Impact of nitrates in drinking water on cancer mortality in Valencia, Spain

A critical review of advances in tumor metabolism abnormalities induced by nitrosamine disinfection by-products in drinking water

Intensified sanitation practices amid the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak might result in the increased release of chloramine disinfectants into surface water, significantly promoting the formation of nitrosamine disinfection by-products (DBPs) in drinking water. Unfortunately, these nitrosamine DBPs exhibit significant genotoxic, carcinogenic, and mutagenic properties, whereas chlorinating disinfectants remain in global practice. The current review provides valuable insights into the occurrence, identification, contamination status, exposure limits, and toxicity of the new unregulated disinfection by-products (nitrosamine DBPs) in drinking water. As a result, concentrations of nitrosamine DBPs far exceed allowable limits in drinking water, and prolonged exposure has the potential to cause metabolic disorders, a critical step in tumor initiation and progression. Importantly, based on recent research, we have concluded the role of nitrosamines DBPs in different metabolic pathways. Remarkably, nitrosamine DBPs can induce chronic inflammation and initiate tumors by activating sphingolipid and polyunsaturated fatty acid metabolism. Regarding amino acid and nucleotide metabolism, nitrosamine DBPs can inhibit tryptophan metabolism and de novo nucleotide synthesis. Moreover, inhibition of de novo nucleotide synthesis fails to repair DNA damage induced by nitrosamines. Additionally, the accumulation of lactate induced by nitrosamine DBPs may act as a pivotal signaling molecule in communication within the tumor microenvironment. However, with the advancement of tumor metabolomics, understanding the role of nitrosamine DBPs in causing cancer by inducing metabolic abnormalities significantly lags behind, and specific mechanisms of toxic effects are not clearly defined. Urgently, further studies exploring this promising area are needed.

Surface-Water Nitrate Exposure to World Populations Has Expanded and Intensified during 1970-2010

Excessive nitrate in surface waters deteriorates the water quality and threatens human health. Human activities have caused increased nitrate concentrations in global surface waters over the past 50 years. An assessment of the long-term trajectory of surface-water nitrate exposure to world populations and the associated potential health risks is imperative but lacking. Here, we used global spatially explicit data on surface-water nitrate concentrations and population density, in combination with thresholds for health risks from epidemiological studies, to quantify the long-term changes in surface-water nitrate exposure to world populations at multiple spatial scales. During 1970-2010, global populations potentially affected by acute health risks associated with surface-water nitrate exposure increased from 6 to 60 million persons per year, while populations at potential chronic health risks increased from 169 to 1361 million persons per year. Potential acute risks have increasingly affected Asian countries. Populations potentially affected by chronic risks shifted from dominance by high-income countries (in Europe and North America) to middle-income countries (in Asia and Africa). To mitigate adverse health effects associated with surface-water nitrate exposure, anthropogenic nitrogen inputs to natural environments should be drastically reduced. International and national standards of maximum nitrate contamination may need to be lowered.

Nitrate and nitrite contamination in drinking water and cancer risk: A systematic review with meta-analysis

BACKGROUND

Pollution of water sources, largely from wide-scale agricultural fertilizer use has resulted in nitrate and nitrite contamination of drinking water. The effects on human health of raised nitrate and nitrite levels in drinking water are currently unclear.

OBJECTIVES

We conducted a systematic review of peer-reviewed literature on the association of nitrate and nitrite in drinking water with human health with a specific focus on cancer.

METHODS

We searched eight databases from 1 January 1990 until 28 February 2021. Meta-analyses were conducted when studies had the same exposure metric and outcome.

RESULTS

Of 9835 studies identified in the literature search, we found 111 studies reporting health outcomes, 60 of which reported cancer outcomes (38 case-control studies; 12 cohort studies; 10 other study designs). Most studies were set in the USA (24), Europe (20) and Taiwan (14), with only 3 studies from low and middle-income countries. Nitrate exposure in water (59 studies) was more commonly investigated than nitrite exposure (4 studies). Colorectal (15 studies) and gastric (13 studies) cancers were the most reported. In meta-analyses (4 studies) we identified a positive association of nitrate exposure with gastric cancer, OR = 1.91 (95%CI = 1.09-3.33) per 10 mg/L increment in nitrate ion. We found no association of nitrate exposure with colorectal cancer (10 studies; OR = 1.02 [95%CI = 0.96-1.08]) or cancers at any other site.

CONCLUSIONS

We identified an association of nitrate in drinking water with gastric cancer but with no other cancer site. There is currently a paucity of robust studies from settings with high levels nitrate pollution in drinking water. Research into this area will be valuable to ascertain the true health burden of nitrate contamination of water and the need for public policies to protect human health.

Reactive nitrogen compounds and their influence on human health: an overview

Nitrogen (N) is a critical component of food security, economy and planetary health. Human production of reactive nitrogen (Nr) via Haber-Bosch process and cultivation-induced biological N₂ fixation (BNF) has doubled global N cycling over the last century. The most important beneficial effect of Nr is augmenting global food supplies due to increased crop yields. However, increased circulation of Nr in the environment is responsible for serious human health effects such as methemoglobinemia ("blue baby syndrome") and eutrophication of coastal and inland waters. Furthermore, ammonia (NH₃) emission mainly from farming and animal husbandary impacts not only human health causing chronic lung disease, inflammation of human airways and irritation of eyes, sinuses and skin but is also involved in the formation of secondary particulate matter (PM) that plays a critical role in environment and human health. Nr also affects human health via global warming, depletion of stratospheric ozone layer resulting in greater intensity of ultra violet B rays (UVB) on the Earth's surface, and creation of ground-level ozone (through reaction of NO₂ with O₂). The consequential indirect human health effects of Nr include the spread of vector-borne pathogens, increased incidence of skin cancer, development of cataracts, and serious respiratory diseases, besides land degradation. Evidently, the strategies to reduce Nr and mitigate adverse environmental and human health impacts include plugging pathways of nitrogen transport and loss through runoff, leaching and emissions of NH₃, nitrogen oxides (NO _x ), and other N compounds; improving fertilizer N use efficiency; reducing regional disparity in access to N fertilizers; enhancing BNF to decrease dependence on chemical fertilizers; replacing animal-based proteins with plant-based proteins; adopting improved methods of livestock raising and manure management; reducing air pollution and secondary PM formation; and subjecting industrial and vehicular NO _x emission to pollution control laws. Strategic implementation of all these presents a major challenge across the fields of agriculture, ecology and public health. Recent observations on the reduction of air pollution in the COVID-19 lockdown period in several world regions provide an insight into the achievability of long-term air quality improvement. In this review, we focus on complex relationships between Nr and human health, highlighting a wide range of beneficial and detrimental effects.

Association between environmental quality and prostate cancer stage at diagnosis

BACKGROUND

Prostate cancer (PC) etiology is up to 57% heritable, with the remainder attributed to environmental exposures. There are limited studies regarding national level environmental exposures and PC aggressiveness, which was the focus of this study METHODS: SEER was queried to identify PC cases between 2010 and 2014. The environmental quality index (EQI) is a county-level metric for 2000-2005 combining data from 18 sources and reports an overall ambient environmental quality index, as well as 5 environmental quality sub-domains (air, water, land, built, and sociodemographic) with higher values representing lower environmental quality. PC stage at diagnosis was determined and, multivariable logistic regression models which adjusted for age at diagnosis (years) and self-reported race (White, Black, Other, Unknown) were used to test associations between quintiles of EQI scores and advanced PC stage at diagnosis.

