To Trichloroethylene Research Articles

テトラクロロエチレン分解菌の分離と諸特性

Fifteen strains of Tetrachloroethylene (PCE)-degrading bacteria were isolated on agar plates from contaminated soils and a culture fluid which was acclimated to PCE with a subsoil of pond. Two strains of the isolates and others degraded PCE to trichloroethylene (TCE) and to cis-1,2-dichloroethylene (DCE) via TCE, respectively. Most of identified isolates were Bacillus species, which is the most common genus of bacteria found in soils. The acclimation of PCE-degrading bacteria with a subsoil of pond was performed readily. These results suggest that some indigenous PCE-degrading bacteria which are present in a PCE-polluted environment grow rapidly and readily acquire a higher degrading ability in the presence of favorable organic compounds as electron donors. The best PCE-degrading bacterium (Pseudomonas species) of isolates thoroughly degraded 160mg·l-1 of PCE to DCE within 4 days at 30°C.

Spermatid micronucleus analyses of trichloroethylene and chloral hydrate effects in mice

Mice were exposed by inhalation to trichloroethylene (TCE) or by i.p. injection to the TCE metabolite, chloral hydrate (CH). Early spermatids were analyzed for micronucleus (MN) frequency and the presence or absence of kinetochore(s) using fluorochrome-labeled anti-kinetochore antibodies. It was determined that 5 consecutive days of exposure to 5, 50 or 500 ppm TCE during preleptotene through early pachytene stages of meiotic cell development do not result in increased frequencies of spermatid MN. CH at 41, 83 or 165 mg/kg was positive for spermatid MN induction when treatments corresponded to spermatogonial stem cell or preleptotene spermatocyte stages of development; negative results were obtained after treatments of leptotene—zygotene or diakinesis—metaphase stages. The significantly increased levels of MN observed were invariably of the kinetochore-negative type.

分解反応モデルを用いたテトラクロロエチレンによる汚染地下水の評価

Biotransformation process of tetrachloroethylene (PCE) to trichloroethylene (TCE) and successively to cis-1,2-dichloroethylene (cis-DCE) in static microcosms under anaerobic condition can be expressed by a consecutive first-order rate expression. This model implies the rules concerning stoichiometric relations and kinetics derived from the theory, and the rules enable us to evaluate the behavior of these three compounds. In this study, the data of groundwater contaminated with PCE at a study area in Yokohama city were analyzed using this kinetic model. The analytical method presented in this paper was of use for evaluating various remedial schemes and for estimating the position of pollutant source and the degree of degradation.

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

In order to elucidate the potential nephrotoxicity of low level occupational exposure to trichloroethylene (TRI), urine analysis of the tubular enzyme N-acetyl-beta-D-glucosaminidase (U-NAG) was included in a cross-sectional study of metal degreasers in central Sweden. Eighty-six percent of 8-h TRI in air measurements were well below 50 mg/m3. Normal levels of NAG were found in morning urine samples from 29 workers compared to a historical reference group. A weak positive correlation (r = 0.48; P < 0.01) was observed between U-NAG activity and the concentration of the TRI metabolite trichloroacetic acid in urine but not with other estimates of recent or long-term exposure. In conclusion, TRI does not seem to be nephrotoxic at low exposure levels.

Biotransformation of tetrachloroethylene by anaerobic attached-films at low temperatures

This study was conducted to examine the feasibility of using an anaerobic attached-film expanded-bed (AAFEB) process for the treatment of tetrachloroethylene (PCE) at 15°C. A laboratory-scale continuous-flow reactor, with an expanded-bed volume of 900 ml, was operated at hydraulic retention times of 1.8-4 h and influent PCE concentrations of 8–12 mg/l. Small samples (50 ml) of attached film media were used for batch testing 3–7 mg/l of PCE in a separate 300 ml AAFEB reactor. The attached films were a mixed anaerobic consortium grown on diatomaceous earth support particles under methanogenic conditions. Sucrose was used as an external electron donor and growth substrate. Reductive dechlorination of PCE to trichloroethylene (TCE), cis-1,2-dichloroethylene (DCE), vinyl chloride (VC) and ethylene (ETH) was observed. The conversion efficiency of PCE and TCE to lesser chlorinated compounds and ETH was above 98% during continuous-flow testing. VC accumulated as the major dechlorination product and ETH was produced at very low rates. The maximum PCE dechlorination rate, q max, was 5.33 mg PCE/g volatile solids-day (32.1 μmol/g VS-d) and the one-half velocity coefficient, K s, was 0.009 mg PCE/l (0.054 μM) under continuous-flow conditions. Since the AAFEB carried more than 20 g volatile solids per liter of bed, low temperature conversion rates would be expected to exceed 60 mg PCE/l bed-day. This indicates removal efficiencies greater than 99% could be obtained at hydraulic retention times of less than 1 h at ambient groundwater temperatures with this process.

