Customer Exposure to Methyl Tert-Butyl Ether during Gasoline Refueling

Abstract

Customer exposure to methyl tert-butyl ether (MTBE) during refueling with gasoline of high MTBE content was studied. Field measurements were carried out in southwestern Finland at two self-service stations during two seasons: May-June and October 1995. Both stations were equipped with stage I vapor recovery systems. The exposure of customers was studied by collecting air samples from their breathing zones into charcoal tubes during refueling with reformulated gasolines of 95, 98, or 99 research octane number (RON), all of which contained 11 percent MTBE. The samples were collected on four consecutive days during each sampling period. Each sample represented a single refueling operation. Samples were analyzed in the laboratory by gas chromatography using mass-selective detection. The concentrations of MTBE in the individual samples ranged from <0.2 to 245 mg/m³ (n = 313) and showed a wide lognormal distribution, with low concentrations being the most frequent. The geometric mean concentrations of MTBE in customers' breathing zones were 7.4 mg/m³ (station 1/May-June), 7.4 mg/m³ (station 1/October), 4.4 mg/m³ (station 2/June), and 6.0 mg/m³ (station 2/October). The corresponding mean refueling times were 71, 58, 70, and 60 seconds, with an overall range of 21 to 275 seconds. An overall geometric mean concentration calculated for a 1-minute refueling time was 6 mg/m³. Despite differences in the physical characteristics of the gasolines and in the ambient conditions during the measurements, no statistically significant differences in MTBE exposures were observed between the two service stations or between the two seasons. The mean air temperatures were above 22°C in May-June and around 10°C in October, and the Reid vapor pressure of the gasoline blend was 20 kPa higher in October. The mean wind speed ranged from 1.0 to 2.2 m/s.