Nitrate in drinking water and bladder cancer risk in Spain

Health Risk Assessment of Nitrate in Drinking Water with Potential Source Identification: A Case Study in Almaty, Kazakhstan

Infant mortality in Kazakhstan is six times higher compared with the EU. There are several reasons for this, but a partial reason might be that less than 30% of Kazakhstan's population has access to safe water and sanitation and more than 57% uses polluted groundwater from wells that do not comply with international standards. For example, nitrate pollution in surface and groundwater continues to increase due to intensified agriculture and the discharge of untreated wastewater, causing concerns regarding environmental and human health. For this reason, drinking water samples were collected from the water supply distribution network in eight districts of Almaty, Kazakhstan, and water quality constituents, including nitrate, were analyzed. In several districts, the nitrate concentration was above the WHO and Kazakhstan's maximum permissible limits for drinking water. The spatial distribution of high nitrate concentration in drinking water was shown to be strongly correlated with areas that are supplied with groundwater, whereas areas with lower nitrate levels are supplied with surface water sources. Based on source identification, it was shown that groundwater is likely polluted by mainly domestic wastewater. The health risk for infants, children, teenagers, and adults was assessed based on chronic daily intake, and the hazard quotient (HQ) of nitrate intake from drinking water was determined. The non-carcinogenic risks increased in the following manner: adult < teenager < child < infant. For infants and children, the HQ was greater than the acceptable level and higher than that of other age groups, thus pointing to infants and children as the most vulnerable age group due to drinking water intake in the study area. Different water management options are suggested to improve the health situation of the population now drinking nitrate-polluted groundwater.

Hydrochemical characteristics and potential health risks of nitrate, fluoride, and uranium in Kota district, Rajasthan, India

This study examines the uranium, fluoride, and nitrate dispositions in groundwater as well as potential health risks in Kota district, Rajasthan, India. Total 198 groundwater samples were collected in both dry and wet periods and analyzed for physicochemical parameters along with U, F^-, and NO₃^- using standard methods. Results indicate that the electrical conductivity, total dissolved solids, total hardness, alkalinity, Ca²⁺, Mg²⁺, HCO₃^-, Cl^-, NO₃^-, and F^- exceed the WHO standard limits of drinking water in both periods. Uranium concentration is at the broader of drinking water permissible limit (30 μg/L) and found about 1.05 times more. Nitrate and fluoride concentrations ranged from 9.8 to 412.0 mg/L and 0.1 to 4.0 mg/L for the dry season, while in the wet period, they varied from 10.0 to 954.0 mg/L and 0.1 to 3.5 mg/L, respectively. Correlation studies show a significantly strong positive correlation between uranium and total alkalinity and carbonate. Natural background levels (NBLs) were explored to assess the source of groundwater pollution. It shows that the second inflection points of NBLs estimated for NO₃^-, F^-, and U are about 168 mg/L, 1.2 mg/L, and 7.3 μg/L, respectively, during the experimental period. The USEPA technique was used to evaluate the non-carcinogenic health risks associated with consuming the NO₃^- and F^--contaminated groundwater. The health risks in Kota district show that children are more at risk than adults. The risk assessment of uranium reveals that the excess cancer risk (ECR) and hazard quotient (HQ) are found to be below the standard limits, but a high concentration of uranium (31.6 μg/L) is observed at Amarpura village of Digod block. This study will provide a baseline of uranium, fluoride, and nitrate dispositions in groundwater for simulating mass transport model and safe use of drinking water.

Nitrate in groundwater and agricultural products: intake and risk assessment in northeastern Iran

The suitability of groundwater and agricultural products for human consumption requires determining levels and assessing the health risks associated with potential pollutants. Here, particularly pollution with nitrate still remains a challenge, especially for those urban areas suffering from insufficient sewage collection systems, resulting in contaminating soil, endangering food safety, and deteriorating drinking water quality. In the present study, nitrate concentrations in the commonly consumed fruit and vegetable species were determined, and the results, together with the groundwater nitrate levels, were used to assess the associated health risks for Mashhad city residents. For this assessment, 261 water samples and 16 produce types were used to compute the daily intake of nitrate. Nitrate in groundwater was analyzed using a spectrophotometer, and produce species were examined using High-Performance Liquid Chromatography. Ward's hierarchical cluster analysis was applied for categorizing produce samples with regard to their nitrate content. Additionally, to account for the sanitation hazards associated with groundwater quality for drinking purposes, total coliform and turbidity were also assessed using the membrane filter (MF) technique and a nephelometer, respectively. Nitrate concentrations exceeded the prescribed permissible limits in 42% of the groundwater wells. The outcomes also exhibit significantly higher nitrate accumulation levels in root-tuber vegetables and leafy vegetables compared to fruit vegetables and fruits. Using cluster analysis, the accumulation of nitrate in vegetables and fruits was categorized into four clusters, specifying that radish contributes to 65.8% of the total content of nitrate in all samples. The Estimated Daily Intake (EDI) of nitrate and Health Risk Index (HRI) associated with consumption of groundwater exceeded the prescribed limit for the children's target group in Mashhad's south and central parts. Likewise, EDI and HRI values for produce consumption, in most samples, were found to be in the tolerable range, except for radish, lettuce, and cabbage, potentially posing risks for both children and adult consumers. The total coliforms in groundwater were found to violate the prescribed limit at 78.93% of the sampling locations and were generally much higher over the city's central and southern areas. A relatively strong correlation (R² = 0.6307) between total coliform and nitrate concentrations suggests the release of anthropogenic pollution (i.e., sewage and manure) in the central and southern Mashhad.

