Volatile N-nitrosamines Research Articles

N-nitrosodimethylamine in Spanish beers

A survey of 21 beers produced in Spain during 1994 was conducted to assess contamination with volatile N-nitrosamines. N-Nitrosodimethylamine (NDMA), the only volatile N-nitrosamine detected, was found in 52% of Spanish beers at or above the detection level (0.05 μg/kg). The mean NDMA level for all samples was 0.11 μg/kg, and the range was from not detected to 0.55 μg/kg. No differences in the NDMA content were observed between the different beer types. Individual daily intake of NDMA may reach up to 0.021 μg/person/day for Spanish people.

Selective determination of volatile N-nitrosamines by derivatization with diethyl chlorothiophosphate and gas chromatography with flame photometric detection

A selective and sensitive method was developed for the determination of volatile N-nitrosamines by gas chromatography (GC). After denitrosation of N-nitrosamines with hydrobromic acid, the resulting secondary amines were converted into their N-diethylthiophosphoryl derivatives and then measured by GC using a DB-1701 capillary column with flame photometric detection. The calibration graphs for N-nitrosamines in the range 0.05–1 nmol were linear and sufficiently reproducible for quantitative determination. This method was successfully applied to cigarette smoke samples without prior clean-up. N-Nitrosamines and secondary amines were completely separated by extraction with diethyl ether containing 25% 2-propanol. Overall recoveries of N-nitrosamines added to cigarette smoke samples were 83–110%. By using this method, N-nitrosamines in these samples could be determined without any interference from coexisting substances. Analytical results for the contents of N-nitrosamines and secondary amines in mainstream and sidestream smokes of several cigarettes are presented.

Nitrosation of nigerian medicinal plant preparations under ‘chemical’ and ‘simulated’ gastric conditions

Preparations of some tropical plants of medicinal importance, collected from the savannah vegetational belt of Nigeria, were nitrosated and analysed for volatile N-nitrosamines formed under chemical and simulated gastric conditions. N-Nitrosamines were determined on a Thermal Energy Analyser following gas chromatographic separation. Mean concentrations of N-nitrosodimethylamine (NDMA) in the range of 7 to 58 ppb and N-nitrosodiethylamine (NDEA) in the range of 23 to 26 ppb were formed in 31 and 7%, respectively, of the preparations using artificial gastric juice (simulated gastric condition). Under chemically optimal conditions, relatively high levels of NDMA (72–2008 ppb), NDEA (23–1528 ppb) and N-nitrosopyrrolidine (20–405 ppb) were formed in 100, 75 and 32% of the preparations, respectively; N-nitrosomethylethylamine, N-nitrosodibutylamine and N-nitrosomorpholine were formed in fewer preparations. These findings suggest that the endogenous formation of N-nitroso compounds from precursors present in medicinal plants might be another source of human exposure to environmental carcinogens in Nigeria and other developing countries.

Volatile N-nitrosamines and their precursors in Chinese salted fish--a possible etological factor for NPC in china.

Epidemiological studies show that the consumption of Chinese salted fish is a causative factor for nasopharyngeal carcinoma (NPC) in southern China. In the present study, N-nitrosamines and their precursors were analyzed in 145 samples of cooked, salted fish collected from various areas in China. The results show that N-dimethylnitrosamine (NDMA), N-diethylnitrosamine (NDEA), N-nitrosopyrrolidine (NPYR) and N-nitrosopiperidine (NPIP) were present in the salted fish. Total volatile N-nitrosamines (TVN) in the salted fish were 0.028 to 4.54 mg/kg. The samples from areas with higher NPC risk showed a higher average level of TVN than those from areas of lower NPC risk. Positive correlations were found between the levels of NDMA, NDEA and TVN and mortality from NPC. Although neither the nitrates nor the nitrites in the salted fish were present at significantly high levels, in vitro data regarding nitrosation of salted fish showed that the N-nitrosamine content had increased substantially. The results support the conclusion that the high NPC risk in southern Chinese may be attributed to consumption of salted fish containing high levels of N-nitrosamines.

