Exposure to Heavy Metals and Polycyclic Aromatic Hydrocarbons and DNA Damage in Taiwanese Trafﬁc Conductors

Published OnlineFirst November 13, 2012; DOI: 10.1158/1055-9965.EPI-12-0706

Cancer Epidemiology, Research Article Biomarkers & Prevention

Han-Bin Huang1,2, Guan-Wen Chen2, Chien-Jen Wang2, Yong-Yang Lin2, Saou-Hsing Liou2, Ching-Huang Lai1, and Shu-Li Wang1,2,3

Abstract Background: Exposure to traffic-related air pollutants, including polycyclic aromatic hydrocarbons (PAH) and heavy metals, has been associated with the etiology and prognosis of many illnesses. However, the specific causal agents and underlying mechanisms for different health outcomes remain unclear. The aims of this study were to assess the relations between urinary biomarkers of exposure to PAHs (1-hydroxypyrene-glucuronide, 1-OHPG) and heavy metals (cadmium, Cd; nickel, Ni; arsenic, As; lead, Pb; and copper, Cu) and the effect of their interaction on DNA damage (8-oxo-7,8-dihydro-guanine, 8-oxodG). Methods: We recruited 91 traffic conductors and 53 indoor office workers between May 2009 and June 2011 in Taipei, Taiwan. Postshift urine samples from 2 consecutive days were analyzed for 1-OHPG, Cd, Ni, As, Pb, Cu, and 8-oxodG. To estimate the effects from PAHs and metals on DNA damage, we constructed a linear mixed model adjusted for confounding variables. Results: We found that urinary 1-OHPG and Cd levels were independent predictors of urinary 8-oxodG levels (b ¼ 0.112; P ¼ 0.015 for 1-OHPG; b ¼ 0.138; P ¼ 0.031 for urinary Cd). The joint effect of urinary 1-OHPG and Cd levels was associated with urinary 8-oxodG levels (P ¼ 0.001). Conclusions: Co-exposure to environmental PAHs and Cd could cause oxidative DNA damage. Impact: These findings suggest that the additive interaction between exposure to environmental PAHs and Cd could enhance the burden of oxidative stress. Cancer Epidemiol Biomarkers Prev; 22(1); 102–8. 2012 AACR.

Introduction matic hydrocarbons (PAH) and heavy metals adsorbed in In urban environments across the globe, air pollution the pores and surfaces of the particles could easily enter from traffic exhaust has been considered an important into the respiratory tract and reach the circulatory system public health issue. Although there is accumulating epi- (2). demiologic evidence that exposure to traffic-related air Previous studies have reported that exposure to PAHs or metals could generate reactive oxidative species (ROS) pollutants plays a role in the etiology and prognosis of in vitro in vivo many illnesses, including cardiovascular disease and can- to induce oxidative stress or (3, 4). Oxidative cer, the role of specific causal agents and the underlying stress could play an important role in the initiation and mechanisms for different health outcomes remain promotion of carcinogenesis. However, few studies have unknown (1). Among these pollutants are polycyclic aro- explored the effect of co-exposure to PAHs and metals on oxidative stress in humans (5, 6). Applying biomarkers of exposure and outcome could Authors' Affiliations: 1Department of Public Health, National Defense be useful both in the quantification of the association and Medical Center, Taipei; 2Division of Environmental Health and Occupa- in providing insight into the specific causal agents and tional Medicine, National Health Research Institutes, Zhunan, Miaoli; and underlying biological mechanism. A major product with 3Institute of Environmental Medicine, College of Public Health, China Medical University and Hospital, Taichung, Taiwan a clear mutagenic potential, deoxyguanosine (dG) in urine, has been commonly used as a biomarker of oxida- Note: Supplementary data for this article are available at Cancer Epide- miology, Biomarkers & Prevention Online (http://cebp.aacrjournals.org/). tive stress in studies on ambient air pollution (7–10). Corresponding Authors: C.-H. Lai, Department of Public Health, National Conversely, urinary 1-hydroxypyrene-glucuronide (1- Defense Medical Center, 161 Min-Chuan E.Rd., Sec 6, Taipei, Taiwan. Fax: OHPG), a PAH metabolite, has been used as a biomarker 886-2-8796485; E-mail: [email protected]; and S.-L. Wang, Divi- of exposure to PAHs (9, 11, 12). Urinary metals, including sion of Environmental Health and Occupational Medicine, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 350, Taiwan. cadmium (Cd), arsenic (As), nickel (Ni), lead (Pb), and Phone: 886-037-246-166 ext. 36503; Fax: 886-037-587-406; E-mail: copper (Cu), indicate short-term or long-term levels of [email protected] internal dose of exposure to metals (13). Most studies doi: 10.1158/1055-9965.EPI-12-0706 showed that exposure to either PAHs or metals could 2012 American Association for Cancer Research. increase levels of urinary 8-oxodG in occupational or

