A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering and Management Inter-University Program on Environmental Toxicology, Technology and Management

Thesis (Ph.D.) - Asian Institute of Technology - Chulabhorn Research Institute - Mahidol University, 2006

The aim of this study is to assess potential health risk of exposure to particleassociated polycyclic aromatic hydrocarbons (PAHs) in children living in a megacity with traffic congestion such as Bangkok through the measurement of ambient exposure concentrations as well as through the use of biornarkers of exposure, early biological effects and individual susceptibility to carcinogens. The study population consisted of 184 Thai schoolboys (aged 8-13 years) attending schools adjacent to high-density traffic areas in Bangkok (high exposure group) and schools located in the provincial area of Chonburi (low exposure group). The ambient concentration of total PAHs at the roadsides in proximity to the Bangkok schools vas approximately 30-fold greater than at the roadsides in proximity the schools in Chonburi province (30.39±5.80 ng/m³ vs. 1.50±0.28; P<0.001). Benzo(g,h,i)perylene (BghiP), an indicator of automobile exhaust emission, was the predominant PAH. Personal exposure to total PAHs and the corresponding benzo(a)pyrene (BaP) equivalent concentrations in schoolchildren in Bangkok were approximately 3.5-fold higher than in children in the provincial area (4.13±0.21 ng/m³ vs. 1.18±0.09; P<0.001, and 1.50±0.12 ng/m³ vs. 0.43±0.05; P<0.001, respectively). The results obtained supported the used of biomarkers of exposure and biomarkers of early biological effects for assessment of exposure and investigation of health risks from genotoxic PAHs exposure in schoolchildren. The concentrations of the biomarker of exposure, urinary 1-hydroxypyrene (1-HOP), revealed significantly higher (P<0.001) in Bangkok schoolchildren for all 3-time points of urine collections, indicating a greater PAHs exposure. Bulky carcinogen-DNA adducts level in peripheral lymphocytes, determined by ³²P-postlabelling was significantly higher in schoolchildren in Bangkok than from outside Bangkok (0.45±0.03 adducts/108 nucleotides vs. 0.09±0.00; P<0.001). Similarly, significantly higher level of DNA strand breaks as measured by the Cornet assay (tail length 1.93±0.09 um vs. 1.28±0.12 and olive tail moment 0.23±0.01 um vs. 0.16±0.01; P<0.001) and significantly lower level of DNA repair capacity as measured by the cytogenetic challenge assay (dicentrics/metaphase 0.34±0.01 vs. 0.21±0.00 and deletions/metaphase 0.45±0.01 vs. 0.26±0.01; P<0.001) were observed in Bangkok schoolchildren. No influence of environmental tobacco smoke exposure was detected in this study. CYP1A1 Ile/Ile, GSTT1 positive- and GSTM1 nulled-genotypes were considered prevalence genotypes observed in schoolchildren in this study. A significant gene-gene interaction was shown by a significantly additive effect of CYP1A1 Ile/Val genotype and GSTTI nulled-genotype on the level of DNA strand breaks in Chonburi schoolchildren. The results obtained in this study were not clearly investigated influence of genetic susceptibility on health effects in these schoolchildren. Larger sample size may be needed for further elucidation. This study indicated that children living in major cities, such as Bangkok where traffic congestion prevails, are exposed to a high level of genotoxic PAHs in ambient air generated from motor vehicle emissions. The results also provided an indication that children who spend a significant amount of time close to traffic-related sources may be more vulnerable to the health impacts associated with the exposure to genotoxic environmental pollutants than children in provincial areas and may have increased health risks for the development of certain diseases such as cancer clue to this exposure