Biomonitoring of human exposure to arylamines.

Extensive industrial use of arylamines started in the middle of the 19th century in the dye industry. Because of the high incidence of bladder cancer, arylamines belong to the first and most intensively studied occupational and environmental carcinogens. In workers, biomonitoring of exposure to arylamines including ortho-toluidine started in the first half of the 20th century. This review highlights the many gaps in our knowledge on the human carcinogen ortho-toluidine.

Nicotine causes genotoxic damage but is not metabolized during long-term exposure of human nasal miniorgan cultures.

Human nasal miniorgan cultures (MOC) are a useful tool in ecogenotoxicology. Repetitive exposure to nicotine showed reversible DNA damage, and stable CYP2A6 expression was demonstrated in nasal MOC in previous investigations. The aim of the present study was to evaluate the genotoxic effect of nicotine in nasal MOC after chronic nicotine exposure, and to monitor possible metabolism capacities. MOC were dissected from human nasal mucosa and cultured under standard cell culture conditions. MOC were exposed to nicotine for 3 weeks at concentrations of 1 µM and 1 mM. The concentrations were chosen based on nicotine plasma levels in heavy smokers, and possible concentrations used in topical application of nicotine nasal spray. DNA damage was assessed by the comet assay at days 7, 14 and 21. Concentrations of nicotine and cotinine were analyzed in cell culture medium by gas chromatography/mass spectrometry to determine a possible metabolism of nicotine by MOC. Distinct DNA damage in MOC could be demonstrated after 1 week of exposure to 1 µM and 1 mM nicotine. This effect decreased after 2 and 3 weeks with no statistically relevant DNA migration. No nicotine metabolism could be detected by changes in nicotine and cotinine concentrations in the supernatants. This is the first time genotoxic effects have been evaluated in nasal MOC after chronic nicotine exposure for up to 3 weeks. Genotoxic effects were present after 1 week of culture with a decrease over time. Down-regulation of nicotinic acetylcholine receptors, which are expressed in nasal mucosa, may be a possible explanation. The lack of nicotine metabolism in this model could be explained by the functional loss of CYP2A6 during chronic nicotine exposure. Further investigations are necessary to provide a more detailed description of the underlying mechanisms involved in DNA damage by nicotine.

Determination of caffeine, myosmine, and nicotine in chocolate by headspace solid-phase microextraction coupled with gas chromatography-tandem mass spectrometry.

The occurrence of the bioactive components caffeine (xanthine alkaloid), myosmine and nicotine (pyridine alkaloids) in different edibles and plants is well known, but the content of myosmine and nicotine is still ambiguous in milk/dark chocolate. Therefore, a sensitive method for determination of these components was established, a simple separation of the dissolved analytes from the matrix, followed by headspace solid-phase microextraction coupled with gas chromatography-tandem mass spectrometry (HS-SPME-GC-MS/MS). This is the first approach for simultaneous determination of caffeine, myosmine, and nicotine with a convenient SPME technique. Calibration curves were linear for the xanthine alkaloid (250 to 3000 mg/kg) and the pyridine alkaloids (0.000125 to 0.003000 mg/kg). Residuals of the calibration curves were lower than 15%, hence the limits of detection were set as the lowest points of the calibration curves. The limits of detection calculated from linearity data were for caffeine 216 mg/kg, for myosmine 0.000110 mg/kg, and for nicotine 0.000120 mg/kg. Thirty samples of 5 chocolate brands with varying cocoa contents (30% to 99%) were analyzed in triplicate. Caffeine and nicotine were detected in all samples of chocolate, whereas myosmine was not present in any sample. The caffeine content ranged from 420 to 2780 mg/kg (relative standard deviation 0.1 to 11.5%) and nicotine from 0.000230 to 0.001590 mg/kg (RSD 2.0 to 22.1%).

Analysis of nicotine-induced DNA damage in cells of the human respiratory tract.

