Renal cell cancer risk and occupational exposure to trichloroethylene: results of a consecutive case-control study in Arnsberg, Germany

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.

The environment and male reproductive system: the potential role and underlying mechanisms of cadmium in testis cancer

Cadmium is a known human carcinogen, and has been shown to profoundly affect male reproductive function, at multiple levels, by exerting both endocrine and non-endocrine actions. Nevertheless, the potential role of cadmium in the etiology of testis cancer has been scantly investigated in humans, and, currently, available epidemiological observational studies are insufficient to draw definitive conclusions in this regard. On the contrary, experimental studies in laboratory animals demonstrated that cadmium is a strong inducer of testis tumors, mostly represented by benign Leydig cell adenoma; moreover, malignant transformation was also reported in few animals, following cadmium treatment. Early experimental studies in animals proposed an endocrine-dependent mechanism of cadmium-induced testis tumorigenesis; however, more recent findings from cell-free assays, in vitro studies, and short-term in vivo studies, highlighted that cadmium might also contribute to testis tumor development by early occurring endocrine-independent mechanisms, which include aberrant gene expression within the testis, and genotoxic effects, and take place well before the timing of testis tumorigenesis. These endocrine-independent mechanisms, however, have not been directly investigated on testis tumor samples retrieved from affected, cadmium-treated animals so far. The present review focuses on the relationship between cadmium exposure and testis cancer, by reporting the few epidemiological observational human studies available, and by providing animal-based experimental evidences of cadmium implication in the pathogenesis and progression of testis tumor. Moreover, the relevance of experimental animal studies to human cadmium exposure and the translational potential of experimental findings will be extensively discussed, by critically addressing strengths and weaknesses of available data.

An Adverse Outcome Pathway Network for Chemically Induced Oxidative Stress Leading to (Non)genotoxic Carcinogenesis

Nongenotoxic (NGTX) carcinogens induce cancer via other mechanisms than direct DNA damage. A recognized mode of action for NGTX carcinogens is induction of oxidative stress, a state in which the amount of oxidants in a cell exceeds its antioxidant capacity, leading to regenerative proliferation. Currently, carcinogenicity assessment of environmental chemicals primarily relies on genetic toxicity end points. Since NGTX carcinogens lack genotoxic potential, these chemicals may remain undetected in such evaluations. To enhance the predictivity of test strategies for carcinogenicity assessment, a shift toward mechanism-based approaches is required. Here, we present an adverse outcome pathway (AOP) network for chemically induced oxidative stress leading to (NGTX) carcinogenesis. To develop this AOP network, we first investigated the role of oxidative stress in the various cancer hallmarks. Next, possible mechanisms for chemical induction of oxidative stress and the biological effects of oxidative damage to macromolecules were considered. This resulted in an AOP network, of which associated uncertainties were explored. Ultimately, development of AOP networks relevant for carcinogenesis in humans will aid the transition to a mechanism-based, human relevant carcinogenicity assessment that involves a substantially lower number of laboratory animals.

Spatial distribution of health risks for residents located close to solvent-consuming industrial VOC emission sources

Emissions derived from the consumption of organic solvents have been proven to be the primary industrial source of volatile organic compounds (VOCs). In conjunction with epidemiologic studies, water-based paints (WBPs) and solvent-based paints (SBPs) were selected as representatives of newly developed solvents and traditional solvents, respectively, to simulate the effects of consuming solvents emitted during industrial production. And non-carcinogenic and carcinogenic risks to residents near emission sources were studied in detail. The results showed that the spatial distribution of health risks varied with meteorological conditions and type of emission source, and the prevailing wind direction strongly affected the distribution range and shape of the influenced area. The areas of influence maximized on heavy-polluting days for both WBP and SBP emission sources with the total span reaching 804 m and 16 km, respectively; meanwhile, the areas of influence for carcinogenic risk resulting from WBP emission sources were 1.2 and 2.3 times greater than those measured on fine and rainy days, respectively, and 1.8 and 2.9 times greater for SBP emission sources. Compared with WBPs, the total spans of negatively influenced regions resulting from SBP emission sources were 10.4, 12.5 and 19.9 times greater on fine, rainy and heavy-polluting days, respectively. Therefore, carcinogenic risk was the dominant health threat for populations residing close to solvent-consuming industrial emission sources. The findings suggest that newly developed solvents are capable of significantly reducing consequent health threats, nevertheless, they could still pose occasional threats to nearby residents under specific meteorological conditions.

Relationship between occupational sunlight exposure and the incidence of renal cancer

BACKGROUND

The risk factors for renal cancer include smoking, obesity, hypertension, and exposure to trichloroethylene. Recent studies have shown that low sunlight exposure increases the risk of developing a range of cancers, including renal cancer. Given that most of the daytime is spent at work, a lack of occupational sunlight exposure can be a risk factor for renal cancer. Therefore, this study examined the relationship between occupational sunlight exposure and the incidence of renal cancer.

METHODS

This was a university hospital-based case-control study on renal cancer. Of the 706 newly diagnosed patients with renal cell carcinoma (RCC), 633 cases were selected; 73 who had no occupational history were excluded. In addition, 633 controls were selected from the general population after 1:1 matching with respect to sex, age (within 5 years), and residential area (constituency-level). Information on sunlight exposure by the occupational group was referred to data from France. To estimate the association between occupational sunlight exposure and the RCC risk, the odds ratios (ORs) were calculated using conditional logistic regression analysis.

RESULTS

Sunlight exposure was divided into quartiles and the risk of RCC was analyzed. The adjusted OR of RCC (OR: 0.664, 95% confidence interval: 0.449-0.983) was significantly lower for the Q4 group than Q1 group but the Q2 and Q3 groups did not show significant results. The risk of RCC tended to decrease with increasing exposure to sunlight (p for trend < 0.028).

CONCLUSIONS

Higher occupational sunlight exposure reduces the risk of RCC.

