Determination of thio compounds in urine of workers exposed to carbon disulfide

Biological Thiols and Carbon Disulfide: The Formation and Decay of Trithiocarbonates under Physiologically Relevant Conditions

Carbon disulfide is an environmental toxin, but there are suggestions in the literature that it may also have regulatory and/or therapeutic roles in mammalian physiology. Thiols or thiolates would be likely biological targets for an electrophile, such as CS₂, and in this context, the present study examines the dynamics of CS₂ reactions with various thiols (RSH) in physiologically relevant near-neutral aqueous media to form the respective trithiocarbonate anions (TTC^-, also known as "thioxanthate anions"). The rates of TTC^- formation are markedly pH-dependent, indicating that the reactive form of RSH is the conjugate base RS^-. The rates of the reverse reaction, that is, decay of TTC^- anions to release CS₂, is pH-independent, with rates roughly antiparallel to the basicities of the RS^- conjugate base. These observations indicate that the rate-limiting step of decay is simple CS₂ dissociation from RS^-, and according to microscopic reversibility, the transition state of TTC^- formation would be simple addition of the RS^- nucleophile to the CS₂ electrophile. At pH 7.4 and 37 °C, cysteine and glutathione react with CS₂ at a similar rate but the trithiocarbonate product undergoes a slow cyclization to give 2-thiothiazolidine-4-carboxylic acid. The potential biological relevance of these observations is briefly discussed.

Carbon disulfide. Just toxic or also bioregulatory and/or therapeutic?

The overview presented here has the goal of examining whether carbon disulfide (CS₂) may play a role as an endogenously generated bioregulator and/or has therapeutic value.

Accumulation of urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) among workers occupationally exposed to carbon disulfide for 1 week

OBJECTIVES

To investigate if carbon disulfide (CS(2)) accumulates after a 1-week exposure period, and how the work-shift duration and exposure magnitude affects this accumulation for the workers in viscose rayon industry.

METHODS

Six 8-h and seven 12-h workers in the spinning department historically known to be exposed to high air CS(2) were recruited as the exposed groups. Seven workers from other non-CS(2)-exposed departments were recruited as non-exposure controls. Exposure monitoring covered a full work shift with personal breathing zone monitoring. Urine was collected pre- and post-shift every day throughout the 5 consecutive days. 2-Thiothiazolidine-4-carboxylic acid levels in the urine (U-TTCA) were determined.

RESULTS

No detectable values were found for airborne (<0.6 ppm) and urinary (<35 ng/ml) monitoring for the control groups. The exposure levels for a 12-h shift (11.3+/-1.47) (AM+/-S.D.) were significantly greater than for an 8-h shift (6.3+/-0.64). The linear accumulation trend for daily U-TTCA across the workdays was only significant for the 12-h shift at pre-shift. Statistical significance was found in the regression of the ratios for pre-shift U-TTCA to airborne CS(2) levels on the preceding day to the day of the exposure at pre-shift for a 12-h shift (r=0.98, P=0.02).

CONCLUSIONS

The U-TTCA accumulation for occupational exposure to CS(2) was exposure-magnitude-dependent. The linear equations derived in this study indicated that the U-TTCA increment at pre-shift for each additional daily 12-h exposure, after an adjustment for the CS(2) exposure level, was 0.02 mg/g creatinine/ppm of CS(2). The long-term exposure response under such repeated and intermittent conditions should be noteworthy.

Biological monitoring of carbon disulphide: kinetics of urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) in exposed workers

The objectives of this study was to establish the kinetics of urinary 2-thiothiazolidine-4-carboxylic acid (U-TTCA) for workers exposed to carbon disulphide (CS2) and to investigate the effects of volume and creatinine adjustment methods for urine measurement. Ten workers in the spinning department of a rayon factory were individually monitored for airborne CS2 concentrations, with consecutive urine samples collected for 24-38 hours after termination of exposure. The U-TTCA, urine volume and creatinine level were measured for each sample. First-order and biphasic kinetics were determined using the curve-fit method, for the measurement series. For the first-order kinetics linearity fit, statistically significant correlation coefficients of 0.74-0.98 and 0.86-0.99 were derived for the volume- and creatinine-adjusted methods, respectively. For the biphasic kinetics approach, the overall correlation coefficients were 0.544-0.999 and 0.171-0.999 for the first and second phases of the creatinine-adjusted method, respectively. A post-shift U-TTCA of 3.0 mg/g Cr. equivalent, 40% below the current BEI setting at nearly PEL exposed level, was found. In conclusion, first-order kinetic response was confirmed for U-ITCA. Both volume- and creatinine-based urine adjustment are satisfactory for TTCA assessment as a biomarker of individual CS2 exposure although the correlation for creatinine-based measurement was modestly superior to the volume-based analogue. Based on the results of this study,we recommend a re-evaluation of the current biological exposure index of 5 mg/g creatinine at a CS2 exposure level of 10 ppm.

