Analysis of pesticide residues in fruit and vegetables after cleanup with solid-phase extraction using ENV+ (Polystyrene-divinylbenzene) cartridges.

A rapid and simple cleanup procedure for the existing multimethod using solid-phase extraction columns to measure pesticide concentrations in fruit and vegetables is presented. After extraction with ethyl acetate, the sample is passed through ENV+, polystyrene-divinylbenzene extraction column, and eluted with ethyl acetate and injected on to capillary GC columns connected to various detectors. The extraction column has the capacity to retain a broad range of pesticides and is widely used in environmental water samples. In this paper, the sample is extracted in an organic solvent. In contrast to what could be expected, it has been found that the column has the capacity to retain pesticides when used as the normal phase.

Immunotoxic effects of smokeless tobacco on the accessory cell function of rat oral epithelium.

Smokeless tobacco (ST) is known to adversely effect the oral mucosa, but knowledge about the influence on immune defence is limited. Few studies have investigated the effect of ST on the local immune response. In the present study, we have assessed the effect of a crude Swedish moist snuff (SS) extract, alkaloids, and nitrosamines on T-cell mitogenic response to Con A using epithelial cells, including Langerhans cells, of the rat oral mucosa as accessory cells. SS extract at a concentration of 4% reduced the T-cell proliferation by 50% (IC50 = 4%). Pretreatment of either oral epithelial cells or T-cells with SS extract also gave a significant inhibition of T-cell proliferation. This effect was not obtained following preincubation with SS components as alkaloids and different tobacco-specific nitrosamines (TSNA). None of the tested compounds were found to possess any mitogenic properties. This in vitro study showed that SS extract can evoke an immunosuppressive effect on mitogen-driven T-cell proliferation using cells from oral epithelium as accessory cells. This effect was more pronounced when SS extract was employed compared to when the single SS components were used alone.

N-nitrosodimethylamine and 7-methylguanine DNA adducts in tissues of rats fed Chinese salted fish.

Previous studies have demonstrated that rats fed Chinese salted fish developed carcinomas of the nasopharynx and nasal cavity. In the present work the contents of nitrosamines in salted fish from the city of Guangzhou, southern China, and the contents of nitrosamines and possible nitrosamine-induced DNA adducts in organs of rats fed the fish were analysed. Similar levels of N-nitrosodimethylamine (NDMA) were detected in tough and soft salted fish. The NDMA content in steamed fish was higher than in raw fish. In vitro incubation of salted fish with gastric juice significantly increased the level of NDMA. NDMA was found in liver and kidney from rats fed salted fish for 2 years, but no dose-dependence was found between salted fish treatment and NDMA content. The level of 7-methylguanine in rat liver DNA was found to be slightly higher than in DNA from nasopharynx. However, there were no significant differences in the level of 7-methylguanine in DNA samples from rats fed salted fish and rats fed standard diet.

N-nitrosodiethanolamine in commercial cutting fluids without nitrites.

We have determined the concentration of N-nitrosodiethanolamine (NDELA) in 11 commercial 'nitrite-free' cutting fluids in Sweden in 1989. The concentrations in diluted fluids after use were 0.02-0.51 ppm. The concentrates contained 0.02-17 ppm. There was no correlation between the occurrence of formaldehyde-releasers, boramines or bacteria and the concentrations of NDELA. An additive in one fluid contained 140 ppm NDELA. The concentration of nitrite in the diluted fluids after use varied between 0 and 40 ppm. There was a correlation between the concentration of nitrite and NDELA. It is concluded that the concentration of NDELA can be low if the suppliers check their additives with regard to NDELA and the users check the concentration of nitrite.

Promoting effect of snuff in rats initiated by 4-nitroquinoline-N-oxide or 7,12-dimethylbenz(a)anthracene.