Risk assessment of effects of cadmium on human health (IUPAC Technical Report)

Chemistry and Human Health, Division VII of the International Union on Pure and Applied Chemistry (IUPAC), provides guidance on risk assessment methodology and, as appropriate, assessment of risks to human health from chemicals of exceptional toxicity. The aim of this document is to describe dose-response relationships for the health effects of low-level exposure to cadmium, in particular, with an emphasis on causation. The term “cadmium” in this document includes all chemical species of cadmium, as well as those in cadmium compounds. Diet is the main source of cadmium exposure in the general population. Smokers and workers in cadmium industries have additional exposure. Adverse effects have been shown in populations with high industrial or environmental exposures. Epidemiological studies in general populations have also reported statistically significant associations with a number of adverse health effects at low exposures. Cadmium is recognized as a human carcinogen, a classification mainly based on occupational studies of lung cancer. Other cancers have been reported, but dose-response relationships cannot be defined. Cardiovascular disease has been associated with cadmium exposure in recent epidemiological studies, but more evidence is needed in order to establish causality. Adequate evidence of dose-response relationships is available for kidney effects. There is a relationship between cadmium exposure and kidney effects in terms of low molecular mass (LMM) proteinuria. Long-term cadmium exposures with urine cadmium of 2 nmol mmol−1 creatinine cause such effects in a susceptible part of the population. Higher exposures result in increases in the size of these effects. This assessment is supported by toxicokinetic and toxicodynamic (TKTD) modelling. Associations between urine cadmium lower than 2 nmol mmol−1 creatinine and LMM proteinuria are influenced by confounding by co-excretion of cadmium with protein. A number of epidemiological studies, including some on low exposures, have reported statistically significant associations between cadmium exposure and bone demineralization and fracture risk. Exposures leading to urine cadmium of 5 nmol mmol−1 creatinine and more increase the risk of bone effects. Similar associations at much lower urine cadmium levels have been reported. However, complexities in the cause and effect relationship mean that a no-effect level cannot be defined. LMM proteinuria was selected as the critical effect for cadmium, thus identifying the kidney cortex as the critical organ, although bone effects may occur at exposure levels similar to those giving rise to kidney effects. To avoid these effects, population exposures should not exceed that resulting in cadmium values in urine of more than 2 nmol mmol−1 creatinine. As cadmium is carcinogenic, a ‘safe’ exposure level cannot be defined. We therefore recommend that cadmium exposures be kept as low as possible. Because the safety margin for toxic effects in kidney and bone is small, or non-existent, in many populations around the world, there is a need to reduce cadmium pollution globally.

Epigenome Aberrations: Emerging Driving Factors of the Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC), the most common form of Kidney cancer, is characterized by frequent mutations of the von Hippel-Lindau (VHL) tumor suppressor gene in ~85% of sporadic cases. Loss of pVHL function affects multiple cellular processes, among which the activation of hypoxia inducible factor (HIF) pathway is the best-known function. Constitutive activation of HIF signaling in turn activates hundreds of genes involved in numerous oncogenic pathways, which contribute to the development or progression of ccRCC. Although VHL mutations are considered as drivers of ccRCC, they are not sufficient to cause the disease. Recent genome-wide sequencing studies of ccRCC have revealed that mutations of genes coding for epigenome modifiers and chromatin remodelers, including PBRM1, SETD2 and BAP1, are the most common somatic genetic abnormalities after VHL mutations in these tumors. Moreover, recent research has shed light on the extent of abnormal epigenome alterations in ccRCC tumors, including aberrant DNA methylation patterns, abnormal histone modifications and deregulated expression of non-coding RNAs. In this review, we discuss the epigenetic modifiers that are commonly mutated in ccRCC, and our growing knowledge of the cellular processes that are impacted by them. Furthermore, we explore new avenues for developing therapeutic approaches based on our knowledge of epigenome aberrations of ccRCC.

Epidemiology of Renal Cell Carcinoma

The increasing incidence of RCC in most populations may in part be due to increasing numbers of incidentally detected cancers with new imaging methods. Further, the increase is not only limited to small local tumours but also includes more advanced tumours, which may to some part explain the still high mortality rates. The variation in incidence between populations may have several other explanations. Traditionally the starting point has included thoughts of environmental exposures, which so far have only in part explained the causes of RCC, by means of cigarette smoking and obesity, which may account for approximately 40% of cases in high-risk countries (Table 2). Further, the genetic variations may be of importance as a cause of the difference between populations. Continued research in RCC is needed with the knowledge that nearly 50% of patients die within 5 years after diagnosis. The further search for environmental exposures should take in account the knowledge that RCC consists of different types with specific genetic molecular characteristics. These genetic alterations have in some cases been suggested to be associated with specific exposures. Furthermore, there might exist a modulating effect of genetic polymorphisms among metabolic activation and detoxification enzymes. Hence, a further understanding of the genetic and molecular processes involved in RCC will hopefully give us a better knowledge how to analyse and interpret exposure associations that have importance for both initiation and progression of RCC.

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.

Renal cell carcinoma: links and risks

This review provides an overview of the incidence of renal cell carcinoma (RCC) and a summary of the most commonly associated risk factors. A literature review was performed with a focus on recent studies with a high level of evidence (large prospective cohort studies and meta-analyses). The incidence rate of RCC varies globally, with the rate rising rapidly in more developed regions, demonstrating the effects of increased use of diagnostic imaging and prevalence of modifiable risk factors. Based on the current evidence, cigarette smoking, obesity, and hypertension are the most well-established risk factors for sporadic RCC worldwide. Acquired cystic kidney disease is also a significant risk factor, specifically in dialysis patients. There is increasing evidence for an inverse association between RCC risk and moderate alcohol consumption. Certain analgesics and occupational exposure have been linked to an increased risk of RCC, although data are limited. Diets rich in fruits and vegetables may provide a protective effect.

Case report of renal cell carcinoma in automobile manufacturing factory worker due to trichloroethylene exposure in Korea

BACKGROUND

The aim of this paper was report first case of renal cell carcinoma developed in a worker who worked in an automobile manufacture line which handles trichloroethylene in Korea.

CASE PRESENTATION

To clarify the relationship between the onset of renal cell carcinoma in 52-years old male worker and the exposure to trichloroethylene, document studies and work environment measurement were done. Past work environment exposure data were reviewed and medical history and surgery records of the worker were also reviewed. The patient had no personal risk factor related to renal cell carcinoma except for his smoking habit of quarter a pack per day for twenty years, and since trichloroethylene was not part of measurement criteria, past work environment risk assessment data could not verify the exposure. The exposure level is deduced by analyzing material exposure level of work environments which has similar processes in data from revised research of chemical exposure standard and work environment validity assessment. Evaluation Committee of Epidemiologic Survey decided that there are relevant relationship between the exposure and the disease, though we do not have exact data during that period, most experts agree that in every factories they used trichloroethylene without any direction.

CONCLUSIONS

From the relevant medical history and the results of the usage of trichloroethylene in the relevant industries, and initial discovery of renal cell carcinoma at health inspection sonogram in 2001, it can be concluded that suggests significant causal relationship between the exposure to trichloroethylene and renal cell carcinoma onset, thus reporting it to be the first domestic case declared to be occupational disease.

