PBPK modeling of impact of nonalcoholic fatty liver disease on toxicokinetics of perchloroethylene in mice

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), a major cause of chronic liver disease in the Western countries with increasing prevalence worldwide, may substantially affect chemical toxicokinetics and thereby modulate chemical toxicity.

OBJECTIVES

This study aims to use physiologically-based pharmacokinetic (PBPK) modeling to characterize the impact of NAFLD on toxicokinetics of perchloroethylene (perc).

METHODS

Quantitative measures of physiological and biochemical changes associated with the presence of NAFLD induced by high-fat or methionine/choline-deficient diets in C57B1/6 J mice are incorporated into a previously developed PBPK model for perc and its oxidative and conjugative metabolites. Impacts on liver fat and volume, as well as blood:air and liver:air partition coefficients, are incorporated into the model. Hierarchical Bayesian population analysis using Markov chain Monte Carlo simulation is conducted to characterize uncertainty, as well as disease-induced variability in toxicokinetics.

RESULTS

NAFLD has a major effect on toxicokinetics of perc, with greater oxidative and lower conjugative metabolism as compared to healthy mice. The NAFLD-updated PBPK model accurately predicts in vivo metabolism of perc through oxidative and conjugative pathways in all tissues across disease states and strains, but underestimated parent compound concentrations in blood and liver of NAFLD mice.

CONCLUSIONS

We demonstrate the application of PBPK modeling to predict the effects of pre-existing disease conditions as a variability factor in perc metabolism. These results suggest that non-genetic factors such as diet and pre-existing disease can be as influential as genetic factors in altering toxicokinetics of perc, and thus are likely contribute substantially to population variation in its adverse effects.

Comparative analysis of metabolism of trichloroethylene and tetrachloroethylene among mouse tissues and strains

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are structurally similar chemicals that are metabolized through oxidation and glutathione conjugation pathways. Both chemicals have been shown to elicit liver and kidney toxicity in rodents and humans; however, TCE has been studied much more extensively in terms of both metabolism and toxicity. Despite their qualitative similarities, quantitative comparison of tissue- and strain-specific metabolism of TCE and PCE has not been performed. To fill this gap, we conducted a comparative toxicokinetic study where equimolar single oral doses of TCE (800 mg/kg) or PCE (1000 mg/kg) were administered to male mice of C57BL/6J, B6C3F1/J, and NZW/LacJ strains. Samples of liver, kidney, serum, brain, and lung were obtained for up to 36 h after dosing. For each tissue, concentrations of parent compounds, as well as their oxidative and glutathione conjugation metabolites were measured and concentration-time profiles constructed. A multi-compartment toxicokinetic model was developed to quantitatively compare TCE and PCE metabolism. As expected, the flux through oxidation metabolism pathway predominated over that through conjugation across all mouse strains examined, it is 1,200-3,800 fold higher for TCE and 26-34 fold higher for PCE. However, the flux through glutathione conjugation, albeit a minor metabolic pathway, was 21-fold higher for PCE as compared to TCE. The degree of inter-strain variability was greatest for oxidative metabolites in TCE-treated and for glutathione conjugation metabolites in PCE-treated mice. This study provides critical data for quantitative comparisons of TCE and PCE metabolism, and may explain the differences in organ-specific toxicity between these structurally similar chemicals.

Simultaneous detection of the tetrachloroethylene metabolites S-(1,2,2-trichlorovinyl) glutathione, S-(1,2,2-trichlorovinyl)-L-cysteine, and N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine in multiple mouse tissues via ultra-high performance liquid chromatography electrospray ionization tandem mass spectrometry

Tetrachloroethylene (perchloroethylene; PERC) is a high-production volume chemical and ubiquitous environmental contaminant that is hazardous to human health. Toxicity attributed to PERC is mediated through oxidative and glutathione (GSH) conjugation metabolites. The conjugation of PERC by glutathione-s-transferase to generate S-(1,2,2-trichlorovinyl) glutathione (TCVG), which is subsequently metabolized to form S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC) is of special importance to human health. Specifically, TCVC may be metabolized to N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine (NAcTCVC) which is excreted through urine, or to electrophilic metabolites that are nephrotoxic and mutagenic. Little is known regarding toxicokinetics of TCVG, TCVC, and NAcTCVC as analytical methods for simultaneous determination of these metabolites in tissues have not yet been reported. Hence, an ultra-high-performance liquid chromatography electrospray ionization tandem mass spectrometry-based method was developed for analysis of TCVG, TCVC, and NAcTCVC in liver, kidneys, serum, and urine. The method is rapid, sensitive, robust, and selective for detection all three analytes in every tissue examined, with limits of detection (LOD) ranging from 1.8 to 68.2 femtomoles on column, depending on the analyte and tissue matrix. This method was applied to quantify levels of TCVG, TCVC, and NAcTCVC in tissues from mice treated with PERC (10 to 1000 mg/kg, orally) with limits of quantitation (LOQ) of 1-2.5 pmol/g in liver, 1-10 pmol/g in kidney, 1-2.5 pmol/ml in serum, and 2.5-5 pmol/ml in urine. This method is useful for further characterization of the GSH conjugative pathway of PERC in vivo and improved understanding of PERC toxicity.

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.

Socioeconomic disparities in indoor air, breath, and blood perchloroethylene level among adult and child residents of buildings with or without a dry cleaner

