Quantitation of urinary volatile nitrosamines from exposure to tobacco smoke

Association of N-nitrosodimethylamine exposure with cognitive impairment based on the clues of mice and humans

N-nitrosodimethylamine (NDMA) is an environmental and food contaminant, but limited data to concern whether NDMA has adverse effects on the brain. This study first determined the concentration of NDMA in foods from aquaculture markets in Shenzhen, then analyzed the effects on C57BL/6 mice and further evaluated on the urine samples of elderly Chinese residents with normal cognition (NC, n = 144), cognitive decline (CD, n = 116) and mild cognitive impairment (MCI, n = 123). The excessive rate of NDMA in foods was 3.32% (27/813), with a exceeding range of 4.78-131.00 μg/kg. Behavioral tests showed that 60 days treatment of mice with 3 mg/kg NDMA reduced cognitive performance. Cognitive impairment in human was significantly associated with sex, educational levels, length of residence in Shenzhen, household registration, passive smoking, rice, fresh vegetables, bacon products. NDMA was detected in 55.4% (212/383) of urine samples, with a median concentration of 0.23 μg/L (1.20 × 10 ^-7-157.39 μg/L). The median concentration for NC, CD and MCI were 0.32, 0.27, and 0 μg/L, respectively. The urinary NDMA concentration had a strong negative correlation with cognitive impairment (Kendall's Tau-b = -0.89, P = 0.024). The median estimated daily intake (EDI) of NDMA was determined to be 6.63 ng/kg-bw/day. Taken together, there appears to be an association between NDMA and human and murine cognition, which provides a new clue to Alzheimer's disease (AD).

Electrodialysis Metathesis (EDM) Desalination for the Effective Removal of Chloride and Nitrate from Tobacco Extract: The Effect of Membrane Type

Electrodialysis Metathesis (EDM) desalination was investigated using a squad of three ion-exchange membranes (ACS, TW-A, and A3) and simulated tobacco extract liquid for selective ions removal. We have studied various factors affecting EDM desalination efficiency using a complete experimental design. First, diffusion dialysis (DD) was conducted to determine the permeation rate of different anions in tobacco liquor with different membrane materials. We conclude that A3 had the fastest permeation rate of anions. However, ACS has the lowest permeation rate for different salts. The investigation of the EDM process showed the excellent ion permeation ability of A3 by detecting the current, conductivity, and ion concentration of the target tobacco liquor in the metathesis chamber of the EDM process. The EDM had shown the most excellent chloride ion removal ability. We found that A3 was the best membrane for the EDM process of tobacco liquor.

Research progress of N-nitrosamine detection methods: a review

N-Nitrosamines (nitrosamines) are attracting increased attention because of their high toxicity and wide distribution. They have been strictly restricted by regulations in many fields. Researchers around the world have conducted substantial work on nitrosamine detection. This paper reviews the progress of research on nitrosamine detection methods with emphasis on biological-matrix samples. After introducing the category, toxicity, regulatory limit and source of nitrosamines, the paper discusses the most commonly used sample-preparation techniques and instrumental-detection techniques for nitrosamine detection, including some typical application cases.

A Comprehensive Analysis of Inorganic Ions and Their Selective Removal from the Reconstituted Tobacco Extract Using Electrodialysis

Many tobacco stalks, dust, and fines are discharged in the tobacco industry, rich in inorganic minerals ions and nicotine salts. The high salinity and nicotine salts are challenging to be addressed by traditional treatment and are a severe threat that ought to be overcome. Thus, proper techniques can regenerate the tobacco stalks into reconstituted tobacco flakes used as cigarette filler. The electrodialysis process has been a viable approach to removing the inorganic ingredients in wastewater. We studied concentration, pH, and co-related influences with the nicotine and sugar/nicotine contents on the desalination performance. The results show that the inorganic ions such as Cl^-, K⁺, Ca²⁺, and Mg²⁺ ions were successfully removed. When the feed concentration ranges from 3 to 15%, the removal ratio of the K⁺ ions is higher than Ca²⁺ and Mg²⁺ ions. As we reported previously, the K⁺ and Ca²⁺ ions are unfavorable for the total particulate matter emission but beneficial to decreasing the HCN delivery in mainstream cigarette smoke. Selective ED is a robust technology to reduce the harmful component delivery in cigarette smoke.

