Influence of cigarette smoking on the toxicokinetics of toluene in humans

To study the influence of cigarette smoking on the toxicokinetics of toluene, 10 habitual smokers who intended to stop smoking were exposed to toluene vapor (3.2 mmol/m3, 4 h) at three different exposure occasions: (I) while the smoking habit was still ongoing, and (II and III) 1 and 3-4 wk, respectively, after the day at which the smoking habit was discontinued. Solvent concentrations in the exhaled air and in the blood as well as hippuric acid concentrations in the urine were measured during the exposure period and for 3 h after the exposure period. The apparent clearance of toluene decreased significantly (p less than 0.05) 3-4 wk after the smoking habit was discontinued. This decrease was not a consequence of the increased body weight noticed in the subjects. No statistically significant differences between the three exposure occasions in the elimination rate of hippuric acid could be demonstrated. Thus, cigarette smoking seems to enhance the elimination rate of toluene from the body, since the apparent clearance was decreased after smoking was stopped.

Simultaneous determination of urinary creatinine and metabolites of toluene, xylene, styrene, ethylbenzene and phenol by automated high performance liquid chromatography

An attempt was made to establish a method for the direct determination of urinary concentrations of creatinine, hippuric acid, methylhippuric acid and mandelic acid by automated high performance liquid chromatography (HPLC). Urine was diluted with distilled water or mobile phase, then the mixture was centrifuged and the supernatant was injected into HPLC. A stainless-steel column packed with octadecyl silanized silicate was used, and the mobile phase was a solution of [20 mM potassium phosphate monobasic containing 3 mM sodium 1-decanesulfonate]/acetonitrile (85/15). Another HPLC method for the determination of urinary concentration of phenol, metabolites of benzene and/or phenol is also described. Phenyl sulfate and phenyl glucuronide in urine were hydrolyzed enzymatically into phenol. The hydrolyzed mixture was injected into HPLC with the ODS column. The mobile phase was a solution of [20 mM potassium phosphate monobasic containing 1 mM sodium 1-decanesulfonate]/acetonitrile (85/15). The ratio of hippuric acid (HA) concentration to creatinine concentration determined by the urine of students after physical exercise was similar to that before exercise. Moreover, the coefficient of correlation found between the toluene concentration in a workshop and the HA concentration in workers' urine, corrected for creatinine, was higher than that obtained between the toluene concentration and the uncorrected HA concentration. For assays on stored urine samples, urine was spotted on filter paper, dried and kept several weeks, and then MA, HA, o-MHA, m-MHA and creatinine in the filter paper were eluted with 50% methanol and their concentrations determined by HPLC.

Neurotoxic effects of solvent exposure on sewage treatment workers

Nineteen Sewage Treatment Workers (STWs) exposed to industrial sewage that contained benzene, toluene, and other organic solvents at a primary sewage treatment plant in New York City (Plant A) were examined for evidence of solvent toxicity. Fourteen (74%) complained of central nervous system (CNS) symptoms consistent with solvent exposure, including lightheadedness, fatigue, increased sleep requirement, and headache. The majority of these symptoms resolved with transfer from the plant. Men working less than 1 yr at Plant A were more likely to complain of two or more CNS symptoms than men who were working there longer than 1 yr (p = .055). Objective abnormalities in neurobehavioral testing were found in all 4 men working longer than 9 yr at this plant, but in only 5 of 15 employed there for a shorter period (p = .03). These results are consistent with the known effects of solvent exposure. Occupational health personnel must be aware that STWs can be exposed to solvents and other industrial wastes.

Toluene abuse and renal tubular acidosis in pregnancy

Five gravidas presented with severe renal tubular acidosis from paint sniffing. Normal acid-base balance returned within 72 hours with cessation of toluene abuse and standard supportive measures. Fetal heart tracings and dynamic ultrasound parameters were normal in four of five cases. Three of five infants were growth-retarded at birth; two showed anomalies and neonatal hyperchloremic acidosis. These and previous cases of renal tubular acidosis in pregnancy suggest that toluene is teratogenic.