In many cities, dry cleaners using perchloroethylene are frequently located in multifamily residential buildings and often cause elevated indoor air levels of perchloroethylene throughout the building. To assess individual perchloroethylene exposures associated with co-located dry cleaners, we measured perchloroethylene in residential indoor air, and in blood and breath of adults and children residing in buildings with a dry cleaner as part of the New York City (NYC) Perc Project. We also measured perchloroethylene in indoor air, and in blood and breath of residents of buildings without a dry cleaner for comparison. Here, we evaluate whether an environmental disparity in perchloroethylene exposures is present. Study participants are stratified by residential building type (dry cleaner or reference) and socioeconomic characteristics (race/ethnicity and income); measures of perchloroethylene exposure are examined; and, the influence of stratified variables and other factors on perchloroethylene exposure is assessed using multivariate regression. All measures of perchloroethylene exposure for residents of buildings with a dry cleaner indicated a socioeconomic disparity. Mean indoor air perchloroethylene levels were about five times higher in minority (82.5 ug/m(3)) than in non-minority (16.5 ug/m(3)) households, and about six times higher in low-income (105.5 ug/m(3)) than in high income (17.8 ug/m(3)) households. Mean blood perchloroethylene levels in minority children (0.27 ng/mL) and adults (0.46 ng/mL) were about two and three times higher than in non-minority children (0.12 ng/mL) and adults (0.15 ng/mL), respectively. Mean blood perchloroethylene levels in low income children (0.34 ng/mL) and adults (0.62 ng/mL) were about three and four times higher than in high income children (0.11 ng/mL) and adults (0.14 ng/mL), respectively. A less marked socioeconomic disparity was observed in perchloroethylene breath levels with minority and low income residents having slightly higher levels than non-minority and high income residents. Multivariate regression affirmed that indoor air perchloroethylene level in dry cleaner buildings was the single most important factor determining perchloroethylene in blood and breath. Neither age, gender, nor socioeconomic status significantly influenced perchloroethylene levels in breath or blood. We previously reported that increased indoor air, breath, and blood perchloroethylene levels among NYC Perc Project child participants were associated with an increased risk for slightly altered vision. Thus, the disproportionately elevated perchloroethylene exposures of minority and low-income child residents of buildings with a dry cleaner shown here constitutes an environmental exposure disparity with potential public health consequences. Among residents of buildings without a dry cleaner, we observed some small increases in perchloroethylene breath and blood levels among non-minority or high income residents compared to minority or low income residents. These differences were not attributable to differences in indoor air levels of perchloroethylene which did not differ across socioeconomic categories, but appear to be associated with more frequent exposures dry cleaned garments.

Biomonitoring study of dry cleaning workers using cytogenetic tests and the comet assay

Perchloroethylene (PCE) is the main solvent used in the dry cleaning industry worldwide. The aim of the present work was to evaluate the genotoxic potential of occupational exposure to PCE in dry cleaning workers. The study was carried out in 59 volunteers (30 workers, 29 controls). The genotoxic effect was evaluated by analyzing chromosome aberrations (CAs), and micronuclei (MN) and DNA damage (assessed by the comet assay) in peripheral blood lymphocytes. Environmental monitoring of exposure was carried out on personal breathing zone air samples collected during two consecutive working days by measuring the concentration of PCE air levels. The mean PCE concentration in workplace air of dry cleaning workers was 31.40 mg/m(3). There were no significant differences in CA frequency between dry cleaning workers and the controls, but analysis showed a significant association of CA frequency with employment duration and frequency of exposure to PCE. The MN frequency and DNA damage detected by alkaline comet assay were significantly increased in dry cleaning workers compared to the controls. The results suggest that (a) chronic occupational exposure to dry cleaning solvents below permissible occupational exposure limit of 70 mg/m(3) (i.e., ~10.3 ppm) may lead to an increased risk of genetic damage among dry cleaning workers, and (b) CA, MN tests, and comet assay are useful to monitor populations exposed to low doses of PCE.

Biological monitoring of exposure to perchloroethylene in dry cleaning workers

BACKGROUND

Perchloroethylene (PCE) is the most widely used solvent in dry cleaning.

OBJECTIVES

The aim was to evaluate PCE pollution and to identify the most reliable biological indicators for the assessment of workers' exposure.

METHODS

The study was performed in 40 dry cleaning shops covering a total of 71 subjects. Environmental monitoring was carried out with personal diffusive samplers (Radiello) for the entire work shift; biological monitoring was performed by measuring PCE in urine and blood and trichloroacetic acid (TCA) in urine on Thursday evening at end-of shift and on Friday morning pre-shift.

RESULTS

The mean concentration of PCE in air was 52.32 mg/m3, about 30% of the TLV-TWA and the mean value of the PCE inpre-shift blood samples was 0.304 mg/l, slightly more than 50% of the BEI. In dry cleaning shops employing less than 3 persons PCE in air exceeded the TLV-TWA in 7.8% of cases; the size of the shops was inversely related to pollution. Statistically significant correlations were found between PCE exposure and PCE in blood end-of-shift (r = 0.67) and pre-shift (r = 0.70), and PCE in urine end-of-shift (r = 0.68); no correlation was found between exposure and PCE in urine pre-shift and urinary TCA.

CONCLUSIONS

Dry cleaning shops still register conditions of exposure and pollution by PCE, although to a lesser extent than in the past. The most reliable indicators for biological monitoring are CE in end-of-shift urine and PCE in blood both at end-of-shift and pre-shift at the end of the workweek.

Visual contrast sensitivity in children exposed to tetrachloroethylene

This study examined relationships between indoor air, breath, and blood tetrachloroethylene (perc) levels and visual contrast sensitivity (VCS) among adult and child residents of buildings with or without a colocated dry cleaner using perc. Decreasing trends in proportions of adults or children with maximum VCS scores indicated decreased VCS at a single spatial frequency (12 cycles per degree [cpd]) among children residing in buildings with colocated dry cleaners when indoor air perc level averaged 336 μg/m³; breath perc level averaged 159.5 μg/m³; and blood perc level averaged 0.51 μg/L. Adjusted logistic regression indicated that increases in indoor air, breath, and blood perc levels among all child participants significantly increased the odds for decreased VCS at 12 cpd. Adult VCS was not significantly decreased by increasing indoor air, breath, or blood perc level. These results suggest that elevated residential perc exposures may alter children's VCS, a possible subclinical central nervous system effect.

Bayesian analysis of a physiologically based pharmacokinetic model for perchloroethylene in humans

Perchloroethylene (PCE) is a widely distributed pollutant in the environment, and is the primary chemical used in dry cleaning. PCE-induced liver cancer was observed in mice, and central nervous system (CNS) effects were reported in dry-cleaning workers. To support reconstruction of human PCE exposures, including the potential for CNS effects, an existing physiologically based pharmacokinetic (PBPK) model for PCE in the human (Covington et al., 2007) was modified by adding a brain compartment. A Bayesian approach, using Markov chain Monte Carlo (MCMC) analysis, was employed to re-estimate the parameters in the modified model by combining information from prior distributions for the model parameters and experimental data. Experimental data were obtained from five different human pharmacokinetic studies of PCE inhalation exposures ranging from 150 ppm to as low as 0.495 ppm. The data include alveolar or exhaled breath concentrations of PCE, blood concentrations of PCE and trichloroacetic acid (TCA), and urinary excretion of TCA. The PBPK model was used to predict target tissue dosimetry of PCE and its key metabolite, TCA, during and after the inhalation exposures. Posterior analysis was performed to see whether convergence criteria for each parameter were satisfied and whether the model with posterior distributions may be used to make accurate predictions of human kinetic data. With posteriors, the trend of percent of PCE metabolized in the liver at low concentrations was predicted under different exposure conditions. The 95th percentile for the fraction PCE metabolized at a concentration of 1 ppb was estimated to be 1.89%.