The cross-sectional study of the health effects of occupational exposure to carbon disulfide in a Chinese viscose plant

This article presents results of carbon disulfide exposure assessment in a Chinese viscose rayon factory and represents the cross-sectional study beginning phase of the occupational epidemiological project. The authors measured external exposure levels to carbon disulfide at a Chinese viscose rayon factory and monitored results as internal exposure indexes by testing urine samples of workers exposed to carbon disulfide levels. The rate at which carbon disulfide is metabolized by exposed subjects was demonstrated by 2-thio-thiazolidine-4-carboxylic acid (TTCA) concentrations in urine of exposed subjects, which was studied to determine best time points for internal exposure sampling. Carbon disulfide concentrations in the air of the workplace were analyzed with gas chromatography with flame photometric detector (GC-FPD); presence of TTCA in urine samples of subjects was determined using a modified high-performance liquid chromatography method. Kinetics of TTCA excretion was studied by analysis at different time points during and after exposure of workers to carbon disulfide. A total of 155 personal samples were obtained. Carbon disulfide concentration at staple viscose hall was found to be 13.72 +/- 1.12 mg/m3 in terms of geometric mean and geometric standard deviation. Carbon disulfide concentration at filament spinning hall was found to be 20.05 +/- 1.33 mg/m3. TTCA values of subjects at staple spinning hall were 1.18 +/- 0.43 and 1.07 +/- 0.38 mg/g creatinine for subjects working at filament spinning hall. The best time for TTCA sampling is at the end of the exposure-working shift.

Urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) as the major urinary marker of carbon disulfide vapor exposure in rats

Male Sprague-Dawley rats (200-250 g; 60 per exposure group) were exposed to carbon disulfide (CS2) air concentrations of 0, 50, 150, and 500 ppm(v/v) for 6 hr/day, 5 days/week over six months. Following the exposures, nine rats from each exposure group had four sets of cumulated urines collected (between 0-8, 8-16, 16-24, and 24-48 hr). The urinary parameters measured were: 2-thiothiazolidine-4-carboxylic acid (TTCA), total thioethers (TE), and the compounds responsive to the iodine-azide (IA) test. Urinary TTCA elimination obeyed pseudo-first-order, one-compartment model kinetics of half-time (t0.5) 5.2 +/- 0.3 hr up to 16 hr of collection. The elimination of TE within 16 hr had a t0.5 of 8.5 +/- 0.6 hr. TTCA, IA, and TE were correlated highly in the first 16 hr. After 16 hr, the t0.5 for TE lengthened to 13.1 hr. At CS2 concentrations of 50, 150, and 500 ppm, the respective t0.5 for IA-responsive compounds were 12.6, 6.1, and 4.4 hr. TTCA had the highest correlation coefficient and p-value relative to CS2 exposure concentration, and also was the most sensitive, precise, and selective urinary marker.

Captan metabolism in humans yields two biomarkers, tetrahydrophthalimide (THPI) and thiazolidine-2-thione-4-carboxylic acid (TTCA) in urine

Captan fungicide (N-(trichloromethylthio)-4-cyclohexene-1,2-dicarboximide) metabolism in two human volunteers rapidly yields THPI (tetrahydrophthalimide) and TTCA (thiazolidine-2-thione-4-carboxylic acid). The work was done to evaluate usefulness of TTCA and THPI as biomarkers of occupational exposure and to compare human and rat dermal absorption and metabolism. THPI in 12h urine ranged from MDL (5 ppb) to 640 ppb and was stable for at least one year. TTCA was also a stable metabolite, but the MDL was 50 ppb. THPI was detectable in urine for 72 hours following oral dosages of 1 mg/kg, but most was eliminated 0-24 h. No THPI was detectable in urine following application of a chloroform solution to hands, forearms, or inguinal region. Dermal absorption and metabolism of captan are substantially different in humans and rats.

