Exposure assessment of benzene, DNA repair capacity and influence of genetic polymorphisms in workers | |
| Author | Sirirat Chanvaivit |
| Call Number | AIT Diss. no.EV-06-1 |
| Subject(s) | Benzene in the body Benzene |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Inter-University Program on Environmental Toxicology, Technology and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Benzene in working environment of the workplace was studied in three quality control laboratories of benzene related factories, seven gasoline service stations and compared to a mail sorting service center. The mean level of benzene from three laboratories was 26.56+5.44 ppb (22.13+2.92 ppb in olefin factory, 64.94+33.71 ppb in petroleum refinery and 24.45+14.12 ppb in Petroleum Distribution Company respectively). The mean benzene level in ambient air of seven gasoline service stations was 46.81±5.10 ppb. A mail sorting service center was selected as a control workplace. The mean benzene level was 0.73±0.07 ppb. The mean levels of individual benzene exposure were 1.39±0.17, 24.40±5.82 and 112.41+13.92 ppb in control workers, laboratory workers and gasoline service attendants respectively. For biomarkers of benzene exposure, blood benzene, urinary benzene and trans, transmuconic acid were determined. Blood benzene level showed good correlation with individual benzene exposure (R2=0.4946, p<0.01) followed by post-shift trans, transmuconic acid (R22=0.4946, p<0.01) and post-shift urinary benzene (R22=0.1376, p<0.001). Mean blood benzene levels in laboratory workers was 4-fold higher than control workers, 169.12±30.60 ppt vs. 43.30±4.89 ppt at p<0.001, while mean blood benzene levels in gasoline service attendant was about 10-fold higher than control workers, 483+59.62 ppt vs. 43.30±4.89 ppt at p<0.001. No difference between mean level of post-shift urinary benzene of laboratory workers and control workers was observed (0.12±0.02 vs. 0.10± 0.02 ug/g creatinine). Gasoline service attendants excreted benzene about 3-fold higher than control workers, 0.28±0.06 ug/g creatinine vs. 0.10+0.02 g/g creatinine at p<0.01. For urinary metabolite, laboratory workers and gasoline service attendants excreted higher post-shift trans, trans-muconic acid compared to control workers, 0.14+0.02 and 0.20+0.02mg/g creatinine vs. 0.04±0.01 mg/g creatinine at p<0.001 respectively. In case of DNA repair capacity, dicentrics per metaphase of laboratory workers and gasoline service attendants were statistically significantly different from control workers, 0.17+0.01 and 0.19+0.01 vs. 0.12+0.01 cells per metaphase at p<0.001. The deletions per metaphase of laboratory workers, 0.22±0.02 cells per metaphase and gasoline service attendants, 0.39+0.03 cells per metaphase were statistically significantly different from control workers, 0.16+0.01 cells per metaphase at p<0.01 and p<0.001 respectively. Toxic effects of benzene can vary dependent on the level of benzene in working environment and duration of exposure. Moreover. gene encoding enzymes that involved in biotransformation of benzene may modify biomarkers levels. From our results, we found high blood benzene levels in benzene exposed workers who carried CYP2E1 *1/*1 metabolizing gene. In sub group, laboratory workers carried CYP2E1 *1/*1 had higher blood benzene. In contrast, gasoline service attendants who carried CYP2E1 *1/* had lower blood benzene level. The results of blood benzene level in gasoline service attendants may result from level of exposure. High blood benzene levels were also found in NQO1 *1/*l genotype of laboratory workers and gasoline service attendants. We cannot observe the influence of NQO1 and G.STT1 genotype on the level of urinary post-shift trans, trans-muconic acid. Benzene exposed workers who carried Arg/Arg genotype had lower mean frequency of dicentrics and deletions in their metaphase than the workers who carried Arg/Gin and Gln/Gln genotypes. In sub group, laboratory workers who carried Arg/Arg genotype had lower dicentrics (p<0.01) and deletions (p<0.01) frequency in their metaphase compared to those workers who carried Arg/Gin and Gln/Gln genotypes. However, we cannot observe the difference in dicentrics and deletions between Arg/Arg genotype and Arg/Gln + Gln/Gln genotypes in gasoline service attendants. Smoking influenced blood benzene levels of laboratory workers and control workers, but not in gasoline service attendants. Smoking laboratory workers excreted higher trans, trans-muconic acid level. However, we cannot observe effect of smoking on the level of post-shift trans, trans-muconic acid in gasoline service attendants. No effects of smoking status on DNA repair capacity were observed as incidence of dicentrics and deletions in both laboratory workers and gasoline service attendants There were no effects of alcoholic consumption on blood benzene level, trans, transmuconic acid and DNA repair capacity. Laboratory workers who had worked more than one year have higher incidence of dicentrics per metaphase. However, the result was not statistically significantly different. No difference between duration of work and incidence of dicentrics per metaphase was observed in gasoline service attendants group. Comparing among working group at the same duration of work, laboratory workers have more incidence of dicentrics per metaphase than control workers, while gasoline service attendants have higher incidence of dicentrics per metaphase than laboratory workers. Duration of work has no effect on incidence of deletions per metaphase in laboratory workers and gasoline service attendants. Among the working groups, gasoline service attendants have highest incidence of deletions per metaphase compared to laboratory workers and control workers at the same working period. No effect of age was observed on the incidence of dicentrics and deletions in both laboratory workers and gasoline service attendants Even though many factors may affect the level of biomarkers of benzene exposure, but it is clear that DNA repair capacity is a good biomarker especially for benzene exposure at current occupational exposure level. Moreover, the interaction with genetic susceptibility should be considered |
| Year | 2006 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Mathuros Ruchirawat;Autrup, Herman.;Chongrak Polprasert; |
| Examination Committee(s) | Panida Navasamrit;Farmer, Peter.; |
| Scholarship Donor(s) | Asian Institute of Technology;CRI;Mahidol Post-Graduate Education, Training and Research Program in Environmental Science, Technology and Management; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2006 |