities to reduce its incidence through prevention and surveillance.

OBJECTIVE

To retrieve and summarize global incidence and mortality rates of KC and risk factors associated with its development, and to describe known familial syndromes and genetic alterations that represent biologic risk factors.

EVIDENCE ACQUISITION

A systematic review was conducted via Medline (PubMed) and Scopus to include meta-analyses, reviews, and original studies regarding renal cell carcinoma, epidemiology, and risk factors.

EVIDENCE SYNTHESIS

Our narrative review provides a detailed analysis of KC incidence and mortality, with significant variations across time, geography, and sex. In particular, while KC incidence has continued to increase, mortality models have leveled off. Among the many risk factors, hypertension, obesity, and smoking are the most well established. The emergence of new genetic data coupled with observational data allows for integrated management and surveillance strategies for KC care.

CONCLUSIONS

KC incidence and mortality rates vary significantly by geography, sex, and age. Associations of the development of KC with modifiable and fixed risk factors such as obesity, hypertension, smoking, and chronic kidney disease (CKD)/end-stage kidney disease (ESKD) are well described. Recent advances in the genetic characterization of these cancers have led to a better understanding of the germline and somatic mutations that predispose patients to KC development, with potential for identification of therapeutic targets that may improve outcomes for these at-risk patients.

PATIENT SUMMARY

We reviewed evidence on the occurrence of kidney cancer (KC) around the world. Currently, the main avoidable causes are smoking, obesity, and high blood pressure. Although other risk factors also contribute, prevention and treatment of these three factors provide the best opportunities to reduce the risk of developing KC at present.

Unveiling the positive effect of mineral induced natural organic matter (NOM) on catalyst properties and catalytic dechlorination performance: An experiment and DFT study

Herein, we report the significant effects of natural organic matter contained in natural zeolite (Z-NOM) on the physicochemical characteristics of a Ni/Fe@natural zeolite (NF@NZ) catalyst and its decontamination performance toward the dechlorination of trichloroethylene (TCE). Z-NOM predominantly consists of humic-like substances and has demonstrable utility in the synthesis of bimetallic catalysts. Compared to NF@NZ_600C (devoid of Z-NOM), NF@NZ had increased dispersibility and mobility and showed significant enhancement in the catalytic dechlorination of TCE owing to the encapsulation of Ni⁰/Fe⁰ nanoparticles by Z-NOM. The results of corrosion experiments, spectroscopic analyses, and H₂ production experiments confirmed that Ni⁰ acted as an efficient cocatalyst with Fe⁰ to enhance the dechlorination of TCE to ethane, and Z-NOM-capped Ni⁰ showed improved adsorption of TCE and atomic hydrogen on their reactive sites and oxidation resistance. The density functional theory (DFT) studies have substantiated the improved adsorption of TCE due to the presence of NOM (especially by COOH structure) and the enhanced charge density at the Ni site in the Ni/Fe bimetal alloy for the stronger adsorption of hydrogen atoms that ultimately enhanced the TCE reduction reaction. These findings illustrate the efficiency of NOM containing natural minerals toward the synthesis of bimetallic catalysts for practical applications.

Palladium-Doped Single-Walled Carbon Nanotubes as a New Adsorbent for Detecting and Trapping Volatile Organic Compounds: A First Principle Study

Volatile organic compounds (VOCs) are in the vapor state in the atmosphere and are considered pollutants. Density functional theory (DFT) calculations with the wb97xd exchange correlation functional and the 6-311+G(d,p) basis set are carried out to explore the potential possibility of palladium-doped single-walled carbon nanotubes (Pd/SWCNT-V), serving as the resource for detecting and/or adsorbing acetonitrile (ACN), styrene (STY), and perchloroethylene (PCE) molecules as VOCs. The suggested adsorbent in this study is discussed with structural parameters, frontier molecular orbital theory, molecular electrical potential surfaces (MEPSs), natural bond orbital (NBO) analyses, and the density of states. Furthermore, following the Bader theory of atoms in molecules (AIM), the topological properties of the electron density contributions for intermolecular interactions are analyzed. The obtained results show efficient VOC loading via a strong chemisorption process with a mean adsorption energy of −0.94, −1.27, and −0.54 eV for ACN, STY, and PCE, respectively. Our results show that the Pd/SWCNT-V can be considered a good candidate for VOC removal from the environment.

Benzene exposure and non-Hodgkin lymphoma: a systematic review and meta-analysis of human studies

BACKGROUND

Non-Hodgkin lymphoma comprises a heterogeneous group of cancers with unresolved aetiology, although risk factors include environmental exposures to toxic chemicals. Although the ubiquitous pollutant benzene is an established leukemogen, its potential to cause non-Hodgkin lymphoma has been widely debated. We aimed to examine the potential link between benzene exposure and risk of non-Hodgkin lymphoma in humans by evaluating a wide array of cohort and case-control studies using electronic systematic review.

