Metabolism and Excretion of Trichloroethylene after Inhalation by Human Subjects

Eight volunteers were exposed to trichloroethylene vapour (1,042 μg./l.) for five hours; 51 to 64% of the inhaled trichloroethylene was retained. The concentration of trichloroethanol and trichloroacetic acid in the urine was studied daily for a three-week period; on the third day both metabolites were determined in faeces, sweat, and saliva. The concentration of trichloroacetic acid in plasma and red blood cells was studied on alternate days. Of the trichloroethylene retained, 38·0 to 49·7% was excreted in the urine as trichloroethanol and 27·4 to 35·7% as trichloroacetic acid. Of both metabolites 8·4% was excreted in the faeces. Sweat collected on the third day of the experiment contained 0·10 to 1·92 mg./100 ml. trichloroethanol and 0·15 to 0·35 mg./100 ml. trichloroacetic acid. In saliva the concentrations were 0·09 to 0·32 mg./100 ml. trichloroethanol and 0·10 to 0·15 mg./100 ml. trichloroacetic acid. The value of the expression trichloroethanol/trichloroacetic acid calculated in the urine within 22 days was within the range 1·15 to 1·81.     

A simple method for the quantitative analysis of urinary trichloroethanol and trichloroacetic acid as an index of trichloroethylene exposure

Ogata, M., Takatsuka, Y., and Tomokuni, K. (1970).Brit. J. industr. Med.,27, 378-381. A simple method for the quantitative analysis of urinary trichloroethanol and trichloroacetic acid as an index of trichloroethylene exposure. A simple method of estimating trichloroethanol and trichloroacetic acid in the urine of workers exposed to trichloroethylene is described. The glucuronide of trichloroethanol was hydrolysed enzymatically to trichloroethanol by β-glucuronidase and the trichloroethanol released was allowed to react with pyridine and potassium hydroxide in that order, thereby avoiding decomposition of trichloroethanol with strong alkali. The colour which developed in 3·5 minutes at 100°C with pyridine was measured at 440 nm and 530 nm. This also allowed trichloroacetic acid to be determined. The results agreed well with those obtained by longer methods.     

Excretion kinetics of urinary metabolites in a patient addicted to trichloroethylene

Ikeda, M., Ohtsuji, H., Kawai, H., and Kuniyoshi, M. (1971).Brit. J. industr. Med.,28, 203-206. Excretion kinetics of urinary metabolites in a patient addicted to trichlorethylene. A male Japanese subject, single, aged 38, who worked at a workshop washing metal parts with trichloroethylene, was admitted to our clinic due to addiction to the solvent. Analyses of urine revealed the presence of up to 160 μg/ml of trichloro-compounds (mostly trichloroacetic acid) which gradually disappeared in three weeks as the psychotic symptoms cleared up. The excretion half-lives of trichloroethylene metabolites for the initial rapid phase (succeeding slow phase in parentheses) were 5·8 (49·7) hours for trichloroethanol, 22·5 (72·6) hours for trichloroacetic acid, and 7·5 (72·6) hours for total trichloro-compounds.     

Effect of Tetraethyl Thiuram Disulphide (Disulfiram) on Metabolism of Trichloroethylene in Man

The amounts of trichloroethanol and trichloroacetic acid excreted in the urine of four subjects who inhaled trichloroethylene in a concentration of about 1 mg./l. for a period of five hours in a laboratory experiment were determined. This experiment was repeated under the same conditions after tetraethyl thiuram disulphide (disulfiram) had been given in divided doses, totalling 3 or 3·5 g. The elimination of trichloroethanol in urine was decreased by 40 to 64%, and of trichloroacetic acid by 72 to 87%. The trichloroethylene excreted by the lungs in two of the subjects increased up to 65% of that retained within five hours. It is concluded that tetraethyl thiuram disulphide (disulfiram) strikingly inhibits the oxidation of trichloroethylene.

The possible therapeutic use of this substance in cases of severe peroral trichloroethylene intoxication is discussed.