Luminarin 9: A new fluorescent reagent for the precolumn derivatizatioin of main volatile and non-volatile N-nitrosamines in RP-HPLC

A sensitive precolumn fluorescence derivatization method for low level detection of the, volatile (N-nitrosodimethylamine and N-nitrosopyrrolidine) and non-volatile N-nitrosamines (N-nitrosoproline and N-nitrosodiethanolamine) an high-performance liquid chromatography was developed. This method is based on the denitrosation of the compounds of interest by a mixture of hydrobromic acid and acetic acid to produce the corresponding secondary amines. These are, then, able to react with, a quinolizinocoumarin derivative (luminarin 9®) to form highly fluorescent labelled N-nitrosamine derivatives. The structural elucidation of the luminarin 9® derivatives of N-nitrosoproline and N-nitrosodimethylamine by way of example, were established by liquid chromatography-mass spectrometry (LC-MS) and by direct chemical ionization-mass spectrometry (CI-MS). The separation, derivatization and detection conditioins were optimized for all the studied compounds. The detection limits (signal to noise ratio=3) were between 0.4 and 1.0 pmol injected depending on the compound. The calibration graphs were linear for derivatized amounts in the range of 0.5–40 nmol for N-nitrosodimethylamine and N-nitrosopyrrolidine, 0.4–2- nmol for N-nitrosoproline and 1.0–40 nmol for N-nitrosodiethanolamine. The repeatability (RSD less than 3.5%, n=6) and reproducibility (RSD less than 4.8%, n-6) were satisfactory.

Absence of volatile N-nitrosamines in cooked nitrite-free cured muscle foods

Nitrite-free cured pork systems were prepared using the preformed cooked cured-meat pigment (CCMP) and sodium ascorbate. Absence of volatile N-nitrosamines in cooked nitrite-free systems was confirmed using a gas chromatography-thermal energy analyzer (GC-TEA) methodology. Similar results were obtained when cod, cod surimi or mixtures containing pork with 15 or 50% cod or cod surimi were used. However, counterpart samples cured with sodium nitrite (156 ppm) and sodium ascorbate (550 ppm) produced N-nitrosodimethylamine at 1·0 ppb levels or less. Results demonstrate that nitrite-free curing of meat and meat/fish systems containing the preformed CCMP is successful in yielding products devoid of volatile N-nitrosamines.

N-nitrosamine generation by urinary tract infections in spine injured patients.

Urine was collected from 33 patients resident at the Welsh Spinal Injuries Unit and analysed for volatile N-nitrosamines by gas chromatography. N-nitrosodime-thylamine, N-nitrosopiperidine or N-nitrosopyrrolidine was detected in 32 of the samples. Thirty-one of the samples were infected by one or more microbial species. Nitrate and N-nitrosamines were not found in the sterile urines of a group of 10 control individuals exposed to the same dietary and environmental influences as the spinal patients. Although N-nitrosamines were found in some of the catheter drainage system products, they did not elute into urine on 24-h exposure. In addition, 6 of the nitrosamine-containing urines had no contact with drainage systems as they were collected from spinal patients who were capable of independent voiding. It was concluded that the nitrosamines detected in the urines arose from the bacterial nitrosation of urinary amines. These results support the hypothesis that chronic urinary tract infection may have a role in the aetiology of bladder cancer in spine injured patients.

Tobacco-Specific and Volatile N-Nitrosamines in Environmental Tobacco Smoke of Offices

The tobacco-specific nitrosamines (TSNA) N-nitrosonornicotine (NNN) and 4-(N-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) as well as the vola tile N-nitrosamines N-nitrosodimethylamine (NDMA) and N-nitrosopyrrol idine (NPYR) were determined in the indoor air of a poorly ventilated office where extensive smoking took place. Under these conditions, moderate to heavy smoking resulted in indoor air concentrations of 7.6-20.0 ppm carbon monoxide, 109-290 ppb nitrogen oxides and 58.5-132 μg/m 3 nicotine. The N-nitrosamine concentrationes were (in nanograms/cubic meter): not de tected (nd)-6.0 NNN, nd-13.5 NNK, 7.9-45.0 NDMA and 3.5-27.0 ng/m3 NPYR. Occupation of the office by a nonsmoker for 1 h would result in a maximum exposure to 0.01 μg TSNA and 0.03 μg volatile N-nitrosamines.