METHODS

We did a comprehensive systematic review and meta-analysis of all qualified human epidemiological studies that assessed the relationship between benzene exposure and non-Hodgkin lymphoma. We queried the PubMed and Embase databases for relevant articles published before June 5, 2019, and applied the SysRev platform for study selection. All peer-reviewed human cohort and case-control studies that reported non-Hodgkin lymphoma risk estimates specifically for benzene exposure were eligible for inclusion. Studies that calculated relative risks (RRs) for industries or job types without identifying those specifically exposed to benzene, that combined non-Hodgkin lymphoma with other cancer types, or that reported many different solvent exposures together were excluded. From each study, two investigators independently extracted information on the study design, location, years, sample size, participation rates, age, sex, sources of cases and controls, diagnosis, histological verification, exposure assessment, results, adjustment, and statistical analysis, and subsequently assessed study quality. We calculated the meta-analysis relative risk (meta-RR) and CIs using the fixed effect and random effect models, as well as assessing publication bias.

FINDINGS

Our search yielded 2481 articles. After screening and removal of duplicates, 20 case-control studies and eight cohort studies were included in our meta-analysis, which included a total of 9587 patients with non-Hodgkin lymphoma. We reported an increased meta-relative risk (meta-RR) of 33% in highly exposed groups, when data were available (meta-RR 1·33 [95% CI 1·13-1·57], n=28). The meta-RR rose to 1·51 (1·22-1·87, n=18) in the studies that provided results specifically for highly exposed individuals. In particular, we reported a doubling of this risk for diffuse large B-cell lymphoma, a major non-Hodgkin lymphoma subtype (1·67 [1·01-2·77]). We also detected increased risks for follicular lymphoma (1·47 [0·95-2·27]) and hairy cell leukaemia (1·77 [0·99-3·16]), though they were not statistically significant. Funnel plot, Egger's test (p=0·77) and Begg's test (p=0·98) did not show evidence of publication bias. We evaluated the major aspects of causal inference and found evidence to support all the Hill considerations for assigning causation.

INTERPRETATION

Our findings suggest a causal link between benzene exposure and non-Hodgkin lymphoma, especially for diffuse large B-cell lymphoma.

FUNDING

National Institute of Environmental Health Sciences.

Curcumin reverses hepatic epithelial mesenchymal transition induced by trichloroethylene by inhibiting IL-6R/STAT3

OBJECTIVE

Epithelial mesenchymal transition (EMT) and inflammation have been identified as carcinogenic agents. This study aims to investigate whether inhibition of trichloroethylene (TCE) associated hepatocellular carcinoma (HCC) by curcumin is associated with inflammation and EMT.

METHODS

In the current study, TCE sub-chronic cell model was induced in vitro, and the effects of TCE on cell proliferation, migration, invasion, and expression of functional proteins were verified by Western blot, MTT, clone formation, wound healing, Transwell. The detoxification effect of curcumin on TCE was explored by a mouse tumor-bearing experiment.

RESULTS

TCE induces hepatocyte migration, colony formation, and EMT in vitro. In vivo studies have shown that curcumin significantly reduces the mortality of mice and control the occurrence and size of liver tumors by inhibiting the IL-6/STAT3 signaling pathway. In vitro, curcumin inhibits the proliferation of HepG2 cells as determined by MTT assay. In addition, curcumin significantly inhibited the protein expression of IL-6R, STAT3, snail, survivin, and cyclin D1 in THLE-2 and HepG2 cells induced by IL-6.

CONCLUSION

Curcumin has anti-inflammatory and anti-proliferative effects, and inhibits the development of HCC induced by TCE by reversing IL-6/STAT3 mediated EMT.

Perchloroethylene and Dry Cleaning: It's Time to Move the Industry to Safer Alternatives

Perchloroethylene (PERC) is the most common solvent used for dry cleaning in the United States. PERC is a reproductive toxicant, neurotoxicant, potential human carcinogen, and a persistent environmental pollutant. The Environmental Protection Agency is evaluating PERC under the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amended the Toxic Substances Control Act (amended TSCA), and has mandated that PERC dry cleaning machines be removed from residential buildings. Some local and state programs are also requiring or facilitating transitions to alternative cleaning technologies. However, the potential for these alternatives to harm human health and the environment is not well-understood. This review describes the issues surrounding the use of PERC and alternative solvents for dry cleaning while highlighting the lessons learned from a local government program that transitioned PERC dry cleaners to the safest current alternative: professional wet cleaning. Implications for future public health research and policy are discussed: (1) we must move away from PERC, (2) any transition must account for the economic instability and cultural aspects of the people who work in the industry, (3) legacy contamination must be addressed even after safer alternatives are adopted, and (4) evaluations of PERC alternatives are needed to determine their implications for the long-term health and sustainability of the people who work in the industry.

