Benzene exposure, assessed by urinary trans,trans-muconic acid, in urban children with elevated blood lead levels.

A pilot study was performed to evaluate the feasibility of using trans,trans-muconic acid (MA) as a biomarker of environmental benzene exposure. A secondary aim was to provide data on the extent of exposure to selected toxicants in a unique population consisting of inner-city children who were already overexposed to one urban hazard, lead. Potential sources of benzene were assessed by a questionnaire. Exposure biomarkers included urinary MA and cotinine and blood lead. Mean MA was 176.6 +/- 341.7 ng/mg creatinine in the 79 children who participated. A wide range of values was found with as many as 10.1%, depending on the comparison study, above the highest levels reported in adults not exposed by occupation. Mean MA was increased in children evaluated in the afternoon compared to morning, those at or above the median for time spent playing near the street, and those studied in the first half of the investigation. MA levels were not associated with blood lead or, consistently, with either questionnaire environmental tobacco smoke (ETS) data or cotinine. As expected, the mean blood lead level was elevated (23.6 micrograms/dl). Mean cotinine was also increased at 79.2 ng/mg creatinine. We conclude that the use of MA as a biomarker for environmental benzene exposure is feasible since it was detectable in 72% of subjects with a wide range of values present. In future studies, correlation of MA with personal air sampling in environmental exposure will be essential to fully interpret the significance of these findings. In addition, these inner-city children comprise a high risk group for exposure to environmental toxicants including ETS, lead, and probably benzene, based on questionnaire sources and its presence in ETS.

Identification of 1-hydroxypyrene glucuronide as a major pyrene metabolite in human urine by synchronous fluorescence spectroscopy and gas chromatography-mass spectrometry.

Humans are exposed to polycyclic aromatic hydrocarbons (PAHs) from various occupational, environmental, medicinal and dietary sources. The measurement of specific PAH metabolites, particularly 1-hydroxypyrene, in human urine treated with deconjugating enzymes (e.g. beta-glucuronidase) has been extensively used as a means of assessing recent exposure to PAHs. We have examined pyrene metabolites in human urine prior to enzymatic deconjugation in order to determine the relative proportions of conjugated and unconjugated pyrene metabolites. The analytical method utilized immunoaffinity chromatography, high performance liquid chromatography (HPLC) and the complementary techniques of synchronous fluorescence spectroscopy (SFS) and gas chromatography-mass spectrometry (GC-MS) to measure pyrene-containing metabolites. SFS analysis of immunoaffinity-purified urine samples showed fluorescence spectra characteristic of the pyrene moiety (using wavelength differences of 34 nm, 54 nm and 102 nm). These spectra are produced by several PAHs containing the pyrene moiety. HPLC analysis with fluorescence detection indicated that the major fluorescent metabolite in immunoaffinity-purified urine was much more polar than simple hydroxylated metabolites of pyrene (1-hydroxypyrene) or benzo[a]pyrene (benzo[a]pyrene-diols or -tetrols). Following digestion with beta-glucuronidase, this metabolite co-chromatographed with authentic 1-hydroxypyrene and exhibited fluorescence spectra characteristic of 1-hydroxypyrene, suggesting that the major metabolite was a glucuronide conjugate of 1-hydroxypyrene. This was subsequently confirmed by GC-MS analysis of trimethylsilyl derivatives of the major metabolite; both 1-hydroxypyrene and glucuronic acid were detected independently as derivatized products. Since 1-hydroxypyrene glucuronide is approximately 5-fold more fluorescent than 1-hydroxypyrene, it may provide a more sensitive biomarker for assessing exposure to pyrene in mixtures of PAHs.

Absence of correlations among three putative in vivo probes of human cytochrome P4503A activity in young healthy men.

In vitro studies with human liver microsomes have shown that erythromycin N-demethylation, dapsone N-hydroxylation, and the 6 beta-hydroxylation of cortisol are all primarily mediated by P4503A4. Trait measurements to assess the in vivo level of activity of these separate oxidations have also been developed previously. This study investigated the relationships among the three phenotypic trait measurements in 30 young healthy white men. The frequency distributions of the trait values were all unimodal, with a twofold range for the erythromycin breath test and the urinary dapsone recovery ratio; the urinary 6 beta-hydroxycortisol/cortisol ratio was more variable, with a 17-fold range of values. No statistically significant correlations were observed among any of the trait measurements (dapsone recovery ratio versus erythromycin breath test: r = -0.07, p = 0.7; urinary 6 beta-hydroxycortisol/cortisol ratio versus erythromycin breath test: r = -0.12, p = 0.6; urinary 6 beta-hydroxycortisol/cortisol ratio versus dapsone recovery ratio: r = 0.13, p = 0.5. This lack of any relationship was unexpected and the reason(s) is unknown; however, it is possible that factors such as route of administration and extrahepatic metabolism in the intestinal epithelium and kidney are involved. Further studies are required to identify and validate the use of an appropriate in vivo probe of P4503A4 in humans.