Epithelium of the upper and lower airways is a common origin of tobacco-related cancer. The main tobacco alkaloid nicotine may be associated with tumor progression. The potential of nicotine in inducing DNA mutations as a step towards cancer initiation is still controversially discussed. Different subtypes of nicotinic acetylcholine receptors (nAChR) are expressed in human nasal mucosa and a human bronchial cell line representing respiratory mucosa as a possible target for receptor-mediated pathways. In the present study, both cell systems were investigated with respect to DNA damage induced by nicotine and its mechanisms. Specimens of human nasal mucosa were harvested during surgery of the nasal air passage. After enzymatic digestion over night, single cells were exposed to an increasing nicotine concentration between 0.001 mM and 4.0mM. In a second step co-incubation was performed using the antioxidant N-acetylcysteine (NAC) and the nAChR antagonist mecamylamine. DNA damage was assessed using the alkali version of the comet assay. Dose finding experiments for mecamylamine to evaluate the maximal inhibitory effect were performed in the human bronchial cell line BEAS-2B with an increasing mecamylamine concentration and a constant nicotine concentration. The influence of nicotine in the apoptotic pathway was evaluated in BEAS-2B cells with the TUNEL assay combined with flow cytometry. After 1h of nicotine exposure with 0.001, 0.01, 0.1, 1.0 and 4.0mM, significant DNA damage was determined at 1.0mM. Further co-incubation experiments with mecamylamine and NAC were performed using 1.0mM of nicotine. The strongest inhibitory effect was measured at 1.0mM mecamylamine and this concentration was used for co-incubation. Both, the antioxidant NAC at a concentration of 1.0mM, based on the literature, as well as the receptor antagonist were capable of complete inhibition of the nicotine-induced DNA migration in the comet assay. A nicotine-induced increase or decrease in apoptosis as assessed by the TUNEL assay in BEAS-2B could not be detected. These results support the hypothesis that oxidative stress is responsible for nicotine-induced DNA damage. Similar results exist for other antioxidants in different cell systems. The decrease in DNA damage after co-incubation with a nAChR antagonist indicates a receptor-dependent pathway of induction for oxidative stress. Further investigations concerning pathways of receptor-mediated DNA damage via nAChR, the role of reactive oxygen species and apoptosis in this cell system will elucidate underlying mechanisms.

DNA adducts of ortho-toluidine in human bladder.

BACKGROUND: 4-Aminobiphenyl (4-ABP) and o-toluidine are known human bladder carcinogens, but only 4-ABP-releasing DNA adducts are known. METHODS: Determination of 4-ABP and o-toluidine-releasing DNA adducts in epithelial and submucosal bladder tissues of sudden death victims (SDV: n=46), and bladder tumours (n=12) by gas chromatography/mass spectrometry. RESULTS: Above background, 4 and 11 of 12 tumour samples contained adducts of 4-ABP (0.057 ± 0.125 fmol/µg DNA) and o-toluidine (8.72 ± 4.49 fmol/µg DNA), respectively. Lower adduct levels were present in both epithelial and submucosal bladder tissues of SDV (4-ABP: 0.011 ± 0.022 and 0.019 ± 0.047 fmol/µg DNA; o-toluidine: 0.24 ± 0.63 and 0.27 ± 0.70 fmol/µg DNA). CONCLUSION: Detection of o-toluidine-releasing DNA adducts support the carcinogenicity of o-toluidine in the human bladder.

Nicotine and methyl methane sulfonate in mini organ cultures of human parotid gland tissue.

The aim was to demonstrate the applicability of using mini organ cultures (MOC) of the human parotid gland for indicating DNA damage by nicotine. Macroscopically healthy specimens of human parotid glands (1 mm3) were cultured for 7 d. Morphology was examined after HE and immunohistochemical staining of alpha-amylase. MOC were exposed to 2.0 mM nicotine or 100 microM methyl methane sulfonate (MMS) for 1, 2 and 3 h, followed by a regeneration period of 24 h. DNA damage was assessed by the comet assay. Histological findings demonstrated healthy acinar cells up to 8 days of culture and a strong expression pattern of alpha-amylase. Cells in the centre of mini organs showed a granular cytoplasm starting at day 3. 1-3 h nicotine exposure significantly increased DNA damage as determined by DNA in the tail (DT), with no significant differences with increasing exposure time and only a trend towards decreased values of DT after regeneration. MMS demonstrated a time-dependent increase in DNA damage and distinctly reduced DT values after regeneration. MOC may be used to study DNA damage and repair after repetitive exposure to xenobiotics. They provide additional information for in vitro studies of cells growing in an intact tissue structure.