Determination of benzoic acid and hippuric acid in human plasma and urine by high-performance liquid chromatography

For patients with inborn errors of urea synthesis, oral administration of sodium benzoate is the usual treatment to increase the nitrogen excretion. Thus, monitoring hippuric acid and benzoic acid simultaneously in human biological fluids is considered to be clinically important. We developed a simple and accurate high-performance liquid chromatographic method for the simultaneous determination of hippuric acid and benzoic acid in human plasma and urine. This method requires no extraction step. Aliquots of urine and plasma are added to a solution of internal standard (o-chlorobenzoic acid) in acetonitrile and directly injected onto a reversed-phase column using an acidic (pH 2.7) eluent and ultraviolet detection at 235 nm. The preliminary plasma concentration-time and urinary excretion rate-time profiles of hippuric acid and benzoic acid from a healthy subject receiving small, medium and large doses of sodium benzoate are reported.

Possible genetic influence on conjugate formation in salicylic acid metabolism

Subjects (7 males and 7 females) were dosed with salicylic acid (1 g) and hourly urinary samples were analyzed for its metabolites. The results obtained showed that the female subjects had higher capacity for salicylurate formation than the male (P less than or equal to 0.025). The urinary hourly excretion ratio of salicylurate and salicylglucuronic acid was about or greater than 1 while in the male this ratio is less than 0.50. A comparison of this ratio between female and male showed a highly significant difference (P less than or equal to 0.001). The high capacity of glucuronic acid pathway in male and the alternate pathway in female suggest a possible genetic influence in salicylic acid metabolism.

On the mechanism of toluene-induced renal tubular acidosis

This study was aimed to investigate the pathogenesis of toluene-induced renal tubular acidosis (RTA). In 5 individuals addicted to toluene sniffing we documented the occurrence of hypokalemia and hyperchloremic metabolic acidosis associated with inability to lower urine pH below 5.5 (6.06 +/- 0.24). Overall kidney bicarbonate reabsorption was normal or enhanced, a feature characteristic of the distal form of RTA (DRTA). These findings resemble those found during the administration of amphotericin B, a drug felt to cause DRTA by increasing hydrogen ion (H+) back-diffusion in the collecting tubule. In toluene sniffers, the urine pCO2 measured in a highly alkaline urine was reduced (47 +/- 8.8 mm Hg), suggesting a decrease in the rate of collecting tubule H+ secretion rather than H+ back-diffusion. To investigate these two mechanisms of altered distal acidification more directly we studied the effect of toluene on acidification by the urinary turtle bladder, an epithelial analogue of the mammalian collecting tubule. In this preparation, toluene resulted in a decrease in the rate of H+ secretion measured by either the pH stat technique or the reverse short circuit current. When mucosal pH was progressively lowered to examine H+ secretion against an H+ gradient, toluene-treated bladders displayed a significant decrease in proton conductance but the lowest mucosal pH required to nullify H+ secretion, (MpH) JH = O, was not different from that of control bladders (4.05 +/- 0.29 and 3.90 +/- 0.13, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Mutual metabolic suppression between benzene and toluene in man

The exposure intensity during a shift and the metabolite levels in the shift-end urine were examined in male workers exposed to either benzene (65 subjects; the benzene group), toluene (35 subjects; the toluene group), or a mixture of both (55 subjects; the mixture group). In addition, 35 non-exposed male workers (the control group) were similarly examined for urinary metabolites to define background levels. A linear relationship was established between the intensity of solvent exposure and the corresponding urinary metabolite levels (i.e. phenol, catechol and quinol from benzene, and hippuric acid and o-cresol from toluene) in each case when one of the three exposed groups was combined with the control group for calculation. Comparison of regression lines in combination with regression analysis disclosed that urinary levels of phenol and quinol (but not catechol) were lower in the mixture group than in the benzene group when the intensities of exposure to benzene were comparable, indicating that the biotransformation of benzene to phenolic compounds (excluding catechol) in man is suppressed by co-exposure to toluene. Conversely, metabolism of toluene to hippuric acid was suppressed by benzene co-exposure. Conversion of toluene to o-cresol was also reduced by benzene, but to a lesser extent. The significance of the present findings on the mutual suppression of metabolism between benzene and toluene is discussed in relation to solvent toxicology and biological monitoring of exposure to the solvents.