Effects of Trichloroethylene on the Expression of Long Intergenic Noncoding RNAs in B6C3F1 Mouse Liver

Trichloroethylene (TCE), a widely used industrial solvent, is a common environmental contaminant. We previously reported that TCE-induced changes in DNA methylation and miRNA expression contributed to the development of a liver tumor in mice. In this study, we investigated the role of long intergenic noncoding RNA (LincRNA), another type of epigenetic modification, in TCE hepatocarcinogenesis. Male B6C3F1 mice were gavaged with TCE at dose levels of 0, 100, 500, and 1000 mg/kg b.w. for 5 days. The expression changes of LincRNAs in liver samples from control and TCE-exposed mice were screened by microarray. When compared to the control group, 21 and 29 LincRNAs were upregulated and downregulated, respectively, in the liver of mice exposed to TCE at 1000 mg/kg b.w. In addition, TCE treatment increased the expression levels of LincRNA-GM8704 but decreased the expression levels of LiverLincs_chr17_4383_2 in a dose-dependent manner. We further found that the mRNAs that are highly correlated with the expression of LiverLincs_chr17_4383_2 are involved in a number of cancer-related signaling pathways including PPARs, cell cycle, and ErbB and p53 signaling pathways. Among the expression-correlated mRNAs, Cdkn1a was found to be a downstream target gene of LiverLincs_chr17_4383_2. To follow up on that, we also found that miR-182-5p might mediate the association between downregulation of LiverLincs_chr17_4383_2 and upregulation of Cdkn1a, leading to increased cell proliferation in TCE exposed liver cells. In conclusion, TCE induced extensive LincRNA expression changes in mouse liver, and the downregulation of LiverLincs_chr17_4383_2 might contribute to TCE hepatocarcinogenesis by interacting with miR-182-5p and Cdkn1a.

Potential applications of extracellular enzymes from Streptomyces spp. in various industries

Extracellular enzymes produced from Streptomyces have the potential to replace toxic chemicals that are being used in various industries. The endorsement of this replacement has not received a better platform in developing countries. In this review, we have discussed the impact of chemicals and conventional practices on environmental health, and the role of extracellular enzymes to replace these practices. Burning of fossil fuels and agriculture residue is a global issue, but the production of biofuel using extracellular enzymes may be the single key to solve all these issues. We have discussed the replacement of hazardous chemicals with the use of xylanase, cellulase, and pectinase in food industries. In paper industries, delignification was done by the chemical treatment, but xylanase and laccase have the efficient potential to remove the lignin from pulp. In textile industries, the conventional method includes the chemicals which affect the nervous system and other organs. The use of xylanase, cellulase, and pectinase in different processes can give a safe and environment-friendly option to textile industries. Hazardous chemical pesticides can be replaced by the use of chitinase as an insecticide and fungicide in agricultural practices.

A mixtures approach to solvent exposures and amyotrophic lateral sclerosis: a population-based study in Denmark

Studies of occupational solvent exposures and amyotrophic lateral sclerosis (ALS) have been conflicting. We conducted a population-based case-control study of mixed occupational solvent exposures and ALS. Using the Danish National Patient Registry, we identified ALS cases in Denmark from 1982 to 2013, and matched them to 100 controls based on sex and birth year. We estimated cumulative exposures to solvents (benzene, methylene chloride, toluene, trichloroethylene, perchloroethylene, and 1,1,1-trichloroethane) via job exposure matrices and applied them to occupational history from the Danish Pension Fund. Sex-stratified conditional logistic regression analyses revealed higher adjusted odds of ALS for men with exposure to benzene (aOR = 1.20; 95% CI 1.02, 1.41) and methylene chloride (aOR = 1.23; 95% CI 1.07, 1.42). We used weighted quantile sum regression to explore combined solvent exposures and risk of ALS in exposed subjects and found increased odds of 26 to 28% in all exposure lag periods for every one-unit increase in the mixture index in men. Weights of methylene chloride predominated the mixture index in all lag periods. Our study suggests an increased risk of ALS in men exposed to multiple solvents, with the greatest influence being from methylene chloride. These findings highlight the need to utilize mixtures analysis when considering co-occurring exposures.

EASL Clinical Practice Guideline: Occupational liver diseases

A variety of chemicals have been linked to occupational liver diseases, including several solvents and mixtures thereof, pesticides, and metals. Workplace exposures have been associated with virtually the entire spectrum of acute and chronic liver diseases. However, their prevalence is inadequately quantified and their epidemiology limited. Occupational liver diseases may result from high accidental or from prolonged lower level exposures. Whereas the former is uncommon and easily recognised, the latter are relatively more frequent but often overlooked because they may display normal values of conventional markers, have an insidious onset and be asymptomatic or be obfuscated and confounded by concurrent conditions. In addition, specific tests of toxicity are not available, histopathology may not be revealing and the assessment of internal dose of chemicals is usually not decisive. Given these circumstances, the diagnosis of these liver disorders is challenging, one of exclusion and often requires an interdisciplinary approach. These recommendations offer a classification of the type of liver injuries associated with occupational exposures - based in part on the criteria for drug-induced liver injury - a grading of their severity, and the diagnostic and preventive criteria for chemically induced occupational liver disease.

