A comparative study of human levels of trichloroethylene and tetrachloroethylene after occupational exposure

Assessment of Exposure to Perchloroethylene and its Clinical Repercussions for 50 Dry-Cleaning Employees

The purpose of this article is the assessment of occupational exposure to perchloroethylene (PCE) and its clinical repercussions for dry-cleaning employees. The authors measured atmospheric levels of PCE and blood levels in a population of 50 exposed employees then conducted a study of clinical symptomatology in exposed and non-exposed subjects linked with this solvent. Fifty employees and 95 controls were studied. The median value of atmospheric PCE was 7 ppm (0.22-33), and the median blood level of PCE was 73.6 μg/l (11.8-144). These levels were correlated statistically to the action of sludge scraping and to the existence of automatic scrapers (p < 0.01). Eight percent of PCE blood levels were higher than the biological levels recently set in France. The exposed population did not show excessive signs of drowsiness nor of pre-narcotic syndrome or other symptoms studied. Dry-cleaning employees were exposed to PCE at atmospheric levels lower than the French and American chronic recommended exposure levels but some results were higher than recommended values. For PCE blood levels for the general working population, results were respectively lower than French and American national recommended levels in 92% and 94% cases. Risk should be considered, however, carefully in women of childbearing age, as 64% exceeded the recommended blood levels for pregnant women. This exposure did not generate any studied neurobehavioral symptomatology.

Different behavioral effect dose-response profiles in mice exposed to two-carbon chlorinated hydrocarbons: influence of structural and physical properties

The present study aimed to clarify whether dose-response profiles of acute behavioral effects of 1,2-dichloroethane (DCE), 1,1,1-trichloroethane (TCE), trichloroethylene (TRIC), and tetrachloroethylene (PERC) differ. A test battery involving 6 behavioral endpoints was applied to evaluate the effects of DCE, TCE, TRIC, and PERC in male ICR strain mice under the same experimental conditions. The behavioral effect dose-response profiles of these compounds differed. Regression analysis was used to evaluate the relationship between the dose-response profiles and structural and physical properties of the compounds. Dose-response profile differences correlated significantly with differences in specific structural and physical properties. These results suggest that differences in specific structural and physical properties of DCE, TCE, TRIC, and PERC are responsible for differences in behavioral effects that lead to a variety of dose-response profiles.

Micronucleus induction by oxidative metabolites of trichloroethylene in cultured human peripheral blood lymphocytes: a comparative genotoxicity study

The genotoxic effects of oxidative metabolites of trichloroethylene (TCE), namely chloral hydrate, trichloroacetic acid (TCA), dichloroacetic acid (DCA), and trichloroethanol (TCEOH) were examined in human peripheral blood lymphocytes. In this context, lymphocytes were exposed in vitro to 25, 50, and 100 μg/ml concentrations of these metabolites separately for a period of 48 h and examined for micronucleus (MN) induction through flow cytometer. At 50 μg/ml TCE metabolites, TCA (6.33 ± 0.56 %), DCA (5.06 ± 0.55), and TCEOH (4.70 ± 1.73) induced highly significant (p<0.001) frequency of MN in comparison to control (1.03 ± 0.40) suggestive of their genotoxic potential. However, exposure of 100 μg/ml of all the metabolites consistently declined the frequencies of MN which in some cases was equable to that of observed at 25 μg/ml. Further, cytotoxicity and cell cycle disturbances were also measured to find out the association of these endpoints with the MN induction. DNA content analysis revealed 3-4-fold elevation of S-phase at all the concentrations tested. Particularly, at 100 μg/ml, treatment elevation of S-phase was significantly (p<0.0001) higher as compared to the control. Present findings together with earlier reports indicate that TCE induces genotoxicity through its metabolites. Interaction of these metabolites with DNA, as evident by elevated S-phase, seems to be the major cause of MN induction. However, involvement of spindle disruption cannot be ruled out. This comparative study also suggests that after TCE exposure, the metabolic efficiency of human to generate oxidative metabolites determines the extent of genotoxicity.