[Health evaluation of trichloroethylene in indoor air : communication from the German ad-hoc working group on indoor guidelines of the Indoor Air Hygiene Committee and of the states' supreme health authorities]

In the European Hazardous Substances Regulation No 1272/2008 trichloroethylene has been classified as a probable human carcinogen and a suspected mutagen. According to several Committees (German Committee on Hazardous Substances, European Scientific Committee on Occupational Exposure Limits, European Chemicals Agency´s Committee for Risk Assessment (ECHA-RAC)) concentrations of trichloroethylene cytotoxic to renal tubuli may increase the risk to develop renal cancer. At non-cytotoxic concentrations of trichloroethylene a much lower cancer risk may be assumed. Therefore, evaluating the cancer risk to the public following inhalation of trichloroethylene ECHA-RAC has assumed a sublinear exposure-response relationship for carcinogenicity of trichloroethylene. Specifically, ECHA-RAC assessed a cancer risk of 6.4 × 10(- 5) (mg/m(3))(- 1) following life time exposure to trichloroethylene below a NOAEC for renal cytotoxicity of 6 mg trichloroethylene/m(3). Further evaluation yields a life-time risk of 10(- 6) corresponding to 0.02 mg trichloroethylene/m(3). This concentration is well above the reference (e.g. background) concentration of trichloroethylene in indoor air. Consequently the Ad-hoc Working Group on Indoor Guidelines recommends 0.02 mg trichloroethylene/m(3) as a risk-related guideline for indoor air. Measures to reduce exposure are considered inappropriate at concentrations below this guideline.

The Relationship between the Occupational Exposure of Trichloroethylene and Kidney Cancer

Trichloroethylene (TCE) has been widely used as a degreasing agent in many manufacturing industries. Recently, the International Agency for Research on Cancer presented “sufficient evidence” for the causal relationship between TCE and kidney cancer. The aim of this study was to review the epidemiologic evidences regarding the relationship between TCE exposure and kidney cancer in Korean work environments. The results from the cohort studies were inconsistent, but according to the meta-analysis and case–control studies, an increased risk for kidney cancer was present in the exposure group and the dose–response relationship could be identified using various measures of exposure. In Korea, TCE is a commonly used chemical for cleaning or degreasing processes by various manufacturers; average exposure levels of TCE vary widely. When occupational physicians evaluate work-relatedness kidney cancers, they must consider past exposure levels, which could be very high (>100 ppm in some cases) and associated with jobs, such as plating, cleaning, or degreasing. The exposure levels at a manual job could be higher than an automated job. The peak level of TCE could also be considered an important exposure-related variable due to the possibility of carcinogenesis associated with high TCE doses. This review could be a comprehensive reference for assessing work-related TCE exposure and kidney cancer in Korea.

Human health risk assessment of trichloroethylene from industrial complex a

This study investigated the human health risks of trichloroethylene from Industrial Complex A. The excessive carcinogenic risks for central tendency exposure were 1.40 × 10(?5) for male and female residents in the vicinity of Industrial Complex A. The excessive cancers risk for reasonable maximum exposure were 2.88 × 10(?5) and 1.97 × 10(?5) for males and females, respectively. These values indicate that there are potential cancer risks for exposure to these concentrations. The hazard index for central tendency exposure to trichloroethylene was 1.71 for male and female residents. The hazard indexes for reasonable maximum exposure were 3.27 and 2.41 for males and females, respectively. These values were over one, which is equivalent to the threshold value. This result showed that adverse cancer and non-cancer health effects may occur and that some risk management of trichloroethylene from Industrial Complex A was needed.

Human health effects of trichloroethylene: key findings and scientific issues

BACKGROUND

In support of the Integrated Risk Information System (IRIS), the U.S. Environmental Protection Agency (EPA) completed a toxicological review of trichloroethylene (TCE) in September 2011, which was the result of an effort spanning > 20 years.

OBJECTIVES

We summarized the key findings and scientific issues regarding the human health effects of TCE in the U.S. EPA's toxicological review.

METHODS

In this assessment we synthesized and characterized thousands of epidemiologic, experimental animal, and mechanistic studies, and addressed several key scientific issues through modeling of TCE toxicokinetics, meta-analyses of epidemiologic studies, and analyses of mechanistic data.

DISCUSSION

Toxicokinetic modeling aided in characterizing the toxicological role of the complex metabolism and multiple metabolites of TCE. Meta-analyses of the epidemiologic data strongly supported the conclusions that TCE causes kidney cancer in humans and that TCE may also cause liver cancer and non-Hodgkin lymphoma. Mechanistic analyses support a key role for mutagenicity in TCE-induced kidney carcinogenicity. Recent evidence from studies in both humans and experimental animals point to the involvement of TCE exposure in autoimmune disease and hypersensitivity. Recent avian and in vitro mechanistic studies provided biological plausibility that TCE plays a role in developmental cardiac toxicity, the subject of substantial debate due to mixed results from epidemiologic and rodent studies.

CONCLUSIONS

TCE is carcinogenic to humans by all routes of exposure and poses a potential human health hazard for noncancer toxicity to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing embryo/fetus.

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

OBJECTIVES

Trichloroethylene (TCE) and Perchloroethylene (PER) are two chlorinated solvents that are applied widely as degreasers of metal parts, and in dry cleaning and other applications. In 2012, the International Agency for Research on Cancer classified TCE as carcinogenic to humans and PER as probably carcinogenic to humans. We explored exposure-response relations for TCE and PER and non-Hodgkin's lymphoma (NHL), multiple myeloma (MM), and cancers of the kidney and liver in the Nordic Occupational Cancer cohort.

METHODS

The cohort was set up by linking occupational information from censuses to national cancer registry data using personal identity codes in use in all Nordic countries. Country, time period, and job-specific exposure estimates were generated for TCE, PER and potentially confounding occupational exposures with a job-exposure matrix. A conditional logistic regression was conducted for exposure groups as well as for continuous cumulative exposure.

RESULTS

HRs for liver cancer, NHL and MM but not kidney cancer were slightly elevated in groups with high exposure to PER (compared to occupationally unexposed subjects). HRs for liver cancer and NHL also increased with increasing continuous exposure to PER. We did not observe evidence for an association between exposure to TCE and NHL, MM or liver and kidney cancer.