LNT and cancer risk assessment: Its flawed foundations part 1: Radiation and leukemia: Where LNT began

This paper evaluates the scientific basis for the adoption of the linear non-threshold (LNT) dose response model for radiation-induced leukemia. This LNT risk assessment application for leukemia is significant because it: (1) was generalized for all tumor types induced by ionizing radiation and chemical carcinogens at relatively high doses and; (2) it was based on the mechanistic assumption of low dose linearity for somatic cell mutations as determined from responses in mature spermatozoa of fruit flies. A serious problem with the latter assumption is that those spermatozoa lack DNA repair. The acceptance of the LNT dose response model for cancer risk assessment was based on the convergence of recommendations of the BEAR I Genetics Panel (1956a) for reproductive cell gene mutations and those of Lewis (1957a) for somatic cell mutation and its capacity to explain apparent and/or predicted linear dose responses of ionizing radiation-induced leukemia in multiple and diverse epidemiological investigations. Use of that model and related dose response beliefs achieved rapid, widespread and enduring acceptance in the scientific and regulatory communities. They provide the key historical foundation for the sustained LNT-based policy for cancer risk assessment to the present. While previous papers in this series have challenged key scientific assessments and ethical foundations of the BEAR I Genetics Panel, the present paper provides evidence that Lewis: 1) incorrectly interpreted the fundamental scientific studies used to support the LNT conclusion even though such studies show consistent hormetic-J-shaped dose response relationships for leukemia in Hiroshima and Nagasaki survivors; and, 2) demonstrated widespread bias in support of an LNT conclusion and related policies, which kept him from making an objective and fair assessment. The LNT recommendation appears to have been uncritically accepted and integrated into scientific and regulatory practice in large part because it inappropriately appealed to existing authority and it garnered the support of those who were willing to risk greatly exaggerating the public's fears of environmentally-induced disease, such as enhanced risk of leukemia, with the goal of stopping the atmospheric testing of atomic bombs. Adoption of the LNT recommendation demonstrated extensive penetration of ideological influence affecting governmental, scientific and regulatory evaluation at the highest levels in the United States. This paper demonstrates that the scientific foundations for cancer risk assessment were inappropriately and inaccurately assessed, unethically adopted and require significant historical, scientific and regulatory remediation.

Development of a Sensitive Headspace Gas Chromatography-Mass Spectrometry Method for the Simultaneous Determination of Nitrosamines in Losartan Active Pharmaceutical Ingredients

Nitrosamine impurities in angiotensin II receptor antagonists (sartans) containing a tetrazole group represent an urgent concern for active pharmaceutical ingredient (API) manufacturers and global regulators. Regarding safety, API manufacturers must develop methods to monitor the levels of each nitrosamine impurity before individual batch release. In this study, we developed and validated a sensitive, selective, and high-throughput method based on headspace gas chromatography-mass spectrometry (HS-GC-MS) for the simultaneous determination of four nitrosamines in losartan potassium API with simple sample preparation. N-Nitrosodimethylamine (NDMA, m/z 74), N-nitrosodiethylamine (NDEA, m/z 102), N-nitrosoethylisopropylamine (EIPNA, m/z 116), and N-nitrosodiisopropylamine (DIPNA, m/z 130) levels were quantified using an electron impact, single quadrupole mass spectrometer under a selected-ion-monitoring acquisition method. The method was validated according to the Q2(R1) ICH guidelines. The calibration curves of the assay ranged from 25 to 5000 ng/mL with limits of quantitation of 25 ppb for NDMA and NDEA and 50 ppb for DIPNA and EIPNA. The accuracy of the developed method ranged from -7.04% to 7.25%, and the precision %CV was ≤11.5. Other validation parameters, including specificity, stability, carryover, and robustness, met the validation criteria. In conclusion, the developed method was successfully applied for the determination of nitrosamines in losartan potassium APIs.

