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In cancer patients, plasma often contains mutant DNA released by cancer cells. We have assessed the significance of plasma DNA mutations for subsequent cancer development in healthy subjects in a large longitudinal prospective study. The European Prospective Investigation into Cancer and Nutrition study was analyzed with a nested case-control design. Cases were nonsmokers or ex-smokers for >10 years and newly diagnosed with lung, bladder, or upper aerodigestive tract cancers or leukemia accrued after a median follow-up of 6.3 years. Controls were matched 2:1 for follow-up, age, sex, area of recruitment, and smoking status. KRAS2 mutations were detected by mutant-enriched PCR and sequencing (n = 1,098). TP53 mutations were detected by denaturing high-performance liquid chromatography, temporal temperature gradient electrophoresis, and sequencing (n = 550). KRAS2 or TP53 mutations were detected in 13 of 1,098 (1.2%) and 20 of 550 (3.6%) subjects, respectively, 16 of whom developed cancer on average after 18.3 months of follow-up. Among 137 subjects who developed bladder cancer, 5 had KRAS2 mutations [odds ratio (OR), 4.25; 95% confidence interval (95% CI), 1.27-14.15] and 7 had TP53 mutations (OR, 1.81; 95% CI, 0.66-4.97). There was a nonsignificant trend for association between TP53 mutations and bulky adducts in lymphocyte DNA (OR, 2.78; 95% CI, 0.64-12.17). This is the first report of TP53 or KRAS2 mutations in the plasma of healthy subjects in a prospective study, suggesting that KRAS2 mutation is detectable ahead of bladder cancer diagnosis. TP53 mutation may be associated with environmental exposures. These observations have implications for monitoring early steps of carcinogenesis. (Cancer Res 2006; 66(13): 6871-6)

Supplementary Table 1 from TP53 and KRAS2 Mutations in Plasma DNA of Healthy Subjects and Subsequent Cancer Occurrence: A Prospective Study

Objective: Exposure to airborne metal nanoparticles causes detrimental health consequences and increases the risk of lung cancer in exposed humans. This study aimed to investigate the effects of metal nanoparticles on oxidative stress-mediated DNA damage and inflammation, both in humans exposed to metal nanoparticles and in human bronchial epithelial cells (BEAS-2B). Method: Effects of exposure to metal nanoparticles were studied in welders using a cross-over design. Concentrations of metals bound to nanoparticles were measured by a personal nanoparticle sampler and analyzed by ICP-MS. Blood and urine samples were collected to determine oxidative DNA damage and transcript expression of DNA damage-related genes. The mechanisms by which iron oxide nanoparticle (FeNP)-induced oxidative DNA damage, apoptosis, and induction of inflammatory genes were investigated in BEAS-2B cells. Results: FeNP is a major form of airborne metal nanoparticles, contributing to 79% of all toxic metals in welding fumes. Exposure to airborne FeNP in welders was positively associated with blood Fe concentrations. Welders exposed to metal nanoparticles without a protective mask had increased oxidative DNA damage, observed as reduced urinary 8-OHdG, which suggest a decrease in DNA repair capacity. This was in line with significantly decreased transcript expression of the DNA repair gene (OGG1) and anti-oxidative response gene (Nrf2), as well as increased expression of the inflammatory response gene (IL-6), compared with those observed in the same welders wearing protective masks. In the in vitro study, BEAS-2B cells treated with FeNP had a decrease in cell viability and an increase in ROS generation, 8-OHdG, and apoptosis activity (caspase3-7) in a dose-dependent manner. FeNP treatment downregulated the expressions of OGG1 and Nrf2 and upregulated the expressions of IL-6 and IL-8. Conclusion: Exposure to FeNP induces oxidative DNA damage and inflammation, and this may contribute to an increased risk of respiratory diseases and cancer development.

This cross-sectional study aimed to assess the adverse effects of benzene and toluene exposure in gasoline station workers via biological screening and health risk assessment. Ambient air benzene a...

Objective This study assessed the health risk of benzene exposure among Thai gasoline station workers through biomarker detection and experience of adverse symptoms. Methods Trans, trans‐muconic acid (tt‐MA) metabolites of benzene were analyzed from spot urine sampled among gasoline station workers after shift work using HPLC‐UV. Air benzene monitoring was done with an active sampler connected to a charcoal sorbent tube, and analyzed by GC‐FID. The health risk was calculated by using the biomatrix of the likelihood of benzene exposure and the severity of adverse symptoms. Results The tt‐MA concentration, among 235 workers, ranged from less than 10–2159 µg/g Cr, which corresponded to the air benzene concentration range of

Silver nanoparticles (AgNPs) are widely used in health and consumer products that routinely contact skin. However, the biological effects and possible mechanisms of AgNPs on skin remain unclear. Gap junctional intercellular communication (GJIC) plays a critical role in multicellular organisms to maintain tissue homeostasis. The aim of this study is to examine if non-coated AgNPs affect GJIC in human keratinocytes (HaCaT cells), and to identify the possible molecular mechanisms responsible for the effects. GJIC, connexin (Cx)43 protein and mRNA expression, and the effect of siRNA-mediated knockdown of Cx43 on GJIC were assessed. HaCaT cells exposed to non-coated AgNPs at different doses after a 24 hour exposure. To explore further the underlying mechanism, reactive oxygen species and mitogen-activated protein kinase pathway were evaluated after 2, 6, 12 and 24 hours. Our results revealed that non-coated AgNP exposure at subcytotoxic doses increase GJIC partially via Cx43 upregulation. Reactive oxygen species and extracellular signal-regulated kinase and activation of c-Jun N-terminal kinase were involved in the AgNP-induced upregulation of Cx43. This study provides new insight into the potential mechanism of AgNP biological activity.

Benzene is a human carcinogen presented in gasoline (1% by volume). It is also found in vehicle exhaust. The aim of this study was to assess the health risk of inhalation exposure to benzene among gasoline station workers. The ambient benzene concentration was measured by personal sampling from 150 gasoline station workers (137 fueling workers and 13 cashiers). Additional data of working characteristics were collected by interviews and on-site observations. All workers were non-smokers and passive smoking was limited. Risk assessment of inhalation exposure was determined using the United State Environmental Protection Agency (USEPA), and showed a high risk of adverse health effect (Hazard Quotients (HQ) &gt, 1) in 51.33% of workers. The cancer risk was increased from 1.35 &times, 10-8 to 1.52 &times, 10-4, and 70.67% of the workers had a lifetime cancer risk (&gt, Inhalation Unit Risk (IUR): 2.2 &times, 10-6). A significantly higher risk was found in fueling workers compared to cashiers, and in workers at gasoline stations in inner-city zones (suburban and urban), compared to rural zones. All risk estimations were based upon a single measurement in an eight hour working period, which was assumed to be the average shift length for all working days in a year (250 days). The increased health risk suggests that there should be health surveillance for workers in order to protect them from exposure to benzene. In addition to benzene, the volatile organic compounds (VOCs) present in gasoline may influence health outcomes.

