04987nas a2200457 a 4500 20260818153801.0 110606s2010 th uu|m rtt 0| a1eng d .b12096325 AIT Diss. no.EV-10-05 Sirilak Wongvijitsuk Low level occupational exposure to styrene and benzene : its effects on DNA damage and DNA repair Pathum Thani, Thailand : Asian Institute of Technology, 2010 100 p. : ill. + 1 online resource Dissertation ; no. EV-10-05 A thesis proposal submitted in partial fulfillment of the requirements for the degree of Doctor of Technical science in Environmental Toxicology, Technology and Management Inter-University Program Thesis (Ph.D.) - Asian Institute of Technology - Chulabhorn Research Institute - Mahidol University, 2010 The present study aimed to evaluate the effects of styrene exposure at levels below the recommended standards of the Threshold Limit Value (TLV-TWA8) of 20 ppm (ACGIH, 2004) in reinforced fiberglass plastics workers. Study subjects comprised 50 exposed workers and 40 control subjects. The exposed workers were stratified by styrene exposure levels, i.e. group I (<10 ppm), group II (10- 20 ppm), and group III (> 20 ppm). The mean styrene exposure levels of exposed workers were significantly higher than those of the control workers. Respiratory particles increased significantly in factory workers (1.05±0.17 mg/m3; p< 0.01) compared to control (0.36±0.93 mg/m3). Factory workers stratified by job activity showed that there was a significant difference of exposure levels among study groups (p<0.01). Respiratory particle level in trimming workers (1.79±0.31mg/m3) was significantly higher than resin laminator workers (0.54±0.05 mg/m3). Biomarkers of exposure to styrene, including blood styrene and the urinary metabolites, mandelic acid (MA) and phenylglyoxylic acid (PGA), were significantly increased with increasing levels of styrene exposure, but were not detected in the control group. DNA damage, such as DNA strand breaks, 8-hydroxydeoxyguanosine (8-OHdG), and DNA repair capacity, were used as biomarkers of early biological effects. DNA strand breaks and 8-OHdG/105 dG levels in peripheral leukocytes of exposed groups were significantly higher compared to the control group (P<0.05). In addition, DNA repair capacity, determined by the cytogenetic challenge assay, was lower in all exposed groups when compared to the control group (P<0.05). The expression of CYP2E1, which is involved in styrene metabolism, in all styrene exposed groups, was higher than that of the control group at a statistically significant level (P<0.05). Levels of expression of the DNA repair genes hOGG1 and XRCC1 were significantly higher in all exposed groups than in the control group (P <0.05). In addition to styrene contamination in ambient air, a trace amount of benzene was also found, but the correlation between benzene exposure and DNA damage or DNA repair capacity was not statistically significant. The results obtained from this study indicate an increase in genotoxic effects and thus health risk from occupational styrene exposure, even at levels below the recommended TLV-TWA8 of 20 ppm. Benzene in the body Styrene DNA damage DNA repair Mathuros Ruchirawat, Chairperson Preeda Pakpian, Examination Committee Panida Navasumrit, Examination committee Au, William Wingkam, Examination committee The center of excellence on Environmental Health,Toxicology and Mangement of Chemicals (ETM) under Science &Technology Post-Graduate Education, Scholarship donor Research Development office (PERDO) of Ministry of Education, Thailand, Scholarship donor Asian Institute of Technology. Dissertation ; no. EV-10-05 Full-Text http://203.159.5.9/ait-thesis/detail.php?q=B00561 .b12096325 mnait u 240403 0 110606 m a u 0 000:001:PDF:b1209632:000658:0:0:0:0:0:0 Abstract-AIT Diss. no.EV-10-05 n mnait mnarc 22 40 Barcode : 30050120553796 CREATED : 2012-08-16 RECORD # : i12687431 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 Barcode : 30050160004080 CREATED : 2016-09-02 RECORD # : i12879198 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 70826 70826 0 0 0 0 MAIN MAIN mnait 2026-08-18 0 AIT Diss. no.EV-10-05 30050120553796 2026-08-18 15:38:02 3 2026-08-18 22 0 0 0 0 MAIN MAIN mnarc 2026-08-18 0 AIT Diss. no.EV-10-05 30050160004080 2026-08-18 15:38:02 2026-08-18 40