Susceptibility Assessment of Groundwater Nitrate Contamination Using an Ensemble Machine Learning Approach

Groundwater pollution susceptibility mapping using parsimonious approaches with limited data is of utmost importance for water resource and health planning, especially in data-scarce regions. Current research assesses groundwater nitrate susceptibility by considering the various combination of explanatory variables. In this study, the novel machine learning models of weighted subspace random forest (WSRF) and generalized additive model using LOESS (GAMLOESS) are applied, and the results are compared with well-known machine learning models of K-nearest neighbors (KKNN) and random forest (RF). The optimum combination of inputs for groundwater nitrate susceptibility mapping is identified using the k-fold cross-validation methodology. Results indicated that the combination of variables of precipitation, groundwater level, and lithology had the best performance among the 16 combinations. Modeling performance using the optimum combination demonstrated that the new ensemble approach, the WSRF model, had superior performance according to the evaluation metrics of accuracy (0.87), kappa (0.73), precision (0.92), false alarm ratio (0.08), and critical success index (0.75). The susceptibility assessment results of this paper can be a useful tool in developing strategies for the prevention and protection of groundwater pollution.

Bamboo Chopstick Biochar Electrodes and Enhanced Nitrate Removal from Groundwater

The nitrate pollution of groundwater can cause serious harm to human health. Biochar electrodes, combined with adsorption and electroreduction, have great potential in nitrate removal from groundwater. In this study, bamboo chopsticks were used as feedstocks for biochar preparation. The bamboo chopstick biochar (BCBC), prepared by pyrolysis at 600 °C for 2 h, had a specific surface area of 179.2 m2/g and an electrical conductivity of 8869.2 μS/cm, which was an ideal biochar electrode material. The maximum nitrate adsorption capacity of BCBC-600-2 reached 16.39 mg/g. With an applied voltage of 4 V and hydraulic retention time of 4 h, the nitrate removal efficiency (NRE) reached 75.8%. In comparison, the NRE was only 32.9% without voltage and 25.7% with graphite cathode. Meanwhile, the average nitrate removal rate of biochar electrode was also higher than that of graphite cathode under the same conditions. Therefore, biochar electrode can provide full play to the coupling effect of adsorption and electroreduction processes and obtain more powerful nitrate removal ability. Moreover, the biochar electrode could inhibit the accumulation of nitrite and improve the selectivity of electrochemical reduction. This study not only provides a high-quality biochar electrode material, but also provides a new idea for nitrate removal in groundwater.

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.

Activity and Stability of Pd Bimetallic Catalysts for Catalytic Nitrate Reduction

In this work, we study the effect of modifying the metal loading (0.5–1.5 wt.% Pd and 0.1–1 wt.% Sn or In), the impregnation order of noble or promoter metal (Pd–Sn or Sn–Pd), and the type of promoter metal (Sn or In) during the preparation process for a Pd bimetallic catalyst, supported on γ-alumina, used in the catalytic reduction of nitrate. The deposition of the noble metal over the promoter metal, especially with Pd:Sn ratios (wt.) of 1:10 and 1:2, favored the hydrogen spillover rate and increased the H concentration on the catalyst surface, enhancing NH4+ production. On the other hand, Pd–In catalysts showed higher activity than the Sn catalysts, as well as higher NH4+ selectivity. The stability of the Pd–Sn/Al2O3 (1.5–1 wt.%) catalyst was evaluated in long-term experiments for the treatment of synthetic water (100 mg L−1 NO3−) and three different commercial drinking waters. This Pd–Sn/Al2O3 catalyst achieved a stable nitrate conversion for a duration of 50 h in the synthetic water treatment. However, the catalyst showed a significant activity loss in the presence of other ions (different to NO3−) in the reaction medium, increasing slightly the selectivity to NH4+.

Appraisal of shallow groundwater quality with human health risk assessment in different seasons in rural areas of the Guanzhong Plain (China)

Groundwater is the major source of water for drinking and irrigation purposes in and around Hua County, Shaanxi Province, China. The main purposes of this research is to evaluate the groundwater quality in the rainy and dry seasons of Hua County and analyze the causes of seasonal differences and determine the areas with serious pollution. Groundwater quality was assessed in this study using entropy water quality index (EWQI) and some graphical approaches such as Gibbs and Piper diagrams. The contour maps of groundwater quality were drawn by Geographical Information System (GIS). According to the obtained results, the locations where groundwater quality was rated as excellent or good in both wet and dry seasons were mainly in the north and east of the research area. COD and NO₃^- are the parameters that have the most serious negative effect on water quality. The dominant factors influencing groundwater chemical evolution in the study area were rock weathering and dissolution, and the precipitation and evaporation during the wet and dry seasons do not cause significant changes in groundwater chemistry. Adults' health risks results revealed that 27.69% and 52.31% of the groundwater samples exceeded the acceptable limit for non-carcinogenic risk in the wet and dry season, respectively, while for children the ratios are 30.16% and 47.62%, respectively. The contributive percentages of nitrate, fluoride and nitrate to the total risk are 61.29%, 28.71% and 10.00% in the wet season and 68.84%, 20.85% and 10.31% in the dry season. The risk is higher in the south than in the north of the study area, and is especially high in the southwest of the study area.