     

A Method for Determination of Trichloroethanol and Trichloroacetic Acid in Urine

When trichloroacetic acid (TCA) and trichloroethanol (TCE) in the urine of human subjects, rabbits, rats, and guinea-pigs were determined by Seto and Schultze's (1956) method, the recovery of TCE, added to urine, varied widely from 81·3% in guinea-pig urine to 16·2% in rat urine. To obtain the maximum recovery of added TCE, Seto and Schultze's method was further modified to give satisfactory results (recovery rate of 95·9 to 98·5%) when applied to human urine as well as to the urine of the above species of animals. Urine samples from human subjects as well as from rats exposed to trichloroethylene were analysed by this modified method. The results showed that the ratio of TCE to TCA varies as a function of environmental trichloroethylene concentration, indicating that the determination of total trichlorocompounds gives a better index of trichloroethylene exposure than does the determination of TCA alone.     

Urinary excretion of total trichloro-compounds, trichloroethanol, and trichloroacetic acid as a measure of exposure to trichloroethylene and tetrachloroethylene

Ikeda, M., Ohtsuji, H., Imamura, T., and Komoike, Y. (1972).Brit. J. industr. Med.,29, 328-333. Urinary excretion of total trichloro-compounds, trichloroethanol, and trichloroacetic acid as a measure of exposure to trichloroethylene and tetrachloroethylene. To investigate the relation between trichloroethylene and tetrachloroethylene concentrations in working environments and metabolite concentrations in urine, a series of surveys was conducted at 17 workshops where the vapour concentration in the air of each workshop was relatively constant. Urine samples collected from 85 male workers were analysed for total trichloro-compounds (TTC), and trichloroacetic acid (TCA). Trichloroethanol (TCE) was estimated by difference. Statistical analyses of the data revealed that the urinary concentrations of both TTC and TCE were proportional to the atmospheric concentration of trichloroethylene. The concentration of TCA was also related to the vapour concentration up to 50 p.p.m. but not at higher concentrations. Further calculations suggested that only one-third of the trichloroethylene absorbed through the lungs was excreted in the urine during working time.

In tetrachloroethylene exposure, urinary metabolite levels increased until the atmospheric concentration of the solvent reached 50 to 100 p.p.m., but little increase occurred at higher concentration. This observation was further confirmed by experimental exposure of rats. The toxicological significance of changes in the metabolism of the two solvents is discussed in relation to the possible necessity of reducing the threshold limit value from the current value of 100 p.p.m.

     

A comparative study of the excretion of Fujiwara reaction-positive substances in urine of humans and rodents given trichloro- or tetrachloro-derivatives of ethane and ethylene

Ikeda, M., and Ohtsuji, H. (1972).Brit. J. industr. Med.,29, 99-104. A comparative study or the excretion of Fujiwara reaction-positive substances in urine of humans and rodents given trichloro- or tetrachloro-derivatives of ethane and ethylene. 1,1,1-Trichloroethane, 1,1,2- trichloroethane, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene, and tetrachloroethylene were administered to rats and mice as vapours at 200 p.p.m. for 8 hours and urine was collected for 48 hours. The urine was analysed by the Fujiwara reaction for total trichlorocompounds (TTC), trichloroacetic acid (TCA), and trichloroethanol (TCE). All compounds except 1,1,2-trichloroethane yielded substantial TCA and TCE but 1,1,1,2-tetrachloroethane and trichloroethylene much more than the rest. The results obtained during two periods of 48 hours after intraperitoneal injection were similar. The variations in the amounts of metabolites are shown to be consistent with the vapour pressures of the solvents (compounds with high vapour pressures are lost from the lungs before being metabolized) and with their known chemical properties, according to which 1,1,1-trichlorocompounds should yield TCE and TCA readily, whereas 1,1,2-chlorocompounds should not.

