Commuter Exposures to VOCs and PM2.5 in Kao-Pin Area of Taiwan

Abstract

P-590 Abstract: With a high density of vehicles, the potential health impact caused by air toxicants emitted from motor vehicles is one of the major concerns for commuters in Taiwan. A series of field studies were conducted in the Kao-Pin area of southern Taiwan in 2005 in which fine particle (PM2.5) and volatile organic compounds (VOCs) personal exposure level measurements were taken for journeys in motorcycle, car, bus and train transport microenvironments. Measurements of vehicle occupants’ exposures to aromatic compounds [benzene, toluene, ethylbenzene, xylenes (BTEX)], methyl tertiary butyl ether (MTBE) and PM2.5 were carried out on five major commuting routes in this area. Air samples of VOCs were collected by multi-adsorbent tubes and analyzed by thermal desorption and GC/MS technique. Monitoring for PM2.5 were accomplished by using direct-reading instruments and sampling processes were recorded by video cameras. All the air samples were collected at morning (07:00–10:30) or afternoon (16:00–19:00) rush hours of weekdays in all transportation modes. During the sampling period, a total of 80 VOCs samples and 84 PM2.5 samples were collected. In some trips, air samples were measured simultaneously for four transportation modes on two major routes. The results indicate that MTBE and toluene were the most abundant VOCs observed while commuting in Kao-Pin metropolitan area, followed by xylenes, benzene and ethylbenzene. The highest exposure levels for VOCs were found for motorcycle riders. The average exposure concentration for motorcyclists to benzene and MTBE ranged from 19 to 459 μg/m3 and 11 to 792 μg/m3, respectively. The highest exposure levels for PM2.5 were found on diesel buses, while lowest levels were measured in the train cabins. For diesel bus commuters, the sources of PM2.5 exposures include the outdoor air on bus routes and reentry of engine emission. Average PM2.5 exposure levels for motorcycle riders ranged from 35 to 250 μg/m3 at different commuting routes. The average PM2.5 levels inside car cabin under ventilation mode were generally 30–60% of the measurements outside cabin. Based on the results of video image analyses, major influences on the levels of PM2.5 on roads and commuter's exposures included traffic conditions, diesel engine emissions and waiting times before traffic lights. The results of this study shows that strategies that encourage commuting by train should be supported and exposure control actions should be taken for motorcycle and bus commuters.