Association between Dietary Nitrate, Nitrite Intake, and Site-Specific Cancer Risk: A Systematic Review and Meta-Analysis

Background: People consume nitrates, nitrites, nitrosamines, and NOCs compounds primarily through processed food. Many studies have yielded inconclusive results regarding the association between cancer and dietary intakes of nitrates and nitrites. This study aimed to quantify these associations across the reported literature thus far. Methods: We performed a systematic review following PRISMA and MOOSE guidelines. A literature search was performed using Web of Science, Embase, PubMed, the Cochrane library, and google scholar up to January 2020. STATA version 12.0 was used to conduct meta-regression and a two-stage meta-analysis. Results: A total of 41 articles with 13 different cancer sites were used for analysis. Of these 13 cancer types/sites, meta-regression analysis showed that bladder and stomach cancer risk was greater, and that pancreatic cancer risk was lower with increasing nitrite intakes. Kidney and bladder cancer risk were both lower with increasing nitrate intakes. When comparing highest to lowest (reference) categories of intake, meta-analysis of studies showed that high nitrate intake was associated with an increased risk of thyroid cancer (OR = 1.40, 95% CI: 1.02, 1.77). When pooling all intake categories and comparing against the lowest (reference) category, higher nitrite intake was associated with an increased risk of glioma (OR = 1.12, 95% CI: 1.03, 1.22). No other associations between cancer risk and dietary intakes of nitrates or nitrites were observed. Conclusion: This study showed varied associations between site-specific cancer risks and dietary intakes of nitrate and nitrite. Glioma, bladder, and stomach cancer risks were higher and pancreatic cancer risk was lower with higher nitrite intakes, and thyroid cancer risk was higher and kidney cancer risk lower with higher nitrate intakes. These data suggest type- and site-specific effects of cancer risk, including protective effects, from dietary intakes of nitrate and nitrite.

Exposure to drinking water trihalomethanes and nitrate and the risk of brain tumours in young people

Brain tumours (BTs) are one of the most frequent tumour types in young people. We explored the association between tap water, exposure to trihalomethanes (THM) and nitrate and neuroepithelial BT risk in young people. Analysis of tap water consumption were based on 321 cases and 919 appendicitis controls (10-24 years old) from 6 of the 14 participating countries in the international MOBI-Kids case-control study (2010-2016). Available historical residential tap water concentrations of THMs and nitrate, available from 3 countries for 86 cases and 352 controls and 85 cases and 343 for nitrate, respectively, were modelled and combined with the study subjects' personal consumption patterns to estimate ingestion and residential exposure levels in the study population (both pre- and postnatal). The mean age of participants was 16.6 years old and 56% were male. The highest levels and widest ranges for THMs were found in Spain (residential and ingested) and Italy and in Korea for nitrate. There was no association between BT and the amount of tap water consumed and the showering/bathing frequency. Odds Ratios (ORs) for BT in relation to both pre- and postnatal residential and ingestion levels of THMs were systematically below 1 (OR = 0.37 (0.08-1.73)) for postnatal average residential THMs higher than 66 μg/L. For nitrate, all ORs were above 1 (OR = 1.80 (0.91-3.55)) for postnatal average residential nitrate levels higher than 8.5 mg/L, with a suggestion of a trend of increased risk of neuroepithelial BTs with increasing residential nitrate levels in tap water, which appeared stronger in early in life. This, to our knowledge, is the first study on this topic in young people. Further research is required to clarify the observed associations.

Dietary N-nitroso compounds intake and bladder cancer risk: A systematic review and meta-analysis

Bladder cancer is the most common cancer of the urinary tract. While tobacco smoking is responsible for more than half of the bladder cancer cases, occupational exposures is also an established risk factor of bladder cancer. Strong evidence of carcinogenicity of N-nitroso compounds (NOCs) have been provided in animal and human studies, but the target organ of occurring cancer in human including bladder cancer is still obscure. A wide range of NOCs sources surrounded us like diet, drinking water, cigarette smoking, workplace, and indoor air population. We conducted a meta-analysis to elucidate the association between NOCs in drinking water and food source and bladder cancer risk. Ten articles were included after removing the duplicates and irrelevant articles. The majority studies of our meta-analysis was done on women, maybe because of cigarette smoking as a main risk factor among men which is more common among men than women. Although the number of articles was limited our meta-analysis showed no significant association between dietary intakes of NOCs and bladder cancer risk (OR = 0.96, 95% CI = 0.88, 1.05; I2 = 50%, P-value = 0.007), neither subgrouping of NOCS type and source of NOCs nor dose of nitrate and nitrite intake indicated any associations.

Double-endpoint Genotoxicity Quantification and PAHs Characterization of Drinking Water Source alongside Polluted Yinghe River with High Tumor Mortality

The etiology for the high tumor mortality in heavy polluted Yinghe river basin is still unclear and polycyclic aromatic hydrocarbons (PAHs) belong to the priority pollutants in water based on the former surveillance data. In order to explore the potential genotoxicants contributing to the double-endpoint genotoxicity of polluted drinking water source, 12 groundwater and 3 surface water samples were collected from 3 villages and the nearby rivers alongside Yinghe river basin, respectively and their comprehensive genotoxicity was estimated with a bioassay group of SOS/umu test and micronucleus (MN) test (MNT). Some groundwater samples showed positive genotoxicity and all surface water samples were highly genotoxic. Eight groundwater samples showed DNA genotoxic effect with the average 4-NQO equivalent concentration (TEQ_(4-NQO)) of 0.067 µg/L and 0.089 µg/L in wet and dry season, respectively. The average MN ratios of groundwater samples were 14.19‰ and 17.52‰ in wet and dry season, respectively. Groundwater samples showed different genotoxic effect among 3 villages. The total PAHs concentrations in all water samples ranged from 8.98 to 25.17 ng/L with an average of 14.97±4.85 ng/L. BaA, CHR, BkF, BaP and DBA were the main carcinogenic PAHs contributing to the genotoxicity of water samples. In conclusion, carcinogenic PAHs are possibly related to the high tumor mortality in the target area. Characterization of carcinogenic PAHs to genotoxicity of drinking water source may shed light on the etiology study for high tumor mortality in Yinghe river basin.