Excretion of metabolites from men exposed intermittently to vapours of tetrachloroethylene and trichloroethylene were also studied. Both gave enough TCE and TCA, but trichloroethylene gave considerably more, in accordance with its relative instability to oxidation.

     

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 μg/l, < 0.010 to 0.239 μg/l, 8.6 to 148.1 μg/l, 1.67 to 102.3 μg/24 h, < 0.05 to 22.93 μg/l, and 0.21 to 7.80 μg/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 μg/l as a basis, demonstrated the same significant relationships as mentioned above. Significant correlations, however, appeared between both In trichloroethylene and In tetrachloroethylene in drinking water, compared with In trichloroacetic acid in plasma and urine, which could be a result of the influence of contaminated drinking water on body burden.     

Hippuric acid, phenol, and trichloroacetic acid levels in the urine of Japanese subjects with no known exposure to organic solvents

Ikeda, M., and Ohtsuji, H. (1969).Brit. J. industr. Med.,26, 162-164. Hippuric acid, phenol, and trichloroacetic acid levels in the urine of Japanese subjects with no known exposure to organic solvents. Urine samples from 36 male and 30 female university students and 31 male factory workers with no known exposure to industrial organic solvents were analysed for hippuric acid, phenol, and trichloroacetic acid, which are the major metabolites of toluene, benzene, and trichloroethylene respectively. The normal levels were less than 1·4 g./l. for hippuric acid, less than 80 mg./l. for phenol, and less than 1 mg./l. for trichloroacetic acid. No evidence was obtained to suggest that correction for urine concentration with either specific gravity or creatinine concentration minimizes individual variation of metabolite levels.     

Measurement of chloral hydrate,trichloroethanol, trichloroacetic acid and monochloroacetic acid in the serum and the urine by gas chromatography

Summary A gas chromatographic method for the determination of trichloroethylene metabolites in the serum and the urine is described.The trichloroethanol glucuronide in the urine was hydrolyzed to trichloroethanol by -glucuronidase. After an extraction with ethyl ether, the extract was dried at 20C, then the residue was extracted with n-hexane and was injected into a gas Chromatograph.Trichloroacetic acid and monochloroacetic acid in the urine were extracted with ethyl ether. After evaporation of the ethyl ether, the acids were methylated with methanolic hydrogen chloride, by heating, and the residue was taken up in n-hexane and was injected into a gas chromatograph. The peak-areas on the gas chromatogram of the trichloroethylene, chloral hydrate and methyl esters of trichloroacetic acid and monochloroacetic acid were measured respectively, using a calibration curve prepared in the same conditions.Procedure for measuring trichloro-compounds in the serum was the same as for that in the urine, except that the ethyl ether extraction of trichloro-compounds was conducted after deproteinization.The serum concentration of trichloro-compounds in the rabbit, after administering trichloroethylene orally, reached the maximum in the following order: trichloroethylene and chloral hydrate > free trichloroethanol, trichloroethanol glucuronide and monochloroacetic acid > trichloroacetic acid. The urinary metabolites of trichloroethylene did so in the following order: free trichloroethanol and monochloroacetic acid > trichloroethanol glucuronide > trichloroacetic acid.Read before the 45th Annual Meeting of Japan Industrial Health Association, Tokyo, April 8, 1972.     

Excretion of Trichloroethylene Metabolites in Human Urine

Five healthy subjects were exposed to known concentrations of trichloroethylene (T.R.I.) for five hours. The amount retained was calculated. The excretion of the metabolites monochloroacetic acid (M.C.A.), trichloroacetic acid (T.C.A.), and trichloroethanol (T.C.E.) in the urine was measured over the next seven to 14 days. Metabolites excreted represented an average of 73% of the dose of T.R.I. retained (M.C.A. 4%, T.C.A. 19%, T.C.E. 50%). The amount and speed of excretion of metabolites in one experiment was increased by giving glucose and insulin. The diurnal variation in the excretion of T.C.A. is emphasized.

