A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management

Thesis (M.Sc.) - Asian Institute of Technology, 2015

Epidemiological studies have shown that exposures of commuters to traffic related air pollutants are associated with health effects. Potential exposure of commuters caused by traffic air pollutants in Bangkok, one of the most congested cities in Asia, has not been comprehensively assessed and reported. This study aims to partly fill the data gap by conducting personal exposure monitoring for commuters on different transport means along almost the same route (18 km) around the city center. The air pollutants, including benzene, toluene, ethylbenzene, m, p-xylenes and o-xylene (BTEX), PM2.5, black carbon (BC) and carbon monoxide (CO), in six transport means (taxi, A/C bus, non-A/C bus, motorcycle, sky train and metro) in dry season (November-December) of 2014 in Bangkok were comparatively assessed. CO was monitored online by CO/CO₂ analyzer, while BTEX samples were collected by SKC charcoal tubes and analyzed by GC-FID. PM2.5 was sampled by personal environmental monitor (PEM) using an impactor. BC component of PM2.5 was determined by OT21 transmissometer. In parallel, a questionnaire survey was also conducted by interviewing commuters to assess the perception of health effects. The highest CO concentration was found in taxi (8.5±2.5 ppm), which significantly higher than that in other transport means (p< 0.05) because filter of A/C system might reduce a little amount of CO. The highest PEM PM2.5 concentration was found in non-A/C bus (190±18 og/m³), while sky train faced the lowest concentration. Non-A/C bus was run by open the windows, air pollutants can be easily entered the bus, whereas sky train used its own route where located above the roadway about 12 meters and applied electricity as driving power. As a result, the concentration inside sky train was lower than that on other transport means (p < 0.05), but nearly the same as inside the metro. BC concentration in motorcycle was 30±7.9 og/m³ which higher than that on other transport means, while the lowest concentration was found inside sky train (6.0±2.7 og/m³). The highest BTEX concentrations were mostly found in taxi and motorcycle, while the lowest concentrations were found in sky train and metro. Average concentration varied from 11.6±12.0 to 76.5±47.9 og/m³ for benzene, 39.5±8.5 to 140.4±69.5 og/m³ for toluene, 3.9±2.2 to 24.7±22.4 og/m³ for ethylbenzene, 9.9±6.9 to 70.6±46.2 og/m³ for m, p-xylenes and 3.1±1.8 to 15.9±15.2 og/m³ for o-xylene. The air inside taxi is rarely exchanged with air outside, as well as the interior trim is likely to emit BTEX into cabin. Therefore, BTEX could accumulate in the vehicle. BTEX concentration in motorcycle is relatively high because the commuters can easily contact to polluted air. The concentrations in sky train and metro were lower than that in other transport means due to no or less pollution emission, and separately run from roadway. When inhalation rate and traveling time were taken into account, non-A/C commuter faced highest whole trip exposure to PM2.5 and BC (474 og and 63 og, respectively). The highest whole trip exposures to CO (13.6 mg)and BTEX were mostly found on taxi commuters, which might because of long traveling time and high pollution concentration. The health risk assessment results showed that non-carcinogenic effects caused by PM2.5, indicated by hazard quotient (HQ), were likely for commuters to experience adverse health effects on all transport means. Moreover, non-carcinogenic effects related to benzene exposure can be experienced when commuting by taxi, motorcycle, A/C bus and non-A/C bus. However, non-carcinogenic effects related to TEX exposure were not expected to occur on all transport means. Carcinogenic effect due to exposure to benzene was higher than acceptable level (10-6), ranged from 8.11x10-6 to 8.40x10-5. Therefore, exposure to benzene on all transport means could cause cancer, such as leukemia.