CONCLUSIONS

Although this study was subject to limitations related to the low prevalence of exposure to PER and TCE in the Nordic population and a limited exposure assessment strategy, we observed some evidence indicative of an excess risk of cancer of the liver and NHL in subjects exposed to PER.

Altered expression of hepatic metabolic enzyme and apoptosis-related gene transcripts in human hepatocytes treated with trichloroethylene

Trichloroethylene (TCE) is a common organic solvent that has been widely used in industrial applications. Hundred cases of allergic reactions occurred after the workers were occupationally exposed to TCE in China in the past decade, but the underlying effector mechanisms of TCE remain unclear. The purpose of the present study is to examine the alteration of hepatic metabolic enzyme gene and apoptosis-related gene messenger RNA (mRNA) expression in L02 human hepatocytes (L02 cells) after treatment with TCE. L02 cells were cultured either with various doses of TCE (0.25, 0.5, 1.0 and 2.0 mmol/L) for 24 h or with a single dose of TCE (1.0 mmol/L) for different time intervals, whereas samples treated with dimethyl sulfoxide served as control. Quantitative real-time polymerase chain reaction analysis was performed to detect the mRNA expression of hepatic metabolic enzyme genes ( CYP1A2, CYP3A4 and CYP2E1) and apoptosis-related genes ( BAX and BAD). It was found that the transcript levels of hepatic metabolic enzyme genes and apoptosis genes including BAX and BAD were significantly increased after TCE treatment at various doses for 24 h when compared with controls. Additionally, when the cells were treated with a single dose of TCE (1.0 mmol/L) for different periods of time (3, 6, 12 and 24 h), the mRNA expression of these genes also increased significantly compared with control ( p < 0.05 or p < 0.01). The conclusion of the study is that TCE could induce alteration of mRNA expression of hepatic metabolic enzyme genes and apoptosis genes, which might be implicated in the effector mechanisms of TCE cytotoxicity in vivo.

Environmental and modifiable risk factors in renal cell carcinoma

OBJECTIVES

Prevention of disease requires a firm understanding of the relevant environmental and modifiable risk factors. We present a comprehensive review of these factors in renal cell carcinoma.

MATERIALS AND METHODS

A literature search of the PubMed database was performed to identify clinical studies examining the relationship between environmental and modifiable factors in the development of renal cell carcinoma (terms utilized: kidney cancer; renal cell carcinoma; risk factors; environment; obesity; hypertension; trichloroethylene). An emphasis was placed on more recent studies.

RESULTS

Case control and large cohort studies have examined the relationship of numerous environmental and modifiable factors and the risk of renal cell carcinoma. Of particular note are dose-dependent increases in smokers, the obese, and hypertensive patients.

CONCLUSIONS

Environmental and modifiable risk factors contribute significantly to the risk of sporadic renal cell carcinoma. Emphasis should be placed on smoking cessation and hypertension control. Emerging evidence would suggest that dietary intake and quality impact renal cell carcinoma risk.

Xenobiotic metabolizing gene variants and renal cell cancer: a multicenter study

BACKGROUND

The countries of Central and Eastern Europe have among the highest worldwide rates of renal cell cancer (RCC). Few studies have examined whether genetic variation in xenobiotic metabolic pathway genes may modify risk for this cancer.

METHODS

The Central and Eastern Europe Renal Cell Cancer study was a hospital-based case-control study conducted between 1998 and 2003 across seven centers in Central and Eastern Europe. Detailed data were collected from 874 cases and 2053 controls on demographics, work history, and occupational exposure to chemical agents. Genes [cytochrome P-450 family, N-acetyltransferases,

NAD(P)H

quinone oxidoreductase I (NQO1), microsomal epoxide hydrolase (mEH), catechol-O-methyltransferase (COMT), uridine diphosphate-glucuronosyltransferase (UGT)] were selected for the present analysis based on their putative role in xenobiotic metabolism. Haplotypes were calculated using fastPhase. Odds ratios and 95% confidence intervals were estimated by unconditional logistic regression adjusted for country of residence, age, sex, smoking, alcohol intake, obesity, and hypertension.

RESULTS

We observed an increased risk of RCC with one SNP. After adjustment for multiple comparisons it did not remain significant. Neither NAT1 nor NAT2 slow acetylation was associated with disease.

CONCLUSION

We observed no association between this pathway and renal cell cancer.

Trichloroethylene and cancer: systematic and quantitative review of epidemiologic evidence for identifying hazards

We conducted a meta-analysis focusing on studies with high potential for trichloroethylene (TCE) exposure to provide quantitative evaluations of the evidence for associations between TCE exposure and kidney, liver, and non-Hodgkin lymphoma (NHL) cancers. A systematic review documenting essential design features, exposure assessment approaches, statistical analyses, and potential sources of confounding and bias identified twenty-four cohort and case-control studies on TCE and the three cancers of interest with high potential for exposure, including five recently published case-control studies of kidney cancer or NHL. Fixed- and random-effects models were fitted to the data on overall exposure and on the highest exposure group. Sensitivity analyses examined the influence of individual studies and of alternative risk estimate selections. For overall TCE exposure and kidney cancer, the summary relative risk (RRm) estimate from the random effects model was 1.27 (95% CI: 1.13, 1.43), with a higher RRm for the highest exposure groups (1.58, 95% CI: 1.28, 1.96). The RRm estimates were not overly sensitive to alternative risk estimate selections or to removal of an individual study. There was no apparent heterogeneity or publication bias. For NHL, RRm estimates for overall exposure and for the highest exposure group, respectively, were 1.23 (95% CI: 1.07, 1.42) and 1.43 (95% CI: 1.13, 1.82) and, for liver cancer, 1.29 (95% CI: 1.07, 1.56) and 1.28 (95% CI: 0.93, 1.77). Our findings provide strong support for a causal association between TCE exposure and kidney cancer. The support is strong but less robust for NHL, where issues of study heterogeneity, potential publication bias, and weaker exposure-response results contribute uncertainty, and more limited for liver cancer, where only cohort studies with small numbers of cases were available.