After the vapour of T.R.I. has been inhaled the metabolites T.C.A., and M.C.A. are excreted in the urine. Trichloroacetic acid was first detected in canine and human urine by Barrett and Johnston (1939) and Barrett, Cunningham, and Johnston (1939), trichloroethanol was found in canine urine by Butler (1948) and in human urine by Souček and Vlachová (1954). These authors also found monochloroacetic acid to be excreted.

A number of quantitative studies of the formation of the metabolites of T.R.I. have been made. Most interest has been taken in trichloroacetic acid. The prolonged excretion (10 to 14 days) of T.C.A. even after a single exposure to T.R.I. is striking (Barrett et al., 1939; Forssman, 1945; Forssman and Ahlmark, 1946; Souček and Pavelková, 1953). The excretion of the sodium salt of T.C.A. introduced into the organism is equally slow (Powell, 1945; Ahlmark and Forssman, 1949) and has not been satisfactorily explained. Fabre (1949) and Fabre and Truhaut (1952) assumed that it became linked to the red cells but experiments in vitro by Souček (1955) did not confirm this view although linkage to the plasma proteins was considered possible (Souček, 1954).

The gradual increase of the T.C.A. concentration in the plasma and urine for some time after the end of the exposure to T.R.I. is similarly unexplained. Ahlmark and Forssman (1949, 1951) found the excretion of T.C.A. began two to four hours after the beginning of exposure but Souček, Teisinger, and Pavelková (1952) showed that it could be detected within a few minutes. Thereafter it is agreed that the concentration of the T.C.A. in the urine rises to a maximum at 24 to 48 hours and subsequently decreases exponentially for a number of days.

The amount of T.C.A. formed from retained T.R.I. appears to vary with the species. In dogs the T.C.A. excreted accounts for 5-8% of the T.R.I. (Barrett et al., 1939); in rats for 4% (Forssman and Holmquist, 1953); in rabbits for 0·5% (Bartoniček and Souček, 1959). In man higher values have been found: 6-16% (Ahlmark and Forssman, 1951); 7-27% (Souček et al., 1952); 13% (Grandjean, Manchinger, Turrian, Haas, Knoepfel, and Rosenmund, 1955).

Trichloroethanol was shown by Butler (1949) to be eliminated in dogs mainly bound to glucuronic acid, and the amount excreted was three to four times that of T.C.A. The relationship of T.C.A. to T.C.E. has been found in man to be 1: 2 to 1: 4 (Souček and Vlachová, 1954); 1: 2 to 1: 7 (Teisinger, Stýblová, and Vlachová, 1955); 1: 0·5 to 1: 5 (Bardoděj and Krivucová, 1958).

In this paper we have investigated the quantitative relationships of the formation, and the course of elimination in the urine of all three trichloroethylene derivatives following inhalation of its vapour.

     

Dose-response relationship for trichloroethylene in man

Summary Twelve volunteer students were experimentally exposed to 0, 27, 81 or 201 ppm trichloroethylene for 4 hours, and suffered from irritation to mucous membrane of eyes and throat at over 27 ppm trichloroethylene. No headache or physiological responses were reported at 27 ppm; headache occurred at levels over 81 ppm. Accumulated urinary excretion of total trichloro-compounds, trichloroacetic acid and trichloroethanol for 6 days after trichloroethylene exposure increased linearly with environmental trichloroethylene concentration in volunteers experimentally exposed to 0–315 ppm trichloroethylene.In 39 trichloroethylene workers also no changes were observed in the metabolic pattern of trichloroethylene in relation to environmental concentration corresponding to excretion of total trichloro-compounds in urine of 0–180 mg/4 hours namely.Those data might support a threshold limit value of 50 ppm for trichloroethylene. This conclusion, however, is based only on the appearance of toxic symptoms, but not on critical changes in trichloroethylene metabolism above 50 ppm.Presented before the 45th Annual Meeting of Japanese Association of Industrial Health at Tokyo on April 9, 1972, and the 43rd Annual Meeting of Japan Society for Hygiene at Sapporo on May 6, 1973     