Urinary exposure of N-nitrosamines and associated risk of esophageal cancer in a high incidence area in China

Esophageal cancer (EC) is a deadly malignancy worldwide with a high incidence and exhibits unevenly geographic prevalence, which suggests that environmental factors are deeply involved in the development of EC. Although the carcinogenesis of nitrosamines in the esophagus has been identified by tremendous toxicological data, the role of nitrosamines in the genesis of human EC has so far proved inconclusive largely due to a lack of convincing evidences. In this study, urinary nitrosamines in population controls and cases with esophageal precancerous lesions, including reflux esophagitis (RE) accompanying with basal cell hyperplasia (BCH) and dysplasia (DYS), and esophageal squamous cell carcinoma (ESCC) were detected by a SPE-LC-MS/MS method and the associated risk was evaluated. Higher excretion concentrations of N-nitrosomethylethylamine (NMEA) in the RE/BCH patients, NMEA and N-nitrosodibutylamine (NDBA) in the DYS patients, and NMEA, NDBA, N-nitrosopyrrolidine (NPyr) and N-nitrosomorpholine (NMor) in the ESCC patients were observed compared with the controls (p < .05). And with the progression of esophageal lesion, the exposure complexity increased in terms of the categories of nitrosamines. Furthermore, the observed positive associations between the hazardous exposure of NMEA, NDBA and NPyr and the increased risk of ESCC, and between NMEA and NDBA and RE/BCH were established. These findings provided direct evidence to support the hypothesis that exposure to nitrosamines are involved in the carcinogenesis of esophageal epithelia in this high incidence area from the perspective of endogenous exposure assessment. However, discoveries in this study need to be confirmed by systematic researches in the future. And the dose-response relationships, the reference ranges or cutoff values to predict the risks of nitrosamines exposure also need to be defined.

Electrodialytic Desalination of Tobacco Sheet Extract: Membrane Fouling Mechanism and Mitigation Strategies

In the papermaking industry (reconstituted tobacco), a large number of tobacco stems, dust, and fines are discharged in the wastewater. This high salinity wastewater rich in ionic constituents and nicotine is difficult to be degraded by conventional biological treatment and is a serious threat that needs to be overcome. Electrodialysis (ED) has proved a feasible technique to remove the inorganic components in the papermaking wastewater. However, the fouling in ion exchange membranes causes deterioration of membranes, which causes a decrease in the flux and an increase in the electrical resistance of the membranes. In this study, the fouling potential of the membranes was analyzed by comparing the properties of the pristine and fouled ion exchange membranes. The physical and chemical properties of the ion exchange membranes were investigated in terms of electrical resistance, water content, and ion exchange capacity, as well as studied by infrared spectroscopy (IR) spectra, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses. The results indicated that the membrane fouling is caused by two different mechanisms. For the anion exchange membranes, the fouling is mainly caused by the charged organic anions. For the cation exchange membrane, the fouling is caused by minerals such as Ca²⁺ and Mg²⁺. These metal ions reacted with OH⁻ ions generated by water dissociation and precipitated on the membrane surface. The chemical cleaning with alkaline and acid could mitigate the fouling potential of the ion exchange membranes.

An Optimization of Liquid-Liquid Extraction of Urinary Volatile and Semi-Volatile Compounds and Its Application for Gas Chromatography-Mass Spectrometry and Proton Nuclear Magnetic Resonance Spectroscopy

