Trichloroethylene exposure in vapour degreasing and the urinary excretion of N-acetyl-beta-D-glucosaminidase

Urinary Malondialdehyde (MDA) and N-Acetyl-β-D-Glucosaminidase (NAG) Associated with Exposure to Trichloroethylene (TCE) in Underground Water

Trichloroethylene (TCE) is commonly used in various industries. If wastewater in factories is not effectively treated, the inflow into and subsequent contamination of underground water is likely. Our study assessed the association of exposure to TCE in underground water with oxidative stress and renal tubule damage. We selected 579 residents from areas with underground water contaminated with TCE. Each participant was interviewed via a questionnaire. We also assessed their urinary trichloroacetic acid (TCA) levels by gas chromatography (GC)-FID. Urinary malondialdehyde (MDA) and N-acetyl-β-D-glucosaminidase (NAG) were taken as indicators of oxidative stress and renal tubule damage. We found about 73% of the residents to have consumed underground water. The average duration of consumption was 26 years, with an average of 1.6 L per day. Currently, only 1.5% of the residents still continuously consume underground water. The consumption of underground water positively correlated with heightened urinary TCA levels (r = 0.554). Heightened urinary TCA levels, in turn, were positively associated with NAG levels (r = 0.180) but negatively associated with MDA levels (r = −0.193). The results held even after we had segmented urinary TCA levels into three groups of different levels. The elimination of the source of heightened TCE levels from various industrial effluents is essential. Residents exposed to TCE-laden underground water should periodically undergo health inspections.

Toxicological effects of trichloroethylene exposure on immune disorders

Trichloroethylene (TCE) is one of the most common ground water contaminants in USA. Even though recent regulation mandates restricted utilization of TCE, its use is not completely prohibited, especially in industrial and manufacturing processes. The risk of TCE on human health is an ongoing field of study and its implications on certain diseases such as cancer has been recognized and well-documented. However, the link between TCE and immune disorders is still an under-studied area. Studies on the risk of TCE on the immune system is usually focused on certain immune class disorders, but consensus on the impact of TCE on the immune system has not been established. This review presents representative work that investigates the effect of TCE on immune disorders and highlights future opportunities. We attempt to provide a broader perspective of the risks of TCE on the immune system and human health.

[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.

Kidney and liver biomarkers in female dry-cleaning workers exposed to perchloroethylene

Blood and urine perchloroethylene and urine trichloroacetic acid, as markers of exposure, and serum AST, ALT, GGT and creatinine, urine total solutes and proteins, angiotensin converting enzyme, N-acetyl-ß-D-glucosaminidase and glutamine synthetase, as markers of effect, were measured in 40 dry-cleaning and 45 ironing-shop female workers. Average perchloroethylene air level in the dry-cleaning shops was 59.7 mg m(-3), i.e. three-fold lower than the current A.C.G.I.H. TLV-TWA (170 mg (m-3)). No statistically significant difference in the mean values of any of the effect markers was observed between the two groups, except for AST which was significantly higher in drycleaners. In addition, a statistically significant correlation was observed in dry-cleaners between environmental perchloroethylene and total urinary solutes (r = 0.308, p < 0.05) or urine glutamine synthetase (r= 0.469, p < 0 .01), between glutamine synthetase and blood perchloroethylene in post-shift (r= 0.406, p < 0.01) or urinary perchloroethylene in post(r= 0.571, p < 0.001) or pre-shift (r= 0.586, p < 0.001), and between urinary perchloroethylene in pre-shift and GGT (r= 0.407, p < 0.05). Interestingly, some statistically significant correlations between exposure and effect indices were found in ironing-shop workers alone, as in all subjects. Finally, transaminases, GGT and total urinary proteins were influenced by age and alcohol consumption which were significantly higher in dry-cleaners, thus providing an explanation for some of the correlations observed. In conclusion, our results show a dose-related increase of glutamine synthetase activity,a marker of damage of the pars recta of the kidney proximal tubule, in the urine of female subjects exposed to perchloroethylene concentrations in the work environment lower than current A.C.G.I.H. TLV-TWA.

Elevated urinary levels of kidney injury molecule-1 among Chinese factory workers exposed to trichloroethylene

Epidemiological studies suggest that trichloroethylene (TCE) exposure may be associated with renal cancer. The biological mechanisms involved are not exactly known although nephrotoxicity is believed to play a role. Studies on TCE nephrotoxicity among humans, however, have been largely inconsistent. We studied kidney toxicity in Chinese factory workers exposed to TCE using novel sensitive nephrotoxicity markers. Eighty healthy workers exposed to TCE and 45 comparable unexposed controls were included in the present analyses. Personal TCE exposure measurements were taken over a 2-week period before urine collection. Ninety-six percent of workers were exposed to TCE below the current US Occupational Safety and Health Administration permissible exposure limit (100 ppm 8h TWA), with a mean (SD) of 22.2 (35.9) ppm. Kidney injury molecule-1 (KIM-1) and Pi-glutathione S transferase (GST) alpha were elevated among the exposed subjects as compared with the unexposed controls with a strong exposure-response association between individual estimates of TCE exposure and KIM-1 (P < 0.0001). This is the first report to use a set of sensitive nephrotoxicity markers to study the possible effects of TCE on the kidneys. The findings suggest that at relatively low occupational exposure levels a toxic effect on the kidneys can be observed. This finding supports the biological plausibility of linking TCE exposure and renal cancer.