A canal was surgically created in the lower lip of male Sprague-Dawley rats and used as a reservoir for moist snuff. A total of 230 animals were randomized into six groups, five containing 40 rats and one containing 30 rats. After 2 wk of recuperation, the animals were treated as follows. Group I was initiated with 7,12-dimethylbenz(a)anthracene 3 times/wk for 4 wk followed by cotton pellet administration. Group II was initiated with 7,12-dimethylbenz(a)anthracene for 4 wk followed by snuff twice a day, 5 days/wk. Group III received snuff twice a day, 5 days/wk. Groups IV and V were initiated with 4-nitroquinoline N-oxide 3 days/wk for 4 wk. Thereafter Group IV received a cotton pellet, and Group V rats were treated with snuff twice a day, 5 days/wk. Group VI received a cotton pellet once a day, 5 days/wk. Treatment of all groups continued for a maximum of 104 wk. Group V rats had a significantly lower mean survival time than did the other groups because of the development of lip sarcomas in 66% of the rats as compared with 23% in Group II and 26% in Group III. One rat in each of Groups IV and VI developed lip sarcomas. The incidence of sarcomas in Group V as compared with the other groups is statistically significant (P less than 0.05 to 0.001). Spindle cell proliferation, a possible precursor lesion of lip sarcoma, was found in five rats of Group II, seven of Group III, and four of Group V. These results show that snuff has strong promoting capability with regard to the development of lip sarcomas after 4-nitroquinoline N-oxide initiation, but not after 7,12-dimethylbenz(a)anthracene initiation. Snuff by itself caused three squamous carcinomas of the palate, two squamous cell papillomas of the lip, and ten lip sarcomas (in 38 rats as compared with one lip sarcoma in 30 control rats), showing snuff to be carcinogenic for the lip and oral cavity.

Occurrence of and exposure to N-nitrosamines in Sweden: a review.

During the last ten years, over 900 samples of foods, snuff and other products on the Swedish market were analysed for N-nitrosamines. The average daily intake of volatile N-nitrosamines from foods was estimated to be 0.29 micrograms/person, and the daily intake of tobacco-specific N-nitrosamines from snuff was calculated to be up to 110 micrograms/snuff user.

Lack of promoting ability of snuff in rats initiated with 4-nitroquinoline-N-oxide.

In an experiment to evaluate the carcinogenicity and promoting capacity of snuff, a reservoir was created in the lower lip of male Sprague-Dawley rats. Groups of 30 rats were treated with snuff only (twice a day on five days a week), propylene glycol (solvent) three times weekly for four weeks, painting of the hard palate with 4-nitroquinoline-N-oxide (4-NQO) three times weekly for four weeks followed by snuff, 4-NQO only for four weeks, or cotton pellets only (twice a day on five days a week). The experiment was continued up to 108 weeks. High levels of tobacco-specific nitrosamines were found in the snuff (a commercial US brand). Rats treated with snuff only, 4-NQO followed by snuff and 4-NQO only had a significantly higher number of squamous-cell tumours and hyperplastic squamous lesions of the lip, oral and nasal cavity and forestomach than solvent or untreated controls. The total number of neoplasms was significantly higher in rats treated with snuff only and with 4-NQO followed by snuff in comparison to the other groups. Thus, snuff and 4-NQO by themselves can induce benign and malignant tumours. Snuff appears to have a general tumorigenic effect but lacked promoting ability after initiation with 4-NQO.

The migration of tobacco-specific nitrosamines into the saliva of chewers of nicotine-containing chewing gum.

In many countries nicotine-containing chewing gum (Nicorette) is used to help to break the habit of smoking. Saliva was collected every 5 min from chewers of nicotine chewing gum and analysed for tobacco-specific nitrosamines. Detectable levels of tobacco-specific nitrosamines were found in all samples collected between 5 and 15 min after chewing had started. The levels of N'-nitrosonornicotine ranged from 0.4 to 19 ng/g of saliva and those for the sum of N'-nitrosoanatabine plus N'-nitrosoanabasine from 1.3 to 46 ng/g. 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone was not detected in the saliva. The nicotine chewing gum was found to contain up to 380 ng tobacco-specific nitrosamines/g of chewing gum.