RESULTS

The study cohort included 252,164 PC cases, of which 92% were localized and 8% metastatic at diagnosis. In the adjusted regression models, overall environmental quality EQI (OR 1.20, CI 1.15-1.26), water EQI (OR: 1.34, CI: 1.27-1.40), land EQI (OR: 1.35, CI: 1.29-1.42) and sociodemographic EQI (OR: 1.29, CI: 1.23-1.35) were associated with metastatic PC at diagnosis. For these domains there was a dose response increase in the OR from the lowest to the highest quintiles of EQI. Black race was found to be an independent predictor of metastatic PC at diagnosis (OR: 1.36, CI: 1.30-1.42) and in stratified analysis by race; overall EQI was more strongly associated with metastatic PC in Black men (OR: 1.53, CI: 1.35-1.72) compared to White men (OR: 1.18, CI: 1.12-1.24).

CONCLUSION(S)

Lower environmental quality was associated with advanced stage PC at diagnosis. The water, land and sociodemographic domains showed the strongest associations. More work should be done to elucidate specific modifiable environmental factors associated with aggressive PC.

Linking DPSIR Model and Water Quality Indices to Achieve Sustainable Development Goals in Groundwater Resources

The achievement of sustainable development goals in groundwater resources related to water quality issues is a critical question in many regions. This study aims to combine powerful tools for helping stakeholders and policymakers achieve sustainable development goals in groundwater resources of agricultural areas. The DPSIR (Driver–Pressure–State–Impact–Response) model in combination with the Canadian Council of Ministers of Environment Water Quality Index and Groundwater Directive 2006/118/European Community—Threshold Values was applied using a hydrogeochemical dataset derived from the analysis of groundwater samples collected from 31 monitoring sites in an unconfined alluvial aquifer. Elevated Cl− (up to 423.2 mg L−1), NO3− (up to 180.1 mg L−1) concentration and electrical conductivity (up to 2037 μS cm−1) value are observed for groundwater samples of the study area. The outcome of the “One Out-All Out” procedure revealed that the groundwater in 42% of the monitored sites is unsuitable for drinking according to the health-based guideline values established by Directive 98/83/European Community. A difficulty to achieve targets under Sustainable Development Goals 3 and 6 in the study area is revealed. The proposed response actions are reported.

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 2^nd 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.

Assessment of hydrogeochemical characteristics and quality of groundwater resources in relation to risk of gastric cancer: comparative analysis of high- and low-risk areas in Iran

The chemical quality of groundwater supplies in two high-risk area (HRA) and low-risk area (LRA) for gastric cancer in Iran was assessed through hydrogeochemical analysis and water quality indices. For this aim, Piper and Schoeller diagrams and water quality index (WQI) were applied. In addition, exposure to nitrate via drinking water and its corresponding risk were also assessed using Monte Carlo simulation technique. Data on physicochemical properties of groundwater resources were obtained from Iran Water Resources Management Company. Sampling and analysis of tap water for nitrate concentration were conducted in two cities of Shiraz (as a representative of LRA) and Ardabil (as a representative of HRA). According to Piper diagrams, the dominant hydrogeochemical facies of groundwater supplies in HRA and LRA were Na-HCO₃ (43.75%) and Ca-HCO₃ (41.77%), respectively. The predominant cations in groundwater resources of HRA were found to be Na⁺ (68.06%) and Ca²⁺ (31.94%). For LRA, the typical cations were in decreasing trend: Ca²⁺ (39.64%) > Mg²⁺ (18.35%) > Na⁺ (17.26%). For two areas, HCO₃^-, SO₄^2- and Cl^- were, respectively, the most frequent anions. Two-sample Wilcoxon test showed that there were statistically significant difference between two areas in terms of anions and cations concentrations (p value < 0.05). The mean of total hardness (Ca²⁺ + Mg²⁺) concentration of water supplies in LRA (528.1 mg/L) was higher than HRA (263.1 mg/L), whereas the mean of Na⁺ concentration was found to be lower in LRA (90.6 mg/L) compared with HRA (108.1 mg/L). The sum of nitrate intake and its risk in LRA was higher than HRA. WQI results showed that drinking water quality in HRA and LRA ranged from excellent to poor and most water resources were of a good quality class. Further studies are suggested to investigate the role of drinking water in the etiology of gastric cancer in Iran.

Exposure-based assessment and economic valuation of adverse birth outcomes and cancer risk due to nitrate in United States drinking water

BACKGROUND

Nitrate ingestion from drinking water has been associated with an increased risk of adverse birth outcomes as well as elevated risk of colorectal cancer and several other cancers. Yet, to date, no studies have attempted to quantify the health and economic impacts due to nitrate in drinking water in the United States.

METHODS

This study presents a first-of-its-kind comprehensive assessment of nitrate exposure from drinking water for the entire United States population. This exposure assessment serves as the basis for our analysis of the annual nitrate-attributable disease cases in the United States and the associated economic losses due to medical costs and lost productivity. Additionally, through a meta-analysis of studies on drinking water nitrate and colorectal cancer, we examine the exposure-response relationship for nitrate and cancer risk.

RESULTS

On the basis of national nitrate occurrence data and relative risk ratios reported in the epidemiology literature, we calculated that annually, 2939 cases of very low birth weight, 1725 cases of very preterm birth, and 41 cases of neural tube defects could be related to nitrate exposure from drinking water. For cancer risk, combining nitrate-specific risk estimates for colorectal, ovarian, thyroid, kidney, and bladder cancers results in a range of 2300 to 12,594 annual nitrate-attributable cancer cases (mean: 6537 estimated cases). For medical expenditures alone, this burden of cancer corresponds to an annual economic cost of 250 million to 1.5 billion U.S. dollars, together with a potential 1.3 to 6.5 billion dollar impact due to lost productivity. With the meta-analysis of eight studies of drinking water nitrate and colorectal cancer, we observed a statistically significant positive association for nitrate exposure and colorectal cancer risk and calculated a one-in-one million cancer risk level of 0.14 mg/L nitrate in drinking water.

CONCLUSION

Health and economic analyses presented here suggest that lowering exposure to nitrate in drinking water could bring economic benefits by alleviating the impacts of nitrate-associated diseases.

New direction in biological nitrogen removal from industrial nitrate wastewater via anammox

Anaerobic ammonium oxidation (anammox) is an important scientific discovery in the field of wastewater treatment. This process is a sustainable option in nitrogen removal due to its energy-efficient and cost-effective advantage. Great effort has been made recently to remove ammonium from industrial and municipal wastewater via the anammox process with a preceding partial nitrification (PN) converting part of NH₄⁺ to NO₂^-. Anammox process is seldom involved in the nitrate removal. Nitrate (NO₃^-), one of the main nitrogen compounds produced from various industries, is typically converted to nitrogen gas via denitrification process where a large amount of carbon source is consumed. Within this context, we reviewed the current technologies for high-strength nitrate wastewater treatment. It is found that nitrite accumulation often occurs during nitrate reduction, and its accumulating level would be increased at certain conditions (i.e., low C/N ratio and high pH). Hence, this provides a great opportunity to employ the anammox process to further convert nitrite in a more sustainable way. In this review, we highlight a new approach for industrial nitrate wastewater treatment via partial denitrification coupled with anammox process (PD-A). We also discuss the conditions to achieve successful PD-A process, economic and environmental benefits, and potential challenges as well as the future perspectives in practical application.