Theoretically, both synthetic endocrine disrupting chemicals (S-EDCs) and natural (exogenous and endogenous) endocrine disrupting chemicals (N-EDCs) can interact with endocrine receptors and disturb hormonal balance. However, compared to endogenous hormones, S-EDCs are only weak partial agonists with receptor affinities several orders of magnitude lower. Thus, to elicit observable effects, S-EDCs require considerably higher concentrations to attain sufficient receptor occupancy or to displace natural hormones and other endogenous ligands. Significant exposures to exogenous N-EDCs may result from ingestion of foods such as soy-based diets, green tea and sweet mustard. While their potencies are lower as compared to natural endogenous hormones, they usually are considerably more potent than S-EDCs. Effects of exogenous N-EDCs on the endocrine system were observed at high dietary intakes. A causal relation between their mechanism of action and these effects is established and biologically plausible. In contrast, the assumption that the much lower human exposures to S-EDCs may induce observable endocrine effects is not plausible. Hence, it is not surprising that epidemiological studies searching for an association between S-EDC exposure and health effects have failed. Regarding testing for potential endocrine effects, a scientifically justified screen should use in vitro tests to compare potencies of S-EDCs with those of reference N-EDCs. When the potency of the S-EDC is similar or smaller than that of the N-EDC, further testing in laboratory animals and regulatory consequences are not warranted.

Introduction A low benzene concentrations in working environment at gasoline stations has been reported with a concern as human carcinogen. Trans, trans-Muconic acid (tt-MA), a metabolite widely used biomarker, is suggested for detection of low benzene exposure. This study aimed to investigate health risk on benzene exposure via biomarker detection and inhaled benzene concentration among gasoline station workers. Methods The study was conducted among 235 gasoline station workers in Thailand. Spot urine was collected from workers at the end of shift-work and analysed for tt-MA concentration using HPLC. Benzene concentration was measured by personal air sampling and analysed using GC-FID. Additional data was collected by questionnaires and observations. Health risk assessment was performed with applied 5 × 5 risk matrix considering the likelihood of exposure frequency (t,t-MA and benzene level) and severity of adverse symptoms related to benzene toxicity. Results Gasoline station workers (85.11%) had experiences of adverse symptoms from mild to severe level. Urinary t,t-MA was detected in 73.62% of workers whereas only 9.25% of them had tt-MA higher than the recommended value (>500 μg/g Creatinine). The risk matrix using tt-MA levels identified worker’s health risk was unacceptable levels (low to high risk; 69.79%). Considering the matrix using benzene concentration which was presented at lower than the occupational exposure level ( IUR; 2.20E-6). Conclusion The finding risk matrix is useful in occupational health surveillance program at gasoline station and for risk control identification. Annual health check-up, monitoring of biomarkers and benzene concentration, and risk communication are necessary to prevent workers adverse health effects and cancer.

Previously we have identified lysenin as a key protein constituent of the secretome from Eisenia fetida coelomocytes and revealed its critical importance in priming interactions between the cells and the protein corona around nanosilver. As alterations of the protein environment can directly affect the corona composition, the extent to which nanoparticles influence the cells’ protein secretion profile is of remarkable interest that has rarely acquired attention. Here, we have probed transcriptional responses of E. fetida coelomocytes to the representative nanosilver NM-300K (15 nm) in a time-dependent manner (2, 4, 8 and 24 h at a low-cytotoxic concentration), and examined the implication of the temporal changes in transcriptional profiles of secretory proteins with a particular reference to that of lysenin. NM-300K was accumulated in/at the cells and lysenin was, after transient induction, gradually suppressed over time indicating a negative feedback cycle. This may limit further enrichment of lysenin in the corona and thereby decrease the lysenin-assisted uptake of the nanoparticles. Other differentially expressed genes were those involved in metal stress (likewise in AgNO3-stressed cells) and in Toll-like receptor (TLR) signaling. This offers an intriguing perspective of the nanosilver pathophysiology in earthworms, in which the conserved pattern recognition receptor TLRs may play an effector role.

Silver nanoparticles (AgNPs) are widely used in health and consumer products that routinely contact skin. However, the biological effects and possible mechanisms of AgNPs on skin remain unclear. Gap junctional intercellular communication (GJIC) plays a critical role in multicellular organisms to maintain tissue homeostasis. The aim of this study is to examine if non-coated AgNPs affect GJIC in human keratinocytes (HaCaT cells), and to identify the possible molecular mechanisms responsible for the effects. GJIC, connexin (Cx)43 protein and mRNA expression, and the effect of siRNA-mediated knockdown of Cx43 on GJIC were assessed. HaCaT cells exposed to non-coated AgNPs at different doses after a 24 hour exposure. To explore further the underlying mechanism, reactive oxygen species and mitogen-activated protein kinase pathway were evaluated after 2, 6, 12 and 24 hours. Our results revealed that non-coated AgNP exposure at subcytotoxic doses increase GJIC partially via Cx43 upregulation. Reactive oxygen species and extracellular signal-regulated kinase and activation of c-Jun N-terminal kinase were involved in the AgNP-induced upregulation of Cx43. This study provides new insight into the potential mechanism of AgNP biological activity.