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environmental fields (7–9, 14). Only a few studies have trometer. The excitation–emission monochromators were investigated the effect of their interaction on biomarkers driven synchronously with a wavelength difference of 34 of oxidative stress, but a joint effect between PAHs and nm. 1-OHPG, purchased from the National Cancer Insti- metals was not found (5, 6). tute (NCI) Chemical Carcinogen Repository (MRI), pro- Therefore, we carried out a study of traffic conductors to duces a characteristic fluorescence emission maximum at examine the relation between urinary biomarkers of 381 nm (347 nm excitation). Fluorescence intensity was PAHs and heavy metals and the effect of their interaction used to quantify 1-OHPG. The recovery of the assay was on DNA damage. 91%. The coefficient of variation of the assay was less than 5% during sample analysis. The limit of detection was 0.05 Materials and Methods ng/mL. Study population We recruited 91 traffic conductors as the exposed group Analysis of urine samples for 8-oxodG and 53 indoor office workers as the reference group, Urinary 8-oxodG concentrations were measured using between May 2009 and June 2011, in Taipei, Taiwan. All liquid chromatography/tandem mass spectrometry (LC/ of the selected subjects were between 20 and 63 years of MS-MS), as described previously (16). Briefly, 20 mLof age. All participants were free of cancer and pulmonary urine was diluted 10-fold with 5% methanol containing m 15 disease, and they had all been working in their current 0.1% formic acid. After the addition of 40 Lof N5-8- position for at least 3 months. oxodG solution (20 mg/L in 5% methanol per 0.1% formic acid) as internal standard, 100 mL of prepared urine Data collection sample was directly injected into the on-line solid-phase The participants underwent health examinations and extraction LC/MS-MS. After automatic sample cleanup, completed a self-administered questionnaire on demo- LC/MS-MS analysis was done using a PE Series 200 HPLC graphic information, lifestyle habits, and history of pre- system interfaced with a PE Sciex API 3000 triple quad- vious and current diseases. Postshift urine was collected rupole mass spectrometer with electrospray ion source. from participants on 2 consecutive days. This study was The samples were analyzed in the positive ion multiple- approved by the Institutional Review Board of the Nation- reaction-monitoring mode, and the transitions of the al Health Research Institutes in Taiwan, and written precursors to the product ions were as follows: m/z 284 informed consent from participants was obtained before ! 168 (quantifier ion) and 284 ! 140 (qualifier ion) for 8- study enrollment. oxodG and m/z 289 ! 173 (quantifier ion) and 289 ! 145 15 (qualifier ion) for N5-8-oxodG. A detection limit of 5.7 Analysis of urine samples for 1-OHPG ng/L was obtained using 7 repeated analyses of deionized The urine samples were collected within half an hour of water. The coefficients of variation in inter- and intraday the end of a work shift. We divided the urine samples into tests were less than 5%. Mean recovery of 8-oxodG in several small-volume aliquots and stored them at 80C urine was between 99% and 102%. Analyses of field in a freezer until analysis. blanks found no significant contamination. Each partici- Urinary 1-OHPG was measured using the assay devel- pant’s urinary 1-OHPG and 8-oxodG concentrations were oped by Strickland and colleagues in 1994 (15). Urine normalized to urinary creatinine. samples (2 mL) were treated with 0.1 N HCl (90C) to hydrolyze acid-labile metabolites. The hydrolyzed sam- Analysis of urinary metals ples were loaded onto Sep-Pak C18 cartridges (Waters) Urinary metal concentration was analyzed by induc- and washed with methanol (30% in water). The relatively tively coupled plasma-mass spectrometer (Agilent 7700X nonpolar metabolites were eluted with methanol (80% in series ICP-MS; Agilent Technologies), as previously water; 4 mL) and the volume was reduced to 0.5 mL by described (17). ICP-MS was used to determine the Cd, a centrifugal and vacuum evaporator (Eyela CVE-100). Ni, As, Pb, and Cu concentrations in the urine. Briefly, the The concentrated samples were diluted to 4 mL with 15 frozen urine samples were first moved to a refrigerator mmol/L PBS. Immunoaffinity columns were prepared and stored at 4 C for several hours, and then thawed at using polyprep columns (0.8 4 cm) filled with CNBr- room temperature. Two milliliters of thawed urine were m activated Sepharose 4B (0.8 mL) coupled with monoclonal diluted 15 times with 1% HNO3 diluent containing 1 g/L antibody 8E11, which recognizes several PAH-DNA yttrium (Y) internal standard in the final sample dilution, adducts and metabolites. Monoclonal antibody 8E11 was then mixed well, and finally aspirated from plastic con- obtained from Trevigen. It was originally produced tainers into the ICP-MS. Standard solutions of 0.1, 0.5, 1, 2, against benzo[a]pyrene-diolepoxide-modifed DNA, and 5, 10, 20, and 50 mg/L were used for sample quantification. has been shown to recognize 1-OHPG. After washing the The spike recoveries using 5 mg/L urinary matrix were: columns twice with 4 mL of 15 mmol/L PBS, samples in Cd, 94.1 2.1; Ni, 100.5 1.4; As, 99.7 4.6; Pb, 99.3 4.8; PBS were loaded on columns and bound material was and Cu, 98.5 3.0. The method detection limits were: Cd, eluted with 2 mL of 40% methanol. Eluted fractions were 0.075; Ni, 0.022; As, 0.184; Pb, 0.095; and Cu, 0.023 mg/L. quantified by synchronous fluorescence spectroscopy The outcome figures below the limit of detection (LOD) (SFS) using a Perkin-Elmer LS 50B luminescence spec- were set to LOD/H2.