Origin and distribution of nitrate in water well of settlement areas in Yogyakarta, Indonesia

Pollution of nitrate in water wells in Yogyakarta City was reported to increase for two decades. This study aimed to describe nitrate contamination in the water wells of colorectal cancer (CRC) and inflammatory bowel disease (IBD) patients, previously described elsewhere. Nitrate and chloride content of 150 water samples from the wells of patients with CRC and IBD who were residing in Yogyakarta, Sleman, or Bantul districts were examined. Description of nitrate contamination was presented in the form of box plot charts and map. Kruskal-Wallis analysis was used to measure the difference of nitrate concentration in three areas of study. Comparisons of nitrate and chloride concentrations were used to determine the source of nitrate contamination in water well. Fisher's exact test was used to describe the relationship of well distance with the septic tank to nitrate concentration in water well. The wells in Yogyakarta City had the highest median nitrate content compared to Sleman and Bantul (P = 0.001) with the median of 56.6, 13.1, and 7.7 for Yogyakarta, Sleman, and Bantul, respectively, and most tested samples exceed WHO safe drinking water standards. The spread of nitrate contamination has occurred in areas adjacent to Yogyakarta City compared to the previous report. The ratio of nitrate to chloride (1-8:1) suggested that the source of nitrate contamination in water wells in the study area came from feces due to inadequate on-site sanitation. The mapping showed nitrate contamination in water wells in Yogyakarta City, Sleman, and Bantul districts had spread according to urban development.

Impact of Calcium and Magnesium in Groundwater and Drinking Water on the Health of Inhabitants of the Slovak Republic

This work aims to evaluate the impact of the chemical composition of groundwater/drinking water on the health of inhabitants of the Slovak Republic. Primary data consists of 20,339 chemical analyses of groundwater (34 chemical elements and compounds) and data on the health of the Slovak population expressed in the form of health indicators (HI). Fourteen HIs were evaluated including life expectancy, potential years of lost life, relative/standardized mortality for cardiovascular and oncological diseases, and diseases of the gastrointestinal and respiratory systems. The chemical and health data were expressed as the mean values for each of the 2883 Slovak municipalities. Artificial neural network (ANN) was the method used for environmental and health data analysis. The most significant relationship between HI and chemical composition of groundwater was documented as Ca + Mg (mmol·L⁻¹), Ca and Mg. The following limit values were set for these most significant groundwater chemical parameters: Ca + Mg 2.9–6.1 mmol·L⁻¹, Ca 78–155 mg·L⁻¹ and Mg 28–54 mg·L⁻¹. At these concentration ranges, the health of the Slovak population is the most favorable and the life expectancy is the highest. These limit values are about twice as high in comparison to the current Slovak valid guideline values for drinking water.

Chemical composition of groundwater/drinking water and oncological disease mortality in Slovak Republic

This study deals with the analysis of relationship between chemical composition of the groundwater/drinking water and the data on mortality from oncological diseases (MOD) in the Slovak Republic. Primary data consist of the Slovak national database of groundwater analyses (20,339 chemical analyses, 34 chemical elements/compounds) and data on MOD (17 health indicators) collected for the 10-year period (1994-2003). The chemical and health data were unified in the same form and expressed as the mean values for each of 2883 municipalities within the Slovak Republic. Pearson and Spearman correlation as well as artificial neural network (ANN) methods were used for analysis of the relationship between chemical composition of groundwater/drinking water and MOD. The most significant chemical elements having influence on MOD were identified together with their limit values (limit and optimal contents). Based on the results of calculations, made through the neural networks, the following eight chemical elements/parameters in the groundwater were defined as the most significant for MOD: Ca + Mg (mmol l^-1), Ca, Mg, TDS, Cl, HCO₃, SO₄ and NO₃. The results document the highest relationship between MOD and groundwater contents of Ca + Mg (mmol l^-1), Ca and Mg. We observe increased MOD with low (deficit) contents of these three parameters of groundwater/drinking water. The following limit values were set for the most significant groundwater chemicals/parameters: Ca + Mg 1.73-5.85 mmol l^-1, Ca 60.5-196.8 mg l^-1 and Mg 25.6-35.8 mg l^-1. At these concentration ranges, the mortality for oncological diseases in the Slovak Republic is at the lowest levels. These limit values are about twice higher in comparison with the current Slovak valid guideline values for the drinking water.

Nitrate in drinking water and risk of colorectal cancer in Yogyakarta, Indonesia

Nitrate concentration in well water in Yogyakarta, Indonesia, and its surroundings tended to increase rapidly from time to time, and it may be associated with an elevated risk for several types of cancer. The purpose of this study was to examine the association between nitrate in drinking water and colorectal cancer (CRC) risk occurrence. A case-control study was conducted in Yogyakarta Special Province. Pathologically confirmed 75 CRC patients and 75 controls were consulted and their individual well water was sampled and examined for nitrate concentrations. Logistic regression analysis was conducted to establish the association between nitrate and CRC risk development. There was a significant correlation between nitrate in drinking water and CRC occurrence, and this value was relatively stable after being adjusted for protein intake, smoking history, age, and family history of cancer. These findings demonstrated that the risk of CRC development was fourfold among those with >10 years of nitrate exposure from well water compared with those with ≤10 years of nitrate exposure. Consequently, a significant association between nitrate in drinking water and occurrence of CRC in Yogyakarta was established.

Industrial water pollution, water environment treatment, and health risks in China

The negative health effects of water pollution remain a major source of morbidity and mortality in China. The Chinese government is making great efforts to strengthen water environment treatment; however, no studies have evaluated the effects of water treatment on human health by water pollution in China. This study evaluated the association between water pollution and health outcomes, and determined the extent to which environmental regulations on water pollution may lead to health benefits. Data were extracted from the 2011 and 2013 China Health and Retirement Longitudinal Study (CHARLS). Random effects model and random effects Logit model were applied to study the relationship between health and water pollution, while a Mediator model was used to estimate the effects of environmental water treatment on health outcomes by the intensity of water pollution. Unsurprisingly, water pollution was negatively associated with health outcomes, and the common pollutants in industrial wastewater had differential impacts on health outcomes. The effects were stronger for low-income respondents. Water environment treatment led to improved health outcomes among Chinese people. Reduced water pollution mediated the associations between water environment treatment and health outcomes. The results of this study offer compelling evidence to support treatment of water pollution in China.

Increased deaths from gastric cancer in communities living close to waste landfills

BACKGROUND

Municipal waste landfills (MWLs) have been linked with some malignancies, but data about gastric cancer (GC) are still uncertain.

METHODS

Number of deaths from GC, death rates, and odds ratios (ORs) were calculated considering all residents in the 258 towns in the Apulia Region (4,099,547 subjects, years 2006-2009), living within 3 km from each of the 16 regional MWLs (n = 716,404) or in control areas (n = 3,383,143).

RESULTS

Males living close to MWLs showed a higher death rate for GC, a twofold higher mean number of GC deaths and higher adjusted ORs of GC, compared with controls areas.

CONCLUSIONS

In a large population and over a wide time period, an increased risk of death from GC has been shown in males living in communities close to MWLs. Primary prevention policies acting through more sustainable waste management might probably partially reduce deaths from GC in areas with MWLs.