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.

分解反応モデルによるテトラクロロエチレンおよびその分解物質の挙動解析

Biodegradation of tetrachloroethylene (PCE) to trichloroethylene (TCE) and successively to cis-1, 2-dichloroethylene (cis-DCE) under an anaerobic condition could be well approximated by a consecutive first-order reaction model.PCE → k1 TCE → k2 cis-DCEThe theory has a rule that the models with the same ratio of kinetic constants k2/k1 show a similar time-concentration profile even if the scales of time-axis are different. This rule enables us to estimate the ratio of kinetic constants in contaminated groundwater from the observed values of the concentrations of the above three compounds. Then we can analyze the present state of the degree of degradation and evaluate the behavior of the three compounds in future.

Effects of maternal exposure to trichloroethylene (TCE) on cell proliferation in the mouse preimplantation embryo

Pregnant mice were treated with trichloroethylene (TCE) at doses ranging from 0.01 μg/kg body weight to 483 mg/kg body weight when embryos were traversing the pronuclear stages of development. No treatment-related effect was seen on total number of embryos recovered from oviducts at the 2 to 4 cell stage of development. The 4-cell embryos were tested for cellular proliferative disadvantage by the embryo chimera assay in which embryos from treated mothers (experimental embryos) are paired with embryos from nontreated mothers (control embryos) to form aggregation chimeras. No significant cell proliferation decreases were observed for any of the experimental embryos across all doses examined.

テトラクロロエチレンの分解反応モデルを用いた地下水汚染解析方法

Biodegradation of tetrachloroethylene (PCE) to trichloroethylene (TCE) and cis-1,2-dichloroethylene (cis-DCE) under the anaerobic condition was studied using static soil microcosms. It was proved that the biodegradation was well approximated by a consecutive firstorder reaction model. This implied that the total of the molar concentration of the above three compounds was always constant and equaled to the initial molarity of PCE, even if the amount of each compound changed as a function of time. On the basis of these facts, two indices for the characterization of the contamination were derived : total contamination level determined as the sum of the molarities of the three compounds and degradation level defined by the total molar percentage of the products (TCE+DCE). These indices enable us to evaluate the initial concentration of the pollutant PCE and the degree of degradation.

A Case of Pneumatosis Cystoides Intestinalis Associated with Trichlor‐oethylene Developing Typical Features during the Follow‐up of Undetermined Sigmoid Lesions

Abstract: A 64‐year‐old male lens grinder with a 43‐year history of occupational exposure to trichloroethylene (TCE) visited Shinshu University Hospital in December 1988 complaining of distention of the lower abdomen. A barium enema study and endoscopic examination showed rosary‐like semilunar folds and edematous mucosa of undetermined etiology in the sigmoid colon. Three months later, the patient visited the hospital again complaining of blood in the stool. An endoscopic examination performed at this time revealed numerous broad‐based, smooth‐surfaced, protruding lesions in the sigmoid colon. A diagnosis of pneumatosis cystoides intestinalis (PCI) associated with TCE was made. After 4‐days treatment with 50% oxygen given by inhalation, the patient's symptoms were completely relieved, and a colonoscopy revealed no evidence of PCI. He returned to his job at the factory which involved dealing with TCE and because of adequate ventilation and a shorter work‐day he has been free of recurrence during a year follow‐up period. The finding of rosary‐like semilunar folds, as demonstrated by the initial endoscopic and barium enema studies in our patient, is a peculiar one in the incipient stage of PCI.

Sensory-evoked potentials in rats chronically exposed to trichloroethylene: Predominant auditory dysfunction

Sensory-evoked potentials (EPs) were studied in male Long-Evans and Fischer-344 rats in order to characterize the electrophysiological consequences of chronic inhalation exposure to trichloroethylene (TCE). Groups of ten Long-Evans rats were exposed to air or 1600 ppm or 3200 ppm TCE for twelve weeks and evaluated periodically with a multisensory test battery. Brainstem auditory-evoked response (BAER) amplitudes were depressed by TCE, whereas somatosensory and visual potentials remained normal. The effects on BAERs, which varied with tone intensity and frequency, suggested that TCE causes a predominantly high-frequency hearing loss. Comparable effects were obtained in both strains of rats and were like those previously observed following exposure to toluene.

