Formation Of N-nitroso Compounds Research Articles

Source-specific nitrate intake and all-cause mortality in the Danish Diet, Cancer, and Health Study.

Nitrate and nitrite are naturally occurring in both plant- and animal-sourced foods, are used as additives in the processing of meat, and are found in water. There is growing evidence that they exhibit a spectrum of health effects, depending on the dietary source. The aim of the study was to examine source-dependent associations between dietary intakes of nitrate/nitrite and both all-cause and cause-specific mortality. In 52,247 participants of the Danish Diet, Cancer and Health Study, associations between source-dependent nitrate and nitrite intakes--calculated using comprehensive food composition and national drinking water quality monitoring databases--and all-cause, cardiovascular disease (CVD)-related, and cancer-related mortality over 27 years were examined using restricted cubic splines within Cox proportional hazards models adjusting for demographic, lifestyle, and dietary confounders. Analyses were stratified by factors hypothesised to influence the formation of carcinogenic N-nitroso compounds (namely, smoking and dietary intakes of vitamin C, vitamin E, folate, and polyphenols). Plant-sourced nitrate intake was inversely associated with all-cause mortality [HRQ5vsQ1: 0.83 (0.80, 0.87)] while higher risks of all-cause mortality were seen for higher intakes of naturally occurring animal-sourced nitrate [1.09 (1.04, 1.14)], additive permitted meat-sourced nitrate [1.19 (1.14, 1.25)], and tap water-sourced nitrate [1.19 (1.14, 1.25)]. Similar source-dependent associations were seen for nitrite and for CVD-related and cancer-related mortality except that naturally occurring animal-sourced nitrate and tap water-sourced nitrate were not associated with cancer-related mortality and additive permitted meat-sourced nitrate was not associated with CVD-related mortality. No clear patterns emerged in stratified analyses. Nitrate/nitrite from plant sources are inversely associated while those from naturally occurring animal-sources, additive-permitted meat sources, and tap water-sources are positively associated with mortality.

Nitrate in drinking water and pregnancy outcomes: A narrative review of epidemiological evidence and proposed biological mechanisms

There is emerging evidence of an association between nitrate contamination in drinking water and adverse pregnancy outcomes. Few studies have discussed the evidence in the context of plausible biological mechanisms. We performed a narrative review of the current evidence investigating associations between nitrate in drinking water and the risk of adverse pregnancy outcomes with a focus on congenital anomalies (CA) and preterm birth (PTB). We also reviewed evidence and discuss several biological mechanisms that may explain the observed associations. We reviewed cohort and case-control epidemiological studies assessing associations between maternal nitrate exposure and adverse pregnancy outcomes published until January 2023. Three plausible mechanisms may explain how maternal exposure to nitrate may impact pregnancy outcomes, which include the formation of N-nitroso compounds (NOC), thyroid dysfunction and oxidative stress. For CA, seven studies were included (two cohort and five case-control studies). The strongest associations observed in epidemiological studies were for neural tube defects. Inconsistent positive and negative associations were observed for anomalies of the limb, eye, ear, face and neck. Of the four PTB studies (all cohort studies), three of the largest cohort studies observed associations between PTB with nitrate levels >5 mg/L while one small cohort study did not. Emerging epidemiological evidence has observed a potential increased risk of adverse pregnancy outcomes with elevated maternal nitrate exposure in drinking water. There are also plausible biological mechanisms to support this association. However, the current evidence lacks homogeneity and additional longitudinal evidence with robust exposure asssessments is required. Given the increasing concentrations of nitrate contamination in drinking water in many countries, and the adverse effects observed at concentrations below the current regulatory standard, a further precautionary approach should be adopted until futher evidence emerges.

Ingested nitrate and nitrite and end-stage renal disease in licensed pesticide applicators and spouses in the Agricultural Health Study.

