Comparative evaluation of urinay MTBE and benzene as biomarkers of exposure to urban traffic

Benzene and methyl tert-butyl ether (MTBE) are found in urban environments as a consequence of autovehicular traffic; in fact both these compounds are added to fuels to increase octane ratings and/or reduce carbon monoxide emissions. Aim of the present study was to evaluate the possibility of using excretion of urinary MTBE (U-MTBE) and benzene (U-BENZ) as biomarkers of exposure to traffic. With this aim 127 Milan urban policemen, working as traffic wardens, were investigated. Spot urine samples were obtained prior to and at the end of the workshift (7.30-13.30 or 13.30-19.30), in different seasons. Analysis was performed by headspace-solid phase microextraction GC-MS. Median levels of airborne benzene was 9.6 µg/m3 (range 4.0-90.2 µg/m3). Urinary levels in the different seasons varied from 74 to 164 ng/L (50-657 ng/L) and from 85 to 277 ng/L (21-5065 ng/L) for U-MTBE and U-BENZ, respectively. U-MTBE increased of about 14% during the workshift, independently from the moment of the shift (morning or afternoon). U-BENZ increased of 27% in the afternoon, but decreased of 15% in the morning. An influence of the different seasons was observed, with lower values in spring and higher in winter. Smoking increased the excretion of U-BENZ but not affected that of U-MTBE. The results of this study suggest that U-MTBE is a reliable marker for the assessment of exposure to urban traffic, while U-BENZ is influenced both from the moment of the day and smoking habit.