Cartilage tissue engineering for auricular reconstruction: in vitro evaluation of potential genotoxic and cytotoxic effects of scaffold materials.

Tissue engineering of autologous cartilage transplants is suggested as a new approach in reconstruction of external auricular deformities. 1.6-Hexanediol (HD), 1.8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 6-hydroxyhexanoic acid (HHA) are matrices of the open-pored polyurethane three-dimensional scaffold. Since these bioresorbable materials may interact with the human organism, cytotoxic effects on human chondrocytes and lymphocytes and genotoxic effects on human lymphocytes were monitored. Staining with propidium iodide and fluorescence diacetate as well as the EZ4U proliferation assay served for the detection of cytotoxic effects of the materials on human chondrocytes. Trypan blue staining was used to monitor cytotoxicity on lymphocytes. Genotoxic effects on lymphocytes in terms of strand breaks, alkali labile sites and incomplete excision repair were determined by the alkaline single cell microgel electrophoresis (Comet) assay. Cytotoxic effects in chondrocytes and lymphocytes as well as genotoxic effects in lymphocytes were dose-dependent with threshold values of 5mg/mL HD, 0.5mg/mL DBU and 0.03 mg/mL HHA showing no effects. These data suggest that these matrices could be safely used for scaffolds made of polyurethane unless these compounds are not released at a rate giving higher concentrations at the site of implantation or in body fluids, respectively.

Inhibition of human aromatase by myosmine.

Myosmine, a minor tobacco alkaloid widely occurring in food products of plant and animal origin, inhibits the conversion of testosterone to estradiol by human aromatase (IC(50): 33+/-2 microM) sevenfold more potent than nicotine (IC(50): 223+/-10 microM) and may have implications for sexual hormone homoeostasis.

Cytotoxic and genotoxic effects of matrices for cartilage tissue engineering.

Customizing auricles with biodegradable polyurethane colonized with autologous chondrocytes as an approach for tissue engineering cartilage transplants has been suggested for the reconstruction of the external ear to repair auricular deformities. Dextrose, triethanolamine and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) are matrices of an open-pored polyurethane three-dimensional scaffold. After release from the polymer, these compounds can be absorbed into the human organism. Therefore, cytotoxic effects on human chondrocytes and lymphocytes and genotoxic effects on human lymphocytes were determined. Propidium iodide and fluoresceine diacetate staining as well as quantitative proliferations testing with EZ4U served to detect cytotoxic effects on chondrocytes. In lymphocytes cytotoxicity was checked by trypan blue staining and the alkaline single cell microgel electrophoresis (Comet) assay was used to study genotoxic effects. Dose-dependent cytotoxicity and genotoxicity of the matrices could be shown. Concentrations up to 4.25mg/ml for dextrose, 0.15 mg/ml for PEG-PPG-PEG and 0.9 mg/ml for triethanolamine did not show cytotoxic effects in chondrocytes or genotoxic effects in lymphocytes. These data suggest that dextrose, triethanolamine and PEG-PPG-PEG could be safely used if scaffolds made of open-pored polyurethane do not release these compounds at a rate giving higher concentrations at the site of implantation or in body fluids, respectively.

Biotransformation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in lung tissue from mouse, rat, hamster, and man.