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Statistical methods statistically significant. All statistical analyses were carried The levels of urinary metals, urinary 1-OHPG, and out using SAS (version 9.1.3; SAS Institute Inc., Carry, NC). urinary 8-oxodG were compared between the exposed and reference groups by mixed-model repeat measure Results analysis (Proc mixed). This model was used to investigate Study population the correlations among urinary metals, urinary 1-OHPG, Certain characteristics of the exposed and reference and 8-oxodG after adjusting for fixed covariates (such as groups of the study population were compared (Table 1). age, sex, education level, smoking habit, season of data The mean age was 49.2 years (SD 9.17) in the exposed group collection, and exposure status). These models treated the and 42.9 years (SD 8.86) in the referencegroup. The exposed participants as random effects, and model selections were group had a lower percentage of women and a lower based on Akaike’s Information Criterion. The compound education level than the reference group. The most com- symmetry and variance components were constructed as mon season for data collection was spring for the exposed the covariance structures. The dependent variables were group, while it was spring and winter for the reference transformed by the natural logarithm (Ln). Residual and group. The distributions of lifestyle factors, such as smok- influence analyses were conducted. ing habits, alcohol consumption habits, and cooking habits, We also assessed the effect of interaction from exposure were similar between the exposed and reference groups. to PAHs and metals on urinary 8-oxodG in nonsmoking workers. We categorized the exposures as greater or less Comparison of urinary heavy metals, 1-OHPG, and than the 50th percentile among nonsmoking workers. We 8-oxodG levels between the exposed and reference compared the geometric mean (GM) levels of urinary 8- groups oxodG according to the combination of these exposures in Regardless of whether the workers were nonsmoking the model. A 2-sided P value less than 0.05 was considered or smoking, the geometric mean levels of urinary Ni, Cu,