Runoff quality from no-till cotton fertilized with broiler litter in subsurface bands

Surface broadcast of broiler litter to no-till row crops exposes the litter and its nutrients to risks of loss in runoff water and volatilization and may limit the potential benefit of litter to the crops. Subsurface banding of litter could alleviate these risks. A field study was conducted in 2008 and 2009 on an upland Falkner silt loam soil to determine the effect of broiler litter placement on runoff nutrient losses from no-till cotton ( L.). Treatments included surface broadcast broiler litter applied manually, subsurface-banded litter applied by tractor-drawn equipment, and no broiler litter, all in combination with or without winter wheat ( L.) cover crop residue. Broiler litter rate was 5.6 Mg ha. The experimental design was a randomized complete block with a split-plot arrangement of treatments replicated three times. In 2008, simulated rainfall was used to generate runoff 27 d after litter application. Subsurface-banded litter reduced runoff total C, N, P, NH, NO, Cu, Zn and water-soluble P (WP) concentrations by 72, 64, 51, 49, 70, 36, 65, and 77%, respectively, compared with surface broadcast. The reductions were greater in 2009 where runoff occurred 1 d after litter application. Bacterial runoff was decreased by one log with subsurface-banded litter compared to surface broadcast. Except for C, NH, N, and WP, the presence of winter cover crop residue did not affect the load or runoff nutrient concentrations in either year. The results indicate that subsurface banding litter to no-till cotton substantially reduces nutrient and bacterial losses in runoff compared with surface broadcasting.

Incidence and mortality trends of gastric and colorectal cancers in Croatia, 1988-2008

AIM

To estimate the incidence and mortality trends of gastric and colorectal cancers in Croatia between 1988 and 2008.

METHODS

Incidence data for the period 1988-2008 were obtained from the Croatian National Cancer Registry. The number of deaths from gastric and colorectal cancers were obtained from the World Health Organization mortality database. Joinpoint regression analysis was used to describe changes in trends by sex.

RESULTS

Gastric cancer incidence rates declined steadily during the study period, with estimated annual percent change (EAPC) of -3.2% for men and -2.8% for women. Mortality rates in men decreased, with EAPC of -5.0% from 1988-1995 and -2.5% from 1995-2008. Mortality rates in women decreased, with EAPC of -3.2% throughout the study period. For colorectal cancer in men, joinpoint analysis revealed increasing trends of both incidence (EAPC 2.9%) and mortality (EAPC 2.1%). In women, the increase in incidence was not significant, but mortality rates in the last 15 years showed a significant increase (EAPC 1.1%).

CONCLUSION

The incidence and mortality trends of gastric cancer in Croatia are similar to other European countries, while the still increasing colorectal cancer mortality calls for more efficient prevention and treatment.

Effect modification by drinking water hardness of the association between nitrate levels and gastric cancer: evidence from an ecological study

The objectives of this study were to (1) examine the relationship between nitrate levels in public water supplies and risk of death from gastric cancer and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of nitrate on the risk of gastric cancer development. A matched cancer case-control study was used to investigate the relationship between the risk of death attributed to gastric cancer and exposure to nitrate in drinking water in Taiwan. All deaths due to gastric cancer in Taiwan residents from 2006 through 2010 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Deaths from other causes served as controls and were pair-matched to cancer cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen (NO(3)-N), Ca, and Mg in drinking water were collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's NO(3)-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO(3)-N exposure levels were <0.38 ppm, the adjusted odds ratio (OR) and 95% confidence interval (CI) for gastric cancer occurrence was 1.16 (1.05-1.29) for individuals who resided in municipalities served by drinking water with a NO(3)-N exposure ≥ 0.38 ppm. There was apparent evidence of an interaction between drinking water NO(3)-N levels and low Ca and Mg intake via drinking water. Our findings showed that the correlation between NO(3)-N exposure and risk of gastric cancer development was influenced by Ca and Mg levels in drinking water. This is the first study to report effects modification by Ca and Mg intake from drinking water on the relationship between NO(3)-N exposure and risk of gastric cancer occurrence. Increased knowledge of the mechanistic interactions between Ca, Mg, and NO(3)-N in reducing risk of gastric cancer development will aid in public policy decisions and setting threshold standards.

Effect of surface incorporation of broiler litter applied to no-till cotton on runoff quality

Surface application of broiler litter to no-till cotton could lead to degradation of water quality. Incorporation of broiler litter into the top surface soil (0.05 m) could alleviate this risk. A 2-yr field study was conducted on a silt loam upland soil to determine the effect of incorporation of broiler litter into the soil surface on nutrient and bacterial transport in runoff. The experimental design was a randomized complete block with four treatments and three replications. Treatments were (i) unfertilized control; (ii) surface-appliedbroiler litter at 7.8 Mg ha(-1) without incorporation; (iii) surface-applied broiler litter at 7.8 Mg ha(-1) with immediate incorporation; and (iv) inorganic fertilizer N (urea ammonium nitrate, 32% N) and inorganic fertilizer P (triple superphosphate) at the recommended rate. Phosphorus was surface appliedat 25 kg ha(-1) and N was injected at 101 kg ha(-1) into the soil using a commercial liquid fertilizer applicator. Runoff was collected from small runoff plots (2.4 m by 1.6 m) established at the bottom side of main plots (13.7 m by 6.0 m). Incorporation of broiler litter reduced total N (TN), NO3-N, water soluble P (WSP), and total P (TP) concentrations in runoffby 35, 25, 61, and 64%, respectively, and litter-associated bacteria by two to three orders of magnitude compared with unincorporated treatment. No significant difference in total suspended solids (TSS) in runoffwas obtained between incorporated and unincorporated treatments. Incorporation of broiler litter into the surface soil in the no-till system immediately after application minimized the potential risk for surface nutrient losses and bacteria transport in runoff.

Estimation of incidence and social cost of colon cancer due to nitrate in drinking water in the EU: a tentative cost-benefit assessment

BACKGROUND

Presently, health costs associated with nitrate in drinking water are uncertain and not quantified. This limits proper evaluation of current policies and measures for solving or preventing nitrate pollution of drinking water resources. The cost for society associated with nitrate is also relevant for integrated assessment of EU nitrogen policies taking a perspective of welfare optimization. The overarching question is at which nitrogen mitigation level the social cost of measures, including their consequence for availability of food and energy, matches the social benefit of these measures for human health and biodiversity.

METHODS

Epidemiological studies suggest colon cancer to be possibly associated with nitrate in drinking water. In this study risk increase for colon cancer is based on a case-control study for Iowa, which is extrapolated to assess the social cost for 11 EU member states by using data on cancer incidence, nitrogen leaching and drinking water supply in the EU. Health costs are provisionally compared with nitrate mitigation costs and social benefits of fertilizer use.

RESULTS

For above median meat consumption the risk of colon cancer doubles when exposed to drinking water exceeding 25 mg/L of nitrate (NO3) for more than ten years. We estimate the associated increase of incidence of colon cancer from nitrate contamination of groundwater based drinking water in EU11 at 3%. This corresponds to a population-averaged health loss of 2.9 euro per capita or 0.7 euro per kg of nitrate-N leaching from fertilizer.

CONCLUSIONS

Our cost estimates indicate that current measures to prevent exceedance of 50 mg/L NO3 are probably beneficial for society and that a stricter nitrate limit and additional measures may be justified. The present assessment of social cost is uncertain because it considers only one type of cancer, it is based on one epidemiological study in Iowa, and involves various assumptions regarding exposure. Our results highlight the need for improved epidemiological studies.