Hydrochemical characteristics and nitrate health risk assessment of groundwater through seasonal variations from an intensive agricultural region of upper Krishna River basin, Telangana, India

Seasonal variations in hydrogeochemical characteristics of groundwater were assessed from an intensive agricultural region to identify contaminants of concern that are a potential risk to human health. A total of 116 groundwater samples were collected grid-wise from an intensive agricultural region of confined Wanaparthy watershed to evaluate seasonal variations in hydrogeochemical processes of dissolved ions, nitrate health risk assessment and water quality during pre-monsoon (PRM) and post-monsoon (POM) seasons. The major ions concentration found in ascending order as PRM: F^- < NO₃^-< SO₄^2-< HCO₃^-< Cl^- and K⁺< Mg⁺²< Ca⁺²< Na⁺ while POM: F^- < NO₃^-< SO₄^2-< Cl^-< HCO₃^- and K⁺< Ca⁺²< Mg⁺²< Na⁺ respectively^. Piper diagram for water-types shows PRM; Na-Cl type (70.68%) while POM; Ca-Mg-Cl type (39^.66%) and Ca-HCO3 type (31.03%). Gibbs diagram explained the favorable environmental conditions as rock and evaporation dominance in both seasons. Spatial distribution map shows samples with higher and above permissible limits are found at/near to adjoining to higher-order streams and streams origin. As per the water quality index (WQI), 36.21% (PRM) and 60.34% (POM) fall in poor to unfit for drinking class. Hazard quotient (HQ) values of nitrate reach as high as for infants 1.31E + 01, children 1.23E + 01 and adults 4.68E + 00 respectively. Subsequently, HQ>1 with 68.97% of infants and 72.41% of children are in danger for non-carcinogenic ingestion of nitrate contaminated groundwater than in adults.

Ingested Nitrate and Nitrite and Bladder Cancer in Northern New England

BACKGROUND

N-nitroso compounds are hypothesized human bladder carcinogens. We investigated ingestion of N-nitroso compound precursors nitrate and nitrite from drinking water and diet and bladder cancer in the New England Bladder Cancer Study.

METHODS

Using historical nitrate measurements for public water supplies and measured and modeled values for private wells, as well as self-reported water intake, we estimated average nitrate concentrations (mg/L NO3-N) and average daily nitrate intake (mg/d) from 1970 to diagnosis/reference date (987 cases and 1,180 controls). We estimated overall and source-specific dietary nitrate and nitrite intakes using a food frequency questionnaire (1,037 cases and 1,225 controls). We used unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). We evaluated interactions with factors that may affect N-nitroso compound formation (i.e., red meat, vitamin C, smoking), and with water intake.

RESULTS

Average drinking water nitrate concentration above the 95th percentile (>2.07 mg/L) compared with the lowest quartile (≤0.21 mg/L) was associated with bladder cancer (OR = 1.5, 95% CI = 0.97, 2.3; P trend = 0.01); the association was similar for average daily drinking water nitrate intake. We observed positive associations for dietary nitrate and nitrite intakes from processed meat (highest versus lowest quintile OR for nitrate = 1.4, 95% CI = 1.0, 2.0; P trend = 0.04; OR for nitrite = 1.5, 95% CI = 1.0, 2.1; P trend = 0.04, respectively), but not other dietary sources. We observed positive interactions between drinking water nitrate and red meat (P-interaction 0.05) and processed red meat (0.07).

CONCLUSIONS

Our results suggest the importance of both drinking water and dietary nitrate sources as risk factors for bladder cancer.

Groundwater quality and non-carcinogenic health risk assessment of nitrate in the semi-arid region of Punjab, India

Groundwater is the main source of water in the study area (Rupnagar District, Punjab), and its quality is essential since it is the primary determinant of the suitability of groundwater for drinking and irrigation purposes. In this study, data from 28 years have been used to evaluate the adequacy of groundwater for domestic and irrigation purposes and assess the potential human health impacts of nitrate contaminants. Results of sodium adsorption ratio, percentage sodium, magnesium hazard ratio, Kelley ratio, and residual sodium carbonate illustrate that most of the sampling locations were suitable for irrigational purposes and drinking water quality of the region mostly belonged to the 'good' class. The maximum nitrate concentration was observed in the northern and north-east parts of the area. Among the three age groups, children > female > male was found to be more prone to health risks with oral ingestion of nitrate. Uncertainties in the risk estimates were quantified using Monte Carlo simulation and sensitivity analyses. Thus, a proper management plan should be adopted by the decision-makers to improve the quality of drinking water in this area to avoid major health problems in the near future.

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.

