Pancreatic cancer and drinking water and dietary sources of nitrate and nitrite

N-Nitroso compounds, known animal carcinogens, are formed endogenously from drinking water and dietary sources of nitrate and nitrite. The authors conducted a population-based case-control study of pancreatic cancer in Iowa to determine whether increased consumption of nitrate and nitrite from drinking water and dietary sources was associated with risk. They linked detailed water source histories to nitrate measurements for Iowa community water supplies. After exclusions for insufficient data, 1,244 controls and 189 pancreatic cancer cases were available for analysis. Among controls, the median average nitrate level (1960-1987) was 1.27 (interquartile range, 0.6-2.8) mg of nitrate nitrogen per liter of water. No association was observed between pancreatic cancer risk and increasing quartiles of the community water supplies' nitrate level. Increasing intake of dietary nitrite from animal sources was associated with an elevated risk of pancreatic cancer among men and women (highest quartile odds ratios = 2.3, 95% confidence interval: 1.1, 5.1, for men and 3.2, 95% confidence interval: 1.6, 6.4, for women). In contrast, dietary nitrate intake showed an inverse association with risk among women and no association among men. This study suggests that long-term exposure to drinking water nitrate at levels below the maximum contaminant level of nitrate nitrogen (10 mg/liter) is not associated with pancreatic cancer; however, the consumption of dietary nitrite from animal products may increase risk.     

Drinking water and dietary sources of nitrate and nitrite and risk of glioma

OBJECTIVE: Dietary nitrite has been associated with increased glioma risk; however, drinking water nitrate has not been extensively evaluated. METHODS: We conducted a population-based case-control study of adult glioma in Nebraska. Water utility nitrate measurements were linked to residential water source histories. We computed average nitrate exposure over a 20-year period. A food frequency questionnaire was used to assess dietary nitrate and nitrite. RESULTS: Increasing quartiles of the average nitrate level in drinking water were not significantly associated with risk (adjusted odd ratios: 1.4, 1.2, 1.3). Risk was similar among those with both higher and lower intakes of vitamin C, an inhibitor of N-nitroso compound formation. Dietary nitrite intake was not associated with risk. CONCLUSIONS: Our study does not support a role for drinking water and dietary sources of nitrate and nitrite in risk of adult glioma.     

Evaluation of nitrate and nitrite accumulation in drinking water supplies]

Levels of the nitrate and nitrite content in water sources of Kiev and Cherkassy regions were studied. Highest concentrations of nitrite (1.33 mg N/l) and nitrate (168 mg N/l) were defined in local water sources. Peculiarity of nitrate and nitrite distribution is discussed.     

Risk of non-Hodgkin lymphoma and nitrate and nitrite from drinking water and diet

INTRODUCTION: Nitrate and nitrite are precursors in the in vivo formation of N-nitroso compounds, potent animal carcinogens. METHODS: We conducted a population-based case-control study of non-Hodgkin lymphoma (NHL) in 1998 to 2000 in Iowa, Detroit, Seattle, and Los Angeles. Because nitrate levels were elevated in many drinking water supplies in Iowa, but not in the other study centers, we evaluated water nitrate levels and risk of NHL in Iowa only. Monitoring data for public supplies were linked to water source histories from 1960 onward. Nitrate was measured at interview homes with private wells. We limited most analyses to those with nitrate estimates for > 70% of their person-years since 1960 (181 cases, 142 controls). For those in the diet arm of the study (458 cases, 383 controls from 4 centers) and for Iowa participants in both the diet and drinking water analyses, we estimated dietary nitrate and nitrite intake using a 117-item food-frequency questionnaire that included foods high in nitrate and nitrite. Odds ratios and 95% confidence intervals were calculated using logistic regression, adjusting for the study matching factors, education, and caloric intake (diet analyses only). RESULTS: We found no overall association with the highest quartile of average drinking water nitrate (> 2.90 mg/L nitrate-N: odds ratios = 1.2; 95% confidence interval = 0.6-2.2) or with years > or = 5 mg/L (10+ years: 1.4; 0.7-2.9). We observed no evidence of an interaction between drinking water nitrate exposure and either vitamin C or red meat intake, an inhibitor and precursor, respectively, of N-nitroso compound formation. Among those in the diet arm, dietary nitrate was inversely associated with risk of NHL (highest quartile: 0.54; 0.34-0.86). Dietary nitrite intake was associated with increasing risk (highest quartile: 3.1; 1.7-5.5) largely due to intakes of bread and cereal sources of nitrite. CONCLUSION: Average drinking water nitrate levels below 3 mg/L were not associated with NHL risk. Our study had limited power to evaluate higher levels that deserve further study.     