Solid-Phase Extraction Method for Volatile N-Nitrosamines in Hams Processed with Elastic Rubber Netting

Abstract A method was developed for the determination of volatile N-nitrosamines in hams processed In elastic rubber nettings. The method was based on a modification of a solid-phase extraction (SPE) procedure used in the past to determine selected nitrosamines in different types of cured meat products. The nitrosamines detected in ham most likely originate from the amine precursors in rubber and from the nitrite commonly used in the meat curing process. The method was compared with 2 established procedures for N-nitrosodibutylamine (NDBA) analysis in cured meat products: the mineral oil distillation procedure (MOD) and the low temperature vacuum distillation procedure (LTVD). All 3 methods used the same gas chromatographic/chemlluminescent detection conditions and system. No significant difference was found between the MOD and LTVD methods. These methods were found to yield significantly higher NDBA levels than the SPE procedure. When 2,6-dimethylmorpholine was added to the sample before analysis in the MOD and LTVD procedures, artifactual nitrosamines were formed. No artifactual formation was noted in the SPE method. We propose that the new SPE method replace the current methods being used for analysis of netted, cured meat products.

Secondary amine precursors to nitrosamines in human saliva, gastric juice, blood, urine and faeces.

It has been suggested that the endogenous nitrosation of aliphatic, cyclic and heterocyclic secondary amines in the urinary bladder of patients with chronic urinary bacterial infections and in the human stomach may provide an important additional source of exposure to carcinogenic volatile N-nitrosamines. The most commonly occurring nitrosatable secondary amines found in human saliva, gastric juice, blood, urine and faeces are dimethylamine (DMA), pyrrolidine (PYR) and piperidine (PIP). All of 40 analysed samples of gastric juice contained 0.87 +/- 0.89 (SEM) microgram/ml DMA, 39 contained 1.35 +/- 2.53 microgram/ml PIP, 36 contained 0.18 +/- 0.15 microgram/ml PYR and 14 contained 0.05 +/- 0.11 microgram/ml diethylamine. Nitrate (14.0 +/- 15.7 microgram/ml) was present in all samples and 11 of 40 samples contained 0.43 +/- 1.38 microgram/ml nitrite. Only one gastric juice sample with pH less than 4.5 contained nitrite (0.1 microgram/ml). In paraplegics, patients with bladder augmentations and two control groups without bacterial infections of the urinary bladder, a mean daily excretion of 40.5-49.7 mg/day DMA, 19.4-23.8 mg/day PYR and 26.1-31.7 mg/day PIP was found. In both patient groups suffering from chronic bacterial infection of the urinary bladder, the corresponding volatile N-nitrosamines were formed by endogenous nitrosation and excreted in urine.

Tobacco-Specific and Volatile N-Nitrosamines in Environmental Tobacco Smoke of Offices

The tobacco-specific nitrosamines (TSNA) N-nitrosonornicotine (NNN) and 4-(N-methylnitrosamino)-l-(3-pyridyl)-l-butanone (NNK) as well as the volatile N-nitrosamines N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) were determined in the indoor air of a poorly ventilated office where extensive smoking took place. Under these conditions, moderate to heavy smoking resulted in indoor air concentrations of 7.6-20.0 ppm carbon monoxide, 109-290 ppb nitrogen oxides and 58.5-132 μg/m^3 nicotine. The N-nitrosamine concentrationes were (in nanograms/cubic meter): not detected (nd)-6.0 NNN, nd-13.5NNK, 7.9-45.0 NDMA and 3.5-27.0 ng/m^3 NPYR. Occupation of the office by a nonsmoker for 1 h would result in a maximum exposure to 0.01 pg TSNA and 0.03 pg volatile N-nitrosamines.

N-nitrosamine and mutagenicity formation in Chinese salted fish after digestion.

Salted and dried fish (Nemipterus virgatus), acquired from Hong Kong, was treated with 0.43-110 mM nitrite during in vitro digestion using gastric enzymes and the volatile N-nitrosamine content and mutagenicity on Salmonella typhimurium TA100 assayed without concentration. N-Nitrosodimethylamine (NDMA; the only nitrosamine detected) formation was second order in nitrite concentration. When 10 g of fish was treated with 6.96 mM nitrite, 394 nM NDMA was formed. Thiocyanate was catalytic for NDMA formation at nitrite concentration greater than 0.87 mM and when the ratio of thiocyanate to nitrite was greater than 1. Approximately a 50% inhibition in NDMA formation by ascorbic acid was seen when the ratio of ascorbate to nitrite was approximately 2 or greater and the nitrite concentration was 1.74 mM. Mutagenicity increased with increasing nitrite concentration but the addition of thiocyanate did not increase mutagenicity over nitrite alone. Ascorbate increased mutagenicity even though NDMA formation was inhibited. Even at nitrite concentrations greater than 100-fold higher than expected in vivo, there was insufficient NDMA formed to account for the observed mutagenicity. These data do not exclude the possibility that the observed mutagenicity was due to non-volatile N-nitroso compounds, however, this possibility seems unlikely given the effects of ascorbate and thiocyanate which would be expected to inhibit and enhance non-volatile N-nitroso compound formation.

