Biomarkers of dose and susceptibility in cyclists exposed to monoaromatic hydrocarbons

A quasi-experimental held study was carried out in 24 volunteers with the aim of: (i) assessing personal exposure to aromatic hydrocarbons polluting urban areas; and (ii) exploring the role of polymorphic enzymes relevant to the biotransformation of benzene in the inter-individual variability of biomarkers. 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 determined during 2-h runs. BTEX were determined by solid-phase micro-extraction (SPME) followed by gas chromatography coupled with mass spectrometry (GC-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 glutathione-S-transferase class mu-1 (GSTM1) were also characterised. As compared to pre-run values, benzene and toluene in blood, and toluene and xylenes in urine significantly increased after urban runs. Urinary t,t-muconic acid was significantly higher in post-run samples after both urban (P < 0.001) 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 distinguished according to EH and GSTM1, subjects bearing both the EH wild type and GSTM 'null' genotype showed significant exposure-related changes in t,t-muconic acid excretion. Even at very low exposure levels, a 2-h bike run in a polluted urban environment may give rise to measurable changes in biomarkers of internal dose of selected aromatic hydrocarbons. Genetically-based metabolic differences may account for part of the inter-individual variability of biomarkers of exposure. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.