Nitrates in municipal drinking water and non-Hodgkin lymphoma: an ecological cancer case-control study in Taiwan

The relationship between nitrate levels in drinking water and increased risk of non-Hodgkin lymphoma (NHL) development has been inconclusive. A matched cancer case-control and a nitrate ecology study was used to investigate the association between mortality attributed to NHL and nitrate exposure from Taiwan's drinking water. All deaths due to NHL in Taiwan residents from 2000 through 2006 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Data on nitrate-nitrogen (NO(3)-N) levels of drinking water throughout Taiwan were collected from the Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's nitrate exposure via drinking water. The adjusted odds ratios (OR) for NHL death for those with high nitrate levels in their drinking water, as compared to the lowest tertile, were 1.02 (0.87-1.2) and 1.05 (0.89-1.24), respectively. The results of the present study show that there was no statistically significant association between nitrates in drinking water at levels in this investigation and increased risk of death attributed to NHL.

Nitrates in drinking water and the risk of death from rectal cancer: does hardness in drinking water matter?

The objectives of this study were to (1) examine the relationship between nitrate levels in public water supplies and increased risk of death from rectal cancer and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of nitrate on development of rectal cancer. A matched case-control study was used to investigate the relationship between the risk of death from rectal cancer and exposure to nitrate in drinking water in Taiwan. All rectal cancer deaths of Taiwan residents from 2003 through 2007 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen (NO(3)-N), Ca, and Mg in drinking water was collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's NO(3)-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO(3)-N exposure level was <0.38 ppm, the adjusted odds ratio (OR) (95% CI) for rectal cancer occurrence was 1.15 (1.01-1.32) for individuals who resided in municipalities served by drinking water with a NO(3)-N exposure > or =0.38 ppm. There was no apparent evidence of an interaction between drinking water NO(3)-N levels with low Mg intake via drinking water. However, evidence of a significant interaction was noted between drinking-water NO(3)-N concentrations and Ca intake via drinking water. Our findings showed that the correlation between NO(3)-N exposure and risk of rectal cancer development was influenced by Ca in drinking water. This is the first study to report effect modification by Ca intake from drinking water on the association between NO(3)-N exposure and risk of rectal cancer occurrence. Increased knowledge of the mechanistic interaction between Ca and NO(3)-N in reducing rectal cancer risk will aid in public policymaking and setting threshold standards.

Gastric cancer mortality trends in Spain, 1976-2005, differences by autonomous region and sex

BACKGROUND

Gastric cancer is the second leading cause of oncologic death worldwide. One of the most noteworthy characteristics of this tumor's epidemiology is the marked decline reported in its incidence and mortality in almost every part of the globe in recent decades. This study sought to describe gastric cancer mortality time trends in Spain's regions for both sexes.

METHODS

Mortality data for the period 1976 through 2005 were obtained from the Spanish National Statistics Institute. Cases were identified using the International Classification of Diseases 9th and 10th revision (codes 151 and C16, respectively). Crude and standardized mortality rates were calculated by geographic area, sex, and five-year period. Joinpoint regression analyses were performed to ascertain whether changes in gastric cancer mortality trends had occurred, and to estimate the annual percent change by sex and geographic area.

RESULTS

Gastric cancer mortality decreased across the study period, with the downward trend being most pronounced in women and in certain regions situated in the interior and north of mainland Spain. Across the study period, there was an overall decrease of 2.90% per annum among men and 3.65% per annum among women. Generally, regions in which the rate of decline was sharpest were those that had initially registered the highest rates. However, the rate of decline was not constant throughout the study period: joinpoint analysis detected a shift in trend for both sexes in the early 1980s.

CONCLUSION

Gastric cancer mortality displayed in both sexes a downward trend during the study period, both nationally and regionally. The different trend in rates in the respective geographic areas translated as greater regional homogeneity in gastric cancer mortality by the end of the study period. In contrast, rates in women fell more than did those in men. The increasing differences between the sexes could indicate that some risk factors may be modifying the sex-specific pattern of this tumor.

The striking geographical pattern of gastric cancer mortality in Spain: environmental hypotheses revisited

BACKGROUND

Gastric cancer is decreasing in most countries. While socioeconomic development is the main factor to which this decline has been attributed, enormous differences among countries and within regions are still observed, with the main contributing factors remaining elusive. This study describes the geographic distribution of gastric cancer mortality at a municipal level in Spain, from 1994-2003.

METHODS

Smoothed relative risks of stomach cancer mortality were obtained, using the Besag-York-Molliè autoregressive spatial model. Maps depicting relative risk (RR) estimates and posterior probabilities of RR being greater than 1 were plotted.

RESULTS

From 1994-2003, 62184 gastric cancer deaths were registered in Spain (7 percent of all deaths due to malignant tumors). The geographic pattern was similar for both sexes. RRs displayed a south-north and coast-inland gradient, with lower risks being observed in Andalusia, the Mediterranean coastline, the Balearic and Canary Islands and the Cantabrian seaboard. The highest risk was concentrated along the west coast of Galicia, broad areas of the Castile & Leon Autonomous community, the province of Cáceres in Extremadura, Lleida and other areas of Catalonia.

CONCLUSION

In Spain, risk of gastric cancer mortality displays a striking geographic distribution. With some differences, this persistent and unique pattern is similar across the sexes, suggesting the implication of environmental exposures from sources, such as diet or ground water, which could affect both sexes and delimited geographic areas. Also, the higher sex-ratios found in some areas with high risk of smoking-related cancer mortality in males support the role of tobacco in gastric cancer etiology.

Nitrate in drinking water and risk of death from pancreatic cancer in Taiwan

The relationship between nitrate levels in drinking water and risk of pancreatic cancer development remains inconclusive. A matched case-control and nitrate ecology study was used to investigate the association between mortality attributed to pancreatic cancer and nitrate exposure from Taiwan's drinking water. All pancreatic cancer deaths of Taiwan residents from 2000 through 2006 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Data on nitrate-nitrogen (NO(3)-N) levels of drinking water throughout Taiwan were collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was assumed to be the source of the subject's nitrate exposure via drinking water. The adjusted odds ratios and confidence limits for pancreatic cancer death for those with high nitrate levels in their drinking water, as compared to the lowest tertile, were 1.03 (0.9-1.18) and 1.1 (0.96-1.27), respectively. The results of the present study show that there was no statistically significant association between the levels of nitrate in drinking water and increased risk of death from pancreatic cancer.

Nitrates in drinking water and risk of death from rectal cancer in Taiwan

The relationship between nitrate levels in drinking water and rectal cancer development has been inconclusive. A matched case-control and nitrate ecology study was used to investigate the association between mortality attributed to rectal cancer and drinking-water nitrate exposure in Taiwan. All deaths due to rectal cancer of Taiwan residents from 1999 through 2003 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair matched to the cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Data on nitrate-nitrogen (NO3-N) levels in drinking water throughout Taiwan were collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was assumed to be the source of the subject's nitrate exposure via drinking water. The adjusted odds ratios for rectal cancer death for those with high nitrate levels in their drinking water, as compared to the lowest tertile, were 1.22 (0.98-1.52) and 1.36 (1.08-1.70), respectively. The findings of this study warrant further investigation of the role of nitrates in drinking water in the etiology of rectal cancer in Taiwan.

Biological denitrification of drinking water in a slow sand filter

Biological removal of nitrate from drinking water was studied in a slow sand filter. Optimum carbon to nitrogen ratio (C/N) was found to be 1.8 when using acetic acid in batch tests. The filtration rates impact on NO(3)-N removal through the sand filter was assessed for 22.6 mgNO(3)-N/l concentrations while keeping C/N ratio as 1.8 for acetic acid. The filtration rates varied from 0.015, 0.02, 0.03, 0.04, 0.05, and 0.06 m/h, respectively, corresponding to an overall average NO(3)-N removal efficiency of 94%. Although increasing filtration rates decreased NO(3)-N removal, effluent NO(3)-N concentrations at the effluent port were lower than the limit value. The slow sand filter process was unable to provide NO(3)-N removal rate more than 27.1 gN/(m(2)day) (0.05 m/h flow rate). The NO(3)-N removal efficiency slightly dropped from 99% to 94% when the loading rate increased from 27.1 to 32.5 g/(m(2)day), but the effluent water contained higher concentration of NO(2)-N than the standard value.