Urinary hippuric acid excretion after use of spray ski-wax and remover

The biological monitoring for exposure to toluene is based on the measurement of urinary hippuric acid concentration (HA-U). In occupational health, workers exposed to toluene are examined for HA-U, because collection of urine samples is easy. The HA-U data of an engineer who did not use toluene occupationally showed relatively high values. It was indicated that he went to ski every weekend in winter and had used spray ski-wax and remover which contained toluene. The ski-club members of Tokai University, School of Medicine who used such sprays were examined for HA-U at the ski training camp. It was revealed that the use of these sprays elevated the HA-U values remarkably. Therefore, the use of sprays, especially in the winter season, can be one of confounding factors for biological monitoring of occupational exposure to toluene based on measurement of HA-U.

Changes in the excretion of endogenous glycine conjugate as a possible artifact in toxicological experiments

Changes in the urinary excretion of hippuric acid (HIA) and phenaceturic acid (PUA) as well as their metabolic precursors, i.e. benzoic (BA) and phenylacetic acid (PAA), in rats housed in glass metabolic cages for 4 days were monitored using gas-liquid chromatography. The amount of HIA excreted was 128 +/- 63 mumol/kg for female and 79 +/- 43 mumol/kg for male rats in the first 24 h and decreased to 11 +/- 7 mumol/kg (p less than 0.01) for female and 3.2 +/- 2.4 mumol/kg (p less than 0.001) for male rats on the 2nd day. These values remained nearly at the same level until the end of the experiment. The amount of PUA decreased from 48 +/- 12 mumol/kg on the 1st day to 22 +/- 9 mumol/kg (p less than 0.05) on the 2nd day by male rats, whereas by the females the decrease from 30 +/- 9 mumol/kg to 21 +/- 8 mumol/kg was not significant. The decrease in the excretion of glycine conjugates was compensated by a parallel increase in the level of unconjugated BA and PAA.

Urinary excretion of 5-oxoproline (pyroglutamic aciduria) as an index of glycine insufficiency in normal man

1. The evidence is accumulating to suggest that glycine, the simplest amino acid, is conditionally essential in man. Benzoic acid, by conjugation with glycine to form hippuric acid, is known to deplete the free glycine pool of the body. Glycine is one substrate for the enzyme glutathione synthase (EC 6.3.2.3) and in the inborn error of metabolism in which glutathione synthase function is defective, increased quantities of 5-oxoproline are excreted in the urine. 2. An oral dose of 4-10 g sodium benzoate was given to six normal adults to deplete the metabolic pool of glycine, and the urinary excretion of 5-oxoproline was followed for 6 h. In five of the six, a significant increase in the urinary 5-oxoproline was seen within 3 h. 3. These findings show that 5-oxoprolinuria can result from limited glycine availability, and may provide a useful test for assessing glycine sufficiency in a range of physiological and pathological states.

A study on the health hazard of toluene in the polythene printing industry in Singapore

A study was conducted to determine if there were any health effects among the polythene printers who were exposed to toluene and to evaluate the use of urinary hippuric acid in biological monitoring. The study covered 54 printers from 6 plants out of the universe population of 32 polythene printing plants who used toluene as ink dilutants. They were matched with 54 controls for age, sex, race and similar occupational status. All were interviewed and examined clinically. 23 patients were selected for neurobehavioural tests. 26% of the printers had more than 10 years of exposure to toluene. No case of clinical encephalopathy or peripheral neuropathy was detected. 38.9% of the printers had hand dermatitis compared with 1.9% among the controls. Results of the neurobehavioural tests for the 23 printers were not statistically different from the controls. The results of the liver function test were within normal limits. The mean toluene-in-air level was 246 +/- 25 mg/m. Mean blood toluene was 0.63 +/- 0.14 microgram/ml. The mean urinary hippuric acid was 2.83 +/- 0.48 mg/ml as compared to 0.35 +/- 0.08 mg/ml in the controls. Urine hippuric acid corrected to SG of 1.016 was well correlated to air toluene level (r = 0.81). Toluene appears not to have any significant nervous system or liver effects in these printers. Urinary hippuric acid is a useful indicator for biological monitoring of atmospheric exposure to toluene.