Urinary volatile compounds (VCs) have been recently assessed for disease diagnoses. They belong to very diverse chemical classes, and they are characterized by different volatilities, polarities and concentrations, complicating their analysis via a single analytical procedure. There remains a need for better, lower-cost methods for VC biomarker discovery. Thus, there is a strong need for alternative methods, enabling the detection of a broader range of VCs. Therefore, the main aim of this study was to optimize a simple and reliable liquid-liquid extraction (LLE) procedure for the analysis of VCs in urine using gas chromatography-mass spectrometry (GC-MS), in order to obtain the maximum number of responses. Extraction parameters such as pH, type of solvent and ionic strength were optimized. Moreover, the same extracts were analyzed using Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR), to evaluate the applicability of a single urine extraction for multiplatform purposes. After the evaluation of experimental conditions, an LLE protocol using 2 mL of urine in the presence of 2 mL of 1 M sulfuric acid and sodium sulphate extracted with dichloromethane was found to be optimal. The optimized method was validated with the external standards and was found to be precise and linear, and allowed for detection of >400 peaks in a single run present in at least 50% of six samples-considerably more than the number of peaks detected by solid-phase microextracton fiber pre-concentration-GC-MS (328 ± 6 vs. 234 ± 4). 1H-NMR spectroscopy of the polar and non-polar extracts extended the range to >40 more (mainly low volatility compounds) metabolites (non-destructively), the majority of which were different from GC-MS. The more peaks detectable, the greater the opportunity of assessing a fingerprint of several compounds to aid biomarker discovery. In summary, we have successfully demonstrated the potential of LLE as a cheap and simple alternative for the analysis of VCs in urine, and for the first time the applicability of a single urine solvent extraction procedure for detecting a wide range of analytes using both GC-MS and 1H-NMR analysis to enhance putative biomarker detection. The proposed method will simplify the transport between laboratories and storage of samples, as compared to intact urine samples.

Progress in the pretreatment and analysis of N-nitrosamines: an update since 2010

As highly toxic substances, N-nitrosamines (NAs) have been proved to cause carcinogenesis and mutagenesis in humans. Therefore, to carefully monitor safety and preserve human health, the development of rapid, accurate, and high-sensitivity determination methods of NAs is of substantial importance. This review provides a current-status comprehensive summary of the pretreatment and determination methods of NAs in various samples since 2010. Common pretreatment methods that have been used to extract and purify targets include solid-phase extraction, liquid-liquid extraction and various microextraction methods, such as solid-phase microextraction and liquid-phase microextraction, among others. Determination methods include liquid chromatography, gas chromatography, supercritical fluid chromatography and electrochemical methods, among others. In addition, we discuss and compare the advantages and disadvantages of various pretreatment and analytical methods and examine the prospects in this area.

Distribution of N-nitrosamines in drinking water and human urinary excretions in high incidence area of esophageal cancer in Huai'an, China

The Huai'an area in Jiangsu Province of East China is an endemic region of esophageal cancer (EC). The regional heterogeneity of EC suggests that the levels of potential carcinogens might vary throughout the environment. It has been suggested that the most likely carcinogens related to EC are a group known as the N-nitrosamines. In this study, we measured the concentrations of nine nitrosamines in drinking water and human urine in two areas in China, one with a high incidence of EC (Huai'an) and one with a low incidence (Nanjing). Among the nine target analytes, N-nitrosodi-n-propylamine (NDPA), N-nitrosodibutylamine (NDBA), N-nitrosopyrrolidine (NPyr), N-nitrosodiethylamine (NDEA) and N-nitrosomorpholine (NMor) occurred at higher concentrations in drinking water in the high incidence area. Inhabitants from the high incidence area also had urinary excretions with significantly higher concentrations of NDEA, NDBA, N-nitrosopiperidine (NPip) and N-nitrosodiphenylamine (NDPhA). These findings indicated that people in the high EC incidence area were exposed to higher levels of nitrosamines. However, the association between the incidence of EC and nitrosamines exposure will need to be evaluated in more detail.

Use of rodent data for cancer risk assessment of smokeless tobacco in the regulatory context

To support risk management decisions, information from different fields has been integrated in this presentation to provide a realistic quantitative cancer risk assessment of smokeless tobacco. Smoking among Swedish men is currently below 10%, while about 20% use a special smokeless tobacco (snus) as a substitute for cigarettes. Epidemiological data and molecular biomarkers demonstrate that rodent bioassays with tobacco specific nitrosamines (TSNA) overestimate cancer risk from snus by more than one order of magnitude. The underlying reasons are discussed. DNA damage constitutes a necessary, although not sufficient prerequisite for cancer initiation. Individuals who have not used tobacco exhibit DNA lesions identical with those induced by TSNA. No increase above this adduct background can be shown from snus, and extensive epidemiological studies in Sweden have failed to demonstrate elevated cancer risks even in long term users. A "bench mark" for acceptable risk of 1/10(6) derived from rodent data has been suggested when regulating snus. By relating similarly derived estimates for some food contaminants, the implementation even of a limit of 1/10(4) may be unrealistic. The management of smokeless tobacco products has rarely been based on a scientifically sound risk assessment, where attention is given to the outstandingly higher hazards associated with smoking.