An experimental examination of extra-hepatic metabolism of trichloroethylene in dogs

To investigate the extra-hepatic organs metabolism of trichloroethylene, the extra-hepatic circulation in dogs was established by operating on the portal vein-right femoral vein bypass and other locations. These dogs were exposed for one hour to trichloroethylene at concentrations of 700 ppm. Metabolite (trichloroethanol (F-TCE), trichloroacetic acid (TCA) and total trichloroethanol (T-TCE) changes in serum and urine were measured from the beginning of exposure until one hour after termination, and compared with previous data as control. The following results were obtained. This operation method gave a very slight invasion on dogs. About two hours after the operation, no abnormal findings were observed clinically or physiologically. This method was considered to be one of the best for study of the metabolism of chemical substances in the extra-hepatic organs of dogs. The produced ratios of F-TCE, TCA and T-TCE in extrahepatic organs were about 60, 10 and 30% exposure to trichloroethylene at 700 ppm, respectively.     

Metabolism of tetrachloroethylene in guinea pigs (author's transl)]

Tetrachloroethylene oxide was chemically prepared from tetrachloroethylene, and the metabolites of the oxide in guinea pigs were analyzed by gaschromatography and Fujiwara reaction. The results obtained are as follows: 1) Trichloroacetic acid appeared in gaschromatogram after injection of tetrachloroethylene oxide, but trichloroethanol did not. 2) The metabolites analyzed by Fujiwara reaction after injection of tetrachloroethylene oxide were composed of large proportion of trichloroacetic acid and small proportion of trichloroethanol. 3) The ratio of trichloroacetic acid to trichloroethanol in the urine in case of tetrachloroethylene oxide was relatively similar to that of tetrachloroethylene. 4) The effects of pH (2.0 and 10.0) and temperature (4 degrees C and 37 degrees C) on the urinary metabolites suggest that the substance equivalent to trichloroethanol by Fujiwara reaction in metabolites may not be a real one. 5) Toxicity of tetrachloroethylene oxide seems to be much higher as compared with that of tetrachloroethylene in consideration of the maximum allowable dose in guinea pigs. 6) It is supposed from our experiments that tetrachloroethylene oxide is an intermediary metabolite of tetrachloroethylene.     

Evaluation of exposure to benzene vapour during the loading of petrol

Sherwood, R. J. (1972).Brit. J. industr. Med.,29, 65-69. Evaluation of exposure to benzene vapour during loading of petrol. The exposure of three workers to benzene vapour has been determined by personal air sampling, and has been related to their intake (assessed by sampling exhaled breath), and to their metabolism of benzene (evaluated from the concentration of phenol in urine.) The results obtained agree in general with those already published in the literature and with a preliminary experimental exposure undertaken as part of the development of techniques.

The two loaders who handled the loading arms were exposed to mean concentrations of 1·6 and 2·5 p.p.m. over the 5-hour period of loading. The probability of their exposure to concentrations greater than 25 p.p.m. was about 0·1 and 1%. The weigher working between the tracks was exposed to a mean concentration of 20 p.p.m. over the same period and had a total exposure of 114 p.p.m.-hour. Samples of exhaled breath taken at the end of work showed 0·14 and 0·18 p.p.m. benzene for the loaders and 0·84 p.p.m. for the weigher. The following morning the latter showed 0·19 p.p.m. Urine samples taken from the loaders at the end of work contained 12 and 25 mg/l total phenol and for the weigher 83 mg/l. The following morning the phenol was not above natural levels in the loaders' urine, and was 38 mg/l in a sample from the weigher.

It is suggested that any or all of the methods developed for this study could be used in conjunction with appropriate clinical studies to provide a more quantitative basis for determining the hazard of occupational exposure to benzene.