The effect of dietary nitrate on nitrate and nitrite excretion in man

Dietary nitrate and nitrite may affect colonic pathophysiology. These anions influence fermentation, and nitrite has been shown to augment sodium absorption by the colon and participate in the formation of N-nitroso compounds. There is, however, no general agreement as to how much dietary nitrate and nitrite reaches the colon. To help resolve this question, balance studies were performed on six healthy ileostomy subjects who were given diets that varied in nitrate content from 0.83 to 5.20 mmol/d. Nitrate and nitrite excretion in ileal effluent and urine were measured by anion-exchange chromatography with conductivity detection. There was no significant nitrite in the diets, urine or ileal effluent. Dietary nitrate was largely excreted in urine (1.31-4.25 mmol/d). The urinary excretion findings indicated net synthesis of nitrate at low dietary intakes and net catabolism of nitrate at high intakes. Nitrate losses in ileal effluent were very low (0.03-0.05 mmol/d, 0.03-0.06 mmol/kg) and unrelated to intake for all the diets. It is concluded that dietary nitrate and nitrite do not enter the colon from the small intestine in amounts that would affect fermentation and mucosal metabolism in man. The possibility of significant amounts of nitrate reaching the colon via blood in normal subjects has not been excluded.     

Geographic distribution of liver and stomach cancers in Thailand in relation to estimated dietary intake of nitrate, nitrite, and nitrosodimethylamine

It is our working hypothesis that the high rate of the liver and gastric cancers in North and Northeast Thailand is associated with increased daily dietary intake of nitrate, nitrite, and nitrosodimethylamine (NDMA). Samples of fresh and preserved Thai foods were systematically collected and analyzed from 1988 to 1996 and from 1998 to 2005. Consumption frequencies of various food items were determined on the basis of a dietary questionnaire given to 467 adults (212 males and 255 females) from 1998 to 2005. Food consumption data for the preceding and current year were collected and intakes (day, week, and month) of nitrate, nitrite, and NDMA were calculated. The trends in liver and stomach cancer age-standardized incidence rates (ASR) in four regions of Thailand were compared with the dietary intake of nitrate, nitrite, and NDMA in those same geographic regions. Mean daily intakes of nitrate of 155.7 mg/kg, of nitrite of 7.1 mg/kg, and of NDMA of 1.08 microg/kg per day were found. Significant differences in dietary nitrate, nitrite, and NDMA intakes were seen between various Thai regions (P < 0.0001), and these corresponded to the variations in liver and stomach cancer ASR values between the regions. Dietary factors are likely to play key roles in different stages of liver and stomach carcinogenesis in Thailand.     

Malignant neoplasms of the stomach and the quality of drinking water

This paper evaluates the influence of the quality of drinking water on the incidence of malignant stomach cancer. Both the author's own data and the data collected from published papers are used in this evaluation. The conclusion is that the quality of drinking water can have some influence on the frequency of stomach cancer incidence, especially among the population of autochthons (who have been using such water for a long time). However, taking into consideration all papers quoted here, it seems that there are also various other factors which can influence the incidence of stomach cancer.     

广州市主城区饮用水中“三氮”含量及健康风险评价

目的 了解广州主城区饮用水中氨氮、亚硝酸盐、硝酸盐氮含量,并评价其对人体健康产生潜在风险.方法 于2010年12月,检测广州市主城区(荔湾区、越秀区、天河区、白云区、黄埔区、海珠区)饮用水水样中氨氮、亚硝酸盐、硝酸盐氮的含量,并进行健康风险评价.结果 广州主城区饮用水中氨氮、亚硝酸盐含量的最高值分别是标准的14.40、21.83倍,超标率分别为50.0％,53.3％;硝酸盐氮含量均合格.各区总年均风险介于0.177× 10-8～2.169×10-8/a,均值为1.064×10-8/a,远低于美国环保局(USEPA)推荐的健康风险水平标准(5.0× 10-5/a).广州主城区饮用水中的健康危害个人年平均风险由高至低依次为亚硝酸盐(0.952× 10-8/a)＞氨氮(1.090× 10-9/a)＞硝酸盐氮(0.276×10-10/a),且以亚硝酸盐为主;各主城区饮用水的健康危害个人年平均风险由高至低依次为荔湾区＞白云区＞越秀区＞天河区＞黄埔区＞海珠区.结论 广州市主城区饮用水中氨氮、亚硝酸盐污染较严重,但不会对暴露人群引起健康危害.     

