Exposure to methyl tertiary butyl ether and benzene in close proximity to service stations

Exposure estimates based solely on proximity to air pollution sources are n ot sound and require confirmation. Accordingly, since a very limited amount of actual data for this type of exposure estimate is currently available, this study was conducted to provide actual data on residents' exposure to t wo important gasoline constituents (methyl tertiary butyl ether (MTBE) and benzene] relative to their proximity to roadside service stations. The resu lts confirmed that residents in neighborhoods near service stations are exp osed to elevated ambient MTBE and benzene levels compared with those living farther from such a source. However, it was also found that the presumed e levated outdoor benzene levels (a mean of 1.7 ppb) even in close proximity to service stations did not exceed the indoor levels (a mean of 2.2 ppb) of exposure for those living nearby. Regardless of residents' distance from s ervice stations, an indoor source (cigarette smoking) appeared to be the ma jor contributor to their benzene exposure. Conversely, for MTBE, roadside service stations were found to be the major contributor to residents' exposure. In addition, the residents close to the stations were exposed to elevated indoor and outdoor MTBE levels. The samp ling period (daytime and nighttime) and season (winter and summer) were add itional parameters for the outdoor MTBE and benzene levels and the indoor M TBE levels. Meanwhile, the breathing zone air concentrations of service sta tion attendants for both MTBE and benzene were significantly higher than th ose of drivers (p < 0.05). In addition, the breathing zone concentrations w ere significantly higher during summer than during winter for both drivers and attendants (p < 0.05).