Biomarkers of dose and susceptibility in cyclists exposed to monoaromatic hydrocarbons

A quasi-experimental held study was carried out in 24 volunteers with the a im of: (i) assessing personal exposure to aromatic hydrocarbons polluting u rban areas; and (ii) exploring the role of polymorphic enzymes relevant to the biotransformation of benzene in the inter-individual variability of bio markers. Each subject covered by bicycle: (i) inner city routes with often jammed traffic; and (ii) open rural routes. Time-weighted average airborne concentrations of benzene, toluene, ethylbenzene and xylenes (BTEX) were de termined during 2-h runs. BTEX were determined by solid-phase micro-extract ion (SPME) followed by gas chromatography coupled with mass spectrometry (G C-MS) in blood and spot urine samples collected just before and immediately after the runs. Urinary t,t-muconic acid was measured by high performance liquid chromatography (HPLC)-UV. Genotypes of epoxide hydrolase (EH) and gl utathione-S-transferase class mu-1 (GSTM1) were also characterised. As comp ared to pre-run values, benzene and toluene in blood, and toluene and xylen es in urine significantly increased after urban runs. Urinary t,t-muconic a cid was significantly higher in post-run samples after both urban (P < 0.00 1) and rural runs (P < 0.05). Despite a narrow range of exposure levels, a significant relationship was observed between airborne benzene and post-run t,t-muconic acid (r(2) = 0.349, P < 0.001). When subgroups were distinguis hed according to EH and GSTM1, subjects bearing both the EH wild type and G STM 'null' genotype showed significant exposure-related changes in t,t-muco nic acid excretion. Even at very low exposure levels, a 2-h bike run in a p olluted urban environment may give rise to measurable changes in biomarkers of internal dose of selected aromatic hydrocarbons. Genetically-based meta bolic differences may account for part of the inter-individual variability of biomarkers of exposure. (C) 1999 Elsevier Science Ireland Ltd. All right s reserved.