Health impacts of inhalation exposure to engineered nanomaterials have attracted increasing attention. In this paper, integrated analytical techniques with high sensitivity were used to study the brain translocation and potential impairment induced by intranasally instilled copper nanoparticles (CuNPs). Mice were exposed to CuNPs in three doses (1, 10, 40 mg/kg bw). The body weight of mice decreased significantly in the 10 and 40 mg/kg group (p

Trans, trans-muconic acid (tt-MA) is a metabolite that is widely used as a biomarker to identify low exposure to benzene, a human carcinogen. This study aimed to investigate occupational factors related to the urinary tt-MA detection of benzene exposed workers in gasoline stations. Spot urine samples were collected and analyzed for tt-MA using a high performance liquid chromatography. Additional data were collected via subject interviews using a structured questionnaire. The personal benzene concentration was measured and analyzed by gas chromatography with a flame ionization detector. Results showed that, among the 170 workers, tt-MA was detected in 24.7% of workers and the concentration ranged from 23.0 to 1127.8 &micro, g/g creatinine. Over 25% of those detections possessing tt-MA exceeding the recommended 500 &micro, g/g creatinine was safe. A multiple logistic regression analysis identified that factors significantly associated with the detectable tt-MA were having no other part-time jobs (ORadj = 4.2), personal benzene concentrations of 0.05 ppm or higher (ORadj = 10.3), close to fuel nozzle during refuelling (ORadj = 93.7), and no job training (ORadj = 2.74). Safety training is recommended for those tt-MA detected workers or under a reference benzene concentration of 0.05 ppm or higher. The proposed reference of occupational action level to benzene exposure is 0.05 ppm and compliance could be assessed tt-MA for biomonitoring of those benzene exposed workers.

Objectives were to investigate prospectively the ability of DNA adducts to predict cancer and to study the determinants of adducts, especially air pollutants. DNA adducts were measured in a case-control study nested in the European Prospective Investigation into Cancer and Nutrition (EPIC) investigation. Cases included newly diagnosed lung cancer (n = 115), upper respiratory cancers (pharynx and larynx; n = 82), bladder cancer (n = 124), leukemia (n = 166), and chronic obstructive pulmonary disease or emphysema deaths (n = 77) accrued after a median follow-up of 7 years among the EPIC former smokers and never-smokers. Three controls per case were matched for questionnaire analyses and two controls per case for laboratory analyses. Matching criteria were gender, age, smoking status, country of recruitment, and follow-up time. Individual exposure to air pollution was assessed using concentration data from monitoring stations in routine air quality monitoring networks. Leukocyte DNA adducts were analyzed blindly using 32P postlabeling technique. Adducts were associated with the subsequent risk of lung cancer, with an odds ratio (OR) of 1.86 [95% confidence interval (95% CI), 0.88-3.93] when comparing detectable versus nondetectable adducts. The association with lung cancer was stronger in never-smokers (OR, 4.04; 95% CI, 1.06-15.42) and among the younger age groups. After exclusion of the cancers occurring in the first 36 months of follow-up, the OR was 4.16 (95% CI, 1.24-13.88). A positive association was found between DNA adducts and ozone (O3) concentration. Our prospective study suggests that leukocyte DNA adducts may predict lung cancer risk of never-smokers. Besides, the association of DNA adduct levels with O3 indicates a possible role for photochemical smog in determining DNA damage.

A public appeal has been advanced by a large group of scientists, concerned that science has been misused in attempting to quantify and regulate unmeasurable hazards and risks.1 The appeal recalls that science is unable to evaluate hazards that cannot be measured, and that science in such cases should not be invoked to justify risk assessments in health, safety and environmental regulations. The appeal also notes that most national and international statutes delineating the discretion of regulators are ambiguous about what rules of evidence ought to apply. Those statutes should be revised to ensure that the evidence for regulatory action is grounded on the standards of the scientific method, whenever feasible. When independent scientific evidence is not possible, policies and regulations should be informed by publicly debated trade-offs between socially desirable uses and social perceptions of affordable precaution. This article explores the premises, implications and actions supporting the appeal and its objectives.

Maternal diet can contribute to carcinogenic exposures and also modify effects of environmental exposures on maternal and fetal genetic stability. In this study, associations between maternal diet and the levels of dioxin-like plasma activity, bulky DNA adducts in white blood cells and micronuclei (MN) in lymphocytes from mother to newborns were examined. From 98 pregnant women living in the greater area of Copenhagen, Denmark in 2006-2007, maternal peripheral blood and umbilical cord blood were collected, together with information on health, environmental exposure and lifestyle. Maternal diet was estimated on the basis of maternal food frequency questionnaire (FFQ) completed by the end of pregnancy. Biomarkers were detected in paired blood samples through the dioxin-responsive chemical-activated luciferase expression (CALUX)(®) bioassay, (32)P-postlabelling technique and cytokinesis-block MN assay. Maternal preference for meats with dark surface were significantly associated with higher bulky DNA adducts in both maternal (β 95%CI; 0.46 (0.08, 0.84)) and cord blood (β 95%CI; 0.46 (0.05, 0.86)) before and after adjustment for potential confounders. No other significant associations between the 18 dietary variables and the biomarkers measured in maternal and fetal samples were identified. The present study suggests that maternal intake of meats with dark surface contributes to the bulky DNA adduct levels in maternal and umbilical cord blood. Relationship between food preparation and bulky DNA adducts appear to be captured by a FFQ while potential associations for other biomarkers might be more complex or need larger sample size.

Little is known about the potential threats of silver nanoparticles (AgNPs) to ecosystem health, with no detailed report existing on the stress and immune responses of soil invertebrates. Here we use earthworm primary cells, cross-referencing to human cell cultures with a particular emphasis on the conserved biological processes, and provide the first in vitro analysis of molecular and cellular toxicity mechanisms in the earthworm Eisenia fetida exposed to AgNPs (83 ± 22 nm). While we observed a clear difference in cytotoxicity of dissolved silver salt on earthworm coelomocytes and human cells (THP-1 cells, differentiated THP-1 cells and peripheral blood mononuclear cells), the coelomocytes and differentiated (macrophage-like) THP-1 cells showed a similar response to AgNPs. Intracellular accumulation of AgNPs in the coelomocytes, predominantly in a phagocytic population, was evident by several methods including transmission electron microscopy. Molecular signatures of oxidative stress and selected biomarker genes probed in a time-resolved manner suggest early regulation of oxidative stress genes and subsequent alteration of immune signaling processes following the onset of AgNP exposure in the coelomocytes and THP-1 cells. Our findings provide mechanistic clues on cellular innate immunity toward AgNPs that is likely to be evolutionarily conserved across the animal kingdom.

