Short- and Long-Term Stability of Aromatic Amines in Human Urine.

Several aromatic amines (AAs) are established by the International Agency for Research on Cancer as carcinogenic (group 1) or probable/possible carcinogens to humans (group 2A/2B). AAs can be found in mainstream and sidestream smoke from combustible tobacco products, as well as in certain environmental pollution and occupational exposure from several chemical industry sectors. Exposure to AAs can be estimated by measuring their concentrations in urine; however, information about the short-term and long-term stabilities of AAs in urine need to be characterized before conducting large-scale population studies on AA exposure and the potentially harmful effects of AA exposure. In this report, the storage stability of o-toluidine, 2,6-dimethylaniline, o-anisidine, 1-aminonaphthalene, 2-aminonaphthalene, and 4-aminobiphenyl fortified in pooled, filtered, non-smokers' urine is analyzed by isotope dilution gas chromatography-triple quadrupole mass spectrometry (ID GC-MS/MS). The six AAs were measured in urine samples stored at ~20 °C (collection temperature), 4 °C and 10 °C (short-term transit temperatures), and -20 °C and -70 °C (long-term storage temperatures) over a 10-day period. All six analytes were stable for 10 days at transit and long-term storage temperatures but showed reduced recovery at 20 °C. The instability of the target AAs at 20 °C suggests that immediate storage of freshly voided urine at low temperatures is needed to attenuate degradation. A subset of the urine samples was analyzed following a longer storage duration at -70 °C: all AAs were stable for up to 14 months at this temperature. The stability of the six AAs in urine samples can be maintained at the various temperature levels and storage times expected in a typical study set.

A New Automated Method for the Analysis of Aromatic Amines in Human Urine by GC-MS/MS.

Cigarette smoking significantly increases the risk of cancer and cardiovascular diseases as well as premature death. Aromatic amines (AAs) such as o-toluidine, 2-aminonaphthalene and 4-aminobiphenyl are found in cigarette smoke and are well-established human bladder carcinogens presumably acting via the formation of DNA adducts. These amines may be metabolized in the liver to acetylated or glucuronidated forms or oxidized to a hydroxylamine which may react with protein and DNA to form adducts. Free, acetylated and glucuronidated AAs are excreted in urine and can be measured as exposure biomarkers. Using isotope dilution GC-MS/MS, our laboratory quantifies six urinary AAs that are known or suspected carcinogens-o-toluidine, 2,6-dimethylaniline, o-anisidine, 1-aminonaphthalene, 2-aminonaphthalene and 4-aminobiphenyl-for large population studies such as the National Health and Nutrition Examination Survey (NHANES). We also monitor two additional corresponding structural isomers-2-aminobiphenyl and 3-aminobiphenyl-to verify isomer separation. A new and improved automated sample preparation method was developed to quantify these AAs, in which, sample cleanup was done via Supported Liquid Extraction (SLE+ ISOLUTE®) on a Hamilton STAR™ workstation. This automated method increased sample throughput by reducing sample cleanup time from 8 to 4 h while maintaining precision (intra and inter-run coefficient of variation <7%) and accuracy (±17%). Recent improvements in our GC/MS method have enhanced our assay sensitivity and specificity, resulting in longer analytical column life and maintaining or reducing the limit of detection for all six analytes. Indigo ASCENTTM software (3.7.1, Indigo BioAutomation, Inc.) is used for peak integration, calibration and quantification. A streamlined sample data flow was created in parallel with the automated method, in which samples can be tracked from receiving to final laboratory information management system output with minimal human intervention, minimizing potential human error. This newly validated, automated method and sample data flow are currently applied in biomonitoring of AAs in the US noninstitutionalized population NHANES 2013-2014 cycle.

Long-Term Stability of Volatile Nitrosamines in Human Urine.

Volatile nitrosamines (VNAs) are established teratogens and carcinogens in animals and classified as probable (group 2A) and possible (group 2B) carcinogens in humans by the IARC. High levels of VNAs have been detected in tobacco products and in both mainstream and sidestream smoke. VNA exposure may lead to lipid peroxidation and oxidative stress (e.g., inflammation), chronic diseases (e.g., diabetes) and neurodegenerative diseases (e.g., Alzheimer's disease). To conduct epidemiological studies on the effects of VNA exposure, short-term and long-term stabilities of VNAs in the urine matrix are needed. In this report, the stability of six VNAs (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosopyrrolidine and N-nitrosomorpholine) in human urine is analyzed for the first time using in vitro blank urine pools fortified with a standard mixture of all six VNAs. Over a 24-day period, analytes were monitored in samples stored at ∼20°C (collection temperature), 4-10°C (transit temperature) and -20 and -70°C (long-term storage temperatures). All six analytes were stable for 24 days at all temperatures (n = 15). The analytes were then analyzed over a longer time period at -70°C; all analytes were stable for up to 1 year (n = 62). A subset of 44 samples was prepared as a single batch and stored at -20°C, the temperature at which prepared samples are stored. These prepared samples were run in duplicate weekly over 10 weeks, and all six analytes were stable over the entire period (n = 22).