Controlling factors and mechanism of groundwater quality variation in semiarid region of South India: an approach of water quality index (WQI) and health risk assessment (HRA)

The study region comprises fractured granitic, basaltic and lateritic aquifer system constituted by Precambrian rocks. Groundwater is the primary source for drinking and household needs. Its quality is a big issue in the three aquifers, which are mostly of human health concern. Many developing regions suffer from lack of safe drinking water, thereby health problems arise in many parts of the regions, and Telangana state is one of them. For this reason, 194 groundwater samples were collected and analyzed for fluoride, nitrate, chloride and other physicochemical parameters. The concentrations of fluoride (F^-), nitrate (NO₃^-), magnesium (Mg²⁺), total dissolved solids and total hardness are above the acceptable limits for drinking purposes, prescribed by the World Health Organization. The higher concentrations of fluoride and nitrate in drinking water cause health hazards, and above 50% of the groundwater samples are not suitable for drinking purposes with respect to fluoride and nitrate. Weathering of rocks and dissolution of fluoride-bearing minerals can be a cause for higher fluoride concentrations, while anthropogenic sources are one of the major reasons for higher nitrate concentrations in the study area. Groundwater suitability for irrigation suggests that more than 90% of the groundwater sampling locations are suitable for irrigation. In addition, health risk assessments were evaluated by using the United States Environmental Protection Agency model, to determine the non-carcinogenic risk of fluoride and nitrate in drinking water for adults (females and males) and children. The ranges of hazard index in all sampling locations are varied from 0.133 to 8.870 for males, 0.146 to 10.293 for females and 0.419 to 29.487 for children, respectively. The health risk assessment results indicated that children were more exposed to health risk, due to the intake of high contaminated drinking water with respective of nitrate and fluoride in the study region.

Development of a Universal Water Quality Index (UWQI) for South African River Catchments

The assessment of water quality has turned to be an ultimate goal for most water resource and environmental stakeholders, with ever-increasing global consideration. Against this backdrop, various tools and water quality guidelines have been adopted worldwide to govern water quality deterioration and institute the sustainable use of water resources. Water quality impairment is mainly associated with a sudden increase in population and related proceedings, which include urbanization, industrialization and agricultural production, among others. Such socio-economic activities accelerate water contamination and cause pollution stress to the aquatic environment. Scientifically based water quality index (WQI) models are then essentially important to measure the degree of contamination and advise whether specific water resources require restoration and to what extent. Such comprehensive evaluations reflect the integrated impact of adverse parameter concentrations and assist in the prioritization of remedial actions. WQI is a simple, yet intelligible and systematically structured, indexing scale beneficial for communicating water quality data to non-technical individuals, policymakers and, more importantly, water scientists. The index number is normally presented as a relative scale ranging from zero (worst quality) to one hundred (best quality). WQIs simplify and streamline what would otherwise be impractical assignments, thus justifying the efforts of developing water quality indices (WQIs). Generally, WQIs are not designed for broad applications; they are customarily developed for specific watersheds and/or regions, unless different basins share similar attributes and test a comparable range of water quality parameters. Their design and formation are governed by their intended use together with the degree of accuracy required, and such technicalities ultimately define the application boundaries of WQIs. This is perhaps the most demanding scientific need—that is, to establish a universal water quality index (UWQI) that can function in most, if not all, the catchments in South Africa. In cognizance of such a need, this study attempts to provide an index that is not limited to certain application boundaries, with a contribution that is significant not only to the authors, but also to the nation at large. The proposed WQI is based on the weighted arithmetic sum method, with parameters, weight coefficients and sub-index rating curves established through expert opinion in the form of the participation-based Rand Corporation’s Delphi Technique and extracts from the literature. UWQI functions with thirteen explanatory variables, which are NH3, Ca, Cl, Chl-a, EC, F, CaCO3, Mg, Mn, NO3, pH, SO4 and turbidity (NTU). Based on the model validation analysis, UWQI is considered robust and technically stable, with negligible variation from the ideal values. Moreover, the prediction pattern corresponds to the ideal graph with comparable index scores and identical classification grades, which signifies the readiness of the model to appraise water quality status across South African watersheds. The research article intends to substantiate the methods used and document the results achieved.

Application of glycerol as carbon source for continuous drinking water denitrification using microorganism from natural biomass

The contamination of water resources by nitrate is a global problem. Indeed, traditional treatment technologies are not able to remove this ion from water. Alternatively, biological denitrification is a useful technique for natural water nitrate removal. This study aimed to evaluate the use of glycerol as a carbon source for drinking water nitrate removal via denitrification in a reactor using microorganisms from natural biomass. The experiment was carried out in a continuous fixed bed reactor using immobilised microorganisms from the vegetal Phyllostachys aurea. The tests were started in batch mode to provide cells growth and further immobilisation on the support. Then, the treatment experiments were accomplished in an up-flow continuous reactor. Ethanol was used as the primary carbon source, and it was gradually replaced by glycerol. The C:N (carbon to nitrogen) ratio and the hydraulic residence time (HRT) were evaluated. It was possible to remove 98.14% of nitrate using a C:N ratio and HRT of 3:1 and 1.51 days, respectively. The results have demonstrated that glycerol is a potential carbon source for denitrification in a continuous reactor using immobilised cells from natural biomass.

Nitrate contamination of water in dug wells and associated health risks of rural communities in southwest Bangladesh

Consumption of drinking water with high nitrate may pose a serious health hazard. This study examined nitrate concentration in the water of dug wells at the Jashore district of Bangladesh. A total of 58 water samples were collected from dug wells which are currently in use for drinking water. Concentrations of nitrate in the water range from 0.05 to 430 mg/l and from 0.24 to 206 mg/l respectively in the wet and dry seasons. About 17% and 14% of the samples during the wet and dry seasons respectively showed nitrate concentration above the WHO guideline value of 50 mg/l. The wells with high nitrate concentration showed health risks for adults and children. About 17% of the samples showed a health hazard index (HQ_nitrate) values above the acceptable limit (HQ_nitrate values > 1) for adults, in both the wet and dry seasons, whereas 26% and 33% of the water samples in the wet and dry seasons respectively showed HQ_nitrate values > 1 for children. Therefore, children are more likely to be affected by intaking nitrate-contaminated dug well water. Health risks of elevated nitrate concentration in the dug wells require proper attention to ensure reliable water supply.

