Customer Exposure to MTBE, TAME, C 6 Alkyl Methyl Ethers, and Benzene during Gasoline Refueling

Abstract

We studied customer exposure durinug refuling by coliecdng air samples from customers' breath- ing zone.The meaurements wer carried out during 4 days in summer 1996 at two Finnish sdf- service gasoline stations with "stage I" vapor recovery systems.The 95-RON (research octane number) gasoline contained -2.7% methyl ~mbuty ether (MTBE), -85% eramyl methyl ether (TAME), -3.2% C6 alkyl methyl ethers (C6 AMEs), and 0.75% benzene.The individual exposure concentrations showed a wide log-normal distribution, with low eposures being the most frequent.In over 90% of the samples, the concentrtion of MTBE was higher (range <0.02-51 mg/m3) than that of TAME The MTBE vlues were well below the short-term (15 min) tehold limits set for ocupational exposure (250-360 mg/m3).At station A, the geometric mean concentrains in individual samples were 3.9 mg/m3 MTBE and 2.2 mg/m3 TAME.The corsponding values at station B were 2.4 and 1.7 mg/m3, respecly.The average refueling (sampling) time was 63 sec at station A and 74 sec at sation B. No statisticaily significant differ- ence was observed in customer eTosures bewen the two service stations.The overall geometrc means (n = 167) for an adjusted 1-min refueling time were 3.3 mg/im3 MTBE and 1.9 mg/m3 TAME.Each day an ntegrate d breathing zone sample was also collected, corresponding to an arithmetic mean of20-21 r lings.The overall arithmetic mean concentrtions in the integrat- ed samples (n -8) were 0.90 mg/mn3 for benzene and 0.56 mg/m3 for C6 AMEs calculated as a group.Mean MTBE concentrations in ambient air (a stationary point in the middle of the pump island) were 0.16 mg/m3 for station A and 0.07 mg/m3 for station B. The mean ambient concen- trations ofTAME, C6 AMEs, and benzene were 0.031 mg/m3, -0.005 mg/nm3, and -0.01 mg/m3, respctiey, at both stations.The mean wind speed was 1.4 m/sec and mean air temperature was