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.

Toxicokinetics of Inhaled Trichloroethylene and Tetrachloroethylene in Humans at 1 ppm: Empirical Results and Comparisons with Previous Studies

Trichloroethylene (TRI) and tetrachloroethylene (TETRA) are solvents that have been widely used in a variety of industries, and both are widespread environmental contaminants. In order to provide a better basis for understanding their toxicokinetics at environmental exposures, seven human volunteers were exposed by inhalation to 1 ppm of TRI or TETRA for 6 h, with biological samples collected for analysis during exposure and up to 6-days postexposure. Concentrations of TRI, TETRA, free trichloroethanol (TCOH), total TCOH (free TCOH plus glucuronidated TCOH), and trichloroacetic acid (TCA) were determined in blood and urine; TRI and TETRA concentrations were measured in alveolar breath. Toxicokinetic time courses and empirical analyses of classical toxicokinetic parameters were compared with those reported in previous human volunteer studies, most of which involved exposures that were at least 10-fold higher. Qualitatively, TRI and TETRA toxicokinetics were consistent with previous human studies. Quantitatively, alveolar retention and clearance by exhalation were similar to those found previously but blood and urine data suggest a number of possible toxicokinetic differences. For TRI, data from the current study support lower apparent blood-air partition coefficients, greater apparent metabolic clearance, less TCA production, and greater glucuronidation of TCOH as compared to previous studies. For TETRA, the current data suggest TCA formation that is similar or slightly lower than that of previous studies. Variability and uncertainty in empirical estimates of total TETRA metabolism are substantial, with confidence intervals among different studies substantially overlapping. Relative contributions to observed differences from concentration-dependent toxicokinetics and interindividual and interoccasion variability remain to be determined.

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.

[Determination of volatile organic compounds in blood by headspace solid-phase microextraction-gas chromatography]

The headspace solid-phase microextraction (HS-SPME) is a novel extraction technique and has been developed rapidly. It is a fast, simple, solventless and sensitive method for sampling, separating, extracting, injecting and analyzing volatile organic compounds. This paper presents the research work in detecting volatile organic compounds(including ten compounds) in blood. The extraction fiber is made by fused-silica fiber with 100 microns polydimethylsiloxane (PDMS). The extraction time of the method was 10 min. The thermal desorption time was 1 min. It was found that the optimized location of the extraction fiber in the injector of GC was to put the whole needle in the injector. The precision of the method was determined to be less 5% relative standard deviation (RSD). The linear range of the detection was rather wide. The lowest detectin limits (LODs) were all < or = 5 ng/ml.

Tetrachloroethylene and trichloroethylene fatality: case report and simple headspace SPME-capillary gas chromatographic determination in tissues

We describe a simple, precise, and sensitive assay of tetrachloroethylene and trichloroethylene in tissues, suitable both for emergency cases and forensic medicine. The method employs headspace solid phase microextraction-capillary gas chromatography and electron capture detection. The case is relative to a 45-year-old woman discovered unconscious in a laundry area. The concentrations of the solvents in tissues were determined and compared to other previously published fatalities.

Optic neuritis with residual tunnel vision in perchloroethylene toxicity

CASE REPORT

In a 57-year-old female owner of a dry-cleaning shop, we describe the association of severe bilateral optic neuritis with unexpectedly high concentrations of perchloroethylene/metabolites in the blood and of chloroform in urine. Visual disturbances consisted of complete blindness for 9 days in the left eye, for 11 days in the right eye, with bright phosphenes and pain on eye rotation. Only central (2-3 degrees radius) vision recovered in the following months.

CONCLUSION

Although environmental concentrations of perchloroethylene were within normal limits, we measured five-fold increases in vapors emitted when ironing freshly dry-cleaned fabrics, and suggest that inhalation of perchloroethylene vapors was the cause of this case of ocular nerve toxicity, recapitulating a previous report of major perchloroethylene toxicity.

Tetrachloroethylene intoxication in an autoerotic fatality

This case report describes an accidental death due to the inhalation of tetrachloroethylene during an autoerotic episode. Tetrachloroethylene was administered from a can of Fix-A-Flat tire repair. Analysis of tetrachloroethylene was performed using headspace gas chromatography and electron capture detection. The blood tetrachloroethylene concentration of 62 mg/L was consistent with acute tetrachloroethylene intoxication.

Schedule-controlled operant behavior of rats following oral administration of perchloroethylene: time course and relationship to blood and brain solvent levels

Previous studies have indicated that human exposure to perchloroethylene (PCE) produces subtle behavioral changes and other neurological effects at concentration at or below the current occupational exposure limit. Since comparable effects in animals may be reflected by changes in schedule-controlled operant behavior, the ability of orally administered PCE to alter fixed-ratio (FR) responding for a food reward was investigated in male Sprague-Dawley rats. Furthermore, since behavioral effects of solvents are likely to be more closely related to blood or target tissue (i.e, brain) concentrations than administered dose, the relationship between the pharmacokinetic distribution of PCE and its effects on operant responding was also evaluated. Rats trained to lever-press for evaporated milk on an FR-40 reinforcement schedule were gavaged with 160 or 480 mg/kg PCE and immediately placed in an operant test cage for 90 min. Separate animals gavaged with equivalent doses of PCE were used to determine profiles of blood and brain concentrations versus time. Perchloroethylene produced changes in responding that varied not only with dose but also among animals receiving the same dose. Changes in the response rates of rats receiving 160 mg/kg PCE were either not readily apparent, restricted to the first 5 min of the operant session, or attributable to gavage stress and the dosing vehicle. However, 480 mg/kg produced either an immediate suppression of responding for 15-30 min before a rapid recovery to control rates or a complete elimination of lever-pressing for the majority of the operant session. Although the two doses of PCE produced markedly different effects on operant behavior during the first 30 min of exposure, differences in brain concentrations of PCE were minimal. Furthermore, the majority of animals receiving 480 mg/kg PCE fully recovered from response suppression while blood and brain levels of the solvent continued to rise. Thus, relationships between blood and brain PCE levels and performance impairment were not discernible over the monitored time course. Since the rapid onset of response suppression suggests that the precipitating event occurs within the first few minutes of exposure, it is possible that altered responding is related to the rate of increase in blood or brain concentrations rather than the absolute solvent concentrations themselves. The relationship between the pharmacokinetic distribution of solvents and their effects on the central nervous system is obviously complex and may involve acute neuronal adaptation as well as the dynamics of solvent distribution among the various body compartments.