Renal cell cancer among African Americans: an epidemiologic review

Incidence rates for renal cell cancer, which accounts for 85% of kidney cancers, have been rising more rapidly among blacks than whites, almost entirely accounted for by an excess of localized disease. This excess dates back to the 1970s, despite less access among blacks to imaging procedures in the past. In contrast, mortality rates for this cancer have been virtually identical among blacks and whites since the early 1990s, despite the fact that nephrectomy rates, regardless of stage, are lower among blacks than among whites. These observations suggest that renal cell cancer may be a less aggressive tumor in blacks. We have reviewed the epidemiology of renal cell cancer, with emphasis on factors which may potentially play a role in the observed differences in incidence and mortality patterns of renal cell cancer among blacks and whites. To date, the factors most consistently, albeit modestly, associated with increased renal cell cancer risk in epidemiologic studies among whites--obesity, hypertension, cigarette smoking--likely account for less than half of these cancers, and there is virtually no epidemiologic evidence in the literature pertaining to their association with renal cell cancer among blacks. There is a long overdue need for detailed etiologic cohort and case-control studies of renal cell cancer among blacks, as they now represent the population at highest risk in the United States. In particular, investigation of the influence on renal cell cancer development of hypertension and chronic kidney disease, both of which occur substantially more frequently among blacks, is warranted, as well as investigations into the biology and natural history of this cancer among blacks.

The dichloroacetate dilemma: environmental hazard versus therapeutic goldmine--both or neither?

BACKGROUND

Dichloroacetate (DCA) is known to environmental scientists as a by-product of water chlorination and as a metabolite of industrial solvents, including Superfund chemicals. In contrast, DCA is studied by clinical investigators for its therapeutic potential in several life-threatening conditions, including genetic mitochondrial diseases, pulmonary arterial hypertension, and cancer. Thus, DCA holds an almost unique position at the interface between environmental science and allopathic medicine.

OBJECTIVE

I critically reviewed laboratory and clinical pharmacological research on DCA to address questions about the current and future status of DCA in relation to human health.

DISCUSSION

Recent information on the clinical toxicogenetics of DCA is interpreted particularly in light of its use as an investigational drug. Adverse effects from chronic DCA exposure have been identified in several target organs in animals. However, in humans, toxicity has so far been limited to reversible effects on the nervous system and liver. DCA is primarily biotransformed to glyoxylate by the bifunctional enzyme glutathione transferase zeta1 and maleylacetoacetate isomerase (GSTz1/MAAI), which also catalyzes the penultimate step in the phenylalanine and tyrosine catabolic pathway. DCA is a suicide inhibitor of GSTz1/MAAI, which can result in delayed plasma clearance of DCA and the accumulation of potentially toxic tyrosine intermediates. Age and GSTz1/MAAI haplotype can markedly affect the toxicokinetics of DCA in humans and rodents.

CONCLUSIONS

I have defined new potential avenues of research that focus on discrete human populations that may be at increased health risk or that may receive increased health benefit from chronic exposure to DCA at both environmentally and clinically relevant concentrations.

Occupational trichloroethylene exposure and renal carcinoma risk: evidence of genetic susceptibility by reductive metabolism gene variants

Trichloroethylene (TCE) is a suspected renal carcinogen. TCE-associated renal genotoxicity occurs predominantly through glutathione S-transferase (GST) conjugation and bioactivation by renal cysteine beta-lyase (CCBL1). We conducted a case-control study in Central Europe (1,097 cases and 1,476 controls) specifically designed to assess risk associated with occupational exposure to TCE through analysis of detailed job histories. All jobs were coded for organic/chlorinated solvent and TCE exposure (ever/never) as well as the frequency and intensity of exposure based on detailed occupational questionnaires, specialized questionnaires, and expert assessments. Increased risk was observed among subjects ever TCE exposed [odds ratio (OR) = 1.63; 95% confidence interval (95% CI), 1.04-2.54]. Exposure-response trends were observed among subjects above and below the median exposure [average intensity (OR = 1.38; 95% CI, 0.81-2.35; OR = 2.34; 95% CI, 1.05-5.21; P(trend) = 0.02)]. A significant association was found among TCE-exposed subjects with at least one intact GSTT1 allele (active genotype; OR = 1.88; 95% CI, 1.06-3.33) but not among subjects with two deleted alleles (null genotype; OR = 0.93; 95% CI, 0.35-2.44; P(interaction) = 0.18). Similar associations for all exposure metrics including average intensity were observed among GSTT1-active subjects (OR = 1.56; 95% CI, 0.79-3.10; OR = 2.77; 95% CI, 1.01-7.58; P(trend) = 0.02) but not among GSTT1 nulls (OR = 0.81; 95% CI, 0.24-2.72; OR = 1.16; 95% CI, 0.27-5.04; P(trend) = 1.00; P(interaction) = 0.34). Further evidence of heterogeneity was seen among TCE-exposed subjects with >or=1 minor allele of several CCBL1-tagging single nucleotide polymorphisms: rs2293968, rs2280841, rs2259043, and rs941960. These findings provide the strongest evidence to date that TCE exposure is associated with increased renal cancer risk, particularly among individuals carrying polymorphisms in genes that are important in the reductive metabolism of this chemical, and provides biological plausibility of the association in humans.

Trichloroethylene induces dopaminergic neurodegeneration in Fisher 344 rats

Trichloroethylene, a chlorinated solvent widely used as a degreasing agent, is a common environmental contaminant. Emerging evidence suggests that chronic exposure to trichloroethylene may contribute to the development of Parkinson's disease. The purpose of this study was to determine if selective loss of nigrostriatal dopaminergic neurons could be reproduced by systemic exposure of adult Fisher 344 rats to trichloroethylene. In our experiments, oral administration of trichloroethylene induced a significant loss of dopaminergic neurons in the substantia nigra pars compacta in a dose-dependent manner, whereas the number of both cholinergic and GABAergic neurons were not decreased in the striatum. There was a robust decline in striatal levels of 3, 4-dihydroxyphenylacetic acid without a significant depletion of striatal dopamine. Rats treated with trichloroethylene showed defects in rotarod behavior test. We also found a significantly reduced mitochondrial complex I activity with elevated oxidative stress markers and activated microglia in the nigral area. In addition, we observed intracellular alpha-synuclein accumulation in the dorsal motor nucleus of the vagus nerve, with some in nigral neurons, but little in neurons of cerebral cortex. Overall, our animal model exhibits some important features of Parkinsonism, and further supports that trichloroethylene may be an environmental risk factors for Parkinson's disease.

Occupation and renal cell cancer in Central and Eastern Europe

OBJECTIVE

Central and Eastern Europe has among the highest rates of renal cell cancer worldwide. Few studies have been conducted in these areas to investigate the possible role of occupational exposures in renal cell cancer aetiology. The purpose of this study was to examine the association of renal cell cancer with employment in specific occupations and industries.

METHODS

From 1999 to 2003, we conducted a hospital-based case-control study in seven areas of the Czech Republic, Poland, Romania and Russia. A detailed occupational history was collected from renal cell cancer cases and controls, together with information on potential confounders. Odds ratios (ORs) and 95% CI of cancer risk were calculated for having ever been employed in selected jobs and industries, with follow-up analyses examining duration of employment.