Table 1. Characteristics of participants in exposed and reference groups

Exposed group (n ¼ 91) Reference group (n ¼ 53) Variables (n,%) (n,%) Pa Age in years (mean SD)b 49.19 9.17 42.85 8.86 <0.001 Gender <0.001 Male 68 (74.7) 12 (22.6) Female 23 (25.3) 41 (77.4) BMI Kg/m2 (mean SD)b 25.11 3.55 29.06 6.60 <0.001 Educational level <0.001 High school 57 (64.0) 9 (17.0) College 32 (36.0) 44 (83.0) Current smoker 0.128 No 70 (76.9) 47 (88.7) Yes 21 (23.1) 6 (11.3) Drinking alcohol 1.000 No 74 (83.1) 43 (82.7) Yes 15 (16.9) 9 (17.3) Vitamin supplement 0.140 No 39 (43.3) 30 (57.7) Yes 51 (56.7) 22 (42.3) Cooking habit 0.122 No 51 (59.3) 22 (44.0) Yes 35 (40.7) 28 (56.0) Season of data collectionc 0.027 Spring 48 (52.7) 20 (37.7) Summer 14 (15.4) 3 (5.7) Fall 11 (12.1) 12 (22.6) Winter 18 (19.8) 18 (34.0)

ac2 test. bStudent t test. cFisher exact test.

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Table 2. Concentrations of urinary heavy metals, 1-OHPG and 8-oxodG, stratiﬁed by smoking and exposure status

All participants Exposed group Reference group Biomarkers a (mg/g creatinine) n GM (95%CI) Median (Q25–Q75) n GM (95%CI) n GM (95%CI) P value Nonsmoking workers Urinary heavy metal Cd 217 0.77 (0.69–0.85) 0.88 (0.48–1.32) 123 0.72 (0.61–0.85) 94 0.83 (0.75–0.92) 0.321 Ni 217 4.03 (3.25–4.99) 5.24 (1.90–12.10) 123 11.23 (9.85–12.80) 94 1.05 (0.78–1.42) <0.001 As 217 54.91 (48.80–61.78) 54.13 (35.31–87.44) 123 54.95 (46.68–64.69) 94 54.85 (46.16 -65.18) 0.979 Pb 217 1.18 (0.99–1.41) 1.41 (0.86–2.02) 123 1.18 (0.87–1.59) 94 1.19 (1.03–1.37) 0.957 Cu 217 13.22 (11.80–14.81) 11.51 (8.17- 22.57) 123 17.19 (14.37–20.56) 94 9.38 (8.66–10.16) <0.001 Urinary 1-OHPG 209 0.23 (0.20–0.26) 0.23 (0.13–0.39) 127 0.29 (0.25–0.35) 82 0.16 (0.14 -0.19) <0.001 Urinary 8-oxodG 211 2.81 (2.59–3.05) 3.04 (2.01–4.14) 129 3.22 (2.94–3.53) 82 2.26 (1.96–2.61) <0.001 Smoking workers Urinary heavy metal Cd 51 0.67 (0.51–0.88) 0.72 (0.41–1.21) 40 0.71 (0.51–0.99) 11 0.54 (0.44–0.67) 0.463 Ni 51 5.50 (3.47–8.74) 7.56 (2.99–14.99) 40 10.55 (7.92–14.05) 11 0.52 (0.18–1.50) <0.001 As 51 45.61 (37.36–55.69) 48.71 (29.93–76.20) 40 47.82 (37.31–61.29) 11 38.41 (30.24–48.79) 0.391 Pb 51 1.01 (0.64–1.59) 1.57 (0.72–2.21) 40 1.01 (0.57–1.78) 11 1.03 (0.71–1.50) 0.939 Cu 51 14.39 (11.13–18.62) 14.77 (7.06–29.12) 40 17.12 (12.60–23.26) 11 7.66 (6.64–8.85) 0.042 Urinary 1-OHPG 48 0.31 (0.24–0.41) 0.44 (0.22–0.55) 37 0.38 (0.29–0.49) 11 0.17 (0.07–0.37) 0.033 Urinary 8-oxodG 52 3.84 (3.35–4.40) 3.67 (2.97–5.24) 41 4.18 (3.66–4.78) 11 2.81 (1.86–4.23) 0.059

Abbreviations: number of observations (n). aMixed model was used to test for differences between the exposed and reference groups.