A New Automated Method and Sample Data Flow for Analysis of Volatile Nitrosamines in Human Urine.

Volatile nitrosamines (VNAs) are a group of compounds classified as probable (group 2A) and possible (group 2B) carcinogens in humans. Along with certain foods and contaminated drinking water, VNAs are detected at high levels in tobacco products and in both mainstream and sidestream smoke. Our laboratory monitors six urinary VNAs-N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPIP), N-nitrosopyrrolidine (NPYR), and N-nitrosomorpholine (NMOR)-using isotope dilution GC-MS/MS (QQQ) for large population studies such as the National Health and Nutrition Examination Survey (NHANES). In this paper, we report for the first time a new automated sample preparation method to more efficiently quantitate these VNAs. Automation is done using Hamilton STAR™ and Caliper Staccato™ workstations. This new automated method reduces sample preparation time from 4 hours to 2.5 hours while maintaining precision (inter-run CV < 10%) and accuracy (85% - 111%). More importantly this method increases sample throughput while maintaining a low limit of detection (<10 pg/mL) for all analytes. A streamlined sample data flow was created in parallel to the automated method, in which samples can be tracked from receiving to final LIMs output with minimal human intervention, further minimizing human error in the sample preparation process. This new automated method and the sample data flow are currently applied in bio-monitoring of VNAs in the US non-institutionalized population NHANES 2013-2014 cycle.

Quantitation of urinary volatile nitrosamines from exposure to tobacco smoke.

A sensitive and selective method was developed and validated to detect six volatile nitrosamines (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosopyrrolidine and N-nitrosomorpholine) in human urine. This method uses a liquid-liquid extraction cartridge followed by analysis with gas chromatography-tandem mass spectrometry (GC-MS-MS) and quantification based on isotopic dilution. This is the first GC-MS-MS method reported for measuring volatile nitrosamines in human urine. This method reduces the sample volume required in other methods from 5-25 to 2 mL. The limits of detection (2.62, 1.99, 2.73, 0.65, 0.25, 3.66 pg/mL, respectively) were better than existing methods, largely because of improved positive chemical ionization achieved by using ammonia gas and reducing background noise. Using nitrogen as the collision gas allowed the confirmation transition in the low mass region to be monitored. The analysis of human urine using this validated method is accurate (relative bias of 0-19%) and precise (relative standard deviation of 0.2-18% over two months of analyses). The validated method was applied to 100 urine samples and the levels of all six volatile nitrosamines were reported for the first time in urine specimens collected from smokers and nonsmokers, with smoking status determined by urinary cotinine measurement. Among 100 smokers and nonsmokers, the levels of three analytes (N-nitrosodimethylamine, N-nitrosomethylethylamine and N-nitrosopiperidine) were significantly higher in smokers than nonsmokers (p < 0.05).

Analysis of 4-aminobiphenyl in smoker's and nonsmoker's urine by tandem mass spectrometry.

The aromatic amine 4-aminobiphenyl (4-ABP) is present in tobacco smoke. In humans, it is also a known bladder carcinogen. We describe here a method for the quantification of total 4-ABP in urine using capillary gas chromatography/tandem mass spectrometry, with an effective detection limit in urine samples of approximately 0.87 pg/mL. We also examined the efficiency of chemical or enzymatic hydrolysis of urinary aromatic amine metabolites. Although we found acidic or basic hydrolysis effective, we found enzymatic hydrolysis (ß-glucuronidase with either Escherichia coli or Helix pomatia) ineffective. As part of this work, we also confirm the presence of N-acetyl-4-ABP and 4-ABP glucuronide in human urine samples from smokers. These metabolites have been reported in animal studies, but previously they have not been identified in human samples. These metabolites, however, were found to be unstable and thus infeasible for biomonitoring. The final validated urinary total 4-ABP assay was applied to the analysis of samples from smokers and nonsmokers, whose status was confirmed from cotinine EIA measurements. Among 41 confirmed nonsmokers, the geometric mean (95% CI) of 4-ABP concentration was 1.64 pg/mg creatinine (1.30-2.07). Conversely, in 89 smokers, the geometric mean of 4-ABP concentration was significantly greater, at 8.69 pg/mg creatinine (7.43-10.16), p < 0.001. Our results indicate that following tobacco smoke exposure, total urinary 4-ABP is a reliable biomarker for exposure to this carcinogen.