RESULTS

A total of 992 histologically confirmed incident renal cell cancer cases and 1459 controls were included in the analysis. An increased risk of renal cell cancer was observed for workers in agricultural labour and animal husbandry (OR 1.43; 95% CI 1.05 to 1.93), particularly among women employed as general farm workers (OR 2.73; 95% CI 1.05 to 7.13). Risk gradients for agricultural work increased with longer employment. An overall increased risk of renal cell cancer was seen among architects and engineers (OR 1.89; 95% CI 1.35 to 2.65), and mechanical engineers (OR 1.71; 95% CI 1.03 to 2.84).

CONCLUSIONS

Our data suggest an association between renal cell cancer and agricultural work, particularly among female workers.

Epidemiologic characteristics and risk factors for renal cell cancer

Incidence rates of renal cell cancer, which accounts for 85% of kidney cancers, have been rising in the United States and in most European countries for several decades. Family history is associated with a two- to four-fold increase in risk, but the major forms of inherited predisposition together account for less than 4% of renal cell cancers. Cigarette smoking, obesity, and hypertension are the most consistently established risk factors. Analgesics have not been convincingly linked with renal cell cancer risk. A reduced risk of renal cell cancer among statin users has been hypothesized but has not been adequately studied. A possible protective effect of fruit and vegetable consumption is the only moderately consistently reported dietary finding, and, with the exception of a positive association with parity, evidence for a role of hormonal or reproductive factors in the etiology of renal cell cancer in humans is limited. A recent hypothesis that moderate levels of alcohol consumption may be protective for renal cell cancer is not strongly supported by epidemiologic results, which are inconsistent with respect to the categories of alcohol consumption and the amount of alcohol intake reportedly associated with decreased risk. For occupational factors, the weight of the evidence does not provide consistent support for the hypotheses that renal cell cancer may be caused by asbestos, gasoline, or trichloroethylene exposure. The established determinants of renal cell cancer, cigarette smoking, obesity, and hypertension, account for less than half of these cancers. Novel epidemiologic approaches, including evaluation of gene–environment interactions and epigenetic mechanisms of inherited and acquired increased risk, are needed to explain the increasing incidence of renal cell cancer.

Lifestyle Factors, Exposures, Genetic Susceptibility, and Renal Cell Cancer Risk: A Review

Malignant kidney tumors account for approximately 2% of all new primary cancer cases diagnosed in the United States, with an estimated 30,000 cases occurring annually. Although a variety of agents, chemical and biological, have been implicated as causal agents in the development of renal cell carcinoma (RCC), the etiology remains enigmatic. The strongest association has been developed between cigarette smoking and renal cancer however consistent, positive associations between RCC and obesity, diabetes, and hypertension have also been reported. In addition, more recent investigations of familial kidney cancer syndromes indicate that a strong genetic component contributes to RCC development. Several genes have been identified through investigation of familial kidney cancer syndromes. This review article describes recent trends in RCC incidence and the currently identifiable etiological causes that account for approximately half of the RCC cases diagnoses. The remainder of this review then focuses on additional risk factors that have thus far not been well examined but may be helpful in explaining the increasing incidence trends and the geographic or racial variation observed nationally and worldwide.

[Renal cell carcinoma and exposure to trichloroethylene: are the French limits of occupational exposure relevant?]

BACKGROUND

Several studies have investigated the association between trichloroethylene (TCE) exposure and renal cell cancer (RCC) but findings were inconsistent. The analysis of a case control study has shown an increased risk of RCC among subjects exposed to high cumulative exposure. The aim of this complementary analysis is to assess the relevance of current exposure limits regarding a potential carcinogenic effect of TCE on kidney.

METHODS

Eighty-six cases and 316 controls matched for age and gender were included in the study. Successive jobs and working circumstances were described using a detailed occupational questionnaire. An average level of exposure to TCE was attributed to each job-period in turn. The main occupational exposures described in the literature as increasing the risk of RCC were assessed as well as non-occupational factors. A conditional logistic regression was performed to test the association between TCE and RCC risk. Three exposure levels were studied (average exposure during the eight-hour shift): 35ppm, 50ppm and 75ppm. Potential confounding factors identified were taken into account at the threshold limit of 10% (p=0.10) (body mass index [BMI], tobacco smoking, occupational exposures to cutting fluids and to other oils).

RESULTS

Adjusted for tobacco smoking and BMI, the odd-ratios associated with exposure to TCE were respectively 1.62 [0.77-3.42], 2.80 [1.12-7.03] and 2.92 [0.85-10.09] at the thresholds of 35ppm, 50ppm and 75ppm. Among subjects exposed to cutting fluids and TCE over 50ppm, the OR adjusted for BMI, tobacco smoking and exposure to other oils was 2.70 [1.02-7.17].

CONCLUSION

Results from the present study as well as those provided in the international literature suggest that current French occupational exposure limits for TCE are too high regarding a possible risk of RCC.

Evaluation of the role of peroxisome proliferator-activated receptor alpha (PPARalpha) in mouse liver tumor induction by trichloroethylene and metabolites

Trichloroethylene (TCE) is an industrial solvent and a widespread environmental contaminant. Induction of liver cancer in mice by TCE is thought to be mediated by two metabolites, dichloroacetate (DCA) and trichloroacetate (TCA), both of which are themselves mouse liver carcinogens. TCE, TCA, and DCA are relatively weak peroxisome proliferators (PP), a group of rodent hepatocarcinogens that activate a nuclear receptor, PP-activated receptor alpha (PPARalpha. The objective of this review is to assess the weight of evidence (WOE) that PPARalpha is or is not mechanistically involved in mouse liver tumor induction by TCE and metabolites. Based on similarities of TCE and TCA to typical PP, including dose-response characteristics showing PPARalpha-dependent responses coincident with liver tumor induction and abolishment of TCE and TCA effects in PPARalpha-null mice, the WOE supports the hypothesis that PPARalpha plays a dominant role in TCE- and TCA-induced hepatocarcinogenesis. Data indicates that the MOA for DCA tumor induction is PPARalpha-independent. Uncertainties remain regarding the genesis of the TCE-induced tumors. In contrast to the TCA-induced tumors, which have molecular features similar to those induced by typical PP, there is evidence, albeit weak, that TCE tumors arise by a mode of action (MOA) different from that of TCA tumors, based largely on dissimilarities in molecular markers found in TCE versus TCA-induced tumors. In summary, the WOE indicates that TCA-induced liver tumors arise by a PPARalpha-dependent MOA. Although the TCE MOA is likely dominated by a PPARalpha-dependent contribution from TCA, the contribution of a PPARalpha-independent MOA from DCA cannot be ruled out.

