The validity of urinary metabolites as indicators of low exposures to toluene

Abstract

Exposure to toluene was studied in a group of 14 subjects working in a printing industry, who were exposed to this solvent only. Environmental monitoring was carried out using personal samplers for the whole workshift over three consecutive days. Toluene TWA concentrations ranged from 37 to 229 mg/m3. At the end of the workshift on each day of investigation, urine samples were collected for the determination of hippuric acid and ortho-cresol. Hippuric acid was also determined for urine before the workshift and on the Saturday and Monday mornings after the end of exposure; hippuric acid was also determined in 16 controls over the same five-day period. At the end of the workshift, hippuricuria levels in exposed workers always turned out to be statistically different from pre-workshift levels and those of the controls. The end-of-workshift hippuricuria levels of exposed workers were significantly correlated with the mean daily environmental concentration (TWA): in the three days of comparative study, we found r = 0.63 (P less than 0.05) on Day 1, r = 0.90 (P less than 0.001) on Day 2, and r = 0.87 (P less than 0.001) on Day 3. Ortho-cresol turned out to be correlated with daily exposure less significantly than hippuric acid: r = 0.49 (n.s.) on Day 1; r = 0.78 (P less than 0.001) on Day 2, and r = 0.65 (P less than 0.05) on Day 3. Using all available data (41 observations), a very significant correlation (P less than 0.001) was found between the TWA and both metabolites (r = 0.80 for hippuric acid; r = 0.68 for o-cresol). The values of the two metabolites in the end-of-workshift urine samples (41 observations) also turned out to be well correlated (r = 0.70; P less than 0.001). The authors conclude that hippuric acid is a valid test for evaluating even low exposures to toluene.

A Modified Method for Determination of Hippuric Acid in Urine by HPLC : İdrarda Hi̇ppuri̇k Asi̇t Tayi̇ni̇nde Kullanilabi̇lecek Bi̇r Modi̇fi̇ye HPLC Yöntemi̇

“…The results of the reproducibility studies can be seen in Table 2. (11). Moreover the urinary HA concentrations were determined significantly higher than the non-exposed (control) group as was expected (Table 3).…”

“…The metabolic pathway of toluene can be seen in Figure 1. Determination of HA in urine is one of the most used and easiest way in monitoring the occupational toluene exposure (11). Therefore several determination procedures including HPLC methods have been developed in order to determine HA in urine (12,13,14,15).…”

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

“…The concomitant excretion of hippuric acid and o-cresol in urine of both occupationally [Apostoli et al, 1982;Hasegawa et al, 1983;De Rosa et al, 1985b] and experimentally [DBssing et al, 1983;Anderson et al, 19831 exposed subjects has recently been studied.…”

Uncertainties in physiologically based pharmacokinetic models caused by several input parameters

“…Another possibility is that the accumulation of toluene in the body might be simulated to be too high, for example, due to incorrect tissue-gas partition coe cients (higher than in reality). Rosa et al 19851.4 Ogata and Taguchi 19881.7 Foo et al 19911.0 Campbell et al 1987 Cum15 ( Table 7 presents the comparison of simulation results obtained with di erent parameters for workers exposed to styrene. Simulation results recorded for blood concentrations and urinary metabolites gave higher concentrations both at the end of the shift and at 15 h postexposure than did the ®eld data.…”