胃癌高、低发区饮用水中化学元素、硝酸盐及亚硝酸盐含量调查

目的分析比较胃癌高、低死亡区饮用水中化学元素、硝酸盐及亚硝酸盐含量,探讨其与胃癌死亡率的关系。方法收集胃癌高死亡区（长乐市）和低死亡区（福安市）饮用水水样各45份和30份,按《生活饮用水检验规范》分析化学元素、硝酸盐及亚硝酸盐含量,采用非参数秩和检验进行比较。结果长乐市饮用水硝酸盐和Mn均值高于生活饮用水卫生标准上限值,长乐市饮用水中亚硝酸盐、硝酸盐、Mn、Mg、Cl显著高于福安市（P〈0.05）,As、F、Fe、Hg显著低于福安市（P〈0.05）。结论长乐市胃癌高死亡率可能与饮用水硝酸盐、亚硝酸盐含量偏高存在联系,饮用水中化学元素与胃癌死亡率间的关系需要进一步深入研究。     

饮用水源的卫生问题和对策

近年,饮用水源中有机物对人体健康的影响,环境内分泌干扰物的健康影响,微囊藻毒素的毒性及健康效应等,成为饮水与健康研究的新热点。因此。如何保证饮用水源的卫生安全,是摆在我们面前的严峻课题。笔者对中山市饮用水源的卫生问题和对策进行探讨。     

直饮水中亚硝酸盐含量测定的若干探讨

目的:直饮水中亚硝酸盐含量测定的若干探讨,为直饮水中亚硝酸盐含量标准提供参考依据,为直饮水中亚硝酸盐含量测定提供检测依据,并将该方法应用于各类直饮水中的亚硝酸盐含量测定,有效指导人们安全饮水。方法:参考GB/T8538-1995《饮用天然矿泉水检验方法》和GB/T5750-2006《生活饮用水标准检验方法》,优化方法中一些测定条件,对直饮水中亚硝酸盐进行分析测定。结果:在0.00～9.90×10-2 mg/L浓度范围内呈线性关系,工作曲线y=2.2134x+0.0007,相关系数为0.9998,最低检出浓度为6.60×10-4 mg/L,相对标准偏差为0.96%～16.0%,加标回收率93.6%～122%。结论:该方法适合于直饮水中亚硝酸盐含量的测定,并能为直饮水中亚硝酸盐标准提供参考依据,为相关监管部门提供相应的检测依据。     

Pancreatic cancer and exposure to dietary nitrate and nitrite in the NIH-AARP Diet and Health Study

Nitrate and nitrite are precursors of N-nitroso compounds, which induce tumors of the pancreas in animals. The authors evaluated the relation of dietary nitrate and nitrite to pancreatic cancer risk in the NIH-AARP Diet and Health Study. Nitrate and nitrite intakes were assessed at baseline using a 124-item food frequency questionnaire. During approximately 10 years of follow-up between 1995 and 2006, 1,728 incident pancreatic cancer cases were identified. There was no association between total nitrate or nitrite intake and pancreatic cancer in men or women. However, men in the highest quintile of summed nitrate/nitrite intake from processed meat had a nonsignificantly elevated risk of pancreatic cancer (hazard ratio = 1.18, 95% confidence interval: 0.95, 1.47; P-trend = 0.11). The authors observed a stronger increase in risk among men for nitrate/nitrite intake from processed meat at ages 12-13 years (highest quintile vs. lowest: hazard ratio = 1.32, 95% confidence interval: 0.99, 1.76; P-trend = 0.11), though the relation did not achieve statistical significance. The authors found no associations between adult or adolescent nitrate or nitrite intake from processed meats and pancreatic cancer among women. These results provide modest evidence that processed meat sources of dietary nitrate and nitrite may be associated with pancreatic cancer among men and provide no support for the hypothesis in women.     

不同水源水与处理工艺对生活饮用水水质的影响

目的了解不同水源水与水质工艺处理方式对饮用水水质的影响。方法按不同源水来源与处理工艺在辖区内设置生活饮用水采样点37个,每月采样检测,共采集水样408件。结果黄浦江源水生活饮用水水质检测总合格率为74.85%,青草沙水库源水的水质检测总合格率为97.47%,二者差异有统计学意义（χ^2=48.07;P〈0.05）。黄浦江源水经深度处理后,生活饮用水水质检测总合格率为83.08%,常规处理水质总合格率仅为48.78%,二者差异有统计学意义（χ^2=19.48;P〈0.05）;青草沙水库源水经2种不同工艺处理后,水质没有明显差异。结论水质以青草沙水库为源水的优于黄浦江源水。源水与处理工艺决定水质的优劣,应逐步选用优质源水和深度处理工艺,去除水中有机物的污染,有效提高水质质量。     

紫外分光光度法测定饮用水中硝酸盐氮

目的:应用紫外分光光度法测定饮用水中硝酸盐氮。方法:同时使用紫外分光光度法和麝香草酚比色法测定饮用水中硝酸盐氮。结果:使用紫外分光光度法测定饮用水中硝酸盐氮呈现良好线性(r>0.999)。结论:实验结果表明,紫外分光光度法操作简单、方便、快捷,干扰少,测定结果准确可靠,适用于饮用水中硝酸盐氮的测定,值得推广使用。