Urinary methyl tert-buthyl ether as biomarker of exposure to urban traffic

Methyl tert-butyl ether (MTBE) is an organic compound added to fuels to increase octane ratings and/or reduce carbon monoxide emissions, and for this reason, it is found in urban environments because of auto vehicular traffic. Aim of the present study was to evaluate the possibility of using excretion of urinary MTBE (U-MTBE) as biomarker of exposure to traffic. With this aim, 127 Milan urban policemen, working as traffic wardens, and 90 controls were investigated. Spot urine samples were obtained before and at the end of the work shift and analysis of U-MTBE was performed by headspace-solid phase microextraction GC-MS. Median level of airborne MTBE for controls was 4 ng/m3 (range <0.5-528 µg/m3), while no data were available for traffic wardens. Median excretion levels of U-MTBE in before and end-shift samples were 118 (50-657) and 147 ng/L (68-556) for traffic wardens and 42 (<10-763) and 78 ng/L (<10-483) for controls. Excretion levels were always significantly higher in traffic wardens than in controls, moreover significant differences were found between before- and end-shift samples in both groups (p<0.01). Airborne and urinary levels were significantly correlated (r = 0.40, p<0.01). Smoking did not affect the excretion of U-MTBE. The results of this study suggest that U-MTBE is a reliable marker for the assessment of exposure to urban traffic.