Contemporary epidemiology of renal cell cancer

We analyzed renal cell cancer incidence patterns in the United States and reviewed recent epidemiologic evidence with regard to environmental and host genetic determinants of renal cell cancer risk. Renal cell cancer incidence rates continued to rise among all racial/ethnic groups in the United States, across all age groups, and for all tumor sizes, with the most rapid increases for localized stage disease and small tumors. Recent cohort studies confirmed the association of smoking, excess body weight, and hypertension with an elevated risk of renal cell cancer, and suggested that these factors can be modified to reduce the risk. There is increasing evidence for an inverse association between renal cell cancer risk and physical activity and moderate intake of alcohol. Occupational exposure to trichloroethylene has been positively associated with renal cell cancer risk in several recent studies, but its link with somatic mutations of the von Hippel-Lindau gene has not been confirmed. Studies of genetic polymorphisms in relation to renal cell cancer risk have produced mixed results, but genome-wide association studies with larger sample size and a more comprehensive approach are underway. Few epidemiologic studies have evaluated risk factors by subtypes of renal cell cancer defined by somatic mutations and other tumor markers.

Applying Mode-of-Action and Pharmacokinetic Considerations in Contemporary Cancer Risk Assessments: An Example with Trichloroethylene

The guidelines for carcinogen risk assessment recently proposed by the U.S. Environmental Protection Agency (U.S. EPA) provide an increased opportunity for the consideration of pharmacokinetic and mechanistic data in the risk assessment process. However, the greater flexibility of the new guidelines can also make their actual implementation for a particular chemical highly problematic. To illuminate the process of performing a cancer risk assessment under the new guidelines, the rationale for a state-of-the-science risk assessment for trichloroethylene (TCE) is presented. For TCE, there is evidence of increased cell proliferation due to receptor interaction or cytotoxicity in every instance in which tumors are observed, and most tumors represent an increase in the incidence of a commonly observed, species-specific lesion. A physiologically based pharmacokinetic (PBPK) model was applied to estimate target tissue doses for the three principal animal tumors associated with TCE exposure: liver, lung, and kidney. The lowest points of departure (lower bound estimates of the exposure associated with 10% tumor incidence) for lifetime human exposure to TCE were obtained for mouse liver tumors, assuming a mode of action primarily involving the mitogenicity of the metabolite trichloroacetic acid (TCA). The associated linear unit risk estimates for mouse liver tumors are 1.5 x 10(-6) for lifetime exposure to 1 microg TCE per cubic meter in air and 0.4 x 10(-6) for lifetime exposure to 1 microg TCE per liter in drinking water. However, these risk estimates ignore the evidence that the human is likely to be much less responsive than the mouse to the carcinogenic effects of TCA in the liver and that the carcinogenic effects of TCE are unlikely to occur at low environmental exposures. Based on consideration of the most plausible carcinogenic modes of action of TCE, a margin-of-exposure (MOE) approach would appear to be more appropriate. Applying an MOE of 1000, environmental exposures below 66 microg TCE per cubic meter in air and 265 microg TCE per liter in drinking water are considered unlikely to present a carcinogenic hazard to human health.

A meta-analysis of occupational trichloroethylene exposure and liver cancer

OBJECTIVE

Findings from epidemiologic studies of trichloroethylene (TCE) exposure and liver cancer have been inconsistent. To quantitatively evaluate this association and to examine sources of heterogeneity, we conducted a meta-analysis of occupational studies of TCE exposure and liver/biliary tract cancer.

METHODS

We identified 14 occupational cohort studies of TCE exposed workers and one case-control study that met our inclusion criteria. Nine studies specifically identified TCE as a workplace exposure, and were classified as Group I cohort studies. Subcohorts of workers, identified within eight of these studies as more likely exposed to TCE than the total cohort, were analyzed separately.

RESULTS

The combined liver/biliary cancer summary relative risk estimate (SRRE) for all studies was 1.08 (95% CI 0.91-1.29; heterogeneity (H)-P-value=0.12). For the total study populations in the Group I cohorts, the SRRE was 1.14 (95% CI 0.93-1.39; H-P-value=0.05) and for the subcohorts, the SRRE was 1.30 (95% CI 1.09-1.55). Within this subcohort analysis, the association for the European studies of workers from various industries (SRRE=1.38; based on four studies) was higher than the association for the US studies of aerospace and aircraft workers (SRRE=0.97, based on four studies).

CONCLUSION

Although positive associations were observed for some analyses, results were inconsistent across occupational groups (aerospace/aircraft vs. other industries combined), study location, and incidence versus mortality endpoints. In addition, exposure-response trends were not observed consistently across studies. Interpretation is also limited by the potential impact of uncontrolled confounding by other occupational or lifestyle exposures such as smoking or alcohol consumption. Given these limitations, the currently available epidemiologic data are not sufficient to support a causal relation between occupational TCE exposure and liver/biliary cancer.

Re-assessment of the influence of polymorphisms of phase-II metabolic enzymes on renal cell cancer risk of trichloroethylene-exposed workers

PROBLEM

Individual differences in susceptibility to trichloroethylene-induced nephrocarcinogenicity may be conferred by genetic polymorphisms of glutathione S-transferases (GST), because enzymes of this group are pivotal for the metabolic activation of trichloroethylene. Because of a potential involvement of N-acetylation in the detoxication of reactive trichloroethylene metabolite(s) to N-acetyl-cysteine derivatives, polymorphisms of the NAT2 gene may also be relevant.

METHODS

The primary collective used for a re-investigation of these questions was that of a hospital-based case-control study by Brüning et al. (Am J Ind Med 43:274-285, 2003) of 134 renal cell cancer cases (20 cases exposed to trichloroethylene) and 401 matched controls. Genetic polymorphisms of GSTT1, GSTM1, GSTP1 and NAT2 were studied. Additional control collectives of non-diseased persons were used for comparison of allele frequencies.

RESULTS

No genetic influences on the development of renal cancer due to trichloroethylene were apparent, related to the deletion polymorphisms of GSTT1 and GSTM1, as well as to the NAT2 rapid/slow acetylator states. However, renal cell cancer cases displayed a somewhat higher proportion of the homozygous GSTP1 313A wild type (GSTP1*A), although this was not statistically significant (chi(2) test: P=0.1071, when using only the original controls of Brüning et al. (2003); P=0.0781 with inclusion of the additional controls).