Subacute intoxication with sodium nitrate induces hematological and biochemical alterations and liver injury in male Wistar rats

Nitrate pollution has emerged as a problem of great importance because in recent years, the levels of nitrate in soil and groundwater have increased, mainly through anthropogenic activities, such as the use of fertilizers in agriculture, domestic wastewater and septic tanks, industrial waste and deforestation. In animals, nitrate reduction to nitrite (NO₂) and nitric oxide (NO) promote the formation of methemoglobin in the blood and the generation of highly reactive intermediates that induce oxidative stress in target organs. Exposition to nitrates has been associated with methemoglobinemia, reproductive toxicity, metabolic and endocrine alterations and cancer. This study analyzed acute intoxication with sodium nitrate (NaNO₃) in male Wistar rats, aged 12-16 weeks. Four groups with n = 10 rats each were formed: group 1 was the control, and group 2, group 3 and group 4 were treated for 10 days with intragastric doses of 19, 66 and 150 mg/kg/d NaNO₃, respectively. Hematological, metabolic and histological biomarkers in the liver were analyzed. The results showed high percentages of methemoglobin, an increase in NO₂ in the plasma and an accumulation in the liver. Moreover, there were high counts of white blood cells and platelets in all treated groups. Additionally, there was an increase in the spleen weight in group 4. High levels of glucose, triglycerides, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were observed and were significantly increased in groups 3 and 4. For oxidative stress biomarkers, there were increases in Thiobarbituric Acid Reactive Substances (TBARS), total GSH and SOD activity, mainly in group 4. Changes in mitochondrial activity were not significant. Histopathological analyses of the liver showed inflammation, infiltration of mononuclear cells, steatosis, ischemia and necrosis, and these findings were more evident at high doses of NaNO₃ in which high of S-nitrosylation were found. In conclusion, NaNO₃ was reduced to NO₂, thereby inducing methemoglobinemia, whereas other reactive species generated oxidative stress, causing hematological and metabolic alterations and injury to the liver.

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.

Groundwater nitrate contamination and associated human health risk assessment in southern districts of Punjab, India

Consumption of high NO₃ containing water may pose serious health hazard especially in children (< 5 years). The source of NO₃ in groundwater includes surface leaching from wastewater and waste dump sites, animal excreta disposal, industrial effluents, and N-based fertilizers, etc. This study aimed to investigate the concentration of NO₃ in groundwater of 14 intensively cultivated districts of Malwa Punjab, India, and its possible health hazards in local residents. The sampling of 76 sites revealed the concentration of NO₃ in ranges of 38.45-198.05 mgL^-1, and over 92% sites showed the high level of it than the safe limits as decided by the Bureau of Indian standards (45 mg L^-1) and World Health Organization (50 mg L^-1). The possible health hazards of high NO₃ intake was estimated using USEPA human health risk assessment (HHRA) model for both adult and children. Results of this study suggested the chronic daily intake (CDI) in the ranges of 1.09-5.65 and 2.56-13.20 in adult and children population of this region, respectively. The hazard quotient (HQ_nitrate) value was > 1 in most sampling locations ranging 1.09-5.65 for the adult and 2.56-13.20 for children population of Malwa. This study indicates that 93.42% adult and 100% young population of the Malwa are at higher risk of chronic toxicity by excess NO₃ intake. The HHRA results suggested a high vulnerability of a local community to NO₃ toxicity in this region; therefore, there is an instant need to take preventive measures to safeguard the health of local residents.

Drinking Water Nitrate and Human Health: An Updated Review

Nitrate levels in our water resources have increased in many areas of the world largely due to applications of inorganic fertilizer and animal manure in agricultural areas. 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 birth defects may be increased when nitrate is ingested under conditions that increase formation of N-nitroso compounds. We previously reviewed epidemiologic studies before 2005 of nitrate intake from drinking water and cancer, adverse reproductive outcomes and other health effects. Since that review, more than 30 epidemiologic studies have evaluated drinking water nitrate and these outcomes. The most common endpoints studied were colorectal cancer, bladder, and breast cancer (three studies each), and thyroid disease (four studies). Considering all studies, the strongest evidence for a relationship between drinking water nitrate ingestion and adverse health outcomes (besides methemoglobinemia) is for colorectal cancer, thyroid disease, and neural tube defects. Many studies observed increased risk with ingestion of water nitrate levels that were below regulatory limits. Future studies of these and other health outcomes should include improved exposure assessment and accurate characterization of individual factors that affect endogenous nitrosation.

Using natural biomass microorganisms for drinking water denitrification

Among the methods that are studied to eliminate nitrate from drinking water, biological denitrification is an attractive strategy. Although several studies report the use of denitrifying bacteria for nitrate removal, they usually involve the use of sewage sludge as biomass to obtain the microbiota. In the present study, denitrifying bacteria was isolated from bamboo, and variable parameters were controlled focusing on optimal bacterial performance followed by physicochemical analysis of water adequacy. In this way, bamboo was used as a source of denitrifying microorganisms, using either Immobilized Microorganisms (IM) or Suspended Microorganisms (SM) for nitrate removal. Denitrification parameters optimization was carried out by analysis of denitrification at different pH values, temperature, nitrate concentrations, carbon sources as well as different C/N ratios. In addition, operational stability and denitrification kinetics were evaluated. Microorganisms present in the biomass responsible for denitrification were identified as Proteus mirabilis. The denitrified water was submitted to physicochemical treatment such as coagulation and flocculation to adjust to the parameters of color and turbidity to drinking water standards. Denitrification using IM occurred with 73% efficiency in the absence of an external carbon source. The use of SM provided superior denitrification efficiency using ethanol (96.46%), glucose (98.58%) or glycerol (98.5%) as carbon source. The evaluation of the operational stability allowed 12 cycles of biomass reuse using the IM and 9 cycles using the SM. After physical-chemical treatment, only SM denitrified water remained within drinking water standards parameters of color and turbidity.