Nitrate and nitrite ingestion has been linked to kidney cancer, possibly via the endogenous formation of carcinogenic N-nitroso compounds. These exposures might also contribute to end-stage renal disease (ESRD). We investigated associations of drinking water nitrate and dietary nitrate and nitrite intakes (total and by food type) with incident ESRD in the Agricultural Health Study. We also explored modifying effects of vitamin C and heme iron intake, which may affect endogenous nitrosation. We performed complete case analyses among private pesticide applicators and their spouses. We obtained water nitrate estimates for participants whose primary drinking water source at enrollment (1993-1997) was public water supplies (PWS) or private wells (N = 59,632). Average nitrate concentrations were computed from historical data for PWS users and predicted from random forest models for private well users. Analysis of dietary nitrate and nitrite was restricted to the 30,177 participants who completed the NCI Dietary History Questionnaire during follow-up (1999-2003). Incident ESRD through 2018 was ascertained through linkage with the U.S. Renal Data System. We estimated adjusted hazard ratios (HRs) and 95%CI for associations of tertiles (T) of exposure with ESRD overall and explored effects in strata of vitamin C and heme iron intake. We identified 469 incident ESRD cases (206 for dietary analysis). Water nitrate and total dietary nitrate/nitrite were not associated with ESRD, but increased ESRD was associated with nitrate and nitrite from processed meats. We found apparent associations between nitrite and ESRD only among participants with vitamin C <median (T3 vs. T1 HR: 2.26, 95%CI: 1.05, 4.86) and with heme iron ≥median (T3 vs. T1 HR: 1.73, 95%CI: 0.89, 3.39). ESRD incidence was associated with dietary nitrate/nitrite from processed meat among all study participants and with total dietary nitrite among participants with lower vitamin C or higher heme iron intake. There are few well-established environmental risk factors for end-stage renal disease (ESRD), a worldwide public health challenge. Ingestion of nitrate and nitrite, which may lead to endogenous formation of carcinogenic N-nitroso compounds, has been linked to some cancers and chronic diseases. We investigated these exposures in relation to ESRD in an agricultural cohort. ESRD incidence was associated with dietary nitrate/nitrite from processed meat and with total dietary nitrite among subgroups with lower vitamin C or higher heme iron intake. This study provides preliminary evidence that points to dietary nitrite and possibly dietary nitrate intake as a potential contributor to ESRD.

The influence of Helicobacter pylori, proton pump inhibitor, and obesity on the gastric microbiome in relation to gastric cancer development

Helicobacter pylori infection is still the main risk factor for the development of gastric cancer (GC). We explore the scientific evidence for the role of the gastric microbiome beyond Helicobacter pylori (H. pylori) in gastric carcinogenesis. The composition of the gastric microbiome in healthy individuals, in presence and absence of H. pylori infection, in proton pump inhibitor (PPI)-users, obese individuals, and GC patients was investigated. Possible mechanisms for microbial involvement, limitations of available research and options for future studies are provided.A common finding amongst studies was increased levels of Streptococcus, Prevotella, Neisseria, and Actinomyces in healthy individuals or those with H. pylori-negative gastritis. In PPI-users the risk for GC increases with the treatment duration, and the gastric microbiome shifts, with the most consistent increase in the genus Streptococcus. Similarly, in obese individuals, Streptococcus was the most abundant genus, with an increased risk for cardia GC. The genera Streptococcus, Lactobacillus and Prevotella were found to be more prominent in GC patients in multiple studies. Potential mechanisms of non-H. pylori microbiota contributing to GC are linked to lipopolysaccharide production, contribution to inflammatory pathways, and the formation of N-nitroso compounds and reactive oxygen species.In conclusion, the knowledge of the gastric microbiome in GC is mainly descriptive and based on sequencing of gastric mucosal samples. For a better mechanistic understanding of microbes in GC development, longitudinal cohorts including precancerous lesions, different regions in the stomach, and subtypes of GC, and gastric organoid models for diffuse and intestinal type GC should be employed.

Multi-DNA Adduct and Abasic Site Quantitation In Vivo by Nano-Liquid Chromatography/High-Resolution Orbitrap Tandem Mass Spectrometry: Methodology for Biomonitoring Colorectal DNA Damage.

