Nitrate, Nitrite, and Ammonium Variability in Drinking Water Distribution Systems

A study into the natural occurrence of inorganic ions relevant to forensic explosives investigations on human hands

The natural occurrence of 16 inorganic ions relevant to forensic explosives investigations on human hands was studied to support the evaluation of activity-level propositions when such traces are found on the hands or in the fingerprints of a suspect. A total of 594 hand swab extracts from 297 participants throughout Europe and the United States of America were analyzed using Ion Chromatography - Mass Spectrometry. The data provides a reference framework for future covert investigations and forensic casework. The results indicate that thiocyanate, chlorate, nitrite, lithium, strontium, and barium are rarely detected on the hands of individuals who have had no direct contact with explosives (P<0.03) and in quantities below 6 µg. Perchlorate contamination sporadically occurs without deliberately handling perchlorates (P=0.03), albeit at low levels (<12 µg). It also seems that the presence of perchlorate on hands is generally related to professions that involve explosives. Detecting substantial amounts of any of these rare ions on a suspect's hands would require a specific explanation. Because legitimate activities exist that can also result in elevated levels of ions of interest on hands, the context surrounding their presence has to be carefully assessed for each individual case.

Perspectives on environment and health research in Denmark

AIMS

We provide an overview of nationwide environmental data available for Denmark and its linkage potentials to individual-level records with the aim of promoting research on the potential impact of the local surrounding environment on human health.

BACKGROUND

Researchers in Denmark have unique opportunities for conducting large population-based studies treating the entire Danish population as one big, open and dynamic cohort based on nationally complete population and health registries. So far, most research in this area has utilised individual- and family-level information to study the clustering of disease in families, comorbidities, risk of, and prognosis after, disease onset, and social gradients in disease risk. Linking environmental data in time and space to individuals enables novel possibilities for studying the health effects of the social, built and physical environment.

METHODS

We describe the possible linkage between individuals and their local surrounding environment to establish the exposome - that is, the total environmental exposure of an individual over their life course.

CONCLUSIONS

The currently available nationwide longitudinal environmental data in Denmark constitutes a valuable and globally rare asset that can help explore the impact of the exposome on human health.

Nitrate Sensor with a Wide Detection Range and High Stability Based on a Cu-Modified Boron-Doped Diamond Electrode

This paper describes an electrochemical sensor based on a Cu-modified boron-doped diamond (BDD) electrode for the detection of nitrate-contaminated water. The sensor utilizes the catalytic effect of copper on nitrate and the stability of the BDD electrode. By optimizing the electrolyte system, the linear detection range was expanded, allowing the sensor to detect highly concentrated nitrate samples up to 100 mg/L with a low detection limit of 0.065 mg/L. Additionally, the stability of the sensor was improved. The relative standard deviation of the current responses during 25 consecutive tests was only 1.03%. The wide detection range and high stability of the sensor makes it suitable for field applications and the on-site monitoring of nitrate-contaminated waters.

Spatiotemporal successions of N, S, C, Fe, and As cycling genes in groundwater of a wetland ecosystem: Enhanced heterogeneity in wet season

Microorganisms in wetland groundwater play an essential role in driving global biogeochemical cycles. However, largely due to the dynamics of spatiotemporal surface water-groundwater interaction, the spatiotemporal successions of biogeochemical cycling in wetland groundwater remain poorly delineated. Herein, we investigated the seasonal coevolution of hydrogeochemical variables and microbial functional genes involved in nitrogen, carbon, sulfur, iron, and arsenic cycling in groundwater within a typical wetland, located in Poyang Lake Plain, China. During the dry season, the microbial potentials for dissimilatory nitrate reduction to ammonium and ammonification were dominant, whereas the higher potentials for nitrogen fixation, denitrification, methane metabolism, and carbon fixation were identified in the wet season. A likely biogeochemical hotspot was identified in the area located in the low permeable aquifer near the lake, characterized by reducing conditions and elevated levels of Fe2+ (6.65-17.1 mg/L), NH4+ (0.57-3.98 mg/L), total organic carbon (1.02-1.99 mg/L), and functional genes. In contrast to dry season, higher dissimilarities of functional gene distribution were observed in the wet season. Multivariable statistics further indicated that the connection between the functional gene compositions and hydrogeochemical variables becomes less pronounced as the seasons transition from dry to wet. Despite this transition, Fe2+ remained the dominant driving force on gene distribution during both seasons. Gene-based co-occurrence network displayed reduced interconnectivity among coupled C-N-Fe-S cycles from the dry to the wet season, underpinning a less complex and more destabilizing occurrence pattern. The rising groundwater level may have contributed to a reduction in the stability of functional microbial communities, consequently impacting ecological functions. Our findings shed light on microbial-driven seasonal biogeochemical cycling in wetland groundwater.