Methanogenic Biotransformation of Chlorinated Hydrocarbons in Ground Water

Chlorinated hydrocarbons enter aquifers by various ways. Bacteria found in ground water transform the dissolved compounds into one or more intermediate compounds, then into a final compound that is sometimes not biodegradable. Biotransformation of tetrachloroefhylene (PCE) to trichloroethylene (TCE), dichloroethylene (DCE), and vinyl chloride (VC) by a reductive dehalogenation process catalyzed by microorganisms has been observed in aquifers and laboratory columns under methanogenic conditions. The pathway for conversion includes the replacement of a chlorine atom by a hydrogen atom. The quantification of these conversion and migration processes of parent and intermediate compounds is achieved by mole balance equations of respective compounds, Michaelis‐Menten kinetic equations, and stoichiometric relations. Following a simplification of the general model for a column experiment, a numerical solution is obtained by using a finite difference scheme to provide estimates of mole fractions of parent and intermediate compounds. The numerical results show a favorable match with experimental data. A significant sensitivity to model parameters, particularly the rate constants of parent compounds, is discovered. It is concluded that biotransformation processes can be satisfactorily quantified by first‐order rate expressions.

No change in serum dopamine-β-hydroxylase activity in workers exposed to trichloroethylene

To determine whether occupational exposure to trichloroethylene (TCE) influences sympathetic nerve activity, serum dopanine-β-hydroxylase (DBH) activities were analyzed in 84 male workers exposed to TCE and 83 male age-matched controls. The workers were exposed to about 22 ppm TCE in air. There were no significant differences between the mean serum DBH activity levels for the exposed workers and the corresponding controls. No significant correlation was found between the serum DBH activities and the urinary TCE-metabolite levels or the duration of employment of the workers. The results suggest that chronic occupational exposure to TCE did not influence sympathetic nerve activity of the workers.

The effect of acute trichloroethylene exposure on electroretinogram components

The effects of acute exposure to trichloroethylene (TCE) on the electroretinogram (ERG) and oscillatory potentials (OPs) were studied on adult New Zealand rabbits anesthetized with urethane. The ERG and OPs were recorded under photopic conditions with a speculum electrode, with pupils fully dilated and the cornea anesthetized. Emulsified (Intralipid) TCE was given intravenously in three consecutive injections of equal volume for a total dose varying between 24 and 85 mg/kg. Averaged ERG and OPs (50 sweeps) were taken up to 250 minutes after the last TCE injection. Our results indicated that, irrespective of the dose used, there was a significant ( p<0.001) reduction (average: 50%) in the amplitude of the b-wave of the ERG following TCE injection. In contrast, the OPs showed a differential effect. At low doses, OP4 showed a significant ( p<0.001) reduction resulting in some cases to its complete extinction, while at higher dose there is a marked increase in amplitude. Our results would suggest that the OPs are a better retinal potential to assess the level of TCE toxicity than is the b-wave of the ERG.

Sister chromatid exchanges in peripheral lymphocytes of workers exposed to benzene, trichloroethylene, or tetrachloroethylene, with reference to smoking habits

The frequencies of sister chromatid exchanges (SCE) were studied in peripheral lymphocytes from four groups of solvent workers, i.e. 36 nonsmoking women exposed to benzene at about 50 ppm on the average, 38 men and women (male smokers and nonsmokers, and female nonsmokers) exposed to trichloroethylene (TRI) at 7 ppm, 27 men and women (both smokers and non-smokers) with tetrachloroethylene (TETRA) exposure, and 19 workers (both smokers and nonsmokers in men, and nonsmokers in women) exposed to a mixture of TRI (at 8 ppm) and TETRA (at 17 ppm) (TRI + TETRA). The results were compared with the findings in control subjects matched by age, sex, smoking habits and place of residence. No significant increase in SCE frequencies was observed in association with exposure to benzene, TRI, TETRA or TRI + TETRA. The SCE frequency was, however, significantly higher in the TRI-, TETRA- or TRI + TETRA-exposed smoking men than in the concurrent nonsmoking controls of the same sex. Possible synergism between solvent exposure and smoking is discussed.

Urinary total protein and β-2-microglobulin in workers exposed to trichloroethylene

Chlorinated solvents are thought to be more nephrotoxic than nonchlorinated solvents in humans. Many workers have been exposed to trichloroethylene (TCE) because TCE is one of the most useful chlorinated solvents in some industries. Thus, to detect adverse effects of human exposure to TCE on kidneys, urinary total protein (U-TP) and beta-2-microglobulin (U-B2M) were determined in 104 male workers occupationally exposed to TCE and 102 male nonexposed controls. The workers have been probably exposed to 15 ppm TCE in air. The U-TP level of the workers, rather than the U-B2M level, was slightly higher than those of the controls. The differences of the U-TP level or the U-B2M level between the two groups, however, were not significant excluding an exception. (The mean U-TP level for 35- to 44-year-old workers was significantly higher than that for corresponding controls.) These results suggest that adverse effects of occupational exposure to TCE on kidney is very mild and glomerular rather than tubular.