Coin-operated dry cleaning machines may be responsible for acute tetrachloroethylene poisoning: report of 26 cases including one death

BACKGROUND

Incorrect operations by customers are not uncommon in coin-operated dry cleaning establishments; dry cleaning machines may also be poorly maintained. This may result in retention of large amounts of the cleaning solvent in dry cleaned items.

CASE REPORT

A 2-year-old boy was found dead in his bed, with a strong odor of solvent in the room. Toxicological analysis demonstrated tetrachloroethylene poisoning. The solvent had been retained in the double curtains of the bedroom which had been dry cleaned in a coin-operated establishment the same day. A retrospective study at the Paris Poison Center revealed 25 additional cases, all with a favorable outcome. Analysis of the circumstances of these accidents showed that the main causes of tetrachloroethylene retention in clothes are overloading of the machine and dry cleaning of bulky items. However, failure of the dry cleaning machine may also be involved.

CONCLUSIONS

To immediately reduce the health risks, consumers were informed both via the mass media and by warnings in coin-operated dry cleaning shops. A second batch of preventive measures is in preparation including modifications of the machines to limit solvent exposure and a specific regulation concerning their inspection and maintenance.

Neurobehavioral and neurophysiological outcome of chronic low-level tetrachloroethene exposure measured in neighborhoods of dry cleaning shops

The effects of chronic low-level tetrachloroethene (TCE) exposure on functions of the central nervous system (CNS) were measured in subjects living in the neighborhood of dry cleaning shops with a mean residential time of 10.6 years. Neurobehavioral tests were performed using a German version of the NES battery. Additionally, a pattern reversal visual-evoked potentials (VEPs) were recorded. the mean blood TCE concentration in the subjects was 17.8 micrograms/liter and the median indoor TCE air concentration measured in the residences was 1.36 mg/m3. The outcome of the NES subtests for vigilance, simple reaction time, as well as visual memory differed statistically significantly between the exposed subjects and the controls, whereas for VEP latencies the differences were statistically not significant. It is concluded that despite the low exposure levels, CNS functions might be affected by TCE in subjects living close to a dry cleaning facility if the exposure lasts for several years.

Physiologically based pharmacokinetic model useful in prediction of the influence of species, dose, and exposure route on perchloroethylene pharmacokinetics

The ability of a physiologically based pharmacokinetic (PBPK) model to predict the uptake and elimination of perchloroethylene (PCE) in venous blood was evaluated by comparison of model simulations with experimental data for two species, two routes of exposure, and three dosage levels. Unanesthetized male Sprague-Dawley rats and beagle dogs were administered 1, 3, or 10 mg PCE/kg body weight in polyethylene glycol 400 as a single bolus, either by gavage or by intraarterial (ia) injection. Serial blood samples were obtained from a jugular vein cannula for up to 96 h following dosing. The PCE concentrations were analyzed by headspace gas chromatography. For each dose and route of administration, terminal elimination half-lives in rats were shorter than in dogs, and areas under the blood concentration-time curve were smaller in rats than in dogs. Over a 10-fold range of doses, PCE blood levels in the rat were well predicted by the PBPK model following ia administration, and slightly underpredicted following oral administration. The PCE concentrations in dog blood were generally overpredicted, except for fairly precise predictions for the 3 mg/kg oral dose. These studies provide experimental evidence of the utility of the PBPK model for PCE in interspecies, route-to-route, and dose extrapolations.

Assessment of urban population exposure to trichloroethylene and tetrachloroethylene by means of biological monitoring

Exposure of the general population to trichloroethylene and tetrachloroethylene under normal environmental conditions, achieved with biological monitoring, was assessed, and the possible influence of these compounds via drinking water on the body burden was revealed. A total of 79 subjects with no known solvent exposure was selected, by stratified sampling, from the residents of the city of Zagreb. Trichloroethylene and tetrachloroethylene were determined in blood, and trichloroethanol and trichloroacetic acid were determined in plasma and urine. Drinking water samples were also analyzed for trichloroethylene and tetrachloroethylene. Concentrations of trichloroethylene and tetrachloroethylene in blood, trichloroacetic acid in plasma, trichloroacetic acid in urine, trichloroethylene in drinking water, and tetrachloroethylene in drinking water were as follows: < 0.015 to 0.090 micrograms/l, < 0.010 to 0.239 micrograms/l, 8.6 to 148.1 micrograms/l, 1.67 to 102.3 micrograms/24 h, < 0.05 to 22.93 micrograms/l, and 0.21 to 7.80 micrograms/l, respectively. The variation in all results presented is probably a reflection of different environmental contamination with trichloroethylene and tetrachloroethylene in the different city areas. Correlation analyses revealed significant relationships between trichloroethylene and tetrachloroethylene in blood (r = .402, p = .0004); trichloroacetic acid in urine and in plasma (r = .522, p = .0000); and trichloroethylene and tetrachloroethylene in drinking water (r = .800, p = .0000). A division of all parameters into a subgroup (n = 58), taking drinking water concentrations of trichloroethylene above 3 micrograms/l as a basis, demonstrated the same significant relationships as mentioned above.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of tissue disposition data from rats and dogs to determine species differences in input parameters for a physiological model for perchloroethylene

Tissue disposition of perchloroethylene (PCE) was determined experimentally in two mammalian species of markedly different size in order to derive input parameters for the development of a physiologically based pharmacokinetic (PBPK) model, which could forecast the disposition of PCE in each species. Male Sprague-Dawley rats and male beagle dogs received a single bolus of 10 mg PCE/kg body wt in polyethylene glycol 400 by gavage. Serial samples of brain, liver, kidney, lung, heart, skeletal muscle, perirenal fat, and blood were taken for up to 72 hr following PCE administration. Blood and tissue PCE concentrations were analyzed using a gas chromatography headspace technique. Dogs exhibited considerably longer tissue and blood half-lives than did rats. The dogs also exhibited larger area under tissue concentration versus time curves for all tissues except the liver. Whole body clearance of PCE in the rat was greater than that in the dog. Model simulations indicated this could be attributed to more rapid and extensive PCE exhalation and metabolism by the rat. The in vivo blood:air partition coefficient determined for rats was similar to an in vitro value previously reported. In vivo tissue: blood partition coefficients, however, were 1.4 to 2.8 times greater than published in vitro values. The PCE in vivo blood:air partition coefficient for the dog was twice that of the rat, but tissue:blood partition coefficients were 1.5 to 3.0 times greater in the rat than in the dog. These results demonstrated the existence of significant differences in partition coefficients in two species commonly used in toxicity testing. The PBPK model was shown to have utility in predicting the impact of metabolism and exhalation on pharmacokinetics of PCE in different species of widely differing size.