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.

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.

Nephrotoxicity of organic solvents: biomarkers for early detection

OBJECTIVES

Evidence for a relationship between chronic kidney diseases or progression of already existing diseases (glomerulonephritides) and occupational solvent exposure has been found in case reports, in case-control studies and also in cross-sectional studies. An analysis of the available literature was performed with respect to markers measured in cross-sectional studies that might be useful for an early detection of solvent-induced effects on the kidney.

METHODS

The relevant cross-sectional studies were evaluated and the following markers were analyzed with respect to their suitability as biomarker for renal damage: total protein, albumin, transferrin, IgG, beta(2)-microglobulin, retinol-binding protein, N-acetyl-beta-D: -glucosaminidase, alanine aminopeptidase, beta-galactosidase, beta-glucuronidase, leucin aminopeptidase, alkaline phosphatase, lysozyme, Tamm-Horsfall protein and laminin fragments in urine as well as E-selectin, laminin and anti-laminin antibodies and anti-glomerular basement membrane antibodies in serum.

RESULTS

An increased albumin excretion was observed more frequently in groups of workers exposed to various solvents (like toluene, styrene, aliphatic/aromatic hydrocarbon mixtures, tetrachloroethene, mixtures of chlorinated hydrocarbons) than in controls. No clear pattern emerged for the other markers.

CONCLUSIONS

The determination of albumin excretion in the urine appears to be a useful parameter for monitoring solvent-exposed workers.

Exposure of Danish workers to trichloroethylene, 1947-1989

The aim of this study was to investigate the exposure of Danish workers to trichloroethylene (TCE) and the factors that affected such exposure. Data from Danish health authorities were evaluated for use in an epidemiological study of possible adverse health effects of TCE. The paper files relating to 1,075 air measurements taken between 1947 and 1989 at 150 companies were examined to extract information about calendar year, company, industry, type of measurement, and worker. Multiple regression models were used to analyze the effects of various factors on the concentration of TCE. TCE concentrations decreased over the four decades studied. The geometric mean was 329 mg/m3 for measurements taken 1947-1959, and 260 mg/m3, 53 mg/m3, and 23 mg/m3, respectively, for the three subsequent decades. Regression analyses showed that 1) TCE concentrations decreased on average 4 percent per year before 1964 and 15 percent per year afterward; 2) area and personal measurements gave similar concentrations (for the same calendar period, industry, and duration of measurement); 3) longer-duration measurements were associated with lower TCE concentrations; 4) high TCE concentrations occurred in the iron and metal industry; and, 5) in this industry men were exposed to concentrations two times those of women. Moreover, this study indicated that both the exposure level and the proportion of exposed workers in Danish companies increased with decreasing number of employees. Epidemiological studies of health effects of TCE may benefit from evaluating potential risk within different strata of calendar time, number of company employees, sex, and type of industry.

The use of mechanistic data and the handling of scientific uncertainty in carcinogen risk assessments. The trichloroethylene example

The purpose of this paper is to explore how risk assessors actually use mechanistic data in carcinogen risk assessment and to discuss how the handling of scientific uncertainty may affect the outcome of the risk assessment. The analysis is performed by comparing 29 trichloroethylene risk assessment documents in general and 2 of these, namely the ECETOC (1994, Trichloroethylene: Assessment of Human Carcinogenic Hazard, Technical Report No. 60) and the OECD/EU (1996, Initial Assessment Report for the 4th SIAM (Screening Information Data Set Initial Assessment Meeting), May 1996: Trichloroethylene, sponsor country, United Kingdom [Draft]), in more detail. It is concluded that in this example the ECETOC required less evidence for considering a carcinogenic mechanism irrelevant to humans than did the OECD/EU risk assessors. There are examples of when two risk assessors have selected different primary data for their argumentation and also examples of how one and the same primary publication was interpreted differently. Biased data selection and evaluation of primary data that correlate to the risk assessor's overall conclusions have also been identified. The general comparison of all 29 TCE risk assessment documents indicates that the assessment of scientific uncertainty in the mechanistic data affects the overall conclusions.