CONCLUSION

The re-investigation does not confirm the working hypothesis of an influence of the deletion polymorphisms of the glutathione S-transferases GSTT1 and GSTM1 on renal cell cancer development due to high occupational exposures to trichloroethylene.

Uses of and exposure to trichloroethylene in U.S. industry: a systematic literature review

This article describes a systematic review of the industrial hygiene literature for uses of trichloroethylene (TCE) in industry for the exposure assessment of two population-based case control studies of brain cancer in the United States. Papers and reports that address uses of and exposures to TCE were identified from MEDLINE, TOXLINE, NIOSHTIC, the NIOSH Health Hazard Evaluation database (keywords: chlorinated solvents and trichloroethylene), and in other reviews. This search was complemented by reviewing the reference lists from the identified literature. The collected information was systematized by the Standard Industrial Classification (SIC) system, and measurement data reported in the literature were summarized in a database. TCE use was extensive from the early 1920s through the 1970s mainly as a degreasing agent in metal-fabricating operations. After the 1970s it became less popular because of environmental concerns. TCE historically has had a multitude of uses in many other industries, e.g., dry cleaning, textile, electronics, leather, and rubber. Also, many products like adhesives, drugs, paints, inks, and various industrial products have contained TCE. It was banned as a food additive and in cosmetics in 1977. The arithmetic mean (AM) of the measurements across all industries and decades was 38.2 ppm. The highest personal and area air levels were reported in vapor degreasing (AM of 44.6 ppm). Most TCE measurements were performed in the 1950s, 1970s, and 1980s. The data described here could be used by exposure assessors as is to identify the presence and approximate levels of exposure. Using the same information as a basis should increase the reliability of the assessments, making it easier to compare both the exposure assessment methods and the epidemiologic results across different studies.

Estimating risk during showering exposure to VOCs of workers in a metal-degreasing facility

The incremental risk of workers in a metal-degreasing facility exposed to volatile organic compounds (VOCs) present in the water supply during showering was estimated. A probabilistic and worst-case approach using specific-site concentration data and a generalized multipathway exposure model was applied. Estimates of hazard index and lifetime cancer risk were analyzed for each chemical and each route of exposure (inhalation and dermal absorption). The results showed that dermal exposure to trichloroethylene (TCE) and tetrachloroethylene (perchloroethylene, PCE) represented the main contribution to total risk. Although the inhalation route did not produce significant exposure, it was mainly influenced by the liquid flow rate of the shower. Lower values of this parameter during showering resulted in a significant reduction of both carcinogenic and noncarcinogenic risk, while decreasing water temperature produced a minimal effect on exposure by this pathway. The results obtained in the present study indicated that significant exposures of workers may be produced during showering in metal degreasing installations where releases to water of VOCs occur. A sensitivity analysis was developed for investigating the effect of scenario parameters on exposure. Although site-specific data were employed, the exposure of workers was assessed in a model scenario and thus the quantification of risk is associated with uncertainty. Considering that occupational exposure to organic solvents of workers in metal-degreasing facilities may also be significant, risk assessment must be included in the planning of this kind of industrial installation.

The epidemiology of renal cell carcinoma

PURPOSE

We identified and examined risk factors for renal cell cancer, some of which may explain in part the trends of steadily increasing incidence rates, particularly in black Americans.

MATERIALS AND METHODS

Epidemiological studies were identified through a MEDLINE(R) search of the literature through February 2006. A qualitative summary of the results of individual studies is presented.

RESULTS

Cigarette smoking and obesity are the most consistently established causal risk factors, accounting for about 20% and 30% of renal cell cancers, respectively. Hypertension appears to independently influence renal cell cancer risk. Neither acetaminophen nor other analgesics have been convincingly linked with renal cell cancer. With respect to diet a general protective effect of fruit and vegetable consumption is the only consistently reported finding. For occupational factors the weight of the evidence provides no consistent support for the hypotheses that renal cell cancer may be caused by asbestos, gasoline or trichloroethylene exposure. Self-reported family history is associated with 2 to 3-fold increases in risk and the major inherited forms of renal cell cancer together account for about 2% of this malignancy.

CONCLUSIONS

A further reduction in cigarette smoking, and a decrease in the rates of obesity and hypertension would likely moderate the increasing incidence of renal cell cancer. Epidemiological studies, including evaluation of gene-environment interactions, are needed to specifically identify reasons for the increasing incidence, particularly for assessing the roles of obesity and hypertension. Special attention should be focused on black Americans since their incidence rate recently increased to significantly surpass that in white Americans.

Occupational kidney cancer: exposure to industrial solvents

We report seven cases of renal cell carcinoma in workers diagnosed with occupational exposure via skin contact and inhalation to industrial solvents containing benzene. The clinical significance of these cases are: (a) all seven patients diagnosed with kidney cancer were seen by private physicians who missed addressing occupational history to industrial solvents; (b) emphasize the importance of taking an in-depth history including occupational history in any patient presented to the clinician, especially like in these cases, kidney cancer; and (c) demonstrate the importance of educating workers. We believe that there exist more patients with renal cancer whose diagnosis has been rendered "idiopathic" due to the lack of detailed occupational, environmental, personal, and family history.

Potential health effects of occupational chlorinated solvent exposure

Based on toxicology, metabolism, animal studies, and human studies, occupational exposure to chlorinated aliphatic solvents (methanes, ethanes, and ethenes) has been associated with numerous adverse health effects, including central nervous system, reproductive, liver, and kidney toxicity, and carcinogenicity. However, many of these solvents remain in active, large-volume use. This article reviews the recent occupational epidemiology literature on the most widely used solvents, methylene chloride, chloroform, trichloroethylene, and tetrachloroethylene, and discusses other chlorinated aliphatics. The impact of studies to date has been lessened because of small study size, inability to control for confounding factors, particularly smoking and mixed occupational exposures, and the lack of evidence for a solid pathway from occupational exposure to biological evidence of exposure, to precursors of health effects, and to health effects. International differences in exposure limits may provide a "natural experiment" in the coming years if countries that have lowered exposure limits subsequently experience decreased adverse health effects among exposed workers. Such decreases could provide some evidence that higher levels of adverse health effects were associated with higher levels of solvent exposure. The definitive studies, which should be prospective biomarker studies incorporating body burden of solvents as well as markers of effect, remain to be done.