Blood and urine concentrations of chemical pollutants in the general population

The concentration of 9 environmental chemical pollutants in the general population was measured in blood and urine. For the 9 different pollutants, the blood samples tested varied from 88 for acetone to 431 for benzene. Urine samples varied from 48 for styrene to 213 for n-hexane. Six of these agents (benzene, toluene, styrene, n-hexane, acetone and carbon disulphide) were present in all or almost all (100-94%) blood samples. The three chlorides (chloroform, trichloroethylene and tetrachloroethylene) were present only in 60-85% of samples. After acetone, with blood concentrations in microgram/1 (mean 840 microgram/l), the highest mean blood levels were those of toluene (1097 ng/l), chloroform (955 ng/l) and n-hexane (642 ng/l). Trichloroethylene and free carbon disulphide showed similar values (458 and 438 ng/l, respectively). Finally, benzene, styrene and tetrachloroethylene showed the lowest values (262, 217 and 149 ng/l, respectively). There was generally a significant difference between rural and urban workers in terms of blood benzene (200 ng/l vs 264 ng/l), trichloroethylene (180 ng/l vs 763 ng/l) and tetrachloroethylene (62 ng/l vs 263 ng/l). In a group of subjects potentially exposed to industrial solvents, classed as chemical workers, blood benzene, toluene, chloroform and n-hexane were significantly higher than in rural and urban workers. Smokers showed a significantly higher blood concentration than non-smokers for benzene (381 ng/l vs 205 ng/1), toluene (1431 ng/l vs 977 ng/l), and n-hexane (838 ng/l vs 532 ng/l). All or almost all urine samples (100-92%) contained all the compounds except trichloroethylene and tetrachloroethylene, present in 79% and 76% of samples, respectively (table 2). Urinary concentrations of all compounds did not differ significantly between rural and urban workers. Benzene and toluene were significantly higher in in urine of smokers than of non-smokers. Chloroform and n-hexane showed significantly higher urinary than blood values. Excluding acetone, with urinary and blood concentrations in pg/l, chloroform, toluene and n-hexane showed the highest mean concentrations both in blood and in urine.

Use of a physiologically based model to predict systemic uptake and respiratory elimination of perchloroethylene

The pharmacokinetics of inhaled perchloroethylene (PCE) were studied in male Sprague-Dawley rats to characterize the pulmonary absorption and elimination of the volatile organic chemical (VOC). The direct measurements of the time course of PCE in the blood and breath were used to evaluate the ability of a physiologically based pharmacokinetic (PBPK) model to predict systemic uptake and elimination of PCE. Fifty or 500 ppm PCE was inhaled for 2 hr through a miniaturized one-way breathing valve by unanesthetized male Sprague-Dawley rats of 325-375 g. Serial samples of the inhaled and exhaled breath streams, as well as arterial blood, were collected during and following PCE inhalation and analyzed by headspace gas chromatography. PCE-exhaled breath concentrations increased rapidly to near steady state (i.e., within 20 min) and were directly proportional to the inhaled concentration. Uptake of PCE into the blood was also rapid, but blood levels continued to increase progressively over the course of the 2-hr exposure at both exposure levels. Cumulative uptake, or total absorbed dose, was not proportional to the exposure level. A PBPK model was developed from in vivo parameters determined from tissue concentration-time data in a companion ia study (Dallas et al., 1994, Toxicol. Appl. Pharmacol. 128, 50-59). PCE concentrations in the blood and exhaled breath during and following PCE inhalation were well predicted by the PBPK model. Despite species differences in blood:air and lung:air partition coefficients, the model was used to account for similar levels of PCE and other VOCs in the expired air of rats and humans. The model also accurately simulated percentage uptake and cumulative uptake of PCE over time. The model's ability to predict systemically absorbed doses of PCE under a variety of exposure scenarios should be useful in assessment of risks in occupational and environmental settings.

Development of a physiologically based pharmacokinetic model for perchloroethylene using tissue concentration-time data

The tissue disposition of perchloroethylene (PCE) was characterized experimentally in rats in order to (1) obtain input parameters from in vivo data for the development of a physiologically based pharmacokinetic (PBPK) model, and (2) use the PBPK model to predict the deposition of PCE in a variety of tissues following inhalation exposure. For the derivation of model input parameters, male Sprague-Dawley rats received a single bolus of 10 mg PCE/kg body wt in polyethylene glycol 400 by ia injection through an indwelling carotid arterial cannula. Other male Sprague-Dawley rats inhaled 500 ppm PCE for 2 hr in dynamic exposure inhalation chambers. Serial samples of brain, liver, kidney, lung, heart, skeletal muscle, perirenal fat, and blood were taken for up to 72 hr following ia injection, during the 2-hr inhalation exposure, and for up to 72 hr postexposure. Blood and tissue PCE concentrations were analyzed using a gas chromatography headspace technique. Following ia administration, the tissues exhibited similar terminal elimination half-lives (t1/2). As comparable tissue t1/2 are consistent with a blood-flow-limited model, tissue:blood partition coefficients were calculated for noneliminating compartments by division of the area under the tissue concentration-time curve (AUC) by the blood AUC. Liver PCE concentration versus time data were employed in the calculation of in vivo metabolic rate constants. A PBPK model was developed using these parameters derived from the ia data set and used to predict tissue PCE concentrations during and following PCE inhalation. Predicted tissue levels were in close agreement with the levels measured over time in the seven tissues and in blood. Tissue concentration-time data can thus provide valuable input for parameter estimation and for validation of PBPK model simulations, as long as independent in vivo data sets are used for each step.