Role of cytochrome P450 and glutathione S-transferase alpha in the metabolism and cytotoxicity of trichloroethylene in rat kidney

The toxicity and metabolism of trichloroethylene (TRI) were studied in renal proximal tubular (PT) and distal tubular (DT) cells from male Fischer 344 rats. TRI was slightly toxic to both PT and DT cells, and inhibition of cytochrome P450 (P450; substrate, reduced-flavoprotein:oxygen oxidoreductase [RH-hydroxylating or -epoxidizing]; EC 1.14.14.1) increased TRI toxicity only in DT cells. In untreated cells, glutathione (GSH) conjugation of TRI to form S-(1,2-dichlorovinyl)glutathione (DCVG) was detected only in PT cells. Inhibition of P450 transiently increased DCVG formation in PT cells and resulted in detection of DCVG formation in DT cells. Formation of DCVG in PT cells was described by a two-component model (apparent Vmax values of 0.65 and 0.47 nmol/min per mg protein and Km values of 2.91 and 0.46 mM). Cytosol isolated from rat renal cortical, PT, and DT cells expressed high levels of GSH S-transferase (GST; RX:glutathione R-transferase; EC 2.5.1.18) alpha (GSTalpha) but not GSTpi. Low levels of GSTmu were detected in cortical and DT cells. Purified rat GSTalpha2-2 exhibited markedly higher affinity for TRI than did GSTalpha1-1 or GSTalpha1-2, but each isoform exhibited similar VmaX values. Triethyltinbromide (TETB) (9 microM) inhibited DCVG formation by purified GSTalpha-1 and GSTalpha2-2, but not GSTalpha1-2. Bromosulfophthalein (BSP) (4 microM) only inhibited DCVG formation by GSTalpha2-2. TETB and BSP inhibited approximately 90% of DCVG formation in PT cytosol but had no effect in DT cytosol. This suggests that GSTalpha1-1 is the primary isoform in rat renal PT cells responsible for GSH conjugation of TRI. These data, for the first time, describe the metabolism of TRI by individual GST isoforms and suggest that DCVG feedback inhibits TRI metabolism by GSTs.

Trichloroethylene cancer risk: simplified calculation of PBPK-based MCLs for cytotoxic end points

Cancer risk assessments for trichloroethylene (TCE) based on linear extrapolation from bioassay results are questionable in light of new data on TCE's likely mechanism of action involving induced cytotoxicity, for which a threshold-type dose-response model may be more appropriate. Previous studies have shown that if a genotoxic mechanism for TCE is assumed, algebraic methods can considerably simplify the use of physiologically based pharmacokinetic (PBPK) models to estimate virtually safe environmental concentrations for humans based on rodent cancer-bioassay data. We show here how such methods can be extended to the case in which TCE is assumed to induce cancer via cytotoxicity, to estimate environmentally safe concentrations based on rodent toxicity data. These methods can be substituted for the numerical methods typically used to calculate PBPK-effective doses when these are defined as peak concentrations. We selected liver and kidney as plausible target tissues, based on an analysis of rodent TCE-bioassay data and on a review of related data bearing on mechanism. Tumor patterns in rodent bioassays are shown to be consistent with our estimates of PBPK-based, effective cytotoxic doses to mice and rats used in these studies. When used with a margin of exposure of 1000, our method yielded maximum concentration levels for TCE of 16 ppb (87 micrograms/m3) for TCE in air respired 24 hr/day, 700 ppb (3.8 mg/m3) for TCE in air respired for relatively brief daily periods (e.g., 0.5 hr while showering/bathing), and 210 micrograms/liter for TCE in drinking water assuming a daily 2-liter ingestion. Cytotoxic effective doses were also estimated for occupational respiratory exposures. These estimates indicate that the current OSHA permissible exposure limit for TCE would produce metabolite concentrations that exceed an acute no observed adverse effect level for hepatotoxicity in mice. On this basis, the OSHA TCE limit is not expected to be protective.

Occupational hydrocarbon exposure and chronic nephropathy

This review aims at discussing the questions raised by the hydrocarbon-related chronic nephropathy and its possible consequence, the hydrocarbon-related chronic renal failure. It has been attempted to adopt the point of view of the clinician. Therefore, the most important part of the review is devoted to a presentation and an analysis of the available data on humans. The main features of the available studies on human subjects are presented, their conclusions discussed in the light of the possible methodological flaws, and practical conclusions drawn. After a discussion of the main difficulties encountered for selecting the suitable exposure indicator, the studies are discussed in order of decreasing quality of the study design (cohort, case-control, cross-sectional studies, and the case reports). It is concluded that a great deal of controversies about chronic hydrocarbon-related nephropathy is explained by differences in the study design and that hydrocarbon-induced nephropathy is probably more than a mere hypothesis, although a causal relationship has not yet been proven. Finally, some practical consequences for dealing with a hydrocarbon-exposed patient diagnosed with a kidney disease and the need for further research are discussed.