Concerns have arisen about the health and environmental impacts of the increasing commercial use of silver nanoparticles (AgNPs). However, the toxic mechanisms and target tissues of AgNPs have not been fully defined. In this paper, we investigated the tissue toxicity of mice after intravenous administration of AgNPs at a single-dose of 0.2, 2 or 5 mg per kg (body weight), respectively. Biodistribution, endoplasmic reticulum stress, and oxidative stress were examined in mouse organs at eight hours after exposure. Stress markers, e.g. HSP70, BIP, p-IRE1, p-PERK, chop and xbp-1s proteins/genes, were significantly upregulated in a dose-dependent manner. In the liver, spleen, lung and kidney, high stress accompanied by apoptosis occurred. Low stress levels were observed in the heart and brain. Thus, it is proposed that the liver, spleen, lung and kidney are dominant target tissues of AgNP exposure. The lower stress and toxicity in the heart and brain were in agreement with lower AgNP accumulation. The present results demonstrated that AgNP exposure eventually resulted in permanent toxic damage by gradually imposing stress impacts on target organs. These findings highlight the potent applications of stress markers in future risk evaluation of silver nanoparticle toxicity.

Combustion of biomass and wood for residential heating and/or cooking contributes substantially to both ambient air and indoor levels of particulate matter (PM). Toxicological characterization of ambient air PM, especially related to traffic, is well advanced, whereas the toxicology of wood smoke PM (WSPM) is poorly assessed. We assessed a wide spectrum of toxicity end points in human A549 lung epithelial and THP-1 monocytic cell lines comparing WSPM from high or low oxygen combustion and ambient PM collected in a village with many operating wood stoves and from a rural background area. In both cell types, all extensively characterized PM samples (1.25-100 mu g/mL) induced dose-dependent formation of reactive oxygen species and DNA damage in terms of strand breaks and formamidopyrimidine DNA glycosylase sites assessed by the comet assay with WSPM being most potent. The WSPM contained more polycyclic aromatic hydrocarbons (PAH), less soluble metals, and expectedly also had a smaller particle size than PM collected from ambient air. All four types of PM combined increased the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine dose-dependently in A549 cells, whereas there was no change in the levels of etheno-adducts or bulky DNA adducts. Furthermore, mRNA expression of the proinflammatory genes monocyte chemoattractant protein-1, interleukin-8, and tumor necrosis factor-alpha as well as the oxidative stress gene heme oxygenase-1 was upregulated in the THP-1 cells especially by WSPM and ambient PM sampled from the wood stove area. Expression of oxoguanine glycosylase 1, lymphocyte function-associated antigen-1, and interleukin-6 did not change. We conclude that WSPM has small particle size, high level of PAR, low level of water-soluble metals, and produces high levels of free radicals, DNA damage as well as inflammatory and oxidative stress response gene expression in cultured human cells.

published

The toxicity of a range of inorganic (Ag, Cu, Ni, Al(2)O(3), SiO(2), TiO(2) and ZrO(2)) nanoparticles (NP) and their corresponding metal salt or bulk metal oxide were screened for toxicity toward the earthworm Eisenia fetida using the limit-test design (1000 mg/kg). This study provides the first ecotoxicological life history trait data on earthworms for each these NPs, as well as for AgNO(3), Al(2)O(3), SiO(2), TiO(2) and ZrO(2). Significant effects were observed on survival for AgNO(3) (2.5% of controls), CuCl(2) (17.5% of controls) and NiCl(2) (32.5% of controls) and on reproduction (AgNO(3), CuCl(2), NiCl(2), Ag-NP, Cu-NP, TiO(2)-NP); with total reproductive failure in both silver treatments. Ag-NP, Cu-NP and TiO(2)-NP were the only NPs that caused toxic effects to E. fetida. The toxicity could not be singularly related to particle size or zeta potential or to the inherent element constituting the NPs (e.g. Ag).

Udgivelsesdato: 2010-Jan Bulky DNA adducts are considered a potential biomarker of cancer risk. In this study, the association between various lifestyle, environmental, and genetic factors and the levels of bulky DNA adducts in peripheral leukocytes was examined in a study group nested within a population-based prospective Danish cohort. At enrollment, blood samples were collected and information on lifestyle, including dietary and smoking habits, obtained. Previously, bulky DNA adducts were measured in 245 individuals who developed lung cancer and 255 control members of the cohort. Of these 500 individuals, data on 375 individuals were included in this study, excluding 125 cases, which developed lung cancer within the first 3 yr after blood sampling. Bulky DNA adduct levels were measured by 32P-postlabeling technique and polymorphisms in carcinogen metabolism and DNA repair genes were determined. Potential predictors of bulky DNA adduct levels were analyzed by univariate and multivariate regression analyses. Women tended to have higher adduct levels than men. Living in central Copenhagen and surface darkness of fried meat and fish were associated with quantitative higher adduct levels. No significant associations were found between dietary factors or smoking and DNA adduct levels. Further, the results showed no prominent associations between any of 12 genetic polymorphisms and adduct levels. Overall, our study showed only few associations between dietary, environmental, and genetic factors and levels of bulky DNA adducts measured in peripheral leukocytes in a general Danish population.

Silver nanoparticles (Ag NPs) are increasingly being used in wound dressings, medical settings, and various household products due to their unique properties and antimicrobial activity. Despite the widespread use of Ag NP products, the molecular mechanisms underlying the biological effects of Ag NPs remain unclear. Gap junctional intercellular communication (GJIC), formed by the connexin protein family, plays a critical role in the maintenance of tissue and organ homeostasis. This study was undertaken to investigate the effects of well characterized, PVP-coated Ag NPs (69 +/- 3 nm) and silver nitrate on GJIC and connexin43 (Cx43) expression in human lung adenocarcinoma cell line A549. Our results showed that Ag NPs increased GJIC in A549 cells as assayed by dye transfer method. Western blot analysis showed that incubation of cells with Ag NPs significantly increased the expression of Cx43 protein. In addition, Ag NPs up-regulated expression of Cx43 mRNA in a dose-dependent manner. Silver nitrate failed to increase GJIC and the expression of Cx43 protein. It, however, increased Cx43 mRNA expression in A549 cells. Taken together, our results provide the first evidence that Ag NPs induced the increase of GJIC activity in A549 cells through up-regulation of Cx43 protein, suggesting that Cx43 and GJIC may be one of the targets for Ag NPs biological effects.