[Blood content of tetrachloroethylene in workers of dry cleaners]

Concentrations of tetrachloroethylene (TCE) in the blood of workers employed in dry-cleaning workshops were measured by gas chromatography method and found to vary from 0,19 to 3,95 mmol/l.

[Blood interface in environmental and occupational exposure to industrial chemical pollutants]

The concentration of 12 environmental chemical pollutants was measured in the blood of the general population. With reference to the 12 different pollutants, the blood samples tested varied from 88 for acetone to 431 for benzene. Nine of these agents (benzene, toluene, styrene, cumene, xilene, n-hexane, nitrous oxide (N20), acetone and carbon disulphide) were present in all or almost all (100-94%) blood samples. The three chlorides (chloroform, trichloroethylene and tetrachloroethylene) were present only in 60-85% of samples. After acetone and carbon disulphide, with blood concentrations in microgram/l (mean 840 micrograms/l and 2.4 micrograms/l respectively), the highest mean blood levels were those of toluene (1097 ng/l), chloroform (955 ng/l), N2O (915 ng/l), and n-hexane (642 ng/l). Trichloroethylene and free carbon disulphide had similar values (458 and 438 ng/l, respectively). Finally, benzene, styrene and tetrachloroethylene had the lowest values (262, 217 and 149 ng/l, respectively). There was generally a significant difference between rural and urban workers in terms of blood benzene (200 ng/l vs. 264 ng/l), trichloroethylene (180 ng/l vs 763 ng/l) and tetrachloroethylene (62 ng/l vs. 263 ng/l). In a group of subjects potentially exposed to industrial solvents, classed as chemical workers, blood benzene, toluene, chloroform and n-hexane were significantly higher than in rural and urban workers. Smokers showed a significantly higher blood concentration than non-smokers for benzene (381 ng/l vs. 205 ng/l), toluene (1431 ng/l vs. 976 ng/l) and n-hexane (803 ng/l vs. 505 ng/l).

Uncertainties in pharmacokinetic modeling for perchloroethylene: II. Comparison of model predictions with data for a variety of different parameters

In this paper we compare expectations derived from 10 different human physiologically based pharmacokinetic models for perchloroethylene with data on absorption via inhalation, and concentrations in alveolar air and venous blood. Our most interesting finding is that essentially all of the models show a time pattern of departures of predictions of air and blood levels relative to experimental data that might be corrected by more sophisticated model structures incorporating either (a) heterogeneity of the fat compartment (with respect to either perfusion or partition coefficients or both) or (b) intertissue diffusion of perchloroethylene between the fat and muscle/VRG groups. Similar types of corrections have recently been proposed to reduce analogous anomalies in the fits of pharmacokinetic models to the data for several volatile anesthetics. A second finding is that models incorporating resting values for alveolar ventilation in the region of 5.4 L/min seemed to be most compatible with the most reliable set of perchloroethylene uptake data.

Biological exposure indices of organic solvents for Korean workers

Biological exposure indices (BEIs) of toluene, perchloroethylene (PCE) and methyl ethyl ketone (MEK) for Korean workers were studied respectively. Exposure in workplace to organic solvents were measured by personal sampling. Blood toluene, blood PCE, urinary trichloroacetic acid and urinary MEK were determined by headspace GC. Urinary hippuric acid was determined by HPLC and corrected for creatinine. BEIs for Korean workers were calculated with the levels of the determinants corresponding to permissible exposure limits in Korea which were the same with TLV of ACGIH. Blood toluene level of 2.2 mg/l and urinary hippuric acid level of 1.7 g/g creatinine corresponded to exposure of 100 ppm toluene. Blood PCE concentration of 1.6 mg/l and urinary trichloroacetic acid concentration of 2.9 mg/l corresponded to exposure to 50 ppm PCE. Urinary MEK concentration of 1.4 mg/l corresponded to exposure to 200 ppm of MEK. In conclusion, BEIs for Korean workers determined in this study were different to ACGIH's BEI as urinary determinants were lower and blood determinants were higher than ACGIH's BEI.

Concentrations of tetrachloroethene in blood and trichloroacetic acid in urine in workers and neighbours of dry-cleaning shops

Tetrachloroethene concentrations in blood and trichloroacetic acid concentrations in urine were determined--primarily over the course of a week--for 29 persons living in the vicinity of dry-cleaning shops. The mean levels of tetrachloroethene increased during the week. In some neighbours concentrations were exceeding the German biological threshold limit value for tetrachloroethene (1000 micrograms/l blood), persisting over the whole week in one case. The concentrations of tetrachloroethene in blood depended on the floor and the construction type of the building where these people were living, but not of the type of system used in the dry-cleaning shops. 5 of 12 dry-cleaners were found to have tetrachloroethene levels exceeding the German biological threshold limit value, some of them by a considerable amount.

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

The rate of trichloroethylene (TRI) and perchloroethylene (PER) absorption was investigated in workers who were (1) occupationally exposed to TRI in four dry-cleaning shops (Group 1, n = 10) and (2) occupationally exposed to PER in one dry-cleaning shop (Group 2, n = 18). Concentrations of TRI and PER in blood were analyzed, and concentrations of trichloroethanol (TCE) and trichloroacetic acid (TCA) in blood and urine were analyzed. Results varied widely: PER was found in the blood of workers in group 1, but TRI was not detected in blood from any worker in group 2; most blood samples from group 2 workers did not contain a detectable quantity of TCE, and urine TCE concentrations in this group were very low. During the work week, a significant difference was found in group 1 for TRI in blood and TCE in blood and urine. In group 2, however, the only significant difference during the work week was for PER in blood. Therefore, the most reliable biological indicators for TRI and PER exposure are TCE in blood and PER in blood, respectively.

Neurophysiological and psychophysical measurements reveal effects of acute low-level organic solvent exposure in humans

The organic solvent tetrachloroethylene (Per) is proposed to be a human neurotoxicant. In order to evaluate whether the sensory system is affected by Per at low concentrations, two groups of male volunteers were exposed in an inhalation chamber to 10 and 50 ppm Per, respectively. During the inhalation exposure, which lasted for 4 h per day on four consecutive days, visually evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs) were measured. In addition, in some of these volunteers, the visual contrast sensitivity was determined psychophysically. In the group exposed to 50 ppm Per, the VEP peak latencies N75, P100 and N150 increased in the course of the inhalation period. A comparison of the two groups revealed statistically significant differences of these latency changes during Per exposure. In contrast, the BAEPs of the two groups did not differ significantly during the whole exposure period. The contrast sensitivity functions showed a tendency of increased threshold contrasts at low and intermediate spatial frequencies during exposure to 50 ppm Per. The results indicate visual system dysfunctions in terms of delayed neuronal processing time and altered contrast perception due to acute Per exposure.