1-OHPG, and 8-oxodG among the exposed group were tively, than workers with low urinary 1-OHPG and low significantly higher than those among the reference group urinary Cd levels. The P value for the interaction term of (Table 2). No differences of geometric mean levels of both exposures (P ¼ 0.001) is consistent with an additive urinary Cd, As, and Pb were observed between the interaction between PAHs and Cd on urinary 8-oxodG exposed and reference groups. levels. Figure 1 shows GM and 95% confidence interval (CI) of adjusted urinary 8-oxodG levels by urinary Relations between biomarkers 1-OHPG and urinary Cd concentrations. Table 3 presents the relations of urinary heavy metals and 1-OHPG levels with urinary 8-oxodG levels. After controlling for the fixed covariates, we found that the Discussion urinary Cd and 1-OHPG levels were positively associated To our understanding, this is the first study to indicate with urinary 8-oxodG levels in all workers and nonsmok- that levels of urinary 1-OHPG and Cd had significant ing workers. Due to small sample size in smokers, further associations with levels of urinary 8-oxodG. With increas- analysis was limited. We also examined this association ing levels of urinary 1-OHPG and Cd, elevated levels of 8- using data separately for each day (Supplementary oxodG in urine were observed. These results provide Table S1A). The conclusion is the same with similar b and evidence that co-exposure to PAHs and Cd could increase P values. levels of oxidative stress. For further analysis of the interaction of exposure to Concentrations of urinary Cd could be regarded as a both PAHs and Cd, we grouped participants according to well-recognized biomarker of chronic Cd exposure (18). the median levels of urinary 1-OHPG and Cd among Cd elicits oxidative stress by inducing the generation of nonsmoking workers. Workers with high urinary 1- ROS, reducing the antioxidant defense systems of cells by OHPG and high urinary Cd levels had, on average, depleting glutathione, and decreasing the activities of 60.3% higher levels of urinary 8-oxodG than did those cellular antioxidant enzymes, leading to mitochondrial with low urinary 1-OHPG and low urinary Cd levels in injuries and increasing the susceptibility of cells to oxi- the adjusted model. Workers with high urinary 1-OHPG dative attack by altering membrane integrity and fatty and low urinary Cd levels and workers with low urinary acid composition (18, 19). Consequently, it is plausible 1-OHPG and high urinary Cd levels had, on average, that the toxic effect from Cd can be partially responsible 25.4% and 36.3% higher levels of urinary 8-oxodG, respec- for the impaired balance between oxidants and

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Table 3. Relations of urinary metal and 1-OHPG levels with urinary 8-oxodG levels

Ln urinary 8-oxodG (mg/g creatinine)

Variables b 95% CI P value Model 1 (all workers)a Urinary heavy metal (mg/g creatinine) Ln Cd 0.129 0.026–0.231 0.014 Ln Ni 0.063 0.126 to 0.006 0.060 Ln As 0.018 0.105 to 0.069 0.676 Ln Pb 0.022 0.070 to 0.026 0.362 Ln Cu 0.003 0.098 to 0.103 0.956 Ln urinary 1-OHPG (mg/g creatinine) 0.095 0.018–0.173 0.016 Model 2 (nonsmoking workers)b Urinary heavy metal (mg/g creatinine) Ln Cd 0.138 0.013–0.264 0.031 Ln Ni 0.068 0.142 to 0.006 0.072 Ln As 0.019 0.119 to 0.081 0.707 Ln Pb 0.024 0.083 to 0.035 0.424 Ln Cu 0.005 0.124 to 0.115 0.939 Ln urinary 1-OHPG (mg/g creatinine) 0.112 0.023 to 0.202 0.015