Biological monitoring of workers occupationally exposed to carbon disulphide in a rayon plant in Brazil: validity of 2-thiothiazolidine-4-carboxylic acid (TTCA) in urine samples taken in different times, during and after the real exposure period

Fifteen workers from a rayon plant in Brazil were monitored. Air samples were taken during a mean period of 5.8 hours out of an 8 hour workshift, in three different adsorbing tubes. Five urine samples were taken at 4 hour interval from the beginning of the shift, and at the beginning of the next shift in which 2-thiothiazolidine-4-carboxylic acid (TTCA) concentration was analysed. Data from seventeen "individuals" were statistically studied, with the aim of establishing the best and the most practical sampling strategy of biological monitoring for workers occupationally exposed to CS2. For those chronically exposed to CS2, TWA air concentration lower than 30 and higher than 10 mg/m3, it was found that the higher the exposure levels, the lower was TTCA concentration in the end of shift urine samples. The results may be explained by dietary habits and/or by the small number of examined population or even eventual casualty. On the other hand they raise other hypothesis involving the chronicity of exposure which may lead to important changes in metabolism influencing the excretion rate of TTCA.

Mercapturic acids, protein adducts, and DNA adducts as biomarkers of electrophilic chemicals

The possibilities and limitations of using mercapturic acids and protein and DNA adducts for the assessment of internal and effective doses of electrophilic chemicals are reviewed. Electrophilic chemicals may be considered as potential mutagens and/or carcinogens. Mercapturic acids and protein and DNA adducts are considered as selective biomarkers because they reflect the chemical structure of the parent compounds or the reactive electrophilic metabolites formed during biotransformation. In general, mercapturic acids are used for the assessment of recent exposure, whereas protein and DNA adducts are used for the assessment of semichronic or chronic exposure. 2-Hydroxyethyl mercapturic acid has been shown to be the urinary excretion product of five different reactive electrophilic intermediates. Classification of these electrophiles according to their acid-base properties might provide a tool to predict their preference to conjugate with either glutathione and proteins or with DNA. Constant relationships appear to exist in the cases of 1,2-dibromoethane and ethylene oxide between urinary mercapturic acid excretion and DNA and protein adduct concentrations. This suggests that mercapturic acids in some cases may also play a role as a biomarker of effective dose. It is concluded that simultaneous determination of mercapturic acids, protein and DNA adducts, and other metabolites can greatly increase our knowledge of the specific roles these biomarkers play in internal and effective dose assessment. If the relationship between exposure and effect is known, similar to protein and DNA adducts, mercapturic acids might also be helpful in (individual) health risk assessment.

Determination of tetrahydrophtalimide and 2-thiothiazolidine-4-carboxylic acid, urinary metabolites of the fungicide captan, in rats and humans

Capillary gas chromatographic (GC) methods using sulphur and mass selective detection for the qualitative and quantitative determination of tetrahydrophtalimide (THPI) and 2-thiothiazolidine-4-carboxylic acid (TTCA), urinary metabolites of the fungicide captan in rat and humans, were developed. Urinary detection limits were 2.7 micrograms/l for THPI and 110 micrograms/l for TTCA. Intraperitoneal and oral administration of captan to rats resulted in a 48-h cumulative urinary excretion of THPI of 1%-2% and 3%-9% of the dose, respectively. Cumulative urinary excretion of TTCA over 48 h ranged from 2% to 5% of the captan dose for the respective routes of administration. In urine of non-exposed human subjects, neither THPI nor TTCA could be detected. In urine of fruit-growers who were occupationally exposed to captan, both THPI and TTCA could be detected. Based on these results, THPI and TTCA are proposed as promising parameters for the biological monitoring of occupational exposure to captan.