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).

Elevated urinary levels of carcinogenic N-nitrosamines in patients with urinary tract infections measured by isotope dilution online SPE LC-MS/MS

N-nitrosamines (NAms) are well-documented for their carcinogenic potential. Human exposure to NAms may arise from the daily environment and endogenous formation via the reaction of secondary amines with nitrites or from bacteria infection. We describe the use of isotope dilution online solid-phase extraction (SPE) LC-MS/MS to quantify nine NAms in human urine. This method was validated and further applied to healthy subjects and patients with urinary tract infection (UTI). N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosopyrrolidine (NPYR) and N-nitrosomorpholine (NMOR) were analyzed with an APCI source, while N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPIP), N-nitrosodi-n-propylamine (NDPA), N-nitrosodibutylamine (NDBA) and N-nitrosodiphenylamine (NDPhA) were quantified with an ESI source, due to their effect on the sensitivity and chromatography. NDMA was the most abundant N-nitrosamine, while NDPhA was firstly identified in human. UTI patients had three to twelve-fold higher concentrations for NDMA, NPIP, NDEA, NMOR and NDBA in urine than healthy subjects, and the NAms were significantly decreased after antibiotics treatment. NDMA concentrations were also significantly correlated with the pH value, leukocyte esterase activity or nitrite in urines of UTI patients. Our findings by online SPE LC-MS/MS method evidenced that UTI patients experienced various NAms exposures, especially the potent carcinogen NDMA, which was likely induced by bacteria infection.

Determination of nine volatile N-nitrosamines in tobacco and smokeless tobacco products by dispersive solid-phase extraction with gas chromatography and tandem mass spectrometry

A method was developed for the determination of nine volatile N-nitrosamines in tobacco and smokeless tobacco products. The targets are N-nitrosodimethylamine, N-nitrosopyrrolidine, N-nitrosopiperidine, N-nitrosomorpholine, N-nitrosoethylmethylamine, N-nitrosodiethylamine, N-nitrosodipropylamine, N-nitrosobuylmethylmine, and N-nitrosodibutylamine. The samples were treated by dispersive solid-phase extraction using 1 g of primary secondary amine and 0.5 g of carbon and then analyzed by gas chromatography with tandem mass spectrometry with an electron impact ion source. The recoveries for the targets ranged from 84 to 118%, with <16% relative standard deviations at three spiking levels of 0.5, 1.25, and 2.5 ng/g. The limits of detection ranged from 0.03 to 0.15 ng/g. With the use of the proposed method, we detected the presence of six nitrosamines in the range of 0.4-30.7 ng/g. The study demonstrated that the method could be used as a rapid, convenient, and high-throughput method for N-nitrosamines analysis in tobacco matrix.

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.

Diethylnitrosamine (DEN)-induced carcinogenic liver injury in mice

The toxic properties of various nitrosamines in animals and humans are well established. The parenteral or oral administration of the smallest quantities of diethylnitrosamine (DEN) or dimethylnitrosamine (DMN) results in severe liver damage. Most prominent are intense neutrophilic infiltration, extensive centrilobular haemorrhagic necrosis, bile duct proliferation, fibrosis, and bridging necrosis that ends in hepatocarcinogenesis. Due to the robustness of the induced hepatic alterations, the application of DEN in rodents has become an attractive experimental model for studies aimed at understanding the pathogenetic alterations underlying the formation of liver cancer, which represents one of the most common malignancies in humans worldwide. However, several studies have shown that the hepatocarcinogenic effects of nitrosamines might vary with the genetic background of the animals, their sex, their age, and other factors that might impact the outcome of experimentation. We present general guidelines for working with DEN, and a detailed protocol that allows the establishment of highly reproducible liver cancer in mice. The outcome of liver injury after the application of DEN in mice, as estimated by the formation of cirrhosis and cancer, appears to be a suitable animal model for the analysis of some aspects and processes that promote the pathogenesis of hepatocellular carcinoma in humans.