Source-specific nitrate and nitrite intakes and associations with sociodemographic factors in the Danish Diet Cancer and Health cohort

Background

The dietary source and intake levels of nitrate and nitrite may govern its deleterious versus beneficial effects on human health. Existing evidence on detailed source-specific intake is limited. The objectives of this study were to assess nitrate and nitrite intakes from different dietary sources (plant-based foods, animal-based foods, and water), characterize the background diets of participants with low and high intakes, and investigate how sociodemographic and lifestyle factors associate with intake levels.

Methods

In the Danish Diet, Cancer and Health Cohort, sociodemographic and lifestyle information was obtained from participants at enrolment (1993-1997). Source-dependent nitrate and nitrite intakes were calculated using comprehensive food composition databases, with tap water nitrate intakes estimated via the national drinking water quality monitoring database linked with participants' residential addresses from 1978 to 2016. Underlying dietary patterns were examined using radar plots comparing high to low consumers while sociodemographic predictors of source-dependent nitrate intakes were investigated using linear regression models.

Results

In a Danish cohort of 55,754 participants aged 50-65 at enrolment, the median [IQR] intakes of dietary nitrate and nitrite were 58.13 [44.27-74.90] mg/d and 1.79 [1.43-2.21] mg/d, respectively. Plant-based foods accounted for ~76% of nitrate intake, animal-based foods ~10%, and water ~5%. Nitrite intake was sourced roughly equally from plants and animals. Higher plant-sourced nitrate intake was associated with healthier lifestyles, better dietary patterns, more physical activity, higher education, lower age and lower BMI. Females and participants who had never smoked also had significantly higher plant-sourced nitrate intakes. Higher water-sourced nitrate intake was linked to sociodemographic risk factors (smoking, obesity, lower education). Patterns for animal-sourced nitrate were less clear.

Conclusion

Participants with higher plant-sourced nitrate intakes tend to be healthier while participants with higher water-sourced nitrate intakes tended to be unhealthier than their low consuming counterparts. Future research in this cohort should account for the sociodemographic and dietary predictors of source-specific nitrate intake we have identified.

Exposure assessment of nitrate and phenol derivatives in Tehran's water distribution system

The presence of organic and inorganic contaminants in drinking water is a global concern. Nitrate and phenol derivatives are examples of pollutants that could be of anthropogenic origin. They are associated with numerous health risks, underscoring the importance of monitoring their presence in drinking water. This study aimed to measure nitrate and phenol derivatives, including 2,4-Dichlorophenol (2,4-DCP), Pentachlorophenol (PCP), 2,4,5-Trichlorophenol (2,4,5-TCP), 2-Chlorophenol (2-CP), 4-Chlorophenol (4-CP), and phenol, in Tehran's water distribution system (WDS). The pollutants in Tehran's WDS were significantly and positively correlated with precipitation. The Hazard Quotient (HQ) and the Excess Lifetime Cancer Risk (ELCR) of the detected pollutants were estimated. The results showed that the regional mean of nitrate and PCP in Tehran's WDS were 35.58±8.71mg L-1 and 76.14±16.93 ng L-1 lower than the guideline values of 50 mg L-1 and 1000 ng L-1, respectively. Some districts exhibited nitrate concentration exceeding the allowable limit by a factor of 1.2 to 2.3. Consequently, the nitrate intake in some districts constituted approximately 50% of the reference dose. While PCP as a phenol derivative with more health concerns was identified in Tehran's WDS, the likelihood of its health effects was determined to be negligible.

Health-economic valuation of lowering nitrate standards in drinking water related to colorectal cancer in Denmark