Volatile, non‐volatile and totalN‐nitroso compounds in bacon

Twenty-five smoked and unsmoked fried bacon samples have been analysed by a group selective procedure to measure the concentration of apparent total N-nitroso compounds (ATNC). The levels of a range of individual N-nitroso compounds, including simple volatile N-nitrosamines, N-nitrosothiazolidines, N-nitrosamino acids and N-nitrosothiazolidine carboxylic acids have also been examined. Concentrations of ATNC varied from 430 to 6800 micrograms(N-NO)/kg with a mean of 2700 micrograms(N-NO)/kg. Protein-bound N-nitrosoproline was the most abundant compound detected in unsmoked bacon, mean 260 micrograms/kg, and on average accounted for 4% of the ATNC concentration. For smoked bacon, bound N-nitrosoproline was detected in levels of up to 890 micrograms/kg and contributed 5% to the ATNC total. The most abundant compound present in smoked bacon was N-nitrosothiazolidine-4-carboxylic acid, mean 660 micrograms/kg, and this accounted for 6% of the ATNC. N-Nitrosothiazolidine, mean 340 micrograms/kg, and 2-(hydroxymethyl)-3-nitrosothiazolidine-4-carboxylic acid, mean 180 micrograms/kg, were the next most prominent compounds detected in smoked bacon. The combined sum of all the individual N-nitroso compounds measured accounted for, on average, 16% of the total ATNC. The identities of the N-nitroso compounds comprising the majority of the ATNC in bacon remain unknown.

Levels of volatileN-nitrosamines in baby bottle rubber nipples commercialized in belo horizonte, Mina Gerais, Brazil

Several reports have been published describing the occurrence of volatile N-nitrosamines in rubber products. The first evidence of the presence of these compounds in baby bottle nipples was published by Ireland et al. Their study showed the presence of N-nitrosamines in elastomers compounded with dialkylamine accelerators and stabilizers. Several countries, through active cooperation with industry, have made considerable progress in eliminating or significantly reducing the levels of N-nitrosamines in baby bottle nipples. The purpose of the present study was to investigate the occurrence of volatile N-nitrosamines in baby bottle rubber nipples in the market of Belo Horizonte, MG, Brazil.

Influence of nitrate, ascorbic acid, and nitrate reductase microorganisms onN‐nitrosamine formation during Korean‐style soysauce fermentation

Traditional Korean soysauce samples were collected from households in Chinju, Gyeongnam, Korea and analysed for volatile N-nitrosamines. Five of 24 samples contained NDMA (range = 1.6-10.4 micrograms/l) which was the only volatile N-nitroso compound found. Soysauce made from well water contained NDMA more often (4 of 6 samples) than soysauce made from tap water (1 of 18). This suggests that the water source is a determinate in the NDMA content of soysauce, probably due to a higher nitrate content of well water. The source of salt used did not clearly influence NDMA content. Soysauce was prepared in the laboratory using traditional methods but with 0 to 400 mg/l nitrate and in some cases made 6.5 to 65 mM in ascorbic acid and fermented for 120 days. The NDMA content of the samples was positively correlated with increasing nitrate concentration. Nitrate at 400 mg/l resulted in an NDMA content of 203 micrograms/l. Ascorbic acid substantially inhibited NDMA formation. All samples contained large numbers of nitrate reductase-containing organisms (greater than 1 x 10(7) CFU/ml).

Polycyclic aromatic hydrocarbon and volatile N-nitrosamine content of wheat grain before and after direct gas-fired drying

The levels of polycyclic aromatic hydrocarbons (PAH) and volatile N-nitrosamines were measured in wheat grain before and after drying with direct natural gas heating. A sampling procedure making it possible to match samples from the ingoing and outgoing grain streams in the drier was used. The PAH levels were generally low, eg benzo[a]pyrene concentrations were 0.1 μg kg−1 or lower. No consistent differences in PAH levels between the ingoing and outgoing grain samples were observed. No detectable amounts of volatile N-nitrosamines were found in any of the samples, before or after drying.