Exposure of rats to high concentrations of 1,1,1-trichloroethane and its effects on brain lipid and fatty acid composition

Exposure of rats to 1,1,1-trichloroethane (TRI) (1200 p.p.m.) for 30 days resulted in changes in the fatty acid pattern of the brain ethanolamine phosphoglyceride. A decrease was observed in stearic acid (18:0) and arachidonic acid (20:4), while the 22-carbon (n-3) fatty acids were increased. These changes in the fatty acid pattern were similar to that observed previously in the rat for another solvent, perchloroethylene, at a lower exposure concentration (320 p.p.m). Both these solvents are little metabolised and it seems that a common mechanism exists whereby these solvents alter the fatty acid pattern of brain phospholipid upon exposure. The relatively low uptake of TRI makes a high exposure level (1200 p.p.m.) necessary to attain a blood concentration high enough for the changes to appear.

Intra and interindividual variability in the kinetics of a poorly and highly metabolising solvent

Human subjects were experimentally exposed three times simultaneously to tetrachloroethene (PER) and trichloroethene (TRI) under conditions of rest and exercise. In each subject the individual kinetics for both PER and TRI were determined three times by means of frequent sampling of alveolar air up to 70-500 and 20-310 hours respectively. For PER the following parameters were found: the weighted pulmonary clearance (Clpul) = 0.27-0.64 l/min, terminal half time (t1/2(z] = 54-250 hours, mean residence time (MRT) = 35-155 hours, and volume of distribution (Vdss) = 1100-3570 1. For TRI the apparent hepatic clearance (CLhep) = 0.5-1.7 l/min, weighted Clpul = 0.41-1.48 l/min, t1/2(z) = 13-55 hours, MRT = 2.3-22 hours, and the Vdss = 420-3100 1. The intra and intersubject variation in the kinetics were reflected in the predictions of the individual time course of the solvent in the blood at repeated exposure up to five weeks (eight hours a day, five days a week). For PER the intrasubject variation in the predicted concentrations on the Monday mornings was within 5-15% whereas the intersubject variation was about twofold. For TRI the intrasubject variation in the predicted morning concentrations was substantial (two to threefold), whereas the intersubject variation was about 10-fold. The intrasubject variation was probably caused mainly by the level of exercise during exposure. The Clhep was not greatly influenced by the level of exercise, whereas exercise during exposure increased the MRT. Exercise during exposure probably speeds up the process of distribution and, therefore, there is a lower concentration in the blood relative to the increased respiratory intake. As a consequence, despite the increased Clpul and the rather unchanged Clhep, pulmonary and metabolic excretion will be delayed and the MRT increased. The MRT is more suited to predict the individual cumulation of both PER and TRI than the terminal t1/2(z).

Urinary excretion of tetrachloroethylene (perchloroethylene) in experimental and occupational exposure

Fifteen human volunteers were exposed to tetrachloroethylene (perchloroethylene, tetrachloroethene) vapor at 3.6-316 mg/m3 for 2-4 hr at rest (10 cases) and during light physical exercise (5 cases). Subsequently, 55 workers who were occupationally exposed to tetrachloroethylene in eight commercial dry cleaning facilities were studied (median value, 66 mg/m3; geometric standard deviation, 3.15 mg/m3). In both the experimentally exposed subjects and occupationally exposed workers the urinary concentration of tetrachloroethylene showed a linear relationship to the corresponding environmental time-weighted average concentration. The findings indicate that the urinary concentration of tetrachloroethylene can be used as an appropriate biological exposure indicator. In occupationally exposed subjects performing moderate work, the urinary tetrachloroethylene concentration corresponding to the time-weighted average of the threshold limit value proved to be 120 mcg/L and its 95% lower confidence limit (biological threshold) 100 mcg/L. The effects of workload on the tetrachloroethylene urinary elimination are also accounted for.

Alveolar sampling and fast kinetics of tetrachloroethene in man. I. Alveolar sampling

Human subjects were exposed to tetrachloroethene (perchloroethylene, PER). The duration of exposure ranged from one to 60 minutes and the concentration of PER in inhaled air ranged from 0.02 to 0.40 mmol/m3. Alveolar air was sampled after several residence times (t*) in the lung. Both during and after exposure, the concentration of PER in alveolar air (C Alv) as a function of the residence time was studied to estimate the concentration in the pulmonary artery (C Ven: mixed venous blood) and in the pulmonary vein (C Art: arterial blood). During exposure C Alv decreased as function of t*. At t* = 10 s C Alv was 70-75% of the value presented at t* = 5 s; this decrease approximates an exponential curve. C Alv seemed to stabilise at t* = 10-12 s, whereas it decreased more rapidly at t* greater than 12 s; this decrease continued up to at least t* = 55 s when C Alv was about 40% of the value it represented at t* = 5 s. In the postexposure period C Alv increased as function of t* from 5 to 10 s. Both during and after exposure, no difference was observed between C Alv at t* = 10 s and C Alv in the exhaled part of the expiratory reserve volume. A simple gas exchange model showed that the decrease or increase of C Alv at t* less than 10 s could be explained by either absorption or excretion by mixed venous blood. C Alv at t* = 10-12 s provided a valid estimate of C Ven. To estimate C Art, its fluctuating character due to the discontinuous breathing with a breathing frequency had to be taken into account. It is shown that C Alv during normal breathing (t* = 5 s) provides a reasonable estimate of the time weighted concentration in arterial blood.

Acute tetrachloroethylene poisoning--blood elimination kinetics during hyperventilation therapy

After ingestion of 12-16 g tetrachloroethylene, a 6-year-old boy was admitted to the clinic in coma. In view of the high initial tetrachloroethylene blood level, hyperventilation therapy was performed. Under this therapeutic regimen, the clinical condition of the patient improved considerably. The tetrachloroethylene blood level profile which was determined under hyperventilation therapy could be computer-fitted to a two-compartment model. Elimination of tetrachloroethylene from the blood compartment occurred via a rapid and a slow process with half-lives of 30 min and 36 hours, respectively. These values compared favourably with the half-lives of 160 min and 33 hours under normal respiratory conditions. During hyperventilation therapy, the relative contribution to the fast elimination process increased from 70% for physiological minute volume to 99.9%. A minor fraction of the ingested dose was excreted with the urine (integral of 1% during the first 3 days). In contrast to previous results, trace amounts of unchanged tetrachloroethylene were detected in the urine besides trichloroacetic acid and trichloroethanol.