Environmental chemicals and breast cancer: An updated review of epidemiological literature informed by biological mechanisms

BACKGROUND

Many common environmental chemicals are mammary gland carcinogens in animal studies, activate relevant hormonal pathways, or enhance mammary gland susceptibility to carcinogenesis. Breast cancer's long latency and multifactorial etiology make evaluation of these chemicals in humans challenging.

OBJECTIVE

For chemicals previously identified as mammary gland toxicants, we evaluated epidemiologic studies published since our 2007 review. We assessed whether study designs captured relevant exposures and disease features suggested by toxicological and biological evidence of genotoxicity, endocrine disruption, tumor promotion, or disruption of mammary gland development.

METHODS

We systematically searched the PubMed database for articles with breast cancer outcomes published in 2006-2016 using terms for 134 environmental chemicals, sources, or biomarkers of exposure. We critically reviewed the articles.

RESULTS

We identified 158 articles. Consistent with experimental evidence, a few key studies suggested higher risk for exposures during breast development to dichlorodiphenyltrichloroethane (DDT), dioxins, perfluorooctane-sulfonamide (PFOSA), and air pollution (risk estimates ranged from 2.14 to 5.0), and for occupational exposure to solvents and other mammary carcinogens, such as gasoline components (risk estimates ranged from 1.42 to 3.31). Notably, one 50-year cohort study captured exposure to DDT during several critical windows for breast development (in utero, adolescence, pregnancy) and when this chemical was still in use. Most other studies did not assess exposure during a biologically relevant window or specify the timing of exposure. Few studies considered genetic variation, but the Long Island Breast Cancer Study Project reported higher breast cancer risk for polycyclic aromatic hydrocarbons (PAHs) in women with certain genetic variations, especially in DNA repair genes.

CONCLUSIONS

New studies that targeted toxicologically relevant chemicals and captured biological hypotheses about genetic variants or windows of breast susceptibility added to evidence of links between environmental chemicals and breast cancer. However, many biologically relevant chemicals, including current-use consumer product chemicals, have not been adequately studied in humans. Studies are challenged to reconstruct exposures that occurred decades before diagnosis or access biological samples stored that long. Other problems include measuring rapidly metabolized chemicals and evaluating exposure to mixtures.

Tracking nitrate sources in groundwater and associated health risk for rural communities in the White Volta River basin of Ghana using isotopic approach (δ15N, δ18ONO3 and 3H)

In this study, we present a first attempt on the use of integrated hydro-chemical and isotopic technique to trace the sources of groundwater nitrate contamination in the Upper East Region of Ghana to aid the sustainable management of this vital resource. The objectives of the study are (1) assess the present status and spatial distribution of the nitrate contamination (2) identify and distinguish the most likely sources of nitrate , (3) identify the relationship between ³H and NO₃^- and F^-, and (4) ascertain the potential human risk from exposure to nitrate contamination. The results showed that, nitrate concentrations varied from 0.42 to 431.17, 0.83 to 143.94, 0.03 to 28.94mg/l with mean values of 36.09, 21.54 and 5.01mg/l for boreholes, hand dug wells and the surface water respectively. These values showed that, about 95% of boreholes and hand dug wells and 45% of the surface water have nitrate concentration above the baseline value in the area. The NO₃^-/Cl^- ratio showed that, 98.4%, 95% and 64% of the NO₃^- in the borehole, hand dug wells and the surface water are from anthropogenic activities. The δ¹⁵NNO₃ and δ¹⁸ONO₃^- data confirmed that NO₃^- in the samples was predominantly derived from manure (human and animal waste) and denitrification occurring in some areas. The isotopic data further affirms the hydro-chemical interpretation that, chemical fertilizer and atmospheric deposition are unlikely sources of NO₃^- in the area. The relationship between ³H and NO₃^- concentrations showed that, higher NO₃^- values are associated with younger waters. Non carcinogenic health risk for adults and children posed by oral ingestion of the NO₃^- contaminated water revealed some degree of health risk, especially to children whose risk is about 72% higher. The study provides a conceptual model of the NO₃^- dynamics and some recommendation for groundwater management in the area.

Nationwide analysis on the impact of socioeconomic land use factors and incidence of urothelial carcinoma

BACKGROUND

Incidence rates for urothelial carcinoma (UC) have been reported to differ between countries within the European Union (EU). Besides occupational exposure to chemicals, other substances such as tobacco and nitrite in groundwater have been identified as risk factors for UC. We investigated if regional differences in UC incidence rates are associated with agricultural, industrial and residential land use.

METHODS

Newly diagnosed cases of UC between 2003 and 2010 were included. Information within 364 administrative districts of Germany from 2004 for land use factors were obtained and calculated as a proportion of the total area of the respective administrative district and as a smoothed proportion. Furthermore, information on smoking habits was included in our analysis. Kulldorff spatial clustering was used to detect different clusters. A negative binomial model was used to test the spatial association between UC incidence as a ratio of observed versus expected incidence rates, land use and smoking habits.