Epidemiological and mechanistic studies suggest that processed and red meat consumption and tobacco smoking are associated with colorectal cancer (CRC) risk. Several classes of carcinogens, including N-nitroso compounds (NOCs) in processed meats and heterocyclic aromatic amines (HAAs) and polycyclic aromatic hydrocarbons (PAHs) in grilled meats and tobacco smoke, undergo metabolism to reactive intermediates that may form mutation-inducing DNA adducts in the colorectum. Heme iron in red meat may contribute to oxidative DNA damage and endogenous NOC formation. However, the chemicals involved in colorectal DNA damage and the paradigms of CRC etiology remain unproven. There is a critical need to establish physicochemical methods for identifying and quantitating DNA damage induced by genotoxicants in the human colorectum. We established robust nano-liquid chromatography/high-resolution accurate mass Orbitrap tandem mass spectrometry (LC/HRAMS2) methods to measure DNA adducts of nine meat and tobacco-associated carcinogens and lipid peroxidation products in the liver, colon, and rectum of carcinogen-treated rats employing fresh-frozen and formalin-fixed paraffin-embedded (FFPE) tissues. Some NOCs form O6-carboxymethyl-2'-deoxyguanosine, O6-methyl-2'-deoxyguanosine, and unstable quaternary N-linked purine/pyrimidine adducts, which generate apurinic/apyrimidinic (AP) sites. AP sites were quantitated following derivatization with O-(pyridin-3-yl-methyl)hydroxylamine. DNA adduct quantitation was conducted with stable isotope-labeled internal standards, and method performance was validated for accuracy and reproducibility. Limits of quantitation ranged from 0.1 to 1.1 adducts per 108 bases using 3 μg of DNA. Adduct formation in animals ranged from ∼1 in 108 to ∼1 in 105 bases, occurring at comparable levels in fresh-frozen and FFPE specimens for most adducts. AP sites increased by 25- to 75-fold in the colorectum and liver, respectively. Endogenous lipid peroxide-derived 3-(2-deoxy-β-d-erythro-pentofuranosyl)pyrimido[1,2-α]purin-10(3H)-one (M1dG) and 6-oxo-M1dG adduct levels were not increased by carcinogen dosing but increased in FFPE tissues. Human biomonitoring studies can implement LC/HRAMS2 assays for DNA adducts and AP sites outlined in this work to advance our understanding of CRC etiology.

Drinking Water Disinfection Byproducts, Ingested Nitrate, and Risk of Endometrial Cancer in Postmenopausal Women.

Background:Disinfection byproducts (DBPs) and N-nitroso compounds (NOC), formed endogenously after nitrate ingestion, are suspected endometrial carcinogens, but epidemiological studies are limited.Objectives:We investigated the relationship of these exposures with endometrial cancer risk in a large prospective cohort.Methods:Among postmenopausal women in the Iowa Women’s Health Study cohort, we evaluated two major classes of DBPs, total trihalomethanes (TTHM) and five haloacetic acids (HAA5), and nitrate-nitrogen () in public water supplies (PWS) in relation to incident primary endometrial cancer (1986–2014). For women using their PWS at enrollment (; ), we computed historical averages of annual concentrations; exposures were categorized into quantiles and when possible percentile. We also computed years of PWS use above one-half the U.S. maximum contaminant level (; TTHM; HAA5; ). Dietary nitrate/nitrite intakes were estimated from a food frequency questionnaire. We estimated hazard ratios (HR) and 95% confidence intervals (CI) via Cox models adjusted for age, endometrial cancer risk factors [e.g., body mass index, hormone replacement therapy (HRT)], and mutually adjusted for . We evaluated associations for low-grade () vs. high-grade () type I tumors. We assessed interactions between exposures and endometrial cancer risk factors and dietary factors influencing NOC formation.Results:Higher average concentrations of DBPs (95th percentile: TTHM , HAA5 ) were associated with endometrial cancer risk (TTHM: , 95% CI: 1.41, 3.40; HAA5: , 95% CI: 1.19, 2.83; ). Associations were similarly observed for women greater than median years of PWS use with levels , in comparison with zero years (TTHM: , 95% CI: 1.18, 2.21; HAA5: , 95% CI: 1.31, 2.62). Associations with DBPs appeared stronger for low-grade tumors (TTHM: , 95% CI: 1.17, 3.83; ) than for high-grade tumors (TTHM: , 95% CI: 0.80, 2.44; ), but differences were not statistically significant (). Associations with TTHM were stronger among ever HRT users than non-HRT users (). We observed no associations with in drinking water or diet.Discussion:We report novel associations between the highest DBP levels and endometrial cancer for our Iowa cohort that warrant future evaluation. https://doi.org/10.1289/EHP10207

Prenatal nitrosatable prescription drug intake, drinking water nitrate, and the risk of stillbirth: a register- and population-based cohort of Danish pregnancies, 1997\u20132017