Exposure to the tobacco-specific N-nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is considered to be an important etiological risk factor for lung cancer in tobacco users. The metabolism of NNK via carbonyl reduction to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), alpha-hydroxylation to form both DNA methylating and pyridyloxobutylating intermediates, and detoxification by pyridyl N-oxidation and glucuronide formation are well-characterized in laboratory animals but less so in man. The in vitro kinetics of 0.03-250 microM [5-(3)H]NNK metabolism were determined under identical experimental conditions using female A/J mouse, male Fischer 344 rat, female Syrian golden hamster, and human lung tissue explants in tissue culture. The concentration-dependent percentage contribution of the three major pathways of NNK metabolism (carbonyl reduction, alpha-hydroxylation, and N-oxidation) showed large interspecies variation. Quantitatively, in mouse, carbonyl reduction to NNAL increased steadily with an increasing substrate concentration (10-74% total NNK metabolism), while concurrent decreases occurred in end products of alpha-hydroxylation (60 to 18%) and N-oxidation (42 to 5%). In rat lung, there were no apparent concentration-dependent trends (NNAL, 42 +/- 4%; alpha-hydroxylation, 35 +/- 2%; and N-oxidation, 24 +/- 3%). In hamster lung, a clear concentration-dependent increase in the contribution of NNAL to total NNK metabolism (from 47 to 87%) was paralleled by a steady decline in end products of alpha-hydroxylation (31 to 11%) and N-oxidation (22 to 2%). Human lung metabolism showed no concentration-dependent tendencies (NNAL, 89 +/- 1%; alpha-hydroxylation, 8.8 +/- 1.1%; and N-oxidation, 2.1 +/- 0.3%). The major alpha-hydroxylation product in human lung was 4-hydroxy-1-(3-pyridyl)-1-butanone (keto alcohol), thus supporting the potential pyridyloxobutylation of lung DNA. Metabolism to 4-(3-pyridyl)-4-oxobutanoic acid (keto acid), which could result in lung DNA methylation, was only sporadically seen in human lung but present to a far greater extent in rodent lung. No evidence for glucuronidation was found in any species. Generally, the rate of formation of all NNK metabolites showed two different enzyme kinetics, resulting in large differences between apparent K(m) and V(max) values in the low (up to 2.8 microM) and high substrate concentration ranges. The metabolism of NNK by alpha-hydroxylation is considerably lower in human lung as compared to that observed in rodent species, suggesting that extrapolation of in vitro rodent data to man may result in invalid conclusions about the capacity of the human lung to activate NNK under realistic conditions of NNK exposure expected to occur in man.

Analysis of myosmine, cotinine and nicotine in human toenail, plasma and saliva.

Myosmine is a minor tobacco alkaloid with widespread occurrence in the human diet. Myosmine is genotoxic in human cells and is readily nitrosated and peroxidated yielding reactive intermediates with carcinogenic potential. For biomonitoring of short-term and long-term exposure, analytical methods were established for determination of myosmine together with nicotine and cotinine in plasma, saliva and toenail by gas chromatography-mass spectrometry (GC/MS). Validation of the method with samples of 14 smokers and 10 non-smokers showed smoking-dependent differences of myosmine in toenails (66 +/- 56 vs 21 +/- 15 ng g(-1), p <0.01) as well as saliva (2.54 +/- 2.68 vs 0.73 +/- 0.65 ng ml(-1), p <0.01). However, these differences were much smaller than those with nicotine (1971 +/- 818 vs 132 +/- 82 ng g(-1), p <0.0001) and cotinine (1237 +/- 818 vs <35 ng g(-1)) in toenail and those of cotinine (97.43 +/- 84.54 vs 1.85 +/- 4.50 ng ml(-1), p <0.0001) in saliva. These results were confirmed in plasma samples from 84 patients undergoing gastro-oesophageal endoscopy. Differences between 25 smokers and 59 non-smokers are again much lower for myosmine (0.30 +/- 0.35 vs 0.16 +/- 0.18 ng ml(-1), p <0.05) than for cotinine (54.67 +/- 29.63 vs 0.61 +/- 1.82 ng ml(-1), p <0.0001). In conclusion, sources other than tobacco contribute considerably to the human body burden of myosmine.

Ultrasensitive method for the determination of 4-hydroxy-1-(3-pyridyl)-1-butanone-releasing DNA adducts by gas chromatography-high resolution mass spectrometry in mucosal biopsies of the lower esophagus.

4-Hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing DNA adducts are formed by metabolic activation of the tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). NNK and NNN are considered carcinogenic to humans by the International Agency for Research on Cancer. Existing analytical methods for determination of HPB-releasing DNA adducts require 0.3-2.0 g of human target tissues such as lung and esophagus. For adduct determination in milligram amounts of biopsy samples, an ultrasensitive and specific method is presented using capillary gas chromatography coupled to a high-resolution mass spectrometer operated in the negative chemical ionization mode (GC-NCI-HRMS). The method has a limit of detection of 4.6 fmol HPB, a limit of quantification of 14.9 fmol HBP and a recovery of 45 +/- 15%. Intra- and inter-day imprecision for N = 6 samples were calculated with coefficients of variation of <3.1%. Method applicability was evaluated with biopsies of esophageal mucosa (N = 14) yielding 5.6 +/- 1.9 mg tissue and a mean adduct level of 6.13 +/- 9.35 pmol HPB/mg DNA.