Use and Reliability of Exposure Assessment Methods in Occupational Case-Control Studies in the General Population: Past, Present, and Future

Introduction

Retrospective occupational exposure assessment has been challenging in case-control studies in the general population. We aimed to review (i) trends of different assessment methods used in the last 40 years and (ii) evidence of reliability for various assessment methods.

Methods

Two separate literature reviews were conducted. We first reviewed all general population cancer case-control studies published from 1975 to 2016 to summarize the exposure assessment approach used. For the second review, we systematically reviewed evidence of reliability for all methods observed in the first review.

Results

Among the 299 studies included in the first review, the most frequently used assessment methods were self-report/assessment (n = 143 studies), case-by-case expert assessment (n = 139), and job-exposure matrices (JEMs; n = 82). Usage trends for these methods remained relatively stable throughout the last four decades. Other approaches, such as the application of algorithms linking questionnaire responses to expert-assigned exposure estimates and modelling of exposure with historical measurement data, appeared in 21 studies that were published after 2000. The second review retrieved 34 comparison studies examining methodological reliability. Overall, we observed slightly higher median kappa agreement between exposure estimates from different expert assessors (~0.6) than between expert estimates and exposure estimates from self-reports (~0.5) or JEMs (~0.4). However, reported reliability measures were highly variable for different methods and agents. Limited evidence also indicates newer methods, such as assessment using algorithms and measurement-calibrated quantitative JEMs, may be as reliable as traditional methods.

Conclusion

The majority of current research assesses exposures in the population with similar methods as studies did decades ago. Though there is evidence for the development of newer approaches, more concerted effort is needed to better adopt exposure assessment methods with more transparency, reliability, and efficiency.

Environmental risk factors for liver cancer and nonalcoholic fatty liver disease

Purpose of review

The objective of this review was to summarize recent epidemiologic research examining the associations between environmental exposures and liver cancer and nonalcoholic fatty liver disease (NAFLD).

Recent findings

There were 28 liver cancer studies showing positive associations for exposures to aflatoxin, air pollution, polycyclic aromatic hydrocarbons, asbestos, chimney sweeping occupation, and paints; an inverse association for ultraviolet radiation; and null/inconsistent results for organic solvents, pesticides, perfluorooctanoic acid, nuclear radiation, iron foundry occupation, and brick kiln pollution. There were n=5 NAFLD studies showing positive associations for heavy metals, methyl tertiary-butyl ether, and selenium; and no association with trihalomethanes.

Summary

Evidence suggests that particular environmental exposures may be associated with liver cancer and NAFLD. Future liver cancer studies should examine specific histological subtypes and assess historical environmental exposures. Future NAFLD research should examine incident, biopsy-confirmed cases and the potential role of obesity and/or diabetes in studies of environmental factors and NAFLD.

Case-control investigation of occupational exposure to chlorinated solvents and non-Hodgkin's lymphoma

OBJECTIVES

Although many studies have investigated the association between trichloroethylene (TCE) exposure and non-Hodgkin's lymphoma (NHL), less is known about other chlorinated solvents. We extended our previous analysis of occupational TCE exposure in a multicentre population-based case-control study of NHL to investigate associations with five additional chlorinated solvents: 1,1,1,-trichloroethane, carbon tetrachloride, chloroform, methylene chloride and perchloroethylene.

METHODS

Cases (n=1189) and controls (n=982) provided detailed information on their occupational histories and workplace exposure to chlorinated solvents for selected occupations using job-specific interview modules. An industrial hygienist used this information and a review of the literature to assess occupational exposure to chlorinated solvents. We computed ORs and 95% CIs for different exposure metrics, with the unexposed group as the referent. We also computed ORs by NHL subtype.

RESULTS

High cumulative hours exposed to carbon tetrachloride was associated with NHL (>520 hours: OR 1.9; 95% CI 1.0 to 3.6; Ptrend=0.04). This association remained after restricting to jobs with high-intensity exposure (OR 2.0; 95% CI 1.1 to 3.8; P=0.03) and ≥90% exposure probability (OR 2.1; 95% CI 1.0 to 4.3; P=0.03), adjusting for TCE (OR 2.1; 95% CI 1.0- to 4.1; P=0.04) and incorporating a 15-year lag (OR 1.9; 95% CI 1.0 to 3.6; P=0.06). The other evaluated chlorinated solvents were not associated with NHL.

CONCLUSIONS

This is the first study using high-quality quantitative exposure assessment methods to identify a statistically significant elevated association between occupational exposure to carbon tetrachloride and NHL. Our findings, although limited by a small number of exposed cases, offer evidence that carbon tetrachloride may be a lymphomagen.