NOTE: Numbers in bold as the statistical signiﬁcance. aAdjusted for age, sex, smoking habit, season, educational level, and group. bAdjusted for age, sex, season, educational level, and group.

antioxidants. The strong association observed between schoolchildren (5). However, the lack of correlation urinary Cd levels and oxidative stress markers in the third between exposure to these metals, including Ni, As, Pb, U.S. National Health and Nutrition Survey suggests that and Cu, and oxidative stress could be attributed to a low Cd could increase the burden of oxidative stress (20). Bae biologically relevant dose in the study population. and colleagues, in 2010, also reported that exposure to Cd Although there were consistent negative associations from air pollution was associated with oxidative stress in between other metals (Ni, As, and Pb) and urinary 8-oxodG, these negative associations might be generated by statistical random variations. We found no differences in urinary Cd levels between the traffic conductors and indoor offices workers. Although air pollution from traffic exhausts was identified as a possible source of Cd (21), contribution from diets 4 cannot be ruled out. Dietary intake is one of the important sources of exposure to Cd in the general nonsmoking 3.22 3 population, especially in consumption of some foods such 2.74 as rice, other crops, and shellfish (22–25). The urinary Cd 2.52 concentrations in our study population were higher than 2 2.01 those reported in the third U.S. National Health and Nutrition Survey (geometric mean: 0.37 mg/g creatinine; ref. 20) and similar to those reported for the Japanese 1 population (geometric mean 0.8 mg/g creatinine; ref. 26).

urinary 8-oxodG (ug/g creatinine) creatinine) (ug/g 8-oxodG urinary Overall, most participants (99%) had urinary Cd levels of

Geometric mean and 95% CI Geometric mean of and 95% CI adjusted 0 less than 5 mg/g creatinine, the World Health Organiza- low 1-OHPG high 1-OHPG low 1-OHPG high 1-OHPG tion (WHO) standard for urinary Cd (27). / low Cd / low Cd / high Cd / high Cd The urinary 1-OHPG levels in traffic conductors were significantly higher than those in indoor office workers, Figure 1. Effects of interaction of urinary 1-OHPG and Cd levels with whichwere similar to the findings in toll-stationworkers (9), urinary 8-oxodG levels in nonsmoking workers. Value showed was busdrivers(7),and policeofficers(28).Theseresultssuggest geometric mean. Cut-off points were determined according to medians (1-OHPG, 0.23 mg/g creatinine; Cd, 0.88 mg/g creatinine) of urinary that traffic sources have been recognized as major contri- creatinine-adjusted levels among nonsmoking workers. (, P < 0.05; butors to PAHs and have an effect on urinary 1-OHPG , P < 0.01; , P < 0.001). levels. Conversely, the urinary 1-OHPG concentrations in