Sequential changes in hepatic and renal glutathione and development of renal karyomegaly in 1-cyano-3,4-epithiobutane toxicity in rats

The effect of 1-cyano-3,4-epithiobutane (CEB) on glutathione (GSH) metabolism was investigated in rat liver, kidney and pancreas. Male Fischer 344 rats were gavaged with a single dose (125 mg/kg body weight or 50 mg/kg body weight) of CEB. Tissue samples were taken for histological examination, determination of GSH and oxidized glutathione (GSSG) concentrations and gamma-glutamyl transpeptidase (GGT) and glutathione S-transferase (GST) activities. Urine samples were analysed for non-protein thiol (NP-RSH) content. The high dose of CEB induced hepatic GSH depletion followed by increased GSH. The low dose of CEB induced elevated hepatic GSH by 12 hr without depletion. Renal GSH was increased with both doses without an observed depletion phase. Renal tubule epithelial cell death was observed only with the high dose of CEB, but both doses caused renal proximal tubule karyomegaly. Pancreatic GSH content was unaffected. No alterations of GSSG were observed. GST activity was unaffected in any tissue. Renal GGT activity was decreased at 12 hr with both doses and at 24 and 48 hr with the high dose. Urinary NP-RSH excretion was increased with both doses. Depletion of hepatic GSH concurrent with increased urinary NP-RSH excretion suggests that conjugation with GSH is a significant pathway in CEB metabolism.

Effects of inhalation exposure to carbon disulfide and its combination with hydrogen sulfide on embryonal and fetal development in rats

Pregnant rats were exposed to 0, 100, 200, 400 or 800 ppm of carbon disulfide (CS2), 100 ppm of hydrogen sulfide (H2S) alone or in combination with 400 and 800 ppm CS2, 6 h/d during days 6-20 of gestation. Maternal reproduction and fetal parameters were evaluated on gestational day 21. Treatment with 100 or 200 ppm CS2 or with 100 ppm H2S caused no maternal toxicity or adverse effects on the developing embryo or fetus. Exposure to 400 or 800 ppm CS2 resulted in a low incidence of club foot and in a significant reduction of maternal weight gain. Significant increases in unossified sternebrae occurred at 800 ppm CS2 and reduction of fetal body weight at 400 and 800 ppm CS2. The latter effect was enhanced by combination with 100 ppm H2S. These results support the conclusion that, at levels of exposure associated with maternal toxicity, CS2 leads to an increase in incidence of club foot and to fetal toxicity which is enhanced by simultaneous exposure to H2S.

Lake Nyos disaster, Cameroon, 1986: the medical effects of large scale emission of carbon dioxide?

Carbon dioxide was blamed for the deaths of around 1700 people in Cameroon, west Africa, in 1986 when a massive release of gas occurred from Lake Nyos, a volcanic crater lake. The clinical findings in 845 survivors seen at or admitted to hospital were compatible with exposure to an asphyxiant gas. Rescuers noted cutaneous erythema and bullae on an unknown proportion of corpses and 161 (19%) survivors treated in hospital; though these lesions were initially believed to be burns from acidic gases, further investigation suggested that they were associated with coma states caused by exposure to carbon dioxide in air. The disaster at Lake Nyos and a similar event at Lake Monoun, Cameroon, two years previously provide new information on the possible medical effects of large scale emissions of carbon dioxide, though the presence of other toxic factors in these gas releases cannot be excluded.

Urinary excretion of mutagens, thioethers and D-glucaric acid in workers exposed to bitumen fumes

The authors carried out biological monitoring of the mutagenic/carcinogenic hazards associated with exposure to bitumen fumes during paving operations, analysing some biological parameters in the urine of a group of exposed workers. The urine samples were studied for mutagenicity by the Ames test and for thioethers concentration. D-Glucaric acid urine excretion was also determined to investigate the enzymatic induction potential of bitumens. Even though, in a previous environmental monitoring phase, a low content of mutagenic/carcinogenic compounds was found in bitumen and air samples, urinary mutagenicity data of exposed workers were statistically higher than those of a group of unexposed subjects. The urinary mutagenicity increased further if exposure to bitumens was associated with cigarette smoking. Thioethers were higher only in subjects exposed simultaneously to bitumens and cigarettes. D-Glucaric acid excretion did not increase significantly. The authors think that this type of coupled environmental and biological monitoring is a valid tool for a better evaluation of the mutagenic/carcinogenic exposure to bitumens or similar complex mixtures.