Analysis of 4-aminobiphenyl hemoglobin adducts in smokers and nonsmokers by pseudo capillary on-column gas chromatography- tandem mass spectrometry.

We describe here a hemoglobin adduct assay applied to an analysis of samples from smokers and nonsmokers. The assay includes a sensitive method for quantification of orthotoluidine 2-aminonaphthylene, and 3- and 4-aminobiphenyl hemoglobin adducts in human blood using capillary gas chromatography-tandem mass spectrometry. Basic hydrolysis and derivatization with pentafluoropropionic acid anhydride are followed by programmable temperature vaporization and pseudo on-column capillary gas chromatography with positive electron ionization tandem mass spectrometry analysis. Standard deviation of calibration curves (n = 6) shows that the limits of detection for o-toluidine, 2-aminonaphthylene, and 3- and 4-aminobiphenyl were 0.23, 0.39, 0.30, and 0.24 pg total on-column, respectively. The effective working limit of detection is estimated at approximately 5.22 pg/g Hb and 18.73 pg/g Hb for 4-aminobiphenyl and 2-aminonaphthylene, respectively. In a group that was predominately male and African-American, the level of 4-aminobiphenyl Hb adducts was significantly different between smokers and nonsmokers. Among 93 nonsmokers with serum cotinine concentrations less than 10 ng/mL, the geometric mean (95% CI) concentration of 4-aminobiphenyl was 29.9 pg/g hemoglobin (Hb; 29.4 to 30.4). Conversely, in 100 smokers the 4-aminobiphenyl adducts geometric mean concentration was significantly greater at 73.0 pg/g Hb (72.6 to 73.4). 4-Aminobiphenyl hemoglobin adduct and serum cotinine concentrations were correlated (r = 0.496; p < 0.0001; n = 193). In 15% of smokers, 3-aminobiphenyl was detected at low concentration. Adduct levels of 2-aminonaphthylene and ortho-toluidine were not significantly different between the smoker and nonsmoker participants. Our study shows that 4-aminobiphenyl Hb adducts remain the preferred biomarker for identifying people exposed to aromatic amines from tobacco smoke.

Increases in tobacco exposure biomarkers measured in non-smokers exposed to sidestream cigarette smoke under controlled conditions.

National surveys of the exposure of non-smokers to secondhand smoke based on serum cotinine analyses have consistently identified certain groups within the population including children, males and non-Hispanic Blacks as having relatively greater exposure. Although these differences in mean serum cotinine concentrations probably represent differences in exposure of individuals in their daily lives, it is also possible that metabolic or other differences in response might influence the results. To better define the nature of those findings, we have examined the response of 40 non-smokers including both men and women and African-Americans and whites to sidestream (SS) cigarette smoke generated by a smoking machine under controlled conditions. In this study, participants were exposed to aged, diluted SS smoke (ADSS) generated in an environmental chamber with a mean air nicotine concentration of 140 microg m(-3) and 8.6 ppm CO for 4 h. Salivary cotinine was measured every 30 min, and serum cotinine samples were taken prior to, and 2 h after exposure. Urinary nicotine metabolites and NNAL, a tobacco-specific nitrosamine, and 4-aminobiphenyl (4-AB) haemoglobin adducts were also measured prior to and 2 h following the exposure. Under these uniform, controlled conditions, we found a similar response to ADSS smoke exposure among all the participants. In all cases a significant increase in biomarker concentration was noted following exposure, and the short-term increases in salivary cotinine concentration were quite similar at approximately 12 pg ml(-1) min(-1) among the groups. In this small study, no significant differences by gender or race were seen in the mean increases observed in cotinine, NNAL or 4-AB adducts following 4 h of exposure. Thus, our results are most consistent with a relatively uniform response in tobacco biomarker concentrations following short-term exposure to ADSS tobacco smoke, and suggest that biomarker measurements are capable of effectively indicating increases in exposure among groups of non-smokers.