BackgroundNitrosatable drugs commonly prescribed during pregnancy can react with nitrite to form N-nitroso compounds which have been associated with an increased risk of stillbirth. Whether maternal residential drinking water nitrate modifies this association is unknown. We investigated, if household drinking water nitrate was associated with stillbirth, and if it modified the association between nitrosatable prescription drug intake and the risk of stillbirth.MethodsWe conducted an individual-level register- and population-based cohort study using 652,810 women with the first recorded singleton pregnancy in the Danish Medical Birth Registry between 1997 and 2017. Nitrosatable drug exposure was recorded by use of the Danish National Patient Registry defined as women with a first redeemed prescription of a nitrosatable drug the first 22 weeks of pregnancy. The reference group was women with no redeemed prescription of a nitrosatable drug in this period. The average individual drinking water nitrate concentration level (mg/L) was calculated in the same period. We categorized nitrosatable drugs as secondary amines, tertiary amines, and amides. Cox hazard regression was used to estimate crude and adjusted hazard ratios with 95% confidence intervals for stillbirth stratified into five categories of nitrate concentrations: ≤1 mg/L, > 1- ≤ 2 mg/L, > 2- ≤ 5 mg/L, > 5- ≤ 25 mg/L, and > 25 mg/L.ResultsDrinking water nitrate exposure in the population was not associated with the risk of stillbirth. Among 100,244 women who had a nitrosatable prescription drug redeemed ≤22 weeks of pregnancy of pregnancy, 418 (0.42%) had a stillbirth compared to 1993 stillbirths (0.36%) among 552,566 referent women. Women with any nitrosatable prescription drug intake and > 1- ≤ 2 mg/L nitrate concentration had an increased risk of stillbirth [adjusted hazard ratio 1.55 (95% confidence interval, 1.15–2.09)] compared with referent women. In the stratified analyses, the highest risk of stillbirth was found among women with secondary amine intake and > 25 mg/L nitrate concentrations [adjusted hazard ratio 3.11 (95% CI, 1.08–8.94)].ConclusionsThe association between nitrosatable prescription drug intake and the risk of stillbirth may depend on the level of nitrate in household drinking water. Evaluations of the effect of nitrosatable drug intake on perinatal outcomes might consider nitrate exposure from drinking water.

Replacement of Nitrite in Meat Products by Natural Bioactive Compounds Results in Reduced Exposure to N-Nitroso Compounds: The PHYTOME Project.

ScopeIt has been proposed that endogenously form N‐nitroso compounds (NOCs) are partly responsible for the link between red meat consumption and colorectal cancer (CRC) risk. As nitrite has been indicated as critical factor in the formation of NOCs, the impact of replacing the additive sodium nitrite (E250) by botanical extracts in the PHYTOME project is evaluated.Method and ResultsA human dietary intervention study is conducted in which healthy subjects consume 300 g of meat for 2 weeks, in subsequent order: conventional processed red meat, white meat, and processed red meat with standard or reduced levels of nitrite and added phytochemicals. Consumption of red meat products enriched with phytochemicals leads to a significant reduction in the faecal excretion of NOCs, as compared to traditionally processed red meat products. Gene expression changes identify cell proliferation as main affects molecular mechanism. High nitrate levels in drinking water in combination with processed red meat intake further stimulates NOC formation, an effect that could be mitigated by replacement of E250 by natural plant extracts.ConclusionThese findings suggest that addition of natural extracts to conventionally processed red meat products may help to reduce CRC risk, which is mechanistically support by gene expression analyses.

Ingestion of Nitrate and Nitrite and Risk of Stomach and Other Digestive System Cancers in the Iowa Women's Health Study.

Nitrate and nitrite are precursors in the endogenous formation of N-nitroso compounds (NOC) which are potent animal carcinogens for the organs of the digestive system. We evaluated dietary intakes of nitrate and nitrite, as well as nitrate ingestion from drinking water (public drinking water supplies (PWS)), in relation to the incidence (1986–2014) of cancers of the esophagus (n = 36), stomach (n = 84), small intestine (n = 32), liver (n = 31), gallbladder (n = 66), and bile duct (n = 58) in the Iowa Women’s Health Study (42,000 women aged from 50 to 75 in 1986). Dietary nitrate and nitrite were estimated using a food frequency questionnaire and a database of nitrate and nitrite levels in foods. Historical nitrate measurements from PWS were linked to the enrollment address by duration. We used Cox regression to compute hazard ratios (HR) and 95% confidence intervals (CI) for exposure quartiles (Q), tertiles (T), or medians, depending on the number of cancer cases. In adjusted models, nitrite intake from processed meats was associated with an increased risk of stomach cancer (HRQ4vsQ1 = 2.2, CI: 1.2–4.3). A high intake of total dietary nitrite was inversely associated with gallbladder cancer (HRQ4vsQ1 = 0.3, CI: 0.1–0.96), driven by an inverse association with plant sources of nitrite (HRQ4vsQ1 = 0.3, CI: 0.1–0.9). Additionally, small intestine cancer was inversely associated with a high intake of animal nitrite (HRT3vsT1 = 0.2, CI: 0.1–0.7). There were no other dietary associations. Nitrate concentrations in PWS (average, years ≥ 1/2 the maximum contaminant level) were not associated with cancer incidence. Our findings for stomach cancer are consistent with prior dietary studies, and we are the first to evaluate nitrate and nitrite ingestion for certain gastrointestinal cancers.