     

Control of industrial exposure to tetrachloroethylene by measuring alveolar concentrations: theoretical approach using a mathematical model

Guberan, E. and Fernandez, J. (1974).British Journal of Industrial Medicine,31, 159-167. Control of industrial exposure to tetrachloroethylene by measuring alveolar concentrations: theoretical approach using a mathematical model. The uptake, distribution, and elimination of tetrachloroethylene were studied using a mathematical model, and predicted alveolar concentrations were compared with experimental data. Because of its high fat solubility the solvent accumulated in adipose tissue with a predicted biological half-life of 71·5 hours. The relation between the alveolar concentrations and the level or duration of exposure was discussed. The alveolar concentrations of tetrachloroethylene during and after similar exposure were predicted in subjects who differed in age, body weight, height, and body fat content, both at rest and during physical effort. Predictions were made of the alveolar concentrations following exposures to steady and variable concentrations in ambient air, and following exposures of several weeks of the type occuring in industry. It was concluded that measurement of the postexposure alveolar concentrations could be used to estimate the mean exposure to tetrachloroethylene in most industrial situations.     

Assessment of intermittent trichloroethylene exposure in vapor degreasing.

To validate various sampling strategies in assessment of trichloroethylene (TCE) exposure, urine and air samples were obtained from 29 metal workers involved in vapor degreasing. Urinary trichloroacetic acid and trichloroethanol were useful metabolites to estimate TCE exposure on a group basis, but the predictive value of a single urine sample was low when related to the air concentration. With intermittent TCE exposure, the best information is obtained by analyzing both metabolites.     

三氯乙烯及其代谢产物的豚鼠皮肤致敏试验

目的　探讨三氯乙烯及其代谢产物三氯乙酸、三氯乙醇及水合三氯乙醛对豚鼠的皮肤致敏作用。方法　按豚鼠最大值试验 (GPMT)法 ,用三氯乙烯、三氯乙酸、三氯乙醇及水合三氯乙醛分别对白化豚鼠进行皮内和涂皮结合法致敏试验 ,并设阳性对照 (二硝基氯苯 )、溶剂对照 (橄榄油 )和福氏完全佐剂 (FCA)对照 ,观察各组动物皮肤的红斑和水肿等情况 ,求出致敏率和平均反应值。结果　三氯乙烯、三氯乙酸和二硝基氯苯的致敏率分别为 71 4%、5 8 3 %和10 0 % ,平均反应值分别为 2 3、1 1和 6 0。三氯乙醇和水合三氯乙醛的致敏率均为 0。结论　三氯乙烯是强度致敏物 ;三氯乙酸是中度致敏物 ;三氯乙醇及水合三氯乙醛未见致敏作用。     

Determination of lead chelated with ethylenediaminetetra-acetic acid in blood after precipitation of protein with perchloric acid

Cernik, A. A. (1970).Brit. J. industr. Med.,27, 40-42. Determination of lead chelated with ethylenediaminetetra-acetic acid in blood after precipitation of protein with perchloric acid. A method is described for the determination of lead in whole blood containing ethylene-diaminetetra-acetic acid. Proteins were precipitated by 2·0 m perchloric acid. The ionized lead in the supernatant was chelated with ammonium pyrrolidine dithiocarbamate and was extracted with xylene. The method agreed well with a dry ashing technique (30 samples, correlation coefficient 0·985). Perchloric acid gave consistently good recoveries, unlike trichloroacetic acid, which frequently produced losses of up to 15%.     

Significance of urinary hippuric acid determination as an index of toluene exposure

Ikeda, Masayuki, and Ohtsuji, Hatsue (1969).Brit. J. industr. Med.,26, 244-246. Significance of urinary hippuric acid determination as an index of toluene exposure. Urine samples from 118 male workers in photogravure printing factories were analysed for hippuric acid. The urinary levels of hippuric acid were proportional to the environmental concentrations of toluene, although within wide variations. The urinary concentration of hippuric acid corresponding to 200 p.p.m. of toluene was 3·5 g./litre (specific gravity 1·016) or 4·3 g./g. creatinine.