The objective of the present study was to investigate the toxicity of silver nanoparticles (Ag NPs) in vitro . Silver ions (Ag+) have been used in medical treatments for decades whereas Ag NPs have been used in a variety of consumer products within recent years. This study was undertaken to compare the effect of well characterized, PVP-coated Ag NPs (69 nm ± 3 nm) and Ag+ in a human monocytic cell line (THP-1). Characterization of the Ag NPs was conducted in both stock suspension and cell media with or without serum and antibiotics. By using the flowcytometric annexin V/propidium iodide (PI) assay, both Ag NPs and Ag+ were shown to induce apoptosis and necrosis in THP-1 cells depending on dose and exposure time. Furthermore, the presence of apoptosis could be confirmed by the TUNEL method. A number of studies have implicated the production of reactive oxygen species (ROS) in cytotoxicity mediated by NPs. We used the fluorogenic probe, 2′,7′-dichlorofluorescein to assess the levels of intracellular ROS during exposure to Ag NPs and Ag+. A drastic increase in ROS levels could be detected after 6–24 h suggesting that oxidative stress is an important mediator of cytotoxicity caused by Ag NPs and Ag+.

Assessing the risk profiles of potentially sensitive populations requires a "tool chest" of methodological approaches to adequately characterize and evaluate these populations. At present, there is an extensive body of literature on methodologies that apply to the evaluation of the pediatric population. The Health and Environmental Sciences Institute Subcommittee on Risk Assessment of Sensitive Populations evaluated key references in the area of pediatric risk to identify a spectrum of methodological approaches. These approaches are considered in this article for their potential to be extrapolated for the identification and assessment of other sensitive populations. Recommendations as to future research needs and/or alternate methodological considerations are also made.

Udgivelsesdato: 2009 OBJECTIVE: Crohn's disease (CD) and ulcerative colitis (UC) are characterized by an impaired mucosal defence to normal constituents of the intestinal flora and a dysregulated inflammatory response. The purpose of the study was to investigate whether single nucleotide polymorphisms (SNPs) in genes involved in these processes were associated with CD and UC. MATERIAL AND METHODS: Allele frequencies of the cyclooxygenase 2 (COX-2/PTGS2/PGHS2) G-765C and breast cancer resistance protein (BCRP/ABCG2) C421A as well as allele and haplotype frequencies of multidrug resistance 1 (MDR1, ABCB1) SNPs G2677T/A, C3435T and G-rs3789243-A (intron 3) were assessed in a Danish case-control study comprising 373 CD and 541 UC patients and 796 healthy controls. RESULTS: Carriers of the homozygous COX-2 and MDR1 intron 3 variant had a relatively high risk of CD, odds ratio (95% CI) (OR (95% CI))=2.86 ((1.34-5.88) p=0.006) and 1.39 ((0.99-1.92) p=0.054), respectively, and for UC of 2.63 ((1.33-5.26) p=0.005) and 1.28 ((0.96-1.51) p=0.093), respectively, assuming complete dominance. No association was found for BCRP or other MDR1 SNPs, or for selected MDR1 haplotypes. No effect-modification of smoking habit at the time of diagnosis was found. CONCLUSIONS: An effect of the COX-2 polymorphism on both CD and UC was shown which is compatible with the presence of a recessive allele in linkage equilibrium with the SNP marker in the COX-2 gene. The polymorphism located in intron 3 of the MDR1 gene showed a weak association with CD, and a marginally suggestive association with UC.

This review examines the large body of toxicological and epidemiological information on human exposures to chlorpyrifos, with an emphasis on the controversial potential for chlorpyrifos to induce neurodevelopmental effects at low doses. The results of this review demonstrate that the use of urinary 3,5,6-trichlorpyridinol (TCPy), a metabolite of chlorpyrifos as a biomarker of nonoccupational exposure is problematic and may overestimate nonoccupational exposures to chlorpyrifos by 10-to 20-fold because of the widespread presence of both TCPy and chlorpyrifos-methyl in the food supply. Current "background" (nonoccupational) levels of exposure to chlorpyrifos are several orders of magnitude lower than those required to inhibit plasma cholinesterase activity, which is a more sensitive target than nervous system cholinesterase. However, several in vitro studies have identified putative neurodevelopmental mechanisms that are altered at concentrations of chlorpyrifos below those that inhibit cholinesterases. Although one human cohort study reported an association between maternal and cord blood chlorpyrifos levels and several measures of neurodevelopment, two other cohort studies that utilized urinary TCPy as a surrogate for chlorpyrifos exposure did not demonstrate an association. Although the weight of the scientific evidence demonstrates that current levels of chlorpyrifos exposure will not have any adverse effects on neurodevelopment that might result from inhibition of nervous system cholinesterases, several recent studies propose alternative mechanisms. Thus, further in vivo investigation on neurodevelopment in an appropriate animal model is needed; additional epidemiological studies may be warranted if a suitable, chlorpyrifos-exposed cohort can be identified and more rigorous measures of exposure are utilized.

Toxicity of silver nanoparticles (Ag NPs) has been reported both in vitro and in vivo. However, the intracellular stability and chemical state of Ag NPs are still not very well studied. In this work, we systematically investigated the cellular uptake pathways, intracellular dissolution and chemical species, and cytotoxicity of Ag NPs (15.9 ± 7.6 nm) in Chinese hamster ovary cell subclone K1 cells, a cell line recommended by the OECD for genotoxicity studies. Quantification of intracellular nanoparticle uptake and ion release was performed through inductively coupled plasma mass spectrometry. X-ray absorption near-edge structure (XANES) was employed to assess the chemical state of intracellular silver. The toxic potential of Ag NPs and Ag(+) was evaluated by cell viability, reactive oxygen species (ROS) production and live-dead cell staining. The results suggest that cellular uptake of Ag NPs involves lipid-raft-mediated endocytosis and energy-independent diffusion. The degradation study shows that Ag NPs taken up into cells dissolved quickly and XANES results directly indicated that the internalized Ag was oxidized to Ag-O- species and then stabilized in silver-sulfur (Ag-S-) bonds within the cells. Subsequent cytotoxicity studies show that Ag NPs decrease cell viability and increase ROS production. Pre-incubation with N-acetyl-L-cysteine, an efficient antioxidant and Ag(+) chelator, diminished the cytotoxicity caused by Ag NPs or Ag(+) exposure. Our study suggests that the cytotoxicity mechanism of Ag NPs is related to the intracellular release of silver ions, followed by their binding to SH-groups, presumably coming from amino acids or proteins, and affecting protein functions and the antioxidant defense system of cells.