Nitrate in drinking water is a contaminant which can affect human health and has been associated with an increased risk of, amongst other diseases, colorectal cancer. Based on epidemiologic data from Denmark on the association between drinking water nitrate and colorectal cancer, the health and economic consequences of lowering the standard of nitrate in drinking water from 50 mg/L to 9.25 mg/L and 3.87 mg/L, respectively are analyzed. The drinking water nitrate attributable number of cases was estimated using the risk in the exposed and unexposed population based on current nationwide exposure distributions. The analysis shows that a lower limit of 9.25 mg/L would decrease the annual number of colorectal cancer cases by 72 (95 % confidence interval: 34-114) and by an additional 55 (95 % CI: 10-100) for a stricter limit of 3.87 mg/L. The resulting avoided health-related costs are $179 million per year for the 9.25 mg/L nitrate limit and another $138 million per year for a further reduction to 3.87 mg/L nitrate. The new requirements would incur costs linked to either i) changes in land use management, ii) well reallocation or iii) use of treatment technologies. The additional costs are estimated to $0.03-1.84 per m3 abstracted water from public water companies, which together with costs for owners of private wells, will result in an average additional cost of $9 and $6 million per year for the two levels. The economic health benefits are higher than the costs for both limits with net gains of $170 million (9.25 mg/L) and additionally $132 million (3.87 mg/L) a year. Even in a worst-case scenario (lowest health-related benefits and highest mitigation costs), there is a likely economic gain for society from lowering the limit to 9.25 mg/L, but this might not be the case for the lower limit of 3.87 mg/L.

Investigation on Applying Biodegradable Material for Removal of Various Substances (Fluorides, Nitrates and Lead) from Water

Sapropel was used as a biodegradable material for water treatment. Sapropel is a sedimentary layer of a mix of organic and inorganic substances accumulated in the bottoms of lakes for thousands of years. It is a jelly-like homogeneous mass and has properties of sorption. Sapropel is used as a biosorbent and an environment-friendly fertiliser, and it is used in building materials and in the beauty industry as well. In water, there are abundant various solutes that may cause a risk to human health. Such substances include fluorides, nitrates and lead in different sources of water. The goal of this investigation is to explore and compare the efficiencies of removal of different pollutants (fluorides, nitrates and lead) from aqueous solutions upon using sapropel as a sorbent. In this research, various doses of sapropel (0.1, 0.5, 1, 5, 10, 20, 50, 100 and 200 g/L) and various mixing times (15, 30, 60, 90 and 120 min) were used for removal of fluorides, nitrates and lead from aqueous solutions. It was found that the maximum efficiency (up to 98.57%) of lead removal from aqueous solutions by sapropel was achieved when the minimum doses of it (0.1 and 0.5 g/L) were used. The most efficient removal of fluorides (64.67%) was achieved by using 200 g/L of sapropel and mixing for 120 min. However, sapropel does not adsorb nitrates from aqueous solutions.

Prenatal Exposure to Nitrate in Drinking Water and Adverse Health Outcomes in the Offspring: a Review of Current Epidemiological Research

PURPOSE OF REVIEW

Recently, several epidemiological studies have investigated whether prenatal exposure to nitrate from drinking water may be harmful to the fetus, even at nitrate levels below the current World Health Organization drinking water standard. The purpose of this review was to give an overview of the newest knowledge on potential health effects of prenatal exposure to nitrate.

RECENT FINDINGS

We included 13 epidemiological studies conducted since 2017. Nine studies investigated outcomes appearing around birth, and four studies investigated health outcomes appearing in childhood and young adulthood. The reviewed studies showed some indications of higher risk of preterm delivery, lower birth weight, birth defects, and childhood cancer related to prenatal exposure to nitrate. However, the numbers of studies for each outcome were sparse, and some of the results were conflicting. We suggest that there is a need for additional studies and particularly for studies that include information on water consumption patterns, intake of nitrate from diet, and intake of nitrosatable drugs.

Impact of industrial air pollution on the quality of atmospheric water production

The atmospheric water generator (AWG) is a commercially available device that produces water from the air in large volumes over short times. This method can be applied in most regions of the world to solve chronic and acute drinking water scarcity. However, knowledge of the effects of air chemical composition on AWG-produced water quality is still very limited. In this study, a comprehensive survey of AWG-produced water quality was conducted in a heavily polluted industrial environment; 83 AWG water samples were analyzed for 99 different quality parameters, including organic, inorganic, and microbial contamination. Two parameters-nickel (15 samples) and dichloromethane (2 samples)-exceeded sporadically their drinking water standards of EPA, EU and IL. Ammonia was the only parameter consistently above standard limits of 0.5 mg/L (61% of samples, relevant to 47 countries) and even higher than 1.5 mg/L. Comparison to real air concentrations of volatile pollutants in the same environment did not reveal any significant correlations; while some pollutants were found at high concentrations in the air, this was not reflected by their presence in the produced water. The findings show that even in areas that are considered excessively polluted relative to the natural environment, the water produced from the air by AWG could be considered suitable for drinking, with careful attention to very specific contaminants.