Nitrate in drinking water and risk of death from colon cancer in Taiwan

The relationship between nitrate levels in drinking water and colon cancer has been inconclusive. A matched case-control and a nitrate ecology study were used to investigate the association between colon cancer mortality and nitrate exposure from Taiwan's drinking water. All colon cancer deaths of Taiwan residents from 1999 through 2003 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair matched to the cases by sex, year-of-birth, and year-of-death. Each matched control was selected randomly from the set of possible controls for each case. Data on nitrate-nitrogen (NO3-N) level of drinking water throughout Taiwan have been collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cases and controls was assumed to be the source of the subject's nitrate exposure via drinking water. The adjusted odds ratios for colon cancer death for those with high NO3-N levels in their drinking water, as compared to the lowest tertile, were 0.98 (0.84-1.14) and 0.98 (0.83-1.16), respectively. The results of the present study show that there was no statistically significant association between NO3-N in drinking water at levels in this study and risk of death from colon cancer.

Nitrate in drinking water and risk of death from bladder cancer: an ecological case-control study in Taiwan

The relationship between nitrate levels in drinking water and bladder cancer development is controversial. A matched cancer case-control with nitrate ecology study was used to investigate the association between bladder cancer mortality occurrence and nitrate exposure from Taiwan drinking water. All bladder cancer deaths of Taiwan residents from 1999 through 2003 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth,and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on nitrate-nitrogen (NO3-N) levels in drinking water throughout Taiwan were collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was assumed to be the source of the subject's nitrate exposure via drinking water. The adjusted odds ratios for bladder cancer death for those with high nitrate levels in their drinking water were 1.76 (1.28-2.42) and 1.96 (1.41-2.72) as compared to the lowest tertile. The results of the present study show that there was a significant positive relationship between the levels of nitrate in drinking water and risk of death from bladder cancer.

Impacts of waste from concentrated animal feeding operations on water quality

Waste from agricultural livestock operations has been a long-standing concern with respect to contamination of water resources, particularly in terms of nutrient pollution. However, the recent growth of concentrated animal feeding operations (CAFOs) presents a greater risk to water quality because of both the increased volume of waste and to contaminants that may be present (e.g., antibiotics and other veterinary drugs) that may have both environmental and public health importance. Based on available data, generally accepted livestock waste management practices do not adequately or effectively protect water resources from contamination with excessive nutrients, microbial pathogens, and pharmaceuticals present in the waste. Impacts on surface water sources and wildlife have been documented in many agricultural areas in the United States. Potential impacts on human and environmental health from long-term inadvertent exposure to water contaminated with pharmaceuticals and other compounds are a growing public concern. This work-group, which is part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards--Searching for Solutions, identified needs for rigorous ecosystem monitoring in the vicinity of CAFOs and for improved characterization of major toxicants affecting the environment and human health. Last, there is a need to promote and enforce best practices to minimize inputs of nutrients and toxicants from CAFOs into freshwater and marine ecosystems.

Nitrate intake does not influence bladder cancer risk: the Netherlands cohort study

OBJECTIVES

N-nitroso compounds, endogenously formed from nitrate-derived nitrite, are suspected to be important bladder carcinogens. However, the association between nitrate exposure from food or drinking water and bladder cancer has not been substantially investigated in epidemiologic studies.

METHODS

We evaluated the associations between nitrate exposure and bladder cancer in the Netherlands Cohort Study, conducted among 120,852 men and women, 55-69 years of age at entry. Information on nitrate from diet was collected via a food frequency questionnaire in 1986 and a database on nitrate content of foods. Individual nitrate exposures from beverages prepared with tap water were calculated by linking the postal code of individual residence at baseline to water company data. After 9.3 years of follow-up and after excluding subjects with incomplete or inconsistent dietary data, 889 cases and 4,441 subcohort members were available for multivariate analyses. We calculated incidence rate ratios (RR) and corresponding 95% confidence intervals (CIs) using Cox regression analyses. We also evaluated possible effect modification of dietary intake of vitamins C and E (low/high) and cigarette smoking (never/ever).

RESULTS

The multivariate RRs for nitrate exposure from food, drinking water, and estimated total nitrate exposure were 1.06 (95% CI, 0.81-1.31), 1.06 (95% CI, 0.82-1.37), and 1.09 (95% CI, 0.84-1.42), respectively, comparing the highest to the lowest quintiles of intake. Dietary intake of vitamins C and E (low/high) and cigarette smoking (never/ever) had no significant impact on these results.

CONCLUSION

Although the association between nitrate exposure and bladder cancer risk is biologically plausible, our results in this study do not support an association between nitrate exposure and bladder cancer risk.

Workgroup report: Drinking-water nitrate and health--recent findings and research needs

Human alteration of the nitrogen cycle has resulted in steadily accumulating nitrate in our water resources. The U.S. maximum contaminant level and World Health Organization guidelines for nitrate in drinking water were promulgated to protect infants from developing methemoglobinemia, an acute condition. Some scientists have recently suggested that the regulatory limit for nitrate is overly conservative; however, they have not thoroughly considered chronic health outcomes. In August 2004, a symposium on drinking-water nitrate and health was held at the International Society for Environmental Epidemiology meeting to evaluate nitrate exposures and associated health effects in relation to the current regulatory limit. The contribution of drinking-water nitrate toward endogenous formation of N-nitroso compounds was evaluated with a focus toward identifying subpopulations with increased rates of nitrosation. Adverse health effects may be the result of a complex interaction of the amount of nitrate ingested, the concomitant ingestion of nitrosation cofactors and precursors, and specific medical conditions that increase nitrosation. Workshop participants concluded that more experimental studies are needed and that a particularly fruitful approach may be to conduct epidemiologic studies among susceptible subgroups with increased endogenous nitrosation. The few epidemiologic studies that have evaluated intake of nitrosation precursors and/or nitrosation inhibitors have observed elevated risks for colon cancer and neural tube defects associated with drinking-water nitrate concentrations below the regulatory limit. The role of drinking-water nitrate exposure as a risk factor for specific cancers, reproductive outcomes, and other chronic health effects must be studied more thoroughly before changes to the regulatory level for nitrate in drinking water can be considered.

Influence of nitrate levels in drinking water on urological malignancies: a community-based cohort study

OBJECTIVE

To evaluate the effect of nitrate levels in the drinking water on the incidence of urological malignancies in a German community.

PATIENTS AND METHODS

For 28 years (1957-86) the community of Bocholt, Germany (70,000 inhabitants) had a drinking water supply with different nitrate levels, i.e. 60 mg/L in group A (57,253 inhabitants) and 10 mg/L in group B (10,037 inhabitants). All newly diagnosed cases of urological malignancies were registered from 1986 to 1997. The incidence was calculated using an age standardization based on the German population.

RESULTS

In all, there were 527 urological malignancies recorded (urothelial cancer 39.8%, renal cell carcinoma 10.8%, testicular tumours 8.0%, penile carcinoma 1.7%, prostate cancer 39.7%). The incidence per 100,000 inhabitants/year of urinary tract tumours was 33.8 in group A and only 17.1 in group B (relative risk, RR 1.98, 95% confidence interval, CI, 1.10-3.54). The RR was 0.87 (0.34-2.22) for renal tumours, 0.66 (0.14-2.88) for penile cancer and 1.06 (0.76-1.48) for prostate cancer. For testicular tumours there was an inverse association with nitrate level, with a RR of 0.43 (0.21-0.90).