Skin absorption as a source of error in biological monitoring

Concentrations of toluene, tetrachloroethylene, and 1,1,1-trichloroethane were determined in blood collected from both forearms of subjects after one of their hands was soaked for 5 min in the corresponding solvent or in a thinner containing toluene, as a simulation of the washing of hands with solvent after work. The concentrations of toluene, tetrachloroethylene, and 1,1,1-trichloroethane on the soaked side were high, maximally 5.4, 9.0, and 4.0 mumol/l, respectively, and 20-, 130-, and 35-fold, respectively, compared to the contralateral side. Intraindividual differences were very marked, and dramatic changes were detected within a short period of time. It was not until after 3 h with toluene and 5 h with the chlorinated solvents that the difference between the two arms vanished. It is concluded that analyses of solvents in blood specimens drawn during or immediately after the workday may lead to markedly erroneous estimations of exposure.

Health surveillance of workers exposed to tetrachloroethylene in dry-cleaning shops

Behavioral, renal, hepatic and pulmonary tests were applied to 22 subjects exposed to tetrachloroethylene in 6 dry-cleaning shops. The results were compared with those obtained in 33 subjects non-occupationally exposed to organic solvents. The intensity of exposure was monitored by personal environmental monitoring and by urine analysis for trichloroacetic acid and expired air and venous blood analysis for tetrachloroethylene. The time-weighted average exposure to tetrachloroethylene amounted to 21 ppm (range 9 to 38 ppm). The correlation between the concentration of tetrachloroethylene in ambient air sampled with the charcoal tube method and with a passive dosimeter indicates that the latter can correctly estimate the time-weighted average exposure to the solvent. In view of the long biological half-life of tetrachloroethylene, the internal dose may be better estimated by measuring its concentration in blood 16 h after the end of exposure (i.e. before resuming work the next morning). The present study suggests that if the blood concentration of tetrachloroethylene does not exceed 1 mg/l, 16 h after the end of exposure, the time-weighted average exposure is likely to have been below 50 ppm. Exposure to such level for 6 years on the average does not seem to exert any adverse effect on the central nervous system, the liver and the kidney.

Cardiopulmonary toxicity of tetrachloroethylene

Tetrachloroethylene (1,1,2,2-tetrachloroethene) is a widely used organic solvent capable of producing adverse renal, hepatic, and central nervous system effects. The cardiac effects of tetrachloroethylene, thus far unexplored, were studied in several species. To standardize the dosimetry, tetrachloroethylene was prepared for intravenous injection in solutions of Tween 80, which had no demonstrable cardiotoxicity. In rabbits under urethane and in cats and dogs under pentobarbital, tetrachloroethylene increased the vulnerability of the ventricles to epinephrine-induced extra-systoles, bigeminal rhythms, and tachycardia. The mean threshold doses of tetrachloroethylene were 10 mg/kg in rabbits, 24 mg/kg in cats, and 13 mg/kg in dogs. In rabbits this threshold dose for cardiac arrhythmias correspond to blood levels between 2.2 and 3.6 microgram/ml. Animals demonstrating a reflex bradycardia to vasopressor doses of epinephrine were relatively resistant to the arrhythmogenic action of tetrachloroethylene. Ventricular arrhythmias occurred in less than 30% of the animals after tetrachloroethylene alone. In cats higher doses of tetrachloroethylene (40 mg/kg) produced acute pulmonary edema. Tetrachloroethylene (30-40 mg/kg) decreased left intraventricular dP/dt (max) in dogs, without significantly increasing left intraventricular end-diastolic pressure, although there was a transient decrease in arterial blood pressure that accompanied the early phase of myocardial depression. These results are being used as the basis for studies of the chronic effects of tetrachloroethylene on cardiac performance.

A tetrachloroethylene fatality

This case report concerns a fatal exposure to tetrachloroethylene at a dry cleaning establishment. A sensitive analytical method was developed and the distribution of the chemical in various fluids and tissues was determined. Although several fatalities from tetrachloroethylene have been reported, little previous quantitative toxicological data have been found in the literature.

Cardiac toxicity of perchloroethylene (a dry cleaning agent)

Perchloroethylene analysis was performed on plasma of a 24-year-old white man who presented with a history of premature ventricular beats, dizziness, and headaches. There was no clinical, electrocardiographic, radiologic, or echocardiographic evidence of heart disease. The occurrence of premature ventricular beats and the patient's symptoms were more pronounced when the plasma level of perchloroethylene was high (3.8 ppm). Removal of exposure to perchloroethylene relieved the patient's symptoms and the premature beats completely disappeared.

[Biochemical and psychological examinations of trichloroenthylene exposed volunteers (author's transl)]

Seven healthy volunteers were exposed to approximately 100 ppm (=520 mg/m3) trichloroethylene for six hours daily during a period of five consecutive days. A corresponding group was exposed a placebo in the same manner. -Biochemical and psychological examinations were accomplished in the beginning and the end of each day respectively the whole period. Thereby the intraindividual as well as the interindividual loads were taken to judge the health impairment. - For this purpose trichloroethylene, trichloroethanol and trichloracetic acid were determined in blood, as well as total trichloroethanol and trichloroacetic acid in urine. For the measurement of the biochemical parameters gaschromatography is considered the best method. The combination of the "intern standard" with the synchronous determination of the metabolites of trichloroethylene is described as a new treatment. These time-efficient and practicable procedures are the most important suppositions for "biological monitoring". Results are confirmed as far as known in literature as well as the course of trichloroethylene in blood is described for the first time. The modern methods of psychology applied to tests and standardized questionaires served to quantify the intellectual and psychological conditions of the solvent exposed volunteers and of their corresponding group. The group results were compared. Thereby no significative differences were visible. Altogother the results show that during the 5 days exposition to 100 ppm (=520 mg/m3) trichloroethylene no impairments of the examined persons' mental and psychological capacities could be determined in spite of the biochemically quantified incorporation of the solvent.