The expression of a number of cellular oncogenes was investigated in human urothelial cell lines with different in vitro growth properties. Constitutively elevated levels of expression of c-myc RNA were found in Hu609, an immortalized, nontumorigenic cell line that was derived from normal urothelium, and in the bladder carcinoma cell line T24. Potential mechanisms that might underlie deregulation of c-myc expression in these cells were investigated. It was found that the c-myc gene was apparently intact and not amplified in Hu609 and T24. No increased stability of c-myc RNA was detected. A c-myc-CAT fusion construct containing 2.5 kb of normal c-myc 5' sequences showed levels of expression that paralleled the overexpression of the endogenous gene, indicating that the high constitutive levels of c-myc expression were due, at least in part, to alterations in the activities of cellular trans-acting transcriptional regulators.

Air pollution is a serious problem in many countries in Southeast Asia, particularly in major metropolises with high levels of traffic congestion generating significant amounts of genotoxic substances. The contribution of such environmental exposure to children's illnesses, such as respiratory diseases and cancer, is a public health concern. Inner-city children may have higher levels of exposure to genotoxic substances in the air than those living in rural areas. This study was conducted in Bangkok, where ambient levels of polycyclic aromatic hydrocarbons (PAHs) and benzene are relatively high. Bangkok school children were exposed to total PAHs at about sixfold higher levels than those in rural areas, with levels of urinary 1-hydroxypyrene (1-OHP) also being significantly higher. PAH-DNA adduct levels in lymphocytes were fivefold higher in Bangkok children. Benzene exposure in Bangkok school children was more than twofold higher than the levels measured in children from the rural areas. This is in agreement with the biomarkers of internal dose, that is, blood benzene and urinary trans, trans-muconic acid (t,t-MA) levels. The potential health risks from exposure to PAHs and benzene were assessed through the use of DNA damage and DNA repair capacity as markers of early biological effect. DNA strand breaks were significantly higher in Bangkok school children, while DNA repair capacity was significantly lower. It appears that children in major cities in developing countries may have an increased health risk for the development of certain diseases, such as cancer due to exposure to genotoxic substances in their environment.

In cancer patients, plasma often contains mutant DNA released by cancer cells. We have assessed the significance of plasma DNA mutations for subsequent cancer development in healthy subjects in a large longitudinal prospective study. The European Prospective Investigation into Cancer and Nutrition study was analyzed with a nested case-control design. Cases were nonsmokers or ex-smokers for >10 years and newly diagnosed with lung, bladder, or upper aerodigestive tract cancers or leukemia accrued after a median follow-up of 6.3 years. Controls were matched 2:1 for follow-up, age, sex, area of recruitment, and smoking status. KRAS2 mutations were detected by mutant-enriched PCR and sequencing (n = 1,098). TP53 mutations were detected by denaturing high-performance liquid chromatography, temporal temperature gradient electrophoresis, and sequencing (n = 550). KRAS2 or TP53 mutations were detected in 13 of 1,098 (1.2%) and 20 of 550 (3.6%) subjects, respectively, 16 of whom developed cancer on average after 18.3 months of follow-up. Among 137 subjects who developed bladder cancer, 5 had KRAS2 mutations [odds ratio (OR), 4.25; 95% confidence interval (95% CI), 1.27-14.15] and 7 had TP53 mutations (OR, 1.81; 95% CI, 0.66-4.97). There was a nonsignificant trend for association between TP53 mutations and bulky adducts in lymphocyte DNA (OR, 2.78; 95% CI, 0.64-12.17). This is the first report of TP53 or KRAS2 mutations in the plasma of healthy subjects in a prospective study, suggesting that KRAS2 mutation is detectable ahead of bladder cancer diagnosis. TP53 mutation may be associated with environmental exposures. These observations have implications for monitoring early steps of carcinogenesis. (Cancer Res 2006; 66(13): 6871-6)

Little is known of the predictive value of the levels of DNA adducts in terms of cancer risk. We examined the association between bulky DNA adducts and risk of lung cancer in a population-based cohort, comprising of 25,717 men and 27,972 women aged 50–64 years at entry. We included 245 cases (137 men and 108 women) with lung cancer and a comparison group of 255 individuals (137 men and 118 women), matched on sex, age and smoking duration. Bulky adducts in white blood cells collected at enrolment and stored at −150°C were analyzed by 32P-postlabeling method, using the butanol enrichment procedure. The median level of bulky DNA adducts was 0.196 adduct/108 nucleotides (5–95 percentiles: 0.094–0.595) among current smokers who were later diagnosed with lung cancer and 0.163 adduct/108 nucleotides (5–95 percentiles: 0.091–0.455) among current smokers in the comparison group. The smoking adjusted incidence rate ratios (IRR) for lung cancer in relation to one log unit (natural logarithm) difference in adduct levels were 1.22 (95% CI 0.85–1.74), 1.33 (95% CI 0.89–1.98) and 0.76 (95% CI 0.39–1.47) among all, current and former smokers, respectively. Current smokers with bulky DNA adduct levels above the median had a significant higher lung cancer rate than those with adduct levels below the median (IRR = 1.61; 95% CI 1.04–2.49). The results are compatible with previous studies, suggesting a slightly higher risk of lung cancer with higher levels of adducts among smokers. Our results indicate that bulky DNA adducts may have a weak association with lung cancer risk. © 2005 Wiley-Liss, Inc.

Exposure to genotoxic compounds present in ambient air has been studied in Cotonou, Benin, a city where two-stroke motorbikes are the major form of transportation and gasoline quality is poor. Personal monitoring and biomarkers were used to assess the exposure. Non-smoking taxi-moto drivers (city) and village residents were the study subjects. Benzene exposure was significantly higher in the city, as compared to the village (76.0+/-26.8 microg/m(3) versus 3.4+/-3.0, p=0.0004). Urinary excretion of benzene and S-phenylmercapturic acid (S-PMA) were also highest in subjects living in the city, whereas 1-hydroxypyrene was not different. The level of total polycyclic aromatic hydrocarbons (PAHs), associated with particles, ranged from 76.21 to 103.23 in Cotonou versus 1.55 ng/m(3) for the village. Determination of DNA damage in lymphocytes showed that subjects from the city had elevated number of lesions compared to subjects in the village in terms of bulky DNA adducts, 8-hydroxy-2'-deoxyguanosine and 5-methylcytosine, whereas DNA fragmentations analysed by alkaline gel electrophoresis was not different between the subjects. In conclusion, this study shows that air pollution is pronounced in Cotonou, Bénin and is associated with elevated levels of DNA damage in residents of the city compared to people living in a non-polluted rural village.

