Customer exposure to MTBE, TAME, C-6 alkyl methyl ethers, and benzene during gasoline refueling

We studied customer exposure during refueling by collecting air samples fro m customers' breathing zone. The measurements were carried out during 4 day s in summer 1996 at two Finnish self-service gasoline stations with "stage I" vapor recovery systems. The 95-RON (research octane number) gasoline con tained similar to 2.7% methyl tert-butyl ether (MTBE), similar to 8.5% tert -amyl methyl ether (TAME), similar to 3.2% C-6 alkyl methyl ethers (C-6 AME s), and 0.75% benzene. The individual exposure concentrations showed a wide log-normal distribution, with low exposures being the most frequent. In ov er 90% of the samples, the concentration of MTBE was higher (range <0.02-51 mg/m(3)) than that of TAME. The MTBE values were well below the short-term (15 min) threshold limits sec for occupational exposure (250-360 mg/m(3)). At station A, the geometric mean concentrations in individual samples were 3.9 mg/m(3) MTBE and 2.2 mg/m(3) TAME. The corresponding values at station B were 2.4 and 1.7 mg/m(3), respectively. The average refueling (sampling) time was 63 sec at station A and 74 sec at station B. No statistically sig nificant difference was observed in customer exposures between the two serv ice stations. The overall geometric means (n = 167) for an adjusted 1-min r efueling time were 3.3 mg/m(3) MTBE and 1.9 mg/m(3) TAME. Each day an integ rated breathing zone sample was also collected, corresponding to an arithme tic mean of 20-21 refuelings. The overall arithmetic mean concentrations in the integrated samples (n = 8) were 0.90 mg/m(3) for benzene and 0.56 mg/m (3) for C-6 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/m(3 ) for station A and 0.07 mg/m(3) for station B. The mean ambient concentrat ions of TAME, C-6 AMEs, and benzene were 0.031 mg/m(3), similar to 0.005 mg /m(3), and similar to 0.01 mg/m(3), respectively, at both stations. The mea n wind speed was 1.4 m/sec and mean air temperature was 21 degrees C. Of th e gasoline refueled during the study, 75% was 95 grade and 25% was 98/99 gr ade, with an oxygenate (MTBE) content of 12.2%.