Tank truck driver exposure to vapors from oxygenated or reformulated gasolines during loading and unloading

Tank truck drivers' exposure to gasoline vapors was studied by collecting breathing zone samples during loading and unloading of gasoline. The field studies were conducted at three dispatches and at seven service stations in Finland. The gasolines included in the study (95, 98, 99 research octane number, RON) were of reformulated or oxygenated grade containing about 2% (w/w) oxygen and 0.5-1.5% (v/v) benzene. The sampling times ranged from 16 to 57 min (mean 35 min), and time-weighted average concentrations for a 30-min period were calculated. Using the time-adjusted values, geometric mean concentrations (GM) were calculated for three periods of dispatch measurements (n = 15,20,7) and a period of unloading measurements at service stations (n = 7). The GM for methyl tert-butyl ether ranged from 0.95 to 7.3 mg/m3 and that for tert-amyl methyl ether from 0.30 to 1.1 mg/m3. The GM concentrations of hexane, benzene, and toluene were in the range of 0.25-2.3 mg/m3, 0.15-0.28 mg/m3, and 0.73-1.7 mg/m3, respectively. Multiple regression analysis yielded an r2 value of 0.98 for the daily mean concentration of toluene and correspondingly 0.94 for benzene when daily wind speed (0.1-3.7 m/sec) and daily air temperature (-7.4(-)+17.2 degrees C) were used as independent variables. The average number of gasoline loads per tank truck was 2.5, corresponding to 23,000 L of gasoline.