Chronic intestinal inflammation drives colorectal tumor formation triggered by dietary heme iron in vivo

The consumption of red meat is associated with an increased risk for colorectal cancer (CRC). Multiple lines of evidence suggest that heme iron as abundant constituent of red meat is responsible for its carcinogenic potential. However, the underlying mechanisms are not fully understood and particularly the role of intestinal inflammation has not been investigated. To address this important issue, we analyzed the impact of heme iron (0.25 µmol/g diet) on the intestinal microbiota, gut inflammation and colorectal tumor formation in mice. An iron-balanced diet with ferric citrate (0.25 µmol/g diet) was used as reference. 16S rRNA sequencing revealed that dietary heme reduced α-diversity and caused a persistent intestinal dysbiosis, with a continuous increase in gram-negative Proteobacteria. This was linked to chronic gut inflammation and hyperproliferation of the intestinal epithelium as attested by mini-endoscopy, histopathology and immunohistochemistry. Dietary heme triggered the infiltration of myeloid cells into colorectal mucosa with an increased level of COX-2 positive cells. Furthermore, flow cytometry-based phenotyping demonstrated an increased number of T cells and B cells in the lamina propria following heme intake, while γδ-T cells were reduced in the intraepithelial compartment. Dietary heme iron catalyzed formation of fecal N-nitroso compounds and was genotoxic in intestinal epithelial cells, yet suppressed intestinal apoptosis as evidenced by confocal microscopy and western blot analysis. Finally, a chemically induced CRC mouse model showed persistent intestinal dysbiosis, chronic gut inflammation and increased colorectal tumorigenesis following heme iron intake. Altogether, this study unveiled intestinal inflammation as important driver in heme iron-associated colorectal carcinogenesis.

Study on sulfur vulcanized natural rubber formulated with nitrosamine safe diisopropyl xanthogen polysulfide/tertiary butyl benzothiazole sulphenamide binary accelerator system

An outstanding interest on elimination of nitrosamine generation in traditional sulfur vulcanization systems has led to introduce nitrosamine safe accelerator/s to produce safe natural rubber (NR) vulcanizates. It is an effective way to prevent formation of carcinogenic N-nitroso compounds during manufacture of rubber products. In the present study, behavior of nitrosamine safe binary accelerator system consisting of diisopropyl xanthogen polysulfide (DIXP) with commonly used non-regulated accelerator N-tert-butyl-2-benzothiazole sulfenamide (TBBS) was investigated in efficient sulfur vulcanization of NR. Cure characteristics, physico-mechanical properties and crosslink density of vulcanizates prepared with different combinations of the accelerator system were evaluated and compared with those of individual accelerators. The study reveals that moduli and strength properties of the vulcanizate prepared with DIXP accelerator are inferior to those of the vulcanizate prepared with TBBS accelerator. Nevertheless, optimum cure time of the DIXP compounds is lower in comparison to TBBS compounds. Moreover, progressive replacement of DIXP with TBBS in the accelerator system showed a synergistic effect in regard to cure characteristics and physico-mechanical properties.

N-nitrosoethylenethiourea formation at environmentally-relevant concentrations of ethylenethiourea in a pooled groundwater sample

N-nitroso compounds form from the interaction between nitrosatable precursors and nitrite under acidic conditions. A majority of N-nitroso compounds tested show evidence of carcinogenicity in animal models. Formation of N-nitroso compounds may occur from exposure to precursors in drinking water, but the extent of formation depends on a number of factors, including concentration of substrates, presence of catalysts and inhibitors, and pH. The objective of this study was to examine these factors in pesticide-associated N-nitroso (PANN) compound formation in drinking water. In preliminary screening experiments, nine nitrosatable pesticides and degradation products were individually reacted at environmentally-relevant concentrations (≤ 20 μg L‐−1) with sodium nitrite (NaNO2) and hydrochloric acid (HCl) in ultra-pure water. Only ethylenethiourea (ETU) showed evidence of PANN compound formation in initial experiments and was further tested for N-nitrosoethylenethiourea (N-ETU) formation in a pooled groundwater sample (comprised of five tap water samples combined into one homogenous sample) collected from an agricultural region of Prince Edward Island in Canada, where nitrate contamination is a known concern. Evidence of N-ETU formation in the groundwater sample was observed within 30 min at concentrations 7.5, 10, and 20 μg L−1. Analysis of target compounds and semi-target PANN compounds was performed using ultra-high pressure liquid chromatography coupled with high resolution orbital ion trap mass spectrometry. These preliminary experiments serve to inform about potential PANN compound formation in groundwater. The results of this study suggest that ETU is capable of forming potentially carcinogenic N-ETU in water containing nitrite/nitrate at trace concentrations under acidic conditions. Thus, these findings suggest that N-ETU formation may be a concern for individuals exposed to low concentrations of ETU in groundwater.