Volatile nitrosamines in microwave-cooked bacon.

Bacon was analysed for volatile nitrosamines after microwave cooking, and the results were compared with those obtained after frying bacon in a pan. Microwave cooking gave statistically significantly lower levels of all three volatile nitrosamines detected in the bacon. NPYR was found in all 20 samples fried in a pan, but in only five microwave-cooked samples. The average volatile nitrosamine levels (micrograms/kg) in microwave-cooked bacon and pan-fried bacon were: NDMA, 0.3 and 1.2; NPIP, 0.04 and 0.2; NPYR, 0.1 and 4.5.

Effect of ascorbic acid on N-nitrosoproline excretion in the urine of lacto-vegetarians and subjects on a free-choice diet.

The amounts of N-nitrosoproline (NPRO) excreted in the urine of lacto-vegetarians and subjects eating a free-choice diet were determined. The study was carried out during four consecutive weeks and specified extra amounts of ascorbic acid were ingested daily during three of them. The average amount of NPRO excreted in the urine of the lacto-vegetarians (1.33 micrograms/24 h) was slightly smaller than that in the urine of the individuals eating a free-choice diet (2.13 micrograms/24 h). Intake of as little as 3 x 20 mg of extra ascorbic acid per day reduced the NPRO excretion. Intake of 3 x 1000 mg of ascorbic acid resulted in a statistically significant decrease in NPRO excretion in the urine.

Snuff-induced carcinogenesis: effect of snuff in rats initiated with 4-nitroquinoline N-oxide.

A canal in the lower lip to function as a reservoir for snuff was surgically created in 150 male Sprague-Dawley rats. The animals were randomized into five groups of 30 each: Group I received snuff twice a day, 5 days a wk; Group II was painted with propylene glycol (solvent control) on the hard palate 3 times a wk during 4 wk; Group III underwent painting on the hard palate with 4-nitroquinoline N-oxide (4-NQO) dissolved in propylene glycol, 3 times a wk for 4 wk; Group IV received 4-NQO as in Group III followed by snuff application as in Group I; and Group V received a cotton pellet dipped in saline twice a day, 5 days a wk. Treatment continued for up to 108 wk. There was no significant difference in mean survival time between the groups. Squamous cell tumors of the lip, oral and nasal cavities, esophagus, and forestomach were seen only in Groups I, III, and IV. Nine tumors of these organs were found in Group I (six carcinomas and three papillomas), nine in Group III (seven carcinomas and two papillomas), and ten in Group IV (eight carcinomas and two papillomas). The difference between each of these groups and the control groups (II and V) with regard to tumor incidence is statistically significant (P less than 0.05). In Group I, four oral cavity or lip carcinomas were found in 29 rats, a significant difference in relation to control rats (P less than 0.05). In addition, hyperplastic lesions of the lip, palate, and forestomach were significantly more common in Groups I and IV compared with Groups II, III, and V. The study has shown that snuff and 4-NQO by themselves have the potential to induce malignant tumors. Initiation with 4-NQO followed by snuff did not significantly enhance tumor formation.

Comparison of radiometric and microbiological assays for the determination of folate in fortified gruel and porridge.

The results obtained by a radiometric assay of folate in fortified gruel and porridge, using a commercially available radioassay kit, were compared with those obtained by a standard microbiological assay with Lactobacillus casei. A lower level of folate was found with the radiometric assay. Comparison of the results obtained with the two methods gave a correlation coefficient of 0.991 when the analysis was performed on samples extracted at the same time. A lower correlation coefficient was obtained between the result if the extractions were carried out on different occasions. The radiometric assay is a acceptable method for the routine determination of folate in fortified gruel and porridge.

Volatile nitrosamines in foods on the Swedish market and estimation of their daily intake.