Systematic literature review of uses and levels of occupational exposure to tetrachloroethylene

Tetrachloroethylene has been one of the most widely used chlorinated solvents in the United States. This review provides a basis for tetrachloroethylene exposure assessment in population-based case-control studies. We performed literature searches in MEDLINE, TOXLINE, NIOSHTIC, and the NIOSH Health Hazard Evaluation databases using relevant search terms. We calculated weighted arithmetic means from the measurement data and compiled these into three summary tables by type of operation: (1) dry cleaning, (2) degreasing, and (3) other operations. We identified 258 relevant documents, of which 179 (69%) contained useful descriptive information. Within the dry cleaning industry, the overall arithmetic mean (AM) for personal tetrachloroethylene exposures was 59 ppm (range: 0-4636, n = 1395). Machine operators who transferred wet garments to a dryer had the highest levels (AM = 150 ppm [range: 0-1000, n = 441]) of the jobs in this industry. The AM for personal measurements associated with degreasing was 95 ppm (range: 0-1800, n = 206). In addition, we identified several other sources of substantial tetrachloroethylene exposure, including cleaning mining equipment, testing coal, cleaning animal coats in taxidermy, and cleaning and duplicating film. Exposure assessment in population-based, case-control studies is a complex process requiring substantial resources. Researchers conducting these types of studies will be able to use results of the measurements to quantify tetrachloroethylene exposure levels for various jobs.

Biological exposure assessment to tetrachloroethylene for workers in the dry cleaning industry

BACKGROUND

The purpose of this study was to assess the feasibility of conducting biological tetrachloroethylene (perchloroethylene, PCE) exposure assessments of dry cleaning employees in conjunction with evaluation of possible PCE health effects.

METHODS

Eighteen women from four dry cleaning facilities in southwestern Ohio were monitored in a pilot study of workers with PCE exposure. Personal breathing zone samples were collected from each employee on two consecutive work days. Biological monitoring included a single measurement of PCE in blood and multiple measurements of pre- and post-shift PCE in exhaled breath and trichloroacetic acid (TCA) in urine.

RESULTS

Post-shift PCE in exhaled breath gradually increased throughout the work week. Statistically significant correlations were observed among the exposure indices. Decreases in PCE in exhaled breath and TCA in urine were observed after two days without exposure to PCE. A mixed-effects model identified statistically significant associations between PCE in exhaled breath and airborne PCE time weighted average (TWA) after adjusting for a random participant effect and fixed effects of time and body mass index.

CONCLUSION

Although comprehensive, our sampling strategy was challenging to implement due to fluctuating work schedules and the number (pre- and post-shift on three consecutive days) and multiplicity (air, blood, exhaled breath, and urine) of samples collected. PCE in blood is the preferred biological index to monitor exposures, but may make recruitment difficult. PCE TWA sampling is an appropriate surrogate, although more field intensive. Repeated measures of exposure and mixed-effects modeling may be required for future studies due to high within-subject variability. Workers should be monitored over a long enough period of time to allow the use of a lag term.

Trichloroethylene: Parkinsonism and complex 1 mitochondrial neurotoxicity

OBJECTIVE

To analyze a cluster of 30 industrial coworkers with Parkinson's disease and parkinsonism subjected to long-term (8-33 years) chronic exposure to trichloroethylene.

METHODS

Neurological evaluations were conducted on the 30 coworkers, including a general physical and neurological examination and the Unified Parkinson's Disease Rating Scale. In addition, fine motor speed was quantified and an occupational history survey was administered. Next, animal studies were conducted to determine whether trichloroethylene exposure is neurotoxic to the nigrostriatal dopamine system that degenerates in Parkinson's disease. The experiments specifically analyzed complex 1 mitochondrial neurotoxicity because this is a mechanism of action of other known environmental dopaminergic neurotoxins.

RESULTS

The three workers with workstations adjacent to the trichloroethylene source and subjected to chronic inhalation and dermal exposure from handling trichloroethylene-soaked metal parts had Parkinson's disease. Coworkers more distant from the trichloroethylene source, receiving chronic respiratory exposure, displayed many features of parkinsonism, including significant motor slowing. Neurotoxic actions of trichloroethylene were demonstrated in accompanying animal studies showing that oral administration of trichloroethylene for 6 weeks instigated selective complex 1 mitochondrial impairment in the midbrain with concomitant striatonigral fiber degeneration and loss of dopamine neurons.

INTERPRETATION

Trichloroethylene, used extensively in industry and the military and a common environmental contaminant, joins other mitochondrial neurotoxins, MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and some pesticides, as a risk factor for parkinsonism.