CONCLUSION

This study showed an association of nitrate load in drinking water and the incidence of urothelial cancer in both genders, with an inverse correlation to testicular tumours and no correlation with renal, penile and prostatic tumours.

Impact des nitrates inorganiques sur l’aspect morphofonctionnel du rein chez le rat

AIM

The aim of our experimental study was to determine the effect of exogenic nitrates on certain biological parameters in relation to renal insufficiency.

RESULTS

Chronic treatment of rats for 5 months with varying nitrate concentrations (50, 100, 150 and 500 mg/L) induced a dose-dependent reduction in plasma concentrations of total proteins and a dose-dependent increase in plasma urea concentrations and creatinine.

DISCUSSION

This histological study of the kidney shows that nitrates at doses of 150 and 500 mg/L cause a deterioration in the epithelia of the renal tubules.

CONCLUSION

In conclusion, a high nitrate intake induces morphofunctional disturbances of the kidney and could thus be regarded as a causative factor in renal insufficiency.

Nitrate in public water supplies and the risk of colon and rectum cancers

BACKGROUND

Nitrate is a widespread contaminant of drinking water, but its potential health effects are unclear. In the body, nitrate is reduced to nitrite, which can react with amines and amides by nitrosation to form N-nitroso compounds, known animal carcinogens. N-nitroso compound formation is inhibited by certain nutrients, such as vitamin C, and increased by meat intake.

METHODS

We investigated the association of nitrate in public water supplies with incident colon and rectum cancers in a case-control study conducted in Iowa from 1986 to 1989. Nitrate levels in Iowa towns were linked to the participants' water source histories. We focused our analyses on the period from 1960 onward, during which nitrate measurements were more frequent, and we restricted analyses to those persons with public water supplies that had nitrate data (actual or imputed) for greater than 70% of this time period (376 colon cancer cases, 338 rectum cancer cases, and 1244 controls).

RESULTS

There were negligible overall associations of colon or rectum cancers with measures of nitrate in public water supplies, including average nitrate and the number of years with elevated average nitrate levels. For more than 10 years with average nitrate greater than 5 mg/L, the odds ratio (OR) for colon cancer was 1.2 (95% confidence interval [CI] = 0.9-1.6) and for rectum the OR was 1.1 (CI = 0.7-1.5). However, nitrate exposure (>10 years with average nitrate >5 mg/L) was associated with increased colon cancer risk among subgroups with low vitamin C intake (OR = 2.0; CI = 1.2-3.3) and high meat intake (OR = 2.2; CI = 1.4-3.6). These patterns were not observed for rectum cancer.

CONCLUSIONS

Our analyses suggest that any increased risk of colon cancer associated with nitrate in public water supplies might occur only among susceptible subpopulations.

Impact of nitrate intake in drinking water on the thyroid gland activity in male rat

The purpose of this study was to determine the effects of nitrate on both the activity of the thyroid gland and other biological parameters. After 5-month treatment, nitrate 150 and 500 mg/l induced a significant decrease in the serum level of thyroid hormone T3. For T4, the 500 mg/l dose only reduced its plasma level. On the other hand, nitrate induced a dose-dependent increase in the weight of the thyroid gland. The histological study of the thyroid gland shows vacuolisation and an increase in the size of the follicles accompanied by a flatness of follicular epithelium with nitrate 150 and 500 mg/l. We concluded that the presence of high concentrations of nitrate in drinking water influence the growth, induce morpho-functional modifications of the thyroid gland and might be considered as a goitrigenic factor.

Nitrate in public water supplies and risk of bladder cancer

BACKGROUND

Nitrate is a precursor compound in the formation of N-nitroso compounds, most of which are potent animal carcinogens. N-nitroso compounds and their precursors have not been extensively evaluated as bladder cancer risk factors.

METHODS

We conducted a population-based case-control study of bladder cancer in Iowa. Cases were men and women newly diagnosed with bladder cancer in 1986-1989. Nitrate data for Iowa public water supplies were sparse before the 1960s. To reduce misclassification by unknown nitrate levels, we included only those who used public supplies with nitrate data for 70% or more of their person-years since 1960 (808 cases, 1259 controls).

RESULTS

Among controls, the median average nitrate level for their Iowa residences with public water supplies was 1.3 mg/liter nitrate-nitrogen (interquartile range = 0.6-3.0). After adjustment for confounders, we found no increased risk of bladder cancer with increasing average nitrate levels in drinking water; the highest quartile odds ratio for women was 0.8 (95% confidence interval = 0.4-0.8), and for men 0.5 (0.4-0.8). We observed no association among those with high water nitrate exposure (>median) and low (<median) vitamin C intake compared with those who had low water nitrate and high vitamin C intake.

CONCLUSIONS

Our data suggest that long-term exposure to nitrate in drinking water at levels in this study (90th percentile 5.5 mg/liter nitrate-nitrogen) is not associated with risk of bladder cancer.

Assessing nitrate metabolism in the intestinal tract by measuring breath nitric oxide and nitrous oxide, and its clinical significance

BACKGROUND

The toxicity of dietary nitrate (NO3-) is controversial. One reason is nitrate metabolism in the intestine is so complicated that it is far from fully understood. There is no study measuring breath nitric oxide (NO) and nitrous oxide (N2O) after ingesting vegetables and high-nitrate food at the same time.

METHODS

Breath samples from 10 healthy young and 10 healthy old subjects were collected at 15-min intervals for 5 h after ingestion of 100 g of lettuce and during fasting (control). Breath NO and N2O were analyzed by a chemiluminescence and an IR-PAS analyzer respectively.

RESULTS

N2O maximum concentration and excretions increased significantly after ingesting lettuce in each group [303 (30) vs. 750 (81) ppb, 771 (72) vs. 1668 (146) microg in young; 442 (52) vs. 1092 (109) ppb, 1088 (125) vs. 2100 (183) microg in old subjects; mean (SE), P<0.01], while NO did not. In addition, breath NO was strongly influenced by ambient NO, which varied greatly. N2O maximum level in old subjects after ingesting lettuce was higher than that of young subjects (750 vs. 1092 ppb, P<0.05), and significantly higher N2O concentration levels were seen at 30, 45, 60, and 105 min in old subjects.

CONCLUSIONS

A large amount of N2O produced in the intestine and normal nitrate intake do not influence the breath NO concentration, probably due to its relatively small production. Higher maximum N2O concentration after ingesting lettuce in old subject is probably because more bacteria, which rapidly reduce dietary nitrate in the upper intestinal tract, inhabit the gut in old age. Our results suggested that breath N2O is a useful noninvasive maker to estimate dietary nitrate reduction in the intestinal tract.