Toluene metabolism during exposure to varying concentrations combined with exercise

The urinary excretion of hippuric acid (HA) and ortho-cresol (O-cr) in man was measured in two studies of 7-h exposure to toluene in a climate chamber, either constant concentration of 100 ppm or varying concentrations containing peaks of 300 ppm but with a time-weighted average of 100 ppm. In Study A, four males were exposed to clean air and to constant and varying concentrations of toluene in combination with rest and with 100 W exercise in 140 min. Exercise increased end exposure excretion rate of HA and O-cr by 47 and 114%, respectively. After exposure, all excess HA was excreted within 4 h, while O-cr was eliminated with a half life of about 3 h. Alveolar air concentration of toluene varied between 21 and 31 ppm during constant exposure and between 13 and 57 ppm during varying exposure, but no difference in mean alveolar toluene concentration or in metabolite excretion was seen between the exposure schedules. In Study B, 32 males and 39 females aged between 31 and 50 years were exposed once to either clean air, constant or varying concentrations of toluene. Background excretion rate of HA was 0.97 +/- 0.75 mg/min (1.25 +/- 1.05 g/g creatinine) and rose to 3.74 +/- 1.40 mg/min (3.90 +/- 1.85 g/g cr) during the last 3 h of exposure to 100 ppm toluene. The corresponding figures for O-cr were 0.05 +/- 0.05 micrograms/min (0.08 +/- 0.14 mg/g cr), and 2.04 +/- 0.84 micrograms/min (2.05 +/- 1.18 mg/g cr). The individual creatinine excretion rate was considerably influenced by sex, body weight and smoking habits, thus influencing the metabolite concentration standardised in relation to creatinine. It is concluded that both metabolites are estimates of toluene exposure. O-cr is more specific than HA, but the individual variation in excretion of both metabolites is large, and when implementing either of them as biological exposure indices, the influence of sex, body size, age as well as consumption of tobacco and alcohol has to be considered.

Metabolic interaction between toluene and ethanol in rabbits

The metabolic interaction of toluene and ethanol was studied in male rabbits having received ethanol (26.0 mmol/kg PO), toluene (5.4 mmol/kg PO) or both. Compared with ethanol alone, toluene given 2 h after ethanol caused a significantly higher and more prolonged concentration of blood alcohol. A similar trend of blood alcohol was observed at the later stage with toluene given prior to ethanol. On the other hand, with simultaneous doses of the two substances, the blood toluene concentration was higher for the first 15-30 min than the ethanol control and the urinary excretion of hippuric acid, a main metabolite of toluene, was markedly decreased for the first 2 h. The blood ethanol in this group, on the contrary, was reduced until 1 h after administration. These results indicate that toluene and ethanol act reciprocally as competitive inhibitors in their metabolism after single administrations.

Effect of food on the absorption of enteric-coated aspirin: correlation with gastric residence time

The Heidelberg capsule is an indigestible indicator of gastrointestinal pH, which was used to evaluate the relationship between gastric residence time (GRT) and variability in aspirin absorption from enteric-coated tablets. In a crossover study, eight healthy subjects (four men and four women) received an enteric-coated aspirin (648 mg) together with a Heidelberg capsule while fasting or with food (breakfast, followed 4 hours later by lunch). Salicylic acid and salicyluric acid concentrations in plasma and urine were measured by HPLC. The mean (+/- SD) GRT was significantly delayed by food (0.8 +/- 0.5 vs. 5.9 +/- 3.3 hours; P less than 0.005). The mean (+/- SD) lag time (TL) and time to peak concentration (expressed as salicylic acid equivalents) were markedly prolonged after the fed regimen (2.7 +/- 0.8 vs. 8.9 +/- 3.7 hours [P less than 0.005] and 8.3 +/- 2.9 vs. 13.8 +/- 4.5 hours [P less than 0.025]). For the combined data from the fasting and fed evaluations, an excellent correlation existed between TL and GRT of the capsule (TL = 1.0 GRT + 1.95; n = 16; r = 0.94; P less than 0.0001). Women demonstrated greater delays in GRT and TL than did men. The delay in aspirin absorption from an enteric-coated tablet is directly related to its GRT, which is gender related and greatly affected by food.