Metabolism of Glutathione S-Conjugates: Multiple Pathways

Many potentially toxic electrophilic xenobiotics and some endogenous compounds are detoxified by conversion to the corresponding glutathione S-conjugate, which is metabolized to the N-acetylcysteine S-conjugate (mercapturate) and excreted. Some mercapturate pathway components, however, are toxic. Bioactivation (toxification) may occur when the glutathione S-conjugate (or mercapturate) is converted to a cysteine S-conjugate that undergoes a β-lyase reaction. If the sulfhydryl-containing fragment produced in this reaction is reactive, toxicity may ensue. Some drugs and halogenated workplace/environmental contaminants are bioactivated by this mechanism. On the other hand, cysteine S-conjugate β-lyases occur in nature as a means of generating some biologically useful sulfhydryl-containing compounds.

Developmental neurotoxic effects of a low dose of TCE on a 3-D neurosphere system

Trichloroethylene (TCE) is one of the industrial toxic byproducts that now persist in the air, soil, and water. Several studies have already illustrated the toxic effect of high doses of TCE on the biological functions of several organs. This study aims to highlight the toxic impact of a low dose of TCE (1 μmol/L) on the development of rat neural stem cells (NSCs). The subventricular zones (SVZ) of rat pup's brains were collected and minced, and the harvested cells were cultured in the presence of neural growth factors B27/N2 to develop neurospheres. The cells were then exposed to a dose of 1 μmol/L TCE for 1 or 2 weeks. The outcomes indicated a remarkable inhibitory effect of TCE on the differentiation capacity of NSCs, which was confirmed by down-regulation of the astrocyte marker GFAP The inhibitory effect of TCE on the proliferation of NSCs was identified by the reductions in neurosphere diameter, Ki67 expression, and cell cycle arrest at the G1/S phase. Immunolabelling with annexin V indicated the proapoptotic effect of TCE exposure. PCR results revealed a TCE-mediated suppression of the expression of the antioxidant enzyme SOD1. This paper illustrates, for the first time, a detailed examination of the toxic effects of an environmentally low dose of TCE on NCSs at the transcriptional, translational, and functional levels.

Contribution of job-exposure matrices for exposure assessment in occupational safety and health monitoring systems: application from the French national occupational disease surveillance and prevention network

OBJECTIVES

To detect new hazards ("signals"), occupational health monitoring systems mostly rest on the description of exposures in the jobs held and on reports by medical doctors; these are subject to declarative bias. Our study aims to assess whether job-exposure matrices (JEMs) could be useful tools for signal detection by improving exposure reporting.

METHODS

Using the French national occupational disease surveillance and prevention network (RNV3P) data from 2001 to 2011, we explored the associations between disease and exposure prevalence for 3 well-known pathology/exposure couples and for one debatable couple. We compared the associations measured when using physicians' reports or applying the JEMs, respectively, for these selected diseases and across non-selected RNV3P population or for cases with musculoskeletal disorders, used as two reference groups; the ratio of exposure prevalences according to the two sources of information were computed for each disease category.

RESULTS

Our population contained 58,188 subjects referred with pathologies related to work. Mean age at diagnosis was 45.8 years (95% CI 45.7; 45.9), and 57.2% were men. For experts, exposure ratios increase with knowledge on exposure causality. As expected, JEMs retrieved more exposed cases than experts (exposure ratios between 12 and 194), except for the couple silica/silicosis, but not for the MSD control group (ratio between 0.2 and 0.8).

CONCLUSIONS

JEMs enhanced the number of exposures possibly linked with some conditions, compared to experts' assessment, relative to the whole database or to a reference group; they are less likely to suffer from declarative bias than reports by occupational health professionals.

A task-based assessment of parental occupational exposure to organic solvents and other compounds and the risk of childhood leukemia in California

PURPOSE

Data on parental occupational exposures and risk of childhood leukemia lack specificity. Using 19 task-based job modules, we examined the relationship between occupational exposure to organic solvents and other compounds and the risk of leukemia in children.

METHODS

Latino (48%) and non-Latino (52%) children with acute lymphoblastic leukemia (ALL; n=670), acute myeloid leukemia (AML; n=104), and controls (n=1021) were enrolled in a study in California (2000-2008). Logistic regression models were used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for socio-demographic factors.

RESULTS

Among children with non-Latino fathers, none of the exposures evaluated were associated with risks of ALL and AML. In contrast, exposure to any organic solvents in Latino fathers was associated with an increased risk of childhood ALL (OR=1.48; 95% CI: 1.01-2.16); in multivariable analyses, the OR for chlorinated hydrocarbons was 2.28 (95% CI: 0.97-5.37) while the ORs were close to one for aromatic hydrocarbons, glycol ethers, and other hydrocarbon mixtures. We also observed an increased risk of ALL with exposure to combustion exhaust/polycyclic aromatic hydrocarbons (PAHs) (ORs=1.70; 95% CI: 1.16-2.57, and 1.46; 95% CI: 0.94-2.26 with and without adjustment for chlorinated hydrocarbons, respectively). Moderately elevated risks of ALL were seen with exposure to metals, paints, and wood dust, although not statistically significant. An increased risk was reported for asbestos based on small numbers of exposed Latino fathers. No associations were reported between maternal exposures to any exposures and childhood ALL and AML.