Drinking-water nitrate and cancer risk: A systematic review and meta-analysis

Background Nitrate is an inorganic compound that occurs naturally in all surface and groundwater, although higher concentrations tend to occur only where fertilizers are used on the land. The regulatory limit for nitrate in public drinking water supplies was set to protect against infant methemoglobinemia, but other health effects were not considered. Risk of specific cancers and congenital disabilities may be increased when the nitrate is ingested, and nitrate is reduced to nitrite, which can react with amines and amides by nitrosation to form N-nitroso compounds which are known animal carcinogens. This study aims to evaluate the association between nitrate ingested through drinking water and the risk of developing cancers in humans. Methods We performed a systematic review following PRISMA and MOOSE guidelines. A literature search was performed using PubMed, EMBASE, the Cochrane Library databases, Web of Science and Google Scholars in the time-frame from their inception to January 2020, for potentially eligible publications. STATA version 12.0 was used to conduct meta-regression and a two-stage meta-analysis. Results A total of 48 articles with 13 different cancer sites were used for analysis. The meta-regression analysis showed stomach cancer had an association with the median dosage of nitrate from drinking water (t = 3.98, p = 0.0001, and adjusted R-squared = 50.61%), other types of cancers didn’t show any association. The first stage of meta-analysis showed there was an association only between the risk of brain cancer & glioma (OR = 1.15, 95% CI: 1.06, 1.24) and colon cancer (OR = 1.11, 95% CI: 1.04, 1.17) and nitrate consumption in the analysis comparing the highest ORs versus the lowest. The 2nd stage showed there was an association only between the risk colon cancer (OR = 1.14, 95% CI: 1.04, 1.23) and nitrate consumption in the analysis comparing all combined higher ORs versus the lowest. Conclusion This study showed that there is an association between the intake of nitrate from drinking water and a type of cancer in humans. The effective way of controlling nitrate concentrations in drinking water is the prevention of contamination (water pollution). Further research work on this topic is needed.

Ingestion of nitrate and nitrite from drinking water and diet and cancers of the gastrointestinal tract in Iowa women

Background: Nitrate and nitrite are precursors in the endogenous formation of N-nitroso compounds (NOC), potent animal carcinogens in the gastrointestinal tract. Methods: We evaluated nitrate ingestion from public drinking water supplies (PWS), private well use, and dietary nitrate and nitrite intakes in relation to incidence (through 2014) of cancers of the esophagus (n=37), stomach (97), small intestine (47), liver (56), and gallbladder (66) in the Iowa Women’s Health Study (42,000 women ages 50-75 in 1986). Historical nitrate measurements from PWS were linked to the enrollment address by duration. We computed average concentrations and number of years &gt;5 mg/L NO3-N (½ the maximum contaminant level [MCL]). Dietary nitrate and nitrite were estimated using a food frequency questionnaire. We used Cox proportional hazards models to compute hazard ratios (HR) and 95% confidence intervals (CI). Results: In adjusted models, liver cancer risk was elevated among private well users (HR=2.5, CI 0.8-8.5) and those with any years &gt;5 mg/L NO3-N (HR=2.0, CI 0.8-4.9); there was no association with average concentrations (HRper1mg/L NO3-N =1.1, CI 0.7-1.7). Private well use and PWS nitrate concentrations were not associated with other cancers. Dietary nitrate and nitrite from plants was inversely associated with small intestine (HRQ4vsQ1=0.4, CI 0.1-0.9) and gall bladder cancer (HRQ4vsQ1=0.3, CI 0.1-0.8), respectively; there were no associations for the other cancers. Nitrite intake from processed meats was associated with increased risk of stomach (HRnitriteQ4vsQ1=1.7, CI 1.0-3.0) and elevated risk of liver cancer (HRnitriteQ4vsQ1=1.8, CI 0.8-4.0) but was inversely associated with small intestine cancer (HRnitriteQ4vsQ1=0.4, CI 0.1-1.0). Power was limited, but there was no evidence for effect modification by vitamin C and red meat, factors affecting nitrosation. Conclusion: We found novel suggestive evidence that private well use and PWS nitrate may increase liver cancer risk. These associations should be evaluated in studies with larger case numbers.