Nicotine induces DNA damage in human salivary glands.

The tobacco alkaloid nicotine is responsible for addiction to tobacco and supposed to contribute to tobacco carcinogensis, too. Recently, genotoxic effects of nicotine have been reported in human cells from blood and upper aerodigestive tract. Because of nicotine accumulation in saliva, the study of possible in vitro genotoxic effects of nicotine have been extended to human salivary gland cells. Specimens of parotid glands of 10 tumor patients were obtained from tumor-free tissue. Single cells were prepared by enzymatic digestion immediately after surgery and exposed for 1h to 0.125-4.0mM of nicotine. Possible genotoxic effects were determined by the Comet assay using the % DNA in tail (DT) as a reliable indicator of DNA damage. Nicotine induced a significant dose-dependent increase of DNA migration in parotid gland single-cells. The mean DT was 1.12-fold (0.125mM) to 2.24-fold (4.0mM) higher compared to control. The lowest concentration eliciting significant DNA damage within 1h, 0.25mM nicotine, is only 10-fold higher than maximal concentrations of nicotine reported in saliva after unrestricted smoking. Although conclusive evidence for a carcinogenic potential of nicotine is still lacking, the safety of long-term nicotine replacement therapy should be carefully monitored.

4-Hydroxy-1-(3-pyridyl)-1-butanone-releasing DNA adducts in lung, lower esophagus and cardia of sudden death victims.

4-Hydroxy-l-(3-pyridyl)-l-butanone (HPB)-releasing adducts are formed by metabolic activation of N'-nitrosonornicotine and 4-(methylnitrosamino)-l-(3-pyridyl)-l-butanone and have been proposed as specific biomarkers for exposure to tobacco smoke. However, in several studies hemoglobin adducts releasing HPB were on average less than threefold higher in smokers compared to nonsmokers. Using an improved analytical method we have recently found a sevenfold difference in DNA adduct levels in the lung from smoking and nonsmoking lung cancer patients. In the present study we extended the determination of HPB-releasing DNA adducts by gas chromatography-negative ion chemical ionization-mass spectrometry (GC-NICI-MS) to samples of peripheral lung, lower esophagus and cardia from tumor-free sudden death victims (primarily road traffic accidents, suicide and sudden cardiac arrest). The donors were classified as either current smokers or nonsmokers based on cotinine in either blood or urine (cut-off values for active smoking: >15 ng cotinine/ml blood or >100 ng cotinine/ml urine). Contrary to our expectation, DNA adduct levels (fmol HPB/mg DNA) in lung tissue from tumor-free smokers (N=32, 92+/-148) were not significantly different from values in nonsmokers (N=56, 61+/-66). The values in tumor-free smokers were on average more than fourfold lower compared to smoking lung cancer patients in our previous study. Adduct levels in the mucosa of esophagus (N=82; 133+/-160) and cardia (N=30; 108+/-102) of sudden death victims did not show any difference according to the current smoking status. HPB-releasing DNA adduct levels in cardia and esophagus were significantly correlated (N=29; Spearman r=0.609; p<0.001). In contrast, adduct levels in lung did not correlate with either esophagus (77 cases) or cardia (28 cases). Further studies are necessary to elucidate the discrepancies in lung DNA adduct levels in smokers with or without lung cancer and to identify obvious additional sources other than tobacco for these adducts.

Mass spectrometric analysis of 4-hydroxy-1-(3-pyridyl)-1-butanone-releasing DNA adducts in human lung.