Albumin synthesis in premature infants: determination of turnover with [15N]glycine

Albumin turnover was studied in seven small premature infants who received a constant infusion of [15N]glycine for 60-72 h. Gas chromatography-mass spectrometry was used to measure the rate of appearance of [15N]glycine in albumin isolated from the blood. By comparing the linear increment of [15N]glycine in blood albumin with plateau labelling of urinary [15N]hippurate, which was assumed to reflect intrahepatic isotopic abundance in [15N]glycine, the fractional synthetic rate for albumin was found to be 0.09-0.177 day-1 (mean +/- SD = 0.122 +/- 0.041 day-1). The absolute synthesis rate for albumin was 0.3 +/- 0.099 g/dl plasma X day-1 and the total plasma synthetic rate was 117.6 +/- 37.0 mg/kg X day-1. The glycine flux was 326.0-927.7 mumol/kg X h-1 (mean +/- SD 516.7 +/- 218.4 mumol/kg hr-1). The percentage of the glycine flux incorporated into albumin in the total vasculature was 0.425 +/- 0.344. The fractional synthetic rate and the absolute synthetic rate for albumin in these small premature infants are much higher than values obtained in healthy young adults studied with a similar methodology. The relatively low serum albumin concentrations typical of premature infants appear to be referable to more rapid turnover of a small plasma pool rather than a diminution in the rate of albumin synthesis.

Hippuric acid and ortho-cresol as biological indicators of occupational exposure to toluene

Industrial exposure to toluene was studied in a group of 18 subjects working in a printing plant, exposed only to this solvent. Environmental monitoring was carried out using personal samplers for the whole work-shift. Urine samples were collected for the determination of hippuric acid and ortho(o)-cresol before toluene exposure, at the end of the work-shift, and 5, 9, and 17 h after the end of the work-shift. The values of two metabolites in all the urinary samples were corrected for g creatinine and specific gravity (1.024). Toluene time weighted average (TWA) concentrations ranged from 51 to 221 mg/m3 (7-h samples; two samplings lasting 3.5 h each). Urinary hippuric acid and o-cresol values at the end of the work-shift were significantly higher than the prework-shift values. Both hippuricuria and o-cresoluria end-of-work-shift values, corrected for creatinine and specific gravity, were significantly related to the mean daily environmental concentration of toluene, the correlation being weaker for o-cresol. Correlation coefficients were 0.88 and 0.84 for hippuric acid and 0.63 and 0.62 for o-cresol after correction for creatinine and specific gravity, respectively. No significant relationship was observed between environmental exposure and the values of the two urinary metabolites 5, 9, and 17 h after the end of the work-shift. Extrapolated values from the linear regression analysis at 375 mg/m3 were in good agreement with the biological exposure index (BEI) suggested by ACGIH for hippuric acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible ethnic difference in toluene metabolism: a comparative study among Chinese, Turkish and Japanese solvent workers

Toluene metabolism was studied in 192 Chinese workers in comparison with that in 130 Japanese and 17 Turks. Time-weighted average concentrations of toluene in the breathing zone of workers were measured utilizing passive dosimeters, and hippuric acid (HA) and omicron-cresol (omicron C) concentrations in shift-end spot urine samples by high-performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. Under similar exposure conditions, male Japanese excreted almost twice as much HA as male Chinese, although such difference was less marked between female Chinese and Japanese. In contrast, the excretion of oC did not differ between the two ethnic groups. The ratio of oC over HA was highest among Turkish workers followed by Chinese, and lowest among Japanese. Possible roles of differences in toxicogenetics as well as in life patterns were discussed.