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traffic conductors (range, 0.08–0.11 mmol/mol) were lower levels. However, the evidence was limited (36, 37). than those reported in toll-station workers (range, 0.12–0.16 Although genetic background (such as DNA repair capa- mmol/mol; ref. 9), painters in shipyards (range, 0.99–1.4 bility) from each participant could confound the estimat- mmol/mol; ref. 12), and incinerator workers (mean, 0.24 ed effect, two measurements on the consecutive days in mmol/mol; ref. 11), indicating a moderate exposure to PAHs the present study could minimize these effects. in the present study. The main pathways of metabolic An early prospective study had reported that elevated activation of PAHs are the formation of anti- and syn-diol levels of urinary 8-oxodG were significantly associated epoxides,theformationofradicalcations,andtheformation with increasing risk of lung cancer among never-smokers of o-quinones (3). The radical cations can generate ROS and (38). Recently, a nested case-control study of lung cancer cause oxidative stress by redox cycling (29, 30). Epidemio- and diesel exhaust indicated that workers in highly pol- logic studies found that exposure to PAHs from air pollu- luted cities over a lifetime had at least a 50% increased risk tion could be positively associated with urinary 8-oxodG of developing lung cancer (39). Exposures to PAHs and levels (9, 31, 32). Cd are known as risk factors of many illnesses. Therefore, Urinary Cd levels and urinary 1-OHPG levels as inde- traffic conductors in urban environments could be more pendent predictors of urinary 8-oxodG levels indicate the susceptible to injury and disease caused by exposure to hypothesis that Cd and PAHs could induce oxidative PAHs and metals. stress through different mechanisms. Environmentally In summary, our results indicate that co-exposure to relevant pollutants seldom occur alone. Little is known urinary 1-OHPG and Cd could increase the levels of on the exact mechanism of carcinogenesis of two or more urinary 8-oxodG, suggesting that the additive interaction pollutants when they are present together. Our results between exposure to environmental PAHs and Cd could support the assumption that the concept of additivity is enhance the burden of oxidative stress. operative on moderate- or low-level exposures to chemical mixtures. Valavanidis and colleagues in 2005 showed Disclosure of Potential Conflicts of Interest that transition metals, redox cycling quinoids, and PAHs No potential conflicts of interest were disclosed. act synergically to produce ROS, to increase the burden of oxidative stress (33). Cd inhibits several enzymes Authors' Contributions involved in DNA repair, and this has been identified as Conception and design: S.-H. Liou, C.-H. Lai, S.-L.J. Wang a major mechanism underlying the carcinogenic potential Development of methodology: C.-J. Wang, S.-H. Liou, C.-H. Lai, S.-L.J. Wang of Cd (19, 34). Thus, the DNA damage might be induced Acquisition of data (provided animals, acquired and managed patients, by oxidative stress from exposure to Cd and/or PAHs, provided facilities, etc.): G.-W. Chen, Y.-Y. Lin, C.-H. Lai, S.-L.J. Wang Analysis and interpretation of data (e.g., statistical analysis, biostatis- and further enhanced by impaired repair from one or tics, computational analysis): H.-B. Huang, Y.-Y. Lin, S.-H. Liou, C.-H. both. In this way, the effect of interaction was observed Lai, S.-L.J. Wang although the concentrations were moderate. Future stud- Writing, review, and/or revision of the manuscript: H.-B. Huang, C.-H. Lai, S.-L.J. Wang ies are required to clarify these findings. Administrative, technical, or material support (i.e., reporting or orga- The urinary excretion of products of damaged nucleo- nizing data, constructing databases): G.-W. Chen, C.-J. Wang, C.-H. Lai, tides in cellular nucleotide pools or in DNA may be S.-L.J. Wang Study supervision: C.-H. Lai, S.-L.J. Wang important biomarkers of exposure to relevant carcinogens and may predict cancer risk. Urinary 8-oxodG in steady state reflects products of DNA damage and repair (35), Grant Support This work was supported by funding from the National Research and could also be regarded as biomarkers of oxidative Program for Genomic Medicine, Taiwan (grant nos. DOH97-TD-G-111- stress in occupational or environmental fields (6–10). Our 032, DOH98-TD-G-111-021, DOH99-TD-G-111-018, and NSC100-2325- B400-010). results also showed that traffic conductors could have The costs of publication of this article were defrayed in part by the higher levels of urinary 8-oxodG than indoor office work- payment of page charges. This article must therefore be hereby marked ers, which were in agreement with previous studies (7, 9). advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Air pollution from traffic exhaust could increase levels of oxidative DNA damage. Other factors, such as cell death Received June 13, 2012; revised October 20, 2012; accepted October 24, and diets, might contribute to increase urinary 8-oxodG 2012; published OnlineFirst November 13, 2012.

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108 Cancer Epidemiol Biomarkers Prev; 22(1) January 2013 Cancer Epidemiology, Biomarkers & Prevention

Exposure to Heavy Metals and Polycyclic Aromatic Hydrocarbons and DNA Damage in Taiwanese Traffic Conductors

Han-Bin Huang, Guan-Wen Chen, Chien-Jen Wang, et al.

Cancer Epidemiol Biomarkers Prev 2013;22:102-108. Published OnlineFirst November 13, 2012.

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