Trichloroethylene and dichloroethylene: a critical review of teratogenicity

Trichloroethylene (TCE) and dichloroethylene (DCE) are high-volume industrial chemicals frequently found as contaminants in public drinking water supplies. The developmental toxicity of both chemicals has been evaluated in laboratory and epidemiologic studies. It has been suggested that TCE and DCE are specific cardiac teratogens and that drinking water contaminated with them increases the risk of congenital heart defects in exposed human populations. In contrast, other laboratory and epidemiologic studies do not find an increase in developmental effects, either in general or specifically affecting the heart. This laboratory and epidemiologic base was reviewed to evaluate the strengths and weaknesses of the conflicting published reports. We conclude that the weight of experimental and epidemiologic evidence does not support the hypothesis that TCE or DCE is a selective developmental toxicant in general or a cardiac teratogen specifically.

Perchloroethylene in Alveolar Air, Blood, and Urine as Biologic Indices of Low-Level Exposure

We studied the reliability of biologic indices for monitoring perchlorethylene (PCE) exposure at low environmental solvent concentrations. Environmental monitoring was performed by personal sampling, biologic monitoring by measuring PCE in alveolar air (PCE-Alv), blood (PCE-B), and urine (PCE-U) in 26 low-exposed dry-cleaners. Correlation coefficients (r) between environmental PCE and PCE-B, PCE-Alv, and PCE-U were 0.94, 0.81, and 0.67 respectively. A high correlation was also found among biologic indices: r value was 0.96 between PCE-B and PCE-Alv, 0.95 between PCE-B and PCE-U, and 0.87 between alveolar PCE-Alv and PCE-U. The examined biologic indices proved sensitive enough for biologic monitoring of low exposure to PCE and can give substantially similar information in terms of exposure evaluation. PCE-Alv offers some advantages because it correlated better with exposure and is analytically simpler.

[Spectrophotometric and gas chromatographic analysis of trichloroacetic acid in urine]

Some chlorinated hydrocarbon solvents--1,1,1-trichloroethane, trichloroethylene and perchloroethylene--have a common biotransformation product, trichloroacetic acid, which can be used as their biological exposure index. The spectrophotometric and gas chromatographic methods for the determination of trichloroacetic acid were studied and used as well as in its determination in the urine of workers exposed to 1,1,1-trichloroethane. Both methods showed good precision and no statistically significant difference was found although the gas chromatographic method presented a lower detection limit.

Developmental toxicity of trichloroethylene, tetrachloroethylene and four of their metabolites in rat whole embryo culture

The embryotoxicity of trichloroethylene (TRI), tetrachloroethylene (PER), and of four of their oxidative metabolites i.e. trichloroacetic acid, dichloroacetic acid, chloral hydrate, and trichloroacetyl chloride, was studied in vitro, using the rat whole embryo culture system. Embryos from Sprague-Dawley rats were explanted on gestational day 10 (plug day = day 0) and cultured for 46 h in the presence of the test chemical. All of the tested chemicals produced concentration-dependent decreases in growth and differentiation and increases in the incidence of morphologically abnormal embryos. TRI and PER produced qualitatively similar patterns of abnormalities, while TRI and/or PER metabolites, each elicited clearly distinguishable dysmorphogenic profiles. The presence of hepatic microsomal fractions in the culture medium produced marked decreases in TRI- and PER-induced embryotoxic effects, including mortality, severity of malformations, and delayed growth and differentiation.

Assessment of exposure to trichloroethylene and tetrachloroethylene in the population of Zagreb, Croatia

Human exposure to trichloroethylene (TRI) and tetrachloroethylene (perchloroethylene, PER) through air, food and drinking water was assessed by biological monitoring. By stratified sampling 39 subjects with no known solvent exposure were selected from the residents of the city of Zagreb (the capital of the Republic of Croatia). TRI and PER were determined in blood and their metabolites trichloroethanol (TCE) and trichloroacetic acid (TCA) in plasma and urine. Drinking water samples were also taken for TRI and PER determination. TRI was present in measurable concentrations in 22 subjects (range: 0.026-0.090 micrograms/l) and PER in 31 subjects (range: 0.031-2.540 micrograms/l). TCE was not detected in any of the samples, while TCA was determined in all plasma (range: 13.54-160.42 micrograms/l) and urine samples (range: 1.64-291.76 micrograms/24h). In drinking water samples TRI and PER values were also in a very wide range: 0.69-35.90 micrograms/l and 0.36-7.80 micrograms/l, respectively. The variation of all results presented is most probably a reflection of the different environmental contamination with TRI and PER in the different city areas.