Prostaglandin synthase 2 (PTGS2) mediated production of prostaglandins is an important step in the inflammatory response. In a population-based case-cohort study, we investigated the relationship between lung cancer and a polymorphism in PTGS2 at site 8473. Among 54,220 cohort members, 265 lung cancer cases and a comparison group of 272 individuals were identified. We found no overall significant association between the PTGS2 polymorphism and lung cancer risk, though the results indicated a lower risk in subjects carrying one copy (RR 0.87; 95% CI 0.61–1.25) or two copies (RR 0.58; 95% CI 0.30–1.12) of the variant allele compared with subjects carrying two copies of the wildtype allele. This tendency seemed to be strongest among the youngest subjects (50–55 years) with a RR on 0.48 (0.19–1.22) in carriers of one variant allele and 0.21 (0.04–1.07) in carriers of two variant alleles, and a significant trend ( P =0.04). These results indicate that PTGS2 could be implicated in the development of lung cancer.

Several large prospective investigations are under way or are planned in different parts of the world, aiming at the investigation of gene-environment interactions for chronic diseases. Technical, practical and ethical issues are raised by such large investigations. Here we describe how such issues were approached within a case-control study nested in EPIC, a large European cohort, and the kind of validation studies that have been set up. The GenAir investigation aimed at measuring the effects of air pollution and environmental tobacco smoke on human health in EPIC with a nested design and with biological measures. Validation studies included (a) comparisons between cotinine measurements, hemoglobin adducts and questionnaire data; (b) an analysis of the determinants of DNA adduct concentration; (c) comparison among different genotyping methods; (d) an analysis of the determinants of plasma DNA amounts. We also describe how the ethical issues were dealt with in our investigation.

The genetic susceptibility hypothesis has been used to explain why only a minority of smokers develop lung cancer. Only few studies have studied the role of polymorphisms in phase-I and II metabolizing genes, among young lung cancer patients. We have pooled the individual data of three studies from Denmark and Norway, including 320 patients diagnosed with non-small cell lung cancer at age 59 or below, and 618 age and gender matched controls. A questionnaire was used to determine relevant demographic and lifestyle characteristics, and polymorphisms in following genotypes were determined GSTM1, GSTM3, GSTP1, GSTT1, GPX1, MPO, NQO1 and NAT2. Based on the literature, the alleles of the genotypes were categorised as high- or low-risk alleles. No individual effect of the genotypes was found on the risk of lung cancer. Given a smoking exposure, the presence of high-risk alleles (or phenotypes) was generally found to increase the risk of lung cancer, although the effect modification did not reach statistical significance. A pattern of stronger protective effect was observed in carriers of more than one allele associated with lower risk of lung cancer, and a higher risk of lung cancer in carriers of one or more alleles associated with higher risk of lung cancer, but the results did not reach statistical significance. The effect modification was generally strongest at lower levels of smoking.

Several chemical mutagens and carcinogens, including polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs, are adsorbed to the surface of diesel exhaust particles (DEP). DEP can induce formation of reactive oxygen species and cause oxidative DNA damage as well as bulky carcinogen DNA adducts. Lung tissue is a target organ for DEP induced cancer following inhalation. Recent studies have provided evidence that the lung is also a target organ for DNA damage and cancer after oral exposure to other complex mixtures of PAHs. The genotoxic effect of oral administration of DEP was investigated, in terms of markers of DNA damage, mutations and repair, in the lung of Big Blue rats fed a diet with 0, 0.2, 0.8, 2, 8, 20 or 80 mg DEP/kg feed for 21 days. There was no significant increase in the mutation frequency in the cII gene. However, an increase of DNA damage measured as DNA strand breaks (comet assay) and bulky DNA adducts (32P post labeling) was observed. The level of DNA strand breaks increased significantly at all dose levels while the level of DNA adducts increased significantly only at the intermediate dose levels. Similarly, the number of oxidized DNA bases measured as endonuclease III and fapyguanine glycosylase (FPG) sensitive sites increased at the intermediate dose levels. The induction of DNA damage by DEP exposure did not increase the expression of the repair genes OGG1 and ERCC1 at the mRNA level. The present study indicates that the lung is a target organ for primary DNA damage following oral exposure to DEP. DNA damage was induced following exposure to relatively low levels of DEP, but under the conditions used in the present experiment DNA damage did not result in an increased mutation rate.

Little is known about the impact of genetic variation on the genetic damage induced by urban air pollution or environmental tobacco smoke (ETS) in exposed populations. The levels of bulky DNA adducts ( 32P-postlabelling, nuclease P1 enrichment) and chromosomal aberrations were measured in lymphocytes of 194 non-smoking students living in the city of Athens, and the rural region of Halkida, Greece. In these individuals personal exposure to PAH was also measured. Furthermore, genetic polymorphisms were examined in cytochromes P450 1A1, 1B1, in the GSTM1, GSTP1 and GSTT1 as well as in microsomal epoxy hydrolase (EPHX) genes. Subjects with the CYP1*2A mutant genotype also suffering significant ETS exposure tended to exhibit higher adduct levels and % aberrant cells. In contrast, CYP1B1 polymorphisms seemed to have an impact on the DNA adduct levels only among individual with negligible ETS exposure. Subjects carrying both the CYP1*2A mutant genotype and the GSTM1 null genotype tended to have higher DNA adduct levels. A similar effect was also observed with the combined CYP1A1*2A/GSTP1 (Ile/Val) and the CYP1A1*2A/mEH "slow" polymorphisms. In both cases, the effect was more pronounced among subjects with higher levels of ETS exposure. Stepwise restriction of the observations to subjects characterised by (a) GSTP1 mutant, (b) GSTM1 null, (c) mEH "slow" (His139His) genotypes and (d) ETS exposure resulted in a significant trend of increasing DNA adduct levels only among individuals with at least one CYP1A1*2A mutated allele, illustrating the importance and complexity of gene-exposure and gene-gene interactions in determining the level of genotoxic damage on an individual levels.