Thioethers, mutagens, and D-glucaric acid in urine of operating room personnel exposed to anesthetics

Mutagenic hazards related to occupational exposure to nitrous oxide and enflurane was studied in the personnel of five operating rooms using a coupled environmental and biological monitoring approach. The environmental monitoring revealed air concentrations of the two anesthetics exceedings the TLVs by 10-15-fold. These values were correlated individually with the concentrations of the two anesthetics in the expired air of the exposed subjects. The biological monitoring was carried out by determining two parameters associated with mutagen exposure (urinary mutagenicity and thioethers) and a parameter associated with the enzymatic induction (D-glucaric acid) in the urine of exposed and unexposed subjects (N = 64 and N = 37, respectively). The results showed no difference in the two groups for urine mutagenicity and D-glucaric acid, but urine thioethers were significantly increased among highly exposed subjects.

Influence of diet and other factors on urinary levels of thioethers

Urinary excretion of thioethers has been used as an indicator of exposure to potentially alkylating agents in several studies. These studies, however, often had the disadvantage of high and varying background values. We have studied methods for sampling and determination of urinary thioethers. Modifications have been made making it possible to increase the sensitivity of the method substantially. The thioethers were extracted with ethyl acetate and hydrolyzed with sodium hydroxide. The thiols were then determined spectrophotometrically with the reagent of Ellman. The extraction procedure and the addition of the reagent were found to be critical steps, whereas the crude urine samples were comparatively stable during storage at -20 degrees C. Diet was found to be the most important factor. Using a standardized diet over 24 h with chicken, potatoes, bread and dairy products as the major components, excluding vegetables of the Cruciferae family, 24 subjects excreted low amounts of thioethers, 3.2 +/- 0.2 mmol/mol creatinine, (mean +/- SEM). Individual values did not exceed 6.5 mmol/mol creatinine. Without food restrictions the mean values and the standard deviations were increased up to five and ten times respectively. Ingestion of certain foodstuffs increased the thioether excretion up to 20 times. Twelve smokers (20 cig/d) excreted 6.7 +/- 0.4 mmol/mol creatinine (mean +/- SEM, afternoon samples and standardized diet). No effects of gender and age of the subject could be observed. It is recommended that diet factors be kept under strict control to increase the sensitivity of the thioether assay and to avoid misleading results due to diet effects.

The influence of simultaneous exposure to carbon disulfide and hydrogen sulfide on the peripheral nerve toxicity and metabolism of carbon disulfide in rats

Three groups of 10 male Sprague-Dawley rats were exposed daily, 5 days a week for 25 weeks, either to 500 ppm carbon disulfide (CS2), 50 ppm hydrogen sulfide (H2S), or to both of them as a mixture and were periodically examined for sensory and motor tail nerve conduction velocity (SNCV, MNCV). A concomitant control group of 10 rats was used. In addition, rats exposed to 500 ppm CS2, and those simultaneously exposed to 500 ppm CS2 and 50 ppm H2S, were twice examined for 24-h urine excretion of 2-thio-thiazolidine-4-carboxylic acid (TTCA) in the course of the experimental period. Simultaneous exposure to CS2 and H2S had no significant interactive effect on nerve conduction velocities. A significant time-dependent slowing down of MNCV and SNCV occurred as the result of chronic exposure to CS2, including exposure to 500 ppm CS2 and to the mixture of 500 ppm CS2 and 50 ppm H2S, but did not occur after chronic exposure to 50 ppm H2S. With combined exposure to 500 ppm CS2 and 50 ppm H2S, the quantity of TTCA excreted in 24-h urine was not significantly different from that occurring in response to CS2 exposure alone. On the basis of these results it is suggested that chronic exposure to H2S would neither influence CS2-induced peripheral nerve toxicity nor obscure the interpretation of the measurement of urinary TTCA as a biological indicator of CS2 exposure.

Characterization of carbon disulfide binding in blood and to other biological substances