CONCLUSIONS

Our data support associations between paternal occupational exposures to chlorinated hydrocarbons, combustion exhaust, metals, and possibly asbestos and the risk of ALL in the children of Latino fathers only.

Target Organ Metabolism, Toxicity, and Mechanisms of Trichloroethylene and Perchloroethylene: Key Similarities, Differences, and Data Gaps

Trichloroethylene (TCE) and perchloroethylene or tetrachloroethylene (PCE) are high-production volume chemicals with numerous industrial applications. As a consequence of their widespread use, these chemicals are ubiquitous environmental contaminants to which the general population is commonly exposed. It is widely assumed that TCE and PCE are toxicologically similar; both are simple olefins with three (TCE) or four (PCE) chlorines. Nonetheless, despite decades of research on the adverse health effects of TCE or PCE, few studies have directly compared these two toxicants. Although the metabolic pathways are qualitatively similar, quantitative differences in the flux and yield of metabolites exist. Recent human health assessments have uncovered some overlap in target organs that are affected by exposure to TCE or PCE, and divergent species- and sex-specificity with regard to cancer and noncancer hazards. The objective of this minireview is to highlight key similarities, differences, and data gaps in target organ metabolism and mechanism of toxicity. The main anticipated outcome of this review is to encourage research to 1) directly compare the responses to TCE and PCE using more sensitive biochemical techniques and robust statistical comparisons; 2) more closely examine interindividual variability in the relationship between toxicokinetics and toxicodynamics for TCE and PCE; 3) elucidate the effect of coexposure to these two toxicants; and 4) explore new mechanisms for target organ toxicity associated with TCE and/or PCE exposure.

NYPD Cancer Incidence Rates 1995-2014 Encompassing the Entire World Trade Center Cohort

OBJECTIVE

The aim of this study was to compare cancer incidence rates (CIRs), between preexposure (1995-2000) and postexposure (2002-2014) periods in the entire New York City Police Department cohort exposed to the 2001 World Trade Center (WTC) disaster.

METHODS

CIR derived from active duty officer records, including postexposure data on retired officers.

RESULTS

We observed 870 cancer cases in 859 officers (1995-2014), including 193 active duty cases pre-WTC and 677 cases (484 active duty, 193 retired) post-WTC. Overall, median CIR increased 1.44-fold compared with pre-WTC, with brain cancer increasing 3.27-fold, and kidney cancer increasing similarly. Thyroid cancer and non-Hodgkin's lymphoma increased 2.29 and 1.68-fold, respectively.

CONCLUSIONS

Findings should be interpreted cautiously, given the small number of cancers at specific sites, and possibility of confounders. However, apparent increases in cancers overall, and in highlighted sites, remain of concern, underscoring the need for continued monitoring of this cohort.

Mitochondrial Dysfunction, Disruption of F-Actin Polymerization, and Transcriptomic Alterations in Zebrafish Larvae Exposed to Trichloroethylene

Trichloroethylene (TCE) is primarily used as an industrial degreasing agent and has been in use since the 1940s. TCE is released into the soil, surface, and groundwater. From an environmental and regulatory standpoint, more than half of Superfund hazardous waste sites on the National Priority List are contaminated with TCE. Occupational exposure to TCE occurs primarily via inhalation, while environmental TCE exposure also occurs through ingestion of contaminated drinking water. Current literature links TCE exposure to various adverse health effects including cardiovascular toxicity. Current studies aiming to address developmental cardiovascular toxicity utilized rodent and avian models, with the majority of studies using relatively higher parts per million (mg/L) doses. In this study, to further investigate developmental cardiotoxicity of TCE, zebrafish embryos were treated with 0, 10, 100, or 500 parts per billion (ppb; μg/L) TCE during embryogenesis and/or through early larval stages. After the appropriate exposure period, angiogenesis, F-actin, and mitochondrial function were assessed. A significant dose-response decrease in angiogenesis, F-actin, and mitochondrial function was observed. To further complement this data, a transcriptomic profile of zebrafish larvae was completed to identify gene alterations associated with the 10 ppb TCE exposure. Results from the transcriptomic data revealed that embryonic TCE exposure caused significant changes in genes associated with cardiovascular disease, cancer, and organismal injury and abnormalities with a number of targets in the FAK signaling pathway. Overall, results from our study support TCE as a developmental cardiovascular toxicant, provide molecular targets and pathways for investigation in future studies, and indicate a need for continued priority for environmental regulation.

Is a long term work in automotive industry a risk factor for renal dysfunction?