The occurrence of volatile N-nitrosamines in French foodstuffs

Volatile N-nitrosamines were estimated in 258 food samples and 53 beverages purchased in Eastern France in 1987–88. N-nitrosodimethylamine (NDMA) was found in 278 samples (89%) with a maximum level of 16 μg/kg. The highest values were found in stone fruit spirits. Nitrite-cured meats, smoked meats and smoked fishes were contaminated with appreciable amounts of this N-nitrosamine. The other N-nitrosamines were found more rarely, and usually below 0·5 μg/kg. Beer NDMA content (mean:0·28 μg/litre) was lower than in the past due to the efforts of the brewing organizations.

Mean daily intake of volatile N-nitrosamines from foods and beverages in West Germany in 1989–1990

The levels of volatile N-nitrosamines were determined in 38 alcoholic drinks and 215 food samples prepared for human consumption using standard culinary practices. The analyses used gas chromatography thermal energy analysis. Detectable levels were found in 80 (31.5%) of the individual samples. The average daily intake of voltaile N-nitrosamines in West Germany in 1989–1990 was found to be: 0.28 μg N-nitrosodimethylamine (NDMA)/day, 0.011 μg N-nitrosopyrrolidine (NPYR)/day and 0.015 μg N-nitrosopiperidine (NPIP)/day for men, and 0.17 μg NDMA/day, 0.011 μg NPYR/day and 0.015 μg/NPIP/day for women. For men, 31% of the daily NDMA exposure results from the consumption of beer.

Increased urinary nitrosamine excretion in paraplegic patients

An increased risk of bladder cancer is a recognized complication in spine-injured patients undergoing long-term urethral catheterization to preserve renal function. Aerobic cultures from 28 of 30 paraplegic patients showed complex bacterial flora containing nitrate-reducing organisms (Escherichia coli, Proteus and Klebsiella spp.). Urine samples from 29 paraplegic patients were also found to contain volatile nitrosamines. Mean N-nitrosamine excretion levels were 0.65 +/- 0.69 micrograms/day N-nitrosodimethylamine, 0.25 +/- 0.44 micrograms/day N-nitrosopiperidine and 0.39 +/- 0.50 micrograms/day N-nitrosopyrrolidine. A mean urinary nitrite excretion of 10.4 +/- 13.2 mg/day was found in 24 out of 30 paraplegic patients. In the sterile urine of control volunteers (medical staff attending the paraplegic patients and in-patients from other wards of the hospital), no urinary excretion of volatile N-nitrosamines and nitrite was found. The results clearly demonstrate a bacterially mediated in vivo formation of N-nitroso compounds in the urinary tracts of paraplegic patients which may be an important etiological risk factor for bladder cancer in this patient group.

Ingestion of CarcinogenicN-Nitrosamines by Infants and Children

Volatile N-nitrosamines are very potent carcinogens. They can be approximately 5 million times more powerful than saccharin. One of two principal methods is generally used when assaying rubber products for nitrosamine content: (1) the German method (aqueous extraction) or (2) the U.S. method (dichloromethane extraction). When 16 types of baby-bottle nipples and children's pacifiers were tested recently, relatively high levels of nitramines, nitrosamines, and nitrosatable precursors were found. Eighty-one percent failed to meet the strict Dutch standards (based on the German method), but only 37.5% would have been banned according to U.S. regulations, which ignore nitrosatable-precursor content. Up to one-third of the nitrosamines present in a rubber nipple may migrate into the milk in the bottle within a few hours. Transfer into infant formula may exceed 40%, and transfer into saliva may be even higher. Thus, a highly contaminated nipple may cause a 5-kg infant who drinks 1 l/d to ingest approximately 2 micrograms/kg body weight.d of nitrosamines. To this, add any exposure resulting from pacifier use or from in vivo nitrosation of precursors. Therefore, daily exposure of infants may, in the worst case, conceivably reach 4-5 micrograms/kg body weight.d. Entire average daily exposure of an American adult to volatile nitrosamines from major sources is estimated to be less than 0.05 micrograms/kg body weight.d. Infants who use products like those tested may, therefore, be exposed daily to less than or equal to 100 times more of these carcinogens than are adults.(ABSTRACT TRUNCATED AT 250 WORDS)