RESULTS

We identified 437,847,834 person years with 171,086 cases of UC. Cluster analysis revealed areas with higher incidence of UC than others (p=0.0002). Multivariate analysis including significant pairwise interactions showed that the environmental factors were independently associated with UC (p<0.001). The RR was 1.066 (95% CI 1.052-1.080), 1.066 (95% CI 1.042-1.089) and 1.067 (95% CI 1.045-1.093) for agricultural, industrial and residential areas, respectively, and 0.996 (95% CI 0.869-0.999) for the proportion of never smokers.

CONCLUSION

This study displays regional differences in incidence of UC in Germany. Additionally, results suggest that socioeconomic factors based on agricultural, industrial and residential land use may be associated with UC incidence rates.

The Sources of Chemical Contaminants in Food and Their Health Implications

Food contamination is a matter of serious concern, as the high concentration of chemicals present in the edibles poses serious health risks. Protecting the public from the degrees of the harmfulness of contaminated foods has become a daunting task. This article highlights the causes, types, and health implications of chemical contamination in food. The food contamination could be due to naturally occurring contaminants in the environment or artificially introduced by the human. The phases of food processing, packaging, transportation, and storage are also significant contributors to food contamination. The implications of these chemical contaminants on human health are grave, ranging from mild gastroenteritis to fatal cases of hepatic, renal, and neurological syndromes. Although, the government regulates such chemicals in the eatables by prescribing minimum limits that are safe for human consumption yet measures still need to be taken to curb food contamination entirely. Therefore, a variety of food needs to be inspected and measured for the presence of chemical contaminants. The preventative measures pertaining about the food contaminants problems are pointed out and discussed.

Nitrate from Drinking Water and Diet and Bladder Cancer Among Postmenopausal Women in Iowa

BACKGROUND

Nitrate is a drinking water contaminant arising from agricultural sources, and it is a precursor in the endogenous formation of N-nitroso compounds (NOC), which are possible bladder carcinogens.

OBJECTIVES

We investigated the ingestion of nitrate and nitrite from drinking water and diet and bladder cancer risk in women.

METHODS

We identified incident bladder cancers among a cohort of 34,708 postmenopausal women in Iowa (1986-2010). Dietary nitrate and nitrite intakes were estimated from a baseline food frequency questionnaire. Drinking water source and duration were assessed in a 1989 follow-up. For women using public water supplies (PWS) > 10 years (n = 15,577), we estimated average nitrate (NO3-N) and total trihalomethane (TTHM) levels and the number of years exceeding one-half the maximum contaminant level (NO3-N: 5 mg/L, TTHM: 40 μg/mL) from historical monitoring data. We computed hazard ratios (HRs) and 95% confidence intervals (CIs), and assessed nitrate interactions with TTHM and with modifiers of NOC formation (smoking, vitamin C).

RESULTS

We identified 258 bladder cancer cases, including 130 among women > 10 years at their PWS. In multivariable-adjusted models, we observed nonsignificant associations among women in the highest versus lowest quartile of average drinking water nitrate concentration (HR = 1.48; 95% CI: 0.92, 2.40; ptrend = 0.11), and we found significant associations among those exposed ≥ 4 years to drinking water with > 5 mg/L NO3-N (HR = 1.62; 95% CI: 1.06, 2.47; ptrend = 0.03) compared with women having 0 years of comparable exposure. TTHM adjustment had little influence on associations, and we observed no modification by vitamin C intake. Relative to a common reference group of never smokers with the lowest nitrate exposures, associations were strongest for current smokers with the highest nitrate exposures (HR = 3.67; 95% CI: 1.43, 9.38 for average water NO3-N and HR = 3.48; 95% CI: 1.20, 10.06 and ≥ 4 years > 5 mg/L, respectively). Dietary nitrate and nitrite intakes were not associated with bladder cancer.

CONCLUSIONS

Long-term ingestion of elevated nitrate in drinking water was associated with an increased risk of bladder cancer among postmenopausal women. Citation: Jones RR, Weyer PJ, DellaValle CT, Inoue-Choi M, Anderson KE, Cantor KP, Krasner S, Robien K, Beane Freeman LE, Silverman DT, Ward MH. 2016. Nitrate from drinking water and diet and bladder cancer among postmenopausal women in Iowa. Environ Health Perspect 124:1751-1758; http://dx.doi.org/10.1289/EHP191.

Advances in nanomaterial based approaches for enhanced fluoride and nitrate removal from contaminated water

Various nanomaterials for fluoride and nitrate removal from contaminated water.

Kinetic analysis of Fe3+reduction coupled with nitrate removal by Klebsiella sp. FC61 under different conditions

Klebsiellasp. FC61, a newly found iron-reducing bacterium, has the ability of simultaneously reducing Fe³⁺and nitrate under different pH and temperature conditions.

Characterization of the anaerobic denitrification bacterium Acinetobacter sp. SZ28 and its application for groundwater treatment

Acinetobacter sp. SZ28 exhibited efficient autotrophic denitrification ability using Mn(2+) as an electron donor. Sequence amplification identified the presence of the nirS gene. Meteorological chromatography analysis showed that N2 was produced as an end product. Response surface methodology experiments showed that the maximum removal of nitrate occurred under the following conditions: Mn(2+) concentration of 143.56 mg/L, C/N ratio of 6.82, initial pH of 5.17, and temperature of 34.26 °C, where the initial Mn(2+) concentration produced the largest effect. In the groundwater experiment, nitrate levels decreased from 1.63 mg/L to 0 mg/L. Three-dimensional fluorescence analysis showed a decrease in the peak intensity of the original humus. Humus and the small-molecule amino acid tryptophan were detected. These results demonstrated that strain SZ28 is a suitable candidate for the simultaneous removal of nitrogen and Mn(2+) in groundwater treatment.