Background:

Disorders of renal system can cause renal failure; therefore screening is necessary especially in workers who are exposed to harmful materials. Hypertension, diabetes mellitus, and hazardous exposures are non-occupational and occupational risk factors for renal diseases.

Aim:

The objective of this study was to determine the effects of working in automotive industry on renal function in Iran.

Subjects and Methods:

In a historical cohort study, workers of automotive industry who worked in production and had low exposure to metal fumes were selected and divided to three groups with 5–10, 11–20, and 21–30 years work duration. risk factors for renal diseases were collected and analyzed with SPSS using one-way ANOVA, correlation coefficient and with P < 0.05 and relative risk with a confidence interval (CI).

Results:

The means of work duration in Groups (A), (B) and (C) were 9.8 (0.6), 13.8 (2.0), 22.3 (1.6) years respectively with ANOVA (F) =187.864 and P < 0.01. Glomerular filtration rate (GFR) was 59.75 (0.70), 59.16 (1.52) and 59.10 (2.23) in Groups (A), (B), and (C) respectfully The relative risk of creatinine clearance, uric acid and mean blood pressure were the highest in Group (B); 1.970 - CI, 0.541–7.169, 1.571 95% CI: 0.198–12.470, and 1.519 95% CI: 0.425–5.426, but the differences were not significant.

Conclusion:

GFRs were decreased with work duration, but the differences were not significant. Working in automotive Industry with low exposure to toxic metals and solvents has no significant effect on GFR, creatinine clearance, uric acid, and mean blood pressure.

Comparative analysis of the relationship between trichloroethylene metabolism and tissue-specific toxicity among inbred mouse strains: liver effects

Trichloroethylene (TCE) is a widely used organic solvent. Although TCE is classified as carcinogenic to humans, substantial gaps remain in our understanding of interindividual variability in TCE metabolism and toxicity, especially in the liver. A hypothesis was tested that amounts of oxidative metabolites of TCE in mouse liver are associated with hepatic-specific toxicity. Oral dosing with TCE was conducted in subacute (600 mg/kg/d; 5 d; 7 inbred mouse strains) and subchronic (100 or 400 mg/kg/d; 1, 2, or 4 wk; 2 inbred mouse strains) designs. The quantitative relationship was evaluated between strain-, dose-, and time-dependent formation of TCE metabolites from cytochrome P-450-mediated oxidation (trichloroacetic acid [TCA], dichloroacetic acid [DCA], and trichloroethanol) and glutathione conjugation [S-(1,2-dichlorovinyl)-L-cysteine and S-(1,2-dichlorovinyl)glutathione] in serum and liver, and various hepatic toxicity phenotypes. In subacute study, interstrain variability in TCE metabolite amounts was observed in serum and liver. No marked induction of Cyp2e1 protein levels in liver was detected. Serum and hepatic levels of TCA and DCA were correlated with increased transcription of peroxisome proliferator-marker genes Cyp4a10 and Acox1 but not with degree of induction in hepatocellular proliferation. In subchronic study, serum and liver levels of oxidative metabolites gradually decreased over time despite continuous dosing. Hepatic protein levels of CYP2E1, ADH, and ALDH2 were unaffected by treatment with TCE. While the magnitude of induction of peroxisome proliferator-marker genes also declined, hepatocellular proliferation increased. This study offers a unique opportunity to provide a scientific data-driven rationale for some of the major assumptions in human health assessment of TCE.

Occupational health risks among trichloroethylene-exposed workers in a clock manufacturing factory

Trichloroethylene (TCE) is an important volatile organic compound once widely used in industry throughout the world. Occupational exposure to TCE can cause a number of health hazards such as allergic reactions and genetic damage. The purpose of this study was to evaluate occupational exposure to TCE, by analysis of the air in the breathing zone and of urine from workers employed in a clock manufacturing factory. A subjective symptom survey was conducted by using a self-administered questionnaire to evaluate the health hazards. Micronucleus (MN) frequency, based on the cytokinesis-block micronucleus assay (CBMN) in peripheral blood lymphocytes, (PBLs) was used as a biomarker for chromosome damage. A total of 244 participants, including 171 workers occupationally exposed to TCE and 73 non-exposed control employees, working mainly in office jobs in the same factory, were enrolled in this study. Analyses of airborne TCE concentrations in the workplace, and of urinary trichloroacetic acid (TCA) of the workers and controls, were performed by Gas Chromatography-Electron Capture Detector (GC-ECD) using the modified headspace technique. The average concentration of TCE in the workplace breathing zone was 27.83 ± 6.02 ppm. The average level of urinary TCA of the exposed workers and controls was 14.84 ± 1.62, 2.95 ± 0.28 mg/L. The frequency of MN/1000BN was 7.029 ± 0.39, significantly higher than for those in the control group (3.57 ± 0.31, p = 0.001). According to multiple linear regression analysis, the results indicated that urinary TCA levels correlated with the increased MN in exposed workers (r = 0.285, p < 0.001). The prevalence rate of subjective symptoms in the exposed group was 9.61-11.76 times higher than the rate of the non-exposed group (p < 0.001). It was found that skin (29.6%) and respiratory symptoms (21.1%) were the most frequent among the exposed workers.