An improved analytical method was developed for the analysis of 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing DNA adducts in lung samples of patients undergoing surgery for lung cancer. HPB-releasing adducts can be formed by metabolic activation of the tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosonornicotine, and have been reported to play an important role in tobacco carcinogenesis. [2,2,3,3-D(4)]HPB (D(4)-HPB) was used as an internal standard, and HPB released by acid hydrolysis of DNA was determined by gas chromatography/mass spectrometry in the negative ion chemical ionisation mode. The method is sensitive with a limit of detection of 5.9 fmol HPB and a limit of quantification of 15.2 fmol HBP/mg DNA. The recovery of HPB was 82+/-17% and the background response was 10.1+/-1.8 fmol HPB/sample. The concentration of HPB-releasing lung DNA adducts was significantly higher (p<0.0001) in 21 self-reported smokers compared to in 11 self-reported nonsmokers (404+/-258 fmol versus 59+/-56 fmol HPB/mg DNA, respectively). HPB-releasing hemoglobin adduct concentrations were only marginally higher in a subset of 12 smokers compared to in 7 nonsmokers (63+/-53 fmol versus 42+/-34 fmol HPB/g hemoglobin; p=0.36). No correlation was found between HPB-releasing adducts in DNA and hemoglobin (p=0.074).

Tissue distribution and excretion of myosmine after i.v. administration to Long-Evans rats using quantitative whole-body autoradiography.

Occurrence of the tobacco alkaloid myosmine has been proven in various staple foods, vegetables and fruits. Myosmine can be easily activated by nitrosation yielding 4-hydroxy-1-(3-pyridyl)-butanone (HPB) and the esophageal carcinogen N'-nitrosonornicotine. Most of the reaction products after myosmine peroxidation were also identified as urinary metabolites after oral administration to rats. Whole-body autoradiography with freeze dried or multiple solvent extracted tissue sections was used to trace [2'-(14)C]myosmine (0.1 mCi/kg bw) 0.1, 0.25, 1, 4 and 24 h after i.v. injection in Long-Evans rats. In addition, in vitro binding of radioactivity to esophageal and eye tissue was determined and excretion of radioactivity via urine and feces was quantified. Radioactivity is rapidly eliminated by renal excretion. Approximately 30% of the administered radioactivity was recovered in urine within the first 4 h and excretion with urine (72%) and feces (15%) was nearly complete after 24 h. A rapid concentration of radioactivity can be seen in the stomach and in the salivary and lachrymal glands. Rats killed 1 and 4 h after treatment showed by far the highest labeling in the accessory genital gland. High levels of nonextractable radioactivity were present in esophageal tissue and melanin. The half lives for the disappearance of radioactivity from various tissues are in the order of about 1 h. Eye and esophagus sections both showed nonextractable labeling after in vitro incubation with (14)C-myosmine. In conclusion, the toxicological significance of myosmine accumulation in esophagus and accessory genital gland requires further investigations. Hair analysis might be applicable for myosmine biomonitoring, because of possible enrichment in melanin containing tissues.

Hemoglobin adducts of the human bladder carcinogen o-toluidine after treatment with the local anesthetic prilocaine.

Prilocaine, a widely used local anesthetic, is metabolized to o-toluidine which is classified as human carcinogen. We aimed to assess the impact of prilocaine-treatment on hemoglobin adducts from o-toluidine. Blood samples were obtained before and 24h after receiving prilocaine local anesthesia (Xylonest, 100mg) from 20 head and neck surgery patients and 6 healthy volunteers. Hemoglobin adducts of o-toluidine and 4-aminobiphenyl were determined by gas chromatography/mass spectrometry. Hemoglobin adducts of o-toluidine were significantly increased 24h after 100mg prilocaine-treatment by 21.6+/-12.8ng/g hemoglobin (mean+/-S.D., N=26; P<0.0001). This corresponds to a 6-360-fold increase of o-toluidine adduct levels in 25 patients from 0.54+/-0.95ng/g before treatment to 22.0+/-13.2ng/g 24h after surgery (mean+/-S.D.). Because of an extremely high background level the increase was only 1.6-fold in one patient (40.9ng/g before and 64.4ng/g 24h after prilocaine injection). Current smoking had no influence on background values and on the increase of o-toluidine adducts. No treatment-related differences were seen in mean hemoglobin adduct levels of 4-aminobiphenyl which were significantly higher in smokers, 0.149+/-0.096ng/g (mean+/-S.D., N=8) as compared to nonsmokers 0.036+/-0.035ng/g (mean+/-S.D., N=16; P<0.01). In conclusion, prilocaine anesthesia leads to a massive increase of hemoglobin adducts of the carcinogenic arylamine o-toluidine. This implies a carcinogenic risk which should be taken into account in preventive hazard minimization.