Foods on the Swedish market in 1980-1986 were analysed for volatile N-nitrosamines using gas chromatography-thermal energy analysis. Detectable levels were found in 474 of the 764 samples analysed. The average daily intake of volatile N-nitrosamines was estimated to be 0.29 microgram per person. Over 93% of the intake comes from meat and malt products.

Tobacco-specific N-nitrosamines in the saliva of habitual male snuff dippers.

Saliva was collected every ten minutes from habitual male snuff dippers and analysed for tobacco-specific N-nitrosamines (TSNA). Detectable levels of at least two TSNA were found in all samples collected between 10 and 30 minutes after the snuff had been placed in the mouth. Total concentrations of TSNA up to 241 ng/g were found in the saliva. Trace levels of TSNA were still found in the saliva 20 minutes after the snuff had been removed.

Excretion of N-mononitrosopiperazine after low level exposure to piperazine in air: effects of dietary nitrate and ascorbate.

The secondary amine piperazine may be nitrosated in vivo, following oral intake or occupational exposure by inhalation. The suspected carcinogen N-mononitrosopiperazine could be formed in the human stomach, and in part excreted in the urine. In this study, 0.4 microgram N-mononitrosopiperazine, determined by gas chromatography-Thermal Energy Analysis, was observed in the urine in one of four volunteers, at an experimental exposure by inhalation of 0.3 mg piperazine/m3. The intake of spinach and beetroot caused an increased nitrosation of piperazine, and up to 1.7 microgram N-mononitrosopiperazine was excreted in the urine in the four individuals. This excretion indicates that about 5% of the absorbed piperazine dose was converted to N-mononitrosopiperazine. With the same nitrate-rich diet, but with the addition of citrus fruits and fresh vegetables, the highest excretion was 0.6 microgram N-mononitrosopiperazine. The excretion was significantly correlated with the ratio between the maximum level of nitrite in saliva and the ascorbate level in plasma. There was also a significant interindividual variation. N,N'-Dinitrosopiperazine was not found in any sample of urine.

Radioisotope dilution determination of vitamin B12 in dietary supplements.

A rapid and sensitive method for the determination of vitamin B12 in dietary supplements has been developed using a commercially available radioisotope dilution (RID) kit. The vitamin B12 was isolated by enzymatic extraction.

Comparison of two radioisotope dilution assay kits for measuring vitamin B12 in gruel.

The results obtained using two commercially available radioisotope dilution (RID) assay kits for determining vitamin B12 were compared. Comparison of the results obtained with the two RID methods gave a correlation coefficient of 0.9390 for gruel samples. The results obtained with one of the kits were slightly lower, probably due to a difference in the RID assay techniques.

Excretion of N-mononitrosopiperazine in urine in workers manufacturing piperazine.

Piperazine has been shown to nitrosate in vivo to N-mononitrosopiperazine (MNPZ) by oral intake. Urine from workers exposed to piperazine in a chemical plant was analysed for nitrosamines by gas chromatography-thermal energy analysis. In five out of 11 exposed cases, MNPZ excretion in urine was 0.3 to 4.7 micrograms/24 h (during and after a work shift). In four cases, MNPZ was detected in some urine samples, and in two cases MNPZ was not detected (less than 0.1 ng/ml). The individual excretion was strongly dependent on piperazine exposure, which ranged from 0.06 to 1.7 mg/m3 (time-weighted average; Spearman's rank correlation 0.78, P = 0.01). The MNPZ excretion showed no significant correlation with nitrite or nitrate in saliva (both: r = 0.50, P = 0.10).

Effect of water on nitrosamine formation in fried bacon.

Bacon was soaked in water before frying and the effect on the formation of N-nitrosodimethylamine and N-nitrosopyrrolidine was studied. Soaking for 5 minutes reduced N-nitrosopyrrolidine levels by as much as 52%, but had little effect on N-nitrosodimethylamine levels. Longer soaking periods, up to 17 hours, gave the same results.