Pathways for N-Nitroso Compound Formation: Secondary Amines and Beyond

Recent drug recalls (e.g., valsartan and ranitidine) linked to the discovery of nitrosamine impurities have led to increased regulatory scrutiny in the manufacturing process of marketed medicines, notably for determining any sources of risk for nitrosamine (or related N-nitroso compound) formation within the manufacturing process. This review seeks to aid the risk assessment process through identifying known conditions and reactants through which N-nitroso compounds can be formed.

Ingested Nitrate and Nitrite and Bladder Cancer in Northern New England.

N-nitroso compounds are hypothesized human bladder carcinogens. We investigated ingestion of N-nitroso compound precursors nitrate and nitrite from drinking water and diet and bladder cancer in the New England Bladder Cancer Study. Using historical nitrate measurements for public water supplies and measured and modeled values for private wells, as well as self-reported water intake, we estimated average nitrate concentrations (mg/L NO3-N) and average daily nitrate intake (mg/d) from 1970 to diagnosis/reference date (987 cases and 1,180 controls). We estimated overall and source-specific dietary nitrate and nitrite intakes using a food frequency questionnaire (1,037 cases and 1,225 controls). We used unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). We evaluated interactions with factors that may affect N-nitroso compound formation (i.e., red meat, vitamin C, smoking), and with water intake. Average drinking water nitrate concentration above the 95th percentile (>2.07 mg/L) compared with the lowest quartile (≤0.21 mg/L) was associated with bladder cancer (OR = 1.5, 95% CI = 0.97, 2.3; P trend = 0.01); the association was similar for average daily drinking water nitrate intake. We observed positive associations for dietary nitrate and nitrite intakes from processed meat (highest versus lowest quintile OR for nitrate = 1.4, 95% CI = 1.0, 2.0; P trend = 0.04; OR for nitrite = 1.5, 95% CI = 1.0, 2.1; P trend = 0.04, respectively), but not other dietary sources. We observed positive interactions between drinking water nitrate and red meat (P-interaction 0.05) and processed red meat (0.07). Our results suggest the importance of both drinking water and dietary nitrate sources as risk factors for bladder cancer.

A Review of the In Vivo Evidence Investigating the Role of Nitrite Exposure from Processed Meat Consumption in the Development of Colorectal Cancer.

The World Cancer Research Fund (WCRF) 2007 stated that the consumption of processed meat is a convincing cause of colorectal cancer (CRC), and therefore, the public should avoid it entirely. Sodium nitrite has emerged as a putative candidate responsible for the CRC-inducing effects of processed meats. Sodium nitrite is purported to prevent the growth of Clostridium botulinum and other food-spoiling bacteria, but recent, contradictory peer-reviewed evidence has emerged, leading to media reports questioning the necessity of nitrite addition. To date, eleven preclinical studies have investigated the effect of consuming nitrite/nitrite-containing meat on the development of CRC, but the results do not provide an overall consensus. A sizable number of human clinical studies have investigated the relationship between processed meat consumption and CRC risk with widely varying results. The unique approach of the present literature review was to include analysis that limited the human studies to those involving only nitrite-containing meat. The majority of these studies reported that nitrite-containing processed meat was associated with increased CRC risk. Nitrite consumption can lead to the formation of N-nitroso compounds (NOC), some of which are carcinogenic. Therefore, this focused perspective based on the current body of evidence links the consumption of meat containing nitrites and CRC risk.

Impact of high drinking water nitrate levels on the endogenous formation of apparent N-nitroso compounds in combination with meat intake in healthy volunteers