An ecologic study of nitrate in municipal drinking water and cancer incidence in Trnava District, Slovakia

Contamination of drinking water by nitrate is an evolving public health concern since nitrate can undergo endogenous reduction to nitrite, and nitrosation of nitrites can form N-nitroso compounds, which are potent carcinogens. We conducted an ecologic study to determine whether nitrate levels in drinking water were correlated with non-Hodgkin lymphoma and cancers of the digestive and urinary tracts in an agricultural district (Trnava District; population 237,000) of the Slovak Republic. Routinely collected nitrate data (1975-1995) for villages using public water supplies were computerized, and each village was categorized into low (0-10 mg/L), medium (10.1-20 mg/L), or high (20.1-50 mg/L) average levels of total nitrate in drinking water. Observed cases of cancer in each of these villages were ascertained through the district cancer registry for the time period 1986-1995. Standardized incidence ratios (SIRs) and 95% confidence intervals (CI) for all cancer and selected cancer sites were calculated by indirect standardization using age- and sex-specific incidence rates from the entire district. For all cancer in women, SIRs increased from villages with low (SIR=0.87; 95% CI 0.72-0.95) to medium (SIR=1.07; 95% CI 1.00-1.13) to high (SIR=1.14; 1.06-1.22) levels of nitrate (P for trend <0.001); there was a similar trend for all cancer in men from low (SIR=0.90; 95% CI 0.81-0.99) to medium (SIR=1.08, 95% CI 1.02-1.16), but not for high (SIR=0.94; 0.88-1.02), nitrate levels (P for trend <0.001). This pattern in the SIRs (from low to high nitrate level) was also seen for stomach cancer in women (0.81, 0.94, 1.24; P for trend=0.10), colorectal cancer in women (0.64, 1.11, 1.29; P for trend <0.001) and men (0.77, 0.99, 1.07; P for trend=0.051), and non-Hodgkin lymphoma in women (0.45, 0.90, 1.35; P for trend=0.13) and men (0.25, 1.66, and 1.09; P for trend=0.017). There were no associations for kidney or bladder cancer. These ecologic data support the hypothesis that there is a positive association between nitrate in drinking water and non-Hodgkin lymphoma and colorectal cancer.

Municipal drinking water nitrate level and cancer risk in older women: the Iowa Women's Health Study

Nitrate contamination of drinking water may increase cancer risk, because nitrate is endogenously reduced to nitrite and subsequent nitrosation reactions give rise to N-nitroso compounds; these compounds are highly carcinogenic and can act systemically. We analyzed cancer incidence in a cohort of 21,977 Iowa women who were 55-69 years of age at baseline in 1986 and had used the same water supply more than 10 years (87% > 20 years); 16,541 of these women were on a municipal supply, and the remainder used a private well. We assessed nitrate exposure from 1955 through 1988 using public databases for municipal water supplies in Iowa (quartile cutpoints: 0.36, 1.01, and 2.46 mg per liter nitrate-nitrogen). As no individual water consumption data were available, we assigned each woman an average level of exposure calculated on a community basis; no nitrate data were available for women using private wells. Cancer incidence (N = 3,150 cases) from 1986 through 1998 was determined by linkage to the Iowa Cancer Registry. For all cancers, there was no association with increasing nitrate in drinking water, nor were there clear and consistent associations for non-Hodgkin lymphoma; leukemia; melanoma; or cancers of the colon, breast, lung, pancreas, or kidney. There were positive associations for bladder cancer [relative risks (RRs) across nitrate quartiles = 1, 1.69, 1.10, and 2.83] and ovarian cancer (RR = 1, 1.52, 1.81, and 1.84), and inverse associations for uterine cancer (RR = 1, 0.86, 0.86, and 0.55) and rectal cancer (RR = 1, 0.72, 0.95, and 0.47) after adjustment for a variety of cancer risk/protective factors, agents that affect nitrosation (smoking, vitamin C, and vitamin E intake), dietary nitrate, and water source. Similar results were obtained when analyses were restricted to nitrate level in drinking water from 1955 through 1964. The positive association for bladder cancer is consistent with some previous data; the associations for ovarian, uterine, and rectal cancer were unexpected.

Effects of high nitrate intake in rats

The purpose of this study was to determine the effects of administration of high dose nitrate in drinking water on weight gain, hematological parameters and osmotic fragility in rats. We compared these parameters in 40 rats divided into four groups (one control and three treatment groups). Control animals drank filtered tap water containing a maximum of 10 mg/l nitrate while the treatment groups drank 100 mg/l, 200 mg/l and 400 mg/l nitrate-containing water ad libitum for 60 days. Animals in the treatment groups gained less weight than the control group and the differences between the control and treatment groups were statistically significant (p < 0.05). At the concentration of 100 mg/l nitrate, platelet counts and hemoglobin levels were significantly increased compared with the control group (p < 0.05). At the concentration of 200 mg/l nitrate, erythrocyte counts, hemoglobin and hematocrit levels were significantly increased compared with the control group (p < 0.05). At the concentration of 400 mg/l nitrate, platelet counts were decreased significantly when compared with the first two treatment groups (p < 0.05). There were statistically significant differences in osmotic fragility ratios between treatment groups and the control group (p < 0.05). We concluded that high nitrate intake in drinking water decreases weight gain, affects hematological parameters by inducing bone marrow activity at low doses and inhibiting it at high doses, and increases erythrocyte osmotic fragility.

Blue babies and nitrate-contaminated well water

The use of nitrate-contaminated drinking water to prepare infant formula is a well-known risk factor for infant methemoglobinemia. Affected infants develop a peculiar blue-gray skin color and may become irritable or lethargic, depending on the severity of their condition. The condition can progress rapidly to cause coma and death if it is not recognized and treated appropriately. Two cases of blue baby syndrome were recently investigated. Both cases involved infants who became ill after being fed formula that was reconstituted with water from private wells. Water samples collected from these wells during the infants' illnesses contained nitrate-nitrogen concentrations of 22.9 and 27.4 mg/L.

Evidence of in vivo peroxynitrite formation in patients with colorectal carcinoma, higher plasma nitrate/nitrite levels, and lower protection against oxygen free radicals

Endogenously formed nitrogen and oxygen free radicals are believed to be involved in human cancer etiology. Plasma nitrate/nitrite originates from endogenous nitric oxide production in fasting humans, decrease in superoxide scavenger activity (SSA), and free sulfhydryl groups (SH) reflects the amount of superoxide anion generated, and nitrotyrosine is believed to be formed by the interaction of tyrosine and peroxynitrite in vivo. The aim of the current study was to measure plasma nitrate/ nitrite, SSA, and SH in 69 patients (mean age +/- standard deviation, 66 +/- 11 years) with colorectal carcinoma. Nitrotyrosine was measured from both the plasma and tumor tissues in 32 patients. All patients had adenocarcinoma of the colon or rectum. Twenty-five patients were classified as stage B according to Dukes classification as modified by Astler-Coller, 13 were classified as stage C, and 31 patients were classified as stage D. To determine whether the changes are specific for colorectal cancer, 20 patients with active inflammatory bowel disease (IBD; mean age, 52 +/- 18 years) and 30 healthy volunteers, who served as control subjects (mean age, 48 +/- 11 years), were studied. Plasma nitrate/nitrite was measured by the modified Griess method, SSA was measured by an electron/spin resonance spin trapping method, free SH was measured by Ellman's method, and the presence of nitrotyrosine in the plasma and tumor tissue was detected by high performance liquid chromatography (HPLC) using C- 18-derivatized silica (5 microm) column (C18S, Crestpaque, New York, NY, USA) and at a wavelength of 274 nm. Patients with colorectal carcinoma and with active IBD had a significantly higher plasma nitrate/ nitrite level (51.2 +/- 26.2 microm and 56.0 +/- 14.6 microm versus. 29.6 +/- 6.3 microm; p < 0.01), and a lower SSA level (39 +/- 11.5 U/g protein and 52.0 +/- 18.9 U/g protein versus. 88 +/- 25.1 U/g protein; p < 0.05) and SH level (7.7 +/- 3.89 microm protein and 6.4