In conclusion, these results indicate that increased micronucleus frequency is associated with occupational trichloroethylene exposure. The use of TCE in the factory is threatening workers’ health.

Human health effects of tetrachloroethylene: key findings and scientific issues

BACKGROUND

The U.S. Environmental Protection Agency (EPA) completed a toxicological review of tetrachloroethylene (perchloroethylene, PCE) in February 2012 in support of the Integrated Risk Information System (IRIS).

OBJECTIVES

We reviewed key findings and scientific issues regarding the human health effects of PCE described in the U.S. EPA's Toxicological Review of Tetrachloroethylene (Perchloroethylene).

METHODS

The updated assessment of PCE synthesized and characterized a substantial database of epidemiological, experimental animal, and mechanistic studies. Key scientific issues were addressed through modeling of PCE toxicokinetics, synthesis of evidence from neurological studies, and analyses of toxicokinetic, mechanistic, and other factors (tumor latency, severity, and background rate) in interpreting experimental animal cancer findings. Considerations in evaluating epidemiological studies included the quality (e.g., specificity) of the exposure assessment methods and other essential design features, and the potential for alternative explanations for observed associations (e.g., bias or confounding).

DISCUSSION

Toxicokinetic modeling aided in characterizing the complex metabolism and multiple metabolites that contribute to PCE toxicity. The exposure assessment approach-a key evaluation factor for epidemiological studies of bladder cancer, non-Hodgkin lymphoma, and multiple myeloma-provided suggestive evidence of carcinogenicity. Bioassay data provided conclusive evidence of carcinogenicity in experimental animals. Neurotoxicity was identified as a sensitive noncancer health effect, occurring at low exposures: a conclusion supported by multiple studies. Evidence was integrated from human, experimental animal, and mechanistic data sets in assessing adverse health effects of PCE.

CONCLUSIONS

PCE is likely to be carcinogenic to humans. Neurotoxicity is a sensitive adverse health effect of PCE.

Toxicogenetic profile and cancer risk in Lebanese

An increasing number of genetic polymorphisms in drug-metabolizing enzymes (DME) were identified among different ethnic groups. Some of these polymorphisms are associated with an increased cancer risk, while others remain equivocal. However, there is sufficient evidence that these associations become significant in populations overexposed to environmental carcinogens. Hence, genetic differences in expression activity of both Phase I and Phase II enzymes may affect cancer risk in exposed populations. In Lebanon, there has been a marked rise in reported cancer incidence since the 1990s. There are also indicators of exposure to unusually high levels of environmental pollutants and carcinogens in the country. This review considers this high cancer incidence by exploring a potential gene-environment model based on available DME polymorphism prevalence, and their impact on bladder, colorectal, prostate, breast, and lung cancer in the Lebanese population. The examined DME include glutathione S-transferases (GST), N-acetyltransferases (NAT), and cytochromes P-450 (CYP). Data suggest that these DME influence bladder cancer risk in the Lebanese population. Evidence indicates that identification of a gene-environment interaction model may help in defining future research priorities and preventive cancer control strategies in this country, particularly for breast and lung cancer.

Occupational exposure to trichloroethylene and risk of non-Hodgkin lymphoma and its major subtypes: a pooled InterLymph [correction of IinterLlymph] analysis

OBJECTIVES

We evaluated the association between occupational exposure to trichloroethylene (TCE) and risk of non-Hodgkin lymphoma (NHL) in a pooled analysis of four international case-control studies.

METHODS

Overall, the pooled study population included 3788 NHL cases and 4279 controls. Risk of NHL and its major subtypes associated with TCE exposure was calculated with unconditional logistic regression and polytomous regression analysis, adjusting by age, gender and study.

RESULTS

Risk of follicular lymphoma (FL), but not NHL overall or other subtypes, increased by probability (p=0.02) and intensity level (p=0.04), and with the combined analysis of four exposure metrics assumed as independent (p=0.004). After restricting the analysis to the most likely exposed study subjects, risk of NHL overall, FL and chronic lymphocytic leukaemia (CLL) were elevated and increased by duration of exposure (p=0.009, p=0.04 and p=0.01, respectively) and with the combined analysis of duration, frequency and intensity of exposure (p=0.004, p=0.015 and p=0.005, respectively). Although based on small numbers of exposed, risk of all the major NHL subtypes, namely diffuse large B-cell lymphoma, FL and CLL, showed increases in risk ranging 2-3.2-fold in the highest category of exposure intensity. No significant heterogeneity in risk was detected by major NHL subtypes or by study.

CONCLUSIONS

Our pooled analysis apparently supports the hypothesis of an increase in risk of specific NHL subtypes associated with occupational exposure to TCE.