BackgroundNitrate is converted to nitrite in the human body and subsequently can react with amines and amides in the gastrointestinal tract to form N-nitroso compounds (NOCs), which are known to be carcinogenic in animals. Humans can be exposed to nitrate via consumption of drinking water and diet, especially green leafy vegetables and cured meat. The contribution of nitrate from drinking water in combination with meat intake has not been investigated thoroughly. Therefore, in the present pilot study, we examined the effect of nitrate from drinking water, and its interaction with the consumption of white and processed red meat, on the endogenous formation of NOCs, taking into account the intake of vitamin C, a nitrosation inhibitor.MethodsTwenty healthy subjects were randomly assigned to two groups consuming either 3.75 g/kg body weight (maximum 300 g per day) processed red meat or unprocessed white meat per day for two weeks. Drinking water nitrate levels were kept low during the first week (< 1.5 mg/L), whereas in week 2, nitrate levels in drinking water were adjusted to the acceptable daily intake level of 3.7 mg/kg bodyweight. At baseline, after 1 and 2 weeks, faeces and 24 h urine samples were collected for analyses of nitrate, apparent total N-nitroso compounds (ATNC), compliance markers, and genotoxic potential in human colonic Caco-2 cells.ResultsUrinary nitrate excretion was significantly increased during the high drinking water nitrate period for both meat types. Furthermore, levels of compliance markers for meat intake were significantly increased in urine from subjects consuming processed red meat (i.e. 1-Methylhistidine levels), or unprocessed white meat (i.e. 3-Methylhistidine). ATNC levels significantly increased during the high drinking water nitrate period, which was more pronounced in the processed red meat group. Genotoxicity in Caco-2 cells exposed to faecal water resulted in increased genotoxicity after the interventions, but results were only significant in the low drinking water nitrate period in subjects consuming processed red meat. Furthermore, a positive correlation was found between the ratio of nitrate/vitamin C intake (including drinking water) and the level of ATNC in faecal water of subjects in the processed red meat group, but this was not statistically significant.ConclusionsDrinking water nitrate significantly contributed to the endogenous formation of NOC, independent of the meat type consumed. This implies that drinking water nitrate levels should be taken into account when evaluating the effect of meat consumption on endogenous formation of NOC.Trial registrationDutch Trialregister: 29707. Registered 19th of October 2018. Retrospectively registered.

Ingested nitrate and nitrite and bladder cancer in Northern New England

OPS 36: Health effects of dietary exposures, Room 210, Floor 2, August 27, 2019, 4:30 PM - 5:30 PM Background/Aim: N-nitroso compounds (NOCs) are hypothesized human bladder carcinogens. Nitrate and nitrite are NOC precursors; sources include contaminated drinking water and diet. We examined nitrate and nitrite ingestion and bladder cancer risk in the New England Bladder Cancer Study, a population-based case-control study in Maine, New Hampshire, and Vermont. Methods: Using historical nitrate measurements for public water supplies, measured and modeled values for private wells and self-reported water intake, we estimated average nitrate concentrations (NO3-N mg/L) and average daily nitrate intake (mg/day) from 1970 to diagnosis/reference date for 987 cases and 1180 controls. We also estimated source-specific (animal, plant, processed meat) dietary nitrate and nitrite intakes using a food frequency questionnaire (1037 cases and 1225 controls). We used unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) adjusting for age, gender, smoking, disinfection by-products, and other factors. We evaluated interactions with factors affecting NOC formation (i.e., red and processed meat, vitamin C, smoking). Results: Average drinking water nitrate concentration above the 95th percentile (>2.07 mg/L) compared with the lowest quartile (<=0.21 mg/L) was associated with bladder cancer risk (OR=1.50, CI: 0.97-2.32; p-trend=0.01); the association was similar for average drinking water nitrate intake. We observed positive associations for dietary nitrate and nitrite intakes from processed meat (highest vs. lowest quintile OR=1.42, CI: 1.01-1.98; p-trend=0.04; OR=1.48, CI: 1.04-2.09; p-trend=0.04, respectively), but no trends for other sources. Risk was highest among those with >2.07 mg/L NO3-N and >median red or processed meat intake vs <0.21 mg/L NO3-N/< median intakes (OR=2.61, CI: 1.33-5.11 and OR=3.47 CI: 1.75-6.87; p-interaction=0.05 and 0.07, respectively). We observed no interaction with vitamin C or smoking. Conclusions: Our results suggest the importance of both drinking water and dietary nitrate sources as risk factors for bladder cancer especially among those with high red or processed meat intake

Inulin-fortification of a processed meat product attenuates formation of nitroso compounds in the gut of healthy rats

Intake of red and processed meat has been suspected to increase colorectal cancer risk potentially via endogenous formation of carcinogenic N-nitroso compounds or increased lipid and protein oxidation. Here we investigated the effect of inulin fortification of a pork sausage on these parameters. For four weeks, healthy Sprague-Dawley rats (n = 30) were fed one of three diets: inulin-fortified pork sausage, control pork sausage or a standard chow diet. Fecal content of apparent total N-nitroso compounds (ATNC), nitrosothiols and nitrosyl iron compounds (FeNO) were analyzed in addition to liver metabolism and oxidation products formed in liver, plasma and diets. Intriguingly, inulin fortification reduced fecal ATNC (p = 0.03) and FeNO (p = 0.04) concentrations. The study revealed that inulin fortification of processed meat could be a strategy to reduce nitroso compounds formed endogenously after consumption.