Effects of trichloroethylene and its metabolites on rodent hepatocyte intercellular communication

Chronic exposure to trichloroethylene (TCE) results in hepatocellular cancer in mice but not rats. The induction of hepatic tumors by TCE appears to be mediated through nongenotoxic or tumor promotion mechanisms. One cellular effect exhibited by a number of nongenotoxic carcinogens and tumor promoters is the inhibition of gap junction mediated intercellular communication. In the present study, the effects of trichloroethylene (TCE) and its metabolites. trichloracetic acid (TCA), trichloroethanol (TCEth), and chloral hydrate (CH) on gap junction mediated intercellular communication in cultured B6C3F1 mouse and F344 rat hepatocytes were assessed. TCE and TCA inhibited intercellular communication in mouse hepatocytes but not in rat hepatocytes. TCEth and CH had no effect on hepatocyte intercellular communication in either rat or mouse cells. TCE and TCA inhibited intercellular communication in both 24-hr-old and freshly plated mouse hepatocytes. Both compounds produced greater inhibition of intercellular communication in freshly plated cells when compared to 24-hr-old cultures. TCE appeared to require cytochrome P450 metabolism by the mouse hepatocytes to exhibit its inhibitory effect on dye coupling since treatment with SKF-525A prevented the inhibition of intercellular communication by TCE. The inhibitory effect of TCA on intercellular communication was unaffected by treatment with SKF-525A. While the species dependent effect of TCE on intercellular communication may be correlated with different rates and extent of metabolism of TCE by rat and mouse hepatocytes, the inhibiting effect of TCA only on mouse hepatocytes suggests that other intrinsic factors in the male mouse make this species more susceptible to the effects of TCE and TCA on gap junction mediated intercellular communication. These findings may account, in part, for the observed species difference in susceptibility to TCE induced liver carcinogenesis.

Metabolic activity of antipyrine in workers occupationally exposed to trichloroethylene.

In order to investigate possible effects of occupational exposure to trichloroethylene (TRI) on the liver cytochrome P-450 dependent monooxygenases, the metabolic activity of salivary antipyrine was determined in workers (I; N = 32) employed in dry-cleaning shops (I-1; N = 17) and in an industrial metal degreasing process (I-2; N = 15). The studies were performed twice: (a) during the working period, (b) and after at least three weeks free of exposure. The control group (II) consisted of 29 subjects with no known exposure to chemicals. Analyses of the solvents used (TRI) showed them to be mixtures. Statistically significant differences were found (P less than 0.01) in antipyrine t1/2 and clearance within the exposed group (Ia:Ib), but not between the exposed (I) and control (II) group. A breakdown of antipyrine pharmacokinetic data by I-1 and I-2 subgroups demonstrated a statistically significant difference in t1/2 (P less than 0.02) and clearance (P less than 0.05) within I-1 subgroup (a:b), in contrast to the I-2 subgroup (a:b). The difference in antipyrine t1/2 between I-1,a and the control group (II) was also statistically significant (P less than 0.05). Although there was no difference in TRI exposure between I-1 and I-2 based on the biological parameters of TRI absorption, the TRI used in I-2 was of higher grade of purity. It can therefore be concluded that TRI itself is not an inducer of liver monooxygenases and that the monooxygenase induction in subgroup I-1 of TRI exposed workers could be due to TRI impurities.

Blink reflex latency after exposure to trichloroethylene in well water.

The electrophysiological measurement of the blink reflex (BR) can quantify the conduction latency in the reflex arc involving the Vth (trigeminal) and VIIth (facial) cranial nerves. We measured the electrophysiological BR in a population (N = 21), which had alleged chronic exposure to trichloroethylene (TCE) through the public drinking water at levels 30-80 times higher than the Environmental Protection Agency (EPA) Maximum Contamination Level (MCL). A highly significant difference was observed in the conduction latency means of the BR components (p less than .0001), when the study population was compared with laboratory controls (N = 27). This difference suggests a subclinical alteration of the Vth cranial nerve function due to chronic, environmental exposure to TCE.

Increased subjective symptom prevalence among workers exposed to trichloroethylene at sub-OEL levels.

Over 100 workers exposed to trichloroethylene (TRI) mostly at less than 50 ppm during the production or vapor degreasing operation and about an equal number of the non-exposed control workers were examined for subjective symptoms, hematology, serum biochemistry, and sugar, protein and occult blood in urine. Essentially all the clinico-laboratory tests stayed normal, and there was no significant differences in the findings between the exposed and the controls. Thus, no clinically significant effects of TRI exposure were found in the blood and liver functions among the exposed workers as compared with the controls. The prevalence of the subjective symptoms was, however, significantly higher in the exposed group than in the controls, and dose-response relationship could be established in some selected symptoms such as nausea, heavy feeling in the head, forgetfulness, tremor in extremities, cramp in extremities and dry mouth, although the exposure was low. The findings warrant further attention to the effects of TRI especially on the central nervous system at the concentration lower than e.g., 50 ppm.