Glutathione S-transferases (GSTs) are involved in detoxification of carcinogens, e.g., from tobacco smoke. Therefore, polymorphisms in the GST genes have been considered as potential modifiers of individual cancer risk. In a population-based case-cohort study where cases and the subcohort sample were matched on duration of smoking, we investigated the occurrence of lung cancer and histological subtypes of lung cancer in relation to deletion polymorphism in both GSTM1 and GSTT1, single nucleotide polymorphisms (SNPs) in GSTP1 (Ile105Val and Ala114Val) and a 3 base pair deletion polymorphism in GSTM3. We further investigated the effects of the GST polymorphisms on lung cancer risk within subgroups of subjects defined by gender and age. The results showed a 2.4-fold (CI = 1.31–4.41) increased risk of lung cancer in GSTT1 null-genotype carriers but no significant effects of the polymorphisms in GSTM1, GSTM3, GSTP1-105 or GSTP1-114. The association was strongest in lower age groups, with a 9.6-fold increase in risk for subjects with the GSTT1 null-genotype in the 50–55 years age interval (CI = 3.03–30.59). Positive associations were found for GSTT1 within all major histological subtypes. Squamous cell carcinoma was the histological type most strongly associated with the GSTT1 genotype, with a 5.0-fold (CI = 2.26–11.18) increase in risk for subjects carrying the GSTT1 null-genotype. The effects of the GSTT1 null-genotype seemed stronger in the presence of the GSTM1 null-genotype or the GSTP1-105 variant allele. These results suggest that the GSTT1 null-genotype is associated with an increased risk of lung cancer, especially in younger individuals. © 2004 Wiley-Liss, Inc.

The contribution of oxidative stress, different types of DNA damage and expression of DNA repair enzymes in colon and liver mutagenesis induced by 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) was investigated in four groups of six Big Blue rats fed diets with 0, 20, 70, and 200 mg IQ/kg for 3 weeks. There were dose-response relationships of DNA adducts ((32)P-postlabeling) and DNA strand breaks (comet assay) in colon and liver tissues, with the highest levels of DNA adducts and strand breaks in the colon. There was dose-dependent induction of mutations in both the colon and the liver, and the same IQ dose produced two-fold more cII mutations in the liver compared with the colon. The IQ-induced mutation spectrum in the colon was not significantly different to that of control rats. The expression of ERCC1 and OGG1 was higher in the colon than liver, and was unaffected by the IQ diet. Investigations of oxidative stress biomarkers produced inconclusive results. Oxidative DNA damage detected by the endonuclease III enzyme and 7-hydro-8-oxo-2'-deoxyguanosine in colon, liver and/or urine was unaltered by IQ. However, there was increased level of gamma-glutamyl semialdehyde in liver proteins, indicating a higher rate of protein oxidation in the liver following IQ administration. In plasma and erythrocytes there were unaltered levels of oxidized protein, malondialdehyde, and antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, catalase, glutathione reductase) indicating no systemic oxidative stress. However, the level of total vitamin C was increased in plasma, with the largest fraction being in the reduced form. In conclusion, our results indicate that DNA adducts rather than oxidative stress are responsible for the initiation of IQ-induced carcinogenesis of the liver and colon. A lower frequency of mutations in the colon than in the liver could be related to higher expression of DNA repair enzymes in the former.

Smoking is a known risk factor for bladder cancer. The product of the GSTM1 gene, glutathione S-transferase M1 (GSTM1), is involved in the detoxification of polycyclic aromatic hydrocarbons found in tobacco smoke; a homozygous deletion of this gene in approximately 50% of Caucasians and Asians results in a lack of GSTM1 enzyme activity. Most studies examining the relation between bladder cancer and GSTM1 have reported an increased risk associated with a lack of GSTM1 activity. The authors performed meta- and pooled analyses of published and unpublished, case-control, genotype-based studies that examined this association (17 studies, 2,149 cases, 3,646 controls) and excluded studies conducted in populations with a high prevalence of exposure to known bladder cancer risk factors other than tobacco smoke. Using random effects models in the meta-analysis, the authors obtained a summary odds ratio of 1.44 (95% confidence interval (CI): 1.23, 1.68) for GSTM1 null status with all studies included. Results from studies with at least 100 cases and 100 controls produced a summary odds ratio of 1.42 (95% CI: 1.26, 1.60). Pooled analyses using original data sets from 10 studies (1,496 cases and 1,444 controls) and adjusting for age, sex, and race produced similar results. There was no evidence of multiplicative interaction between the GSTM1 null genotype and ever smoking in relation to bladder cancer, although there was a suggestion of additive interaction (additive interaction = 0.45, 95% CI: -0.03, 0.93). These results indicate that, among populations studied to date, GSTM1 null status is associated with a modest increase in the risk of bladder cancer.

Exposure to genotoxic compounds in ambient air has been studied in Bangkok, Thailand, by analysis of polycyclic aromatic hydrocarbons (PAHs) associated with particles and using different biomarkers of exposure. Eighty-nine male, non-smoking Royal Thai police officers were investigated. The police officers were divided into a high exposure group (traffic police) and low exposure (office duty). Particulate matter was collected using personal pumps (2 l/min) and the eight carcinogenic PAHs were analysed by standard procedures. The traffic police was exposed to a 20-fold higher level of total PAHs than office police (74.25 ng/m3 vs. 3.11; P= 0.001). A two-fold variation was observed between the different police stations. The major PAHs in all groups was benzo[g,h,l]pyrelene. Large inter-individual differences in biomarker levels were observed, but the level of all markers was statistically significantly higher in the traffic police group than in the office group. The level of 1-hydroxypyrene (1-HOP) was 0.181+/-0.078 (range 0.071-0.393) micromol/mol creatinine in the traffic group and 0.173+/-0.151 (P = 0.044) in the office group. The bulky carcinogen DNA-adduct level, determined by P32-post-labelling, was 1.6+/-0.9 (range 0.4-4.3) adducts/10(8) nucleotides in the traffic group and 1.2+/-1.0 (0.2-4.9) in the office group (P = 0.029; Mann-Whitney U-test). The serum PAH-albumin adduct level was 1.76 (0.51-3.07) fmol adducts/microg albumin in the traffic group and 1.35+/-0.77 (0.11-3.45; P = 0.001) in the office group. Lower biomarker levels were observed during the period when the traffic police officers were wearing a simple facemask, indicating that these masks protect against particle-associated PAHs. No statistically significant correlations were observed between biomarker levels and the level of individual PAHs or total PAH. Our data show, that people in Bangkok, who spend most of the day outside air-conditioned offices, are exposed to high levels of genotoxic PAHs. However, for people who spend their working day in offices, the exposure is similar to people living in other metropolitan areas.