Urinary 1-Hydroxypyrene Level Relative to Vehicle Exhaust Exposure Mediated by Metabolic Enzyme Polymorphisms

Abstract

Polycyclic aromatic hydrocarbons (PAH) are common air pollutants generated from incomplete combustion. The inhalation of exhaust fumes in urban areas has been suggested to be an additional contributing factor. This study investigated the influence of urban traffic exposure, personal lifestyle factors and metabolic enzyme polymorphisms on the urinary 1-hydroxypyrene (1-OHP) level, approximating exposure to PAH. With consents, 95 male taxi drivers exposed to vehicle exhaust in traffic and 75 male office employees received health interviews and provided urine samples. The results showed taxi drivers had higher urinary 1-OHP than the office employees (mean ± standard deviation were 0.17 ± 0.10 vs. 0.10 ± 0.07 mol/mol creatinine, p<0.001). The average urinary 1-OHP level increased from 0.07 μmol/mol creatinine for non-smoking office employees to 0.17 μmol/mol creatinine for those who smoked more than 20 cigarettes daily. The values for taxi drivers with similar smoking statuses were 0.12 and 0.25 μmol/mol creatinine, respectively. Among non-smokers, taxi drivers still had higher 1-OHP level than office employees (0.12 ± 0.05 vs. 0.07 ± 0.03 μmol/mol creatinine). The subjects with the m1/m2 or m2/m2 genotype of CYP1A1 MspI or GSTM1 deficiency had significantly higher urinary 1-OHP levels than those with other CYP1A1 MspI and GSTM1 genotypes. Multivariate logistic regression analysis showed that taxi drivers (adjusted odds ratio (OR)=5.1, 95% confidence interval (CI)=1.1-13.6), smokers (OR=5.5, 95% CI=1.6-18.4) and subjects with the m1/m2 or m2/m2 genotype of CYP1A1 MspI (OR=9.7, 95% CI=2.7-35.0) had elevated urinary 1-OHP (greater than the overall median value, 0.11 μmol/mol creatinine). The results of this study suggest smoking contributes to the elevated urinary 1-OHP levels in taxi drivers in addition to taxi driving, and the excess level contributed from traffic exhaust and smoke was regulated by the CYP1A1 MspI genotype. Traffic exhaust exposure, smoking and CYP1A1 MspI genotype contributed to the variation in levels of urinary 1-OHP excretion.