Exposure to benzene and MTBE in Italian gasoline station attendants

Gasoline is added with a mixture of aromatic hydrocarbons and oxygenated compounds to increase antiknock power. Among these chemicals benzene and methyl ter butyl ether (MTBE) are of particularly interest due to their toxicological properties. In the present study exposure to benzene and MTBE in 90 gasoline station attendants and in a matched group of 89 controls working in the area surrounding Milan, Italy was evaluated. Median personal exposure to airborne benzene and MTBE, as time weighted average during the monitored period (7:30-12:30) was 59 (from 3-3246) and 408 (2-57616) µg/m3 in gasoline station attendants, and 4 (1-48) and 4 (1-528) µg/m3 in controls. Biological monitoring was performed collecting urine spot samples before the beginning of the work week (BL), prior to the investigated shift (BS) and at the end of the air monitoring (ES). In gasoline station attendants median urinary benzene was 283, 337, 339 ng/L, urinary MTBE was 81, 246 and 780 ng/L at BL, BS and ES. In controls urinary benzene was 146, 86 and 157 ng/L, and urinary MTBE was 70, 42, 78 ng/L at BL, BS and ES. Higher levels were found in gasoline attendants than in controls at all moments. A relevant influence of cigarette smoking was found on urinary benzene, but not on MTBE. Significant correlations between all environmental and biological markers were found. The highest correlations were those between urinary MTBE and airborne MTBE or benzene (r=0.871 or 0.816), whereas urinary benzene correlated with airborne benzene with lower correlation coefficient (r=0.439), and this was due, at least in part, to the confounding effect exerted by cigarette smoking. In conclusion gasoline station attendants are exposed to significant concentration of benzene; for biomonitoring their exposure to gasoline vapours the use of urinary MTBE might represent the most useful marker.