Free and bound forms of CS2 are present in subjects exposed to CS2. In rats exposed to 2 mg/liter (approximately 640 ppm) of CS2 for 4 hr, concentrations of acid-labile CS2 (AL CS2, a form of bound CS2 that can be recovered from biological samples by acid treatment) in plasma and red blood cells (RBCs) increased linearly with exposure time. The majority (90%) of the blood AL CS2 was present in the RBCs. About 95% of the AL CS2 in plasma and in RBCs of exposed rats was found in the precipitates after treatment with ammonium sulfate. Incubation of fractionated human RBC lysates with CS2 showed that CS2 binding in these fractions was proportional to the hemoglobin concentration. These observations show that in blood, CS2 binds (in the form of AL CS2) mainly to hemoglobin and to a small extent to other blood proteins. Binding of CS2 to small molecules, including amino acids, accounted for only a small fraction of blood AL CS2. In in vitro studies, CS2 also bound to human albumin, gamma-globulin, and horse heart myoglobin. It was also found that CS2 binds to amino and sulfhydryl compounds at physiological pH. Plasma incubated with CS2 was found to chelate copper. Chelation of copper-containing enzyme by the reaction products of CS2 and biological amines has been observed and has been proposed as one of the mechanisms by which CS2 induces neurotoxicity (M.J. McKenna and V. DiStefano, 1977b, J. Pharmacol. Exp. Ther. 202, 253-266). Radioisotope studies showed that a substantial portion of the radioactivity could not be released from 14CS2-treated plasma and serum upon acid treatment at elevated temperature. These studies suggest the existence of non-acid-labile bound CS2, besides AL CS2, in plasma and serum treated with CS2.

A procedure for the analysis of S-benzyl-N-acetylcysteine and S-(o-methylbenzyl)-N-acetylcysteine in human urine

Analytical methods for mercapturic acids, the end-products of glutathione metabolism of the industrial solvents toluene and o-xylene (i.e., S-benzyl-N-acetylcysteine and S-(o-methylbenzyl)-N-acetylcysteine), added to human urine have been developed. The sensitivity is 2 ng/microliter (R.S.D. = +/- 13%) and 1 ng/microliter (R.S.D. = +/- 6.4%) urine for S-benzyl-N-acetylcysteine and S-(o-methylbenzyl-N-acetylcysteine, respectively, when using the h.p.l.c. method. The corresponding sensitivities for the g.l.c.-mass spectrometric method are 0.5 and 0.3 ng/microliter urine, respectively.

Evaluation of occupational exposure to carbon disulphide by blood, exhaled air, and urine analysis

This paper compares three analytical methods that may be considered for monitoring workers who are exposed to carbon disulphide (CS2). An estimate of the uptake of CS2 was assessed by the measurement of "bound" CS2 in blood, CS2 in expired alveolar air, and 2-thiothiazolidine-4-carboxylic acid (TTCA) in urine. The concentration of TTCA in end-of-shift urine samples was related to exposure and appears to be a good measure of uptake of CS2.

Relation between the iodine azide test and the TTCA test for exposure to carbon disulphide

Exposure to carbon disulphide (CS2) in a viscose plant was measured by personal monitoring and by application of the iodine azide test and quantification of 2-thio-thiazolidine-4-carboxylic-acid (TTCA) in urine samples. A relation was found between the rise in urinary TTCA concentration during the workshift and the exposure index E1. The correlation (r) between the exposure index and the atmospheric concentrations of CS2 in workroom air below 100 mg CS2/m3 was 0.59 (n = 9). The correlation between the increase in TTCA concentrations during the workshift and the atmospheric CS2 concentrations was found to be higher when urine samples at the end of the workshift with creatinine concentrations below 1 mg/ml and above 3 mg/ml were disregarded (from r = 0.61; n = 20 to r = 0.84; n = 14). A high correlation was found (r = 0.86; n = 13) when the end of workshift urine samples were analysed, provided that their creatinine concentrations are not beyond the limits given above.

Application and results of whole-body autoradiography in distribution studies of organic solvents

With the growing concern for the health hazards of occupational exposure to toxic substances attention has been focused on the organic solvents, which are associated with both deleterious nervous system effects and specific tissue injuries. Relatively little is known about the distribution of organic solvents and their metabolites in the living organism. Knowledge of the specific tissue localizations and retention of solvents and solvent metabolites is of great value in revealing and understanding the sites and mechanisms of organic solvent toxicity. Whole-body autoradiography has been modified and applied to distribution studies of benzene, toluene, m-xylene, styrene, methylene chloride, chloroform, carbon tetrachloride, trichloroethylene and carbon disulfide. The high volatility of these substances has led to the development of cryo-techniques. Whole-body autoradiographic techniques applicable to the study of volatile substances are reviewed. The localizations of nonvolatile solvent metabolites and firmly bound metabolites have also been examined. The obtained results are discussed in relation to toxic effects and evaluated by comparison with other techniques used in distribution studies of organic solvents and their metabolites.