The Minus Approach Can Redefine the Standard of Practice of Drinking Water Treatment

Chlorine-based disinfection for drinking water treatment (DWT) was one of the 20th century's great public health achievements, as it substantially reduced the risk of acute microbial waterborne disease. However, today's chlorinated drinking water is not unambiguously safe; trace levels of regulated and unregulated disinfection byproducts (DBPs), and other known, unknown, and emerging contaminants (KUECs), present chronic risks that make them essential removal targets. Because conventional chemical-based DWT processes do little to remove DBPs or KUECs, alternative approaches are needed to minimize risks by removing DBP precursors and KUECs that are ubiquitous in water supplies. We present the "Minus Approach" as a toolbox of practices and technologies to mitigate KUECs and DBPs without compromising microbiological safety. The Minus Approach reduces problem-causing chemical addition treatment (i.e., the conventional "Plus Approach") by producing biologically stable water containing pathogens at levels having negligible human health risk and substantially lower concentrations of KUECs and DBPs. Aside from ozonation, the Minus Approach avoids primary chemical-based coagulants, disinfectants, and advanced oxidation processes. The Minus Approach focuses on bank filtration, biofiltration, adsorption, and membranes to biologically and physically remove DBP precursors, KUECs, and pathogens; consequently, water purveyors can use ultraviolet light at key locations in conjunction with smaller dosages of secondary chemical disinfectants to minimize microbial regrowth in distribution systems. We describe how the Minus Approach contrasts with the conventional Plus Approach, integrates with artificial intelligence, and can ultimately improve the sustainability performance of water treatment. Finally, we consider barriers to adoption of the Minus Approach.

Prenatal exposure to tap water containing nitrate and the risk of small-for-gestational-age: A nationwide register-based study of Danish births, 1991-2015

BACKGROUND

Prenatal nitrate exposure from household tap water has been associated with increased risk of fetal growth restriction, preterm birth, birth defects, and childhood cancer. We aim to examine the association between maternal consumption of drinking-water nitrate during pregnancy and small-for-gestational-age (SGA) in a nationwide study of Danish-born children, as only one prior study has examined this association.

METHODS

We linked individual-level household estimates of nitrate in tap water and birth registry data to all live singleton Danish births during 1991-2015 from Danish-born parents where the mother resided in Denmark throughout the pregnancy. Exposure was both binned into four categories and modeled as an ln-transformed continuous variable. SGA was defined as the bottom 10% of births by birth weight per sex and gestational week. Multiple logistic regression models with generalized estimating equations were used to account for siblings born to the same mother while controlling for relevant confounders.

RESULTS

In the cohort of 1,078,892 births, the median pregnancy nitrate exposure was 1.9 mg/L nitrate. Compared to the reference group (≤2 mg/L), we found an increased risk of SGA in the second category (>2-5 mg/L) (OR = 1.04, 95% CI: 1.03-1.06) and third category (>5-25 mg/L) (OR = 1.02, 95% CI: 1.00-1.04) but not in the highest (>25 mg/L). There was strong (p = 0.002) evidence of an increase in SGA with nitrate in the model with continuous exposure (OR = 1.02, 95% CI: 1.01-1.04 per 10-fold increase in nitrate). Results were robust when restricting to households with nitrate levels at or below the current Danish and European Union regulatory drinking water standard (50 mg/L nitrate).

CONCLUSIONS

Our findings suggest that exposure from nitrate in household tap water, even below current regulatory standards, may increase risk of SGA, raising concerns of whether current allowable nitrate levels in drinking water protect children from SGA.

Advanced hematite nanomaterials for newly emerging applications

Because of the combined merits of rich physicochemical properties, abundance, low toxicity, etc., hematite (α-Fe2O3), one of the most chemically stable compounds based on the transition metal element iron, is endowed with multifunctionalities and has steadily been a research hotspot for decades. Very recently, advanced α-Fe2O3 materials have also been developed for applications in some cutting-edge fields. To reflect this trend, the latest progress in developing α-Fe2O3 materials for newly emerging applications is reviewed with a particular focus on the relationship between composition/nanostructure-induced electronic structure modulation and practical performance. Moreover, perspectives on the critical challenges as well as opportunities for future development of diverse functionalities are also discussed. We believe that this timely review will not only stimulate further increasing interest in α-Fe2O3 materials but also provide a profound understanding and insight into the rational design of other materials based on transition metal elements for various applications.

Prenatal nitrate exposure from diet and drinking water and timing of puberty in sons and daughters: A nationwide cohort study

BACKGROUND

In Western countries, age at pubertal development has declined during the last century in girls, and probably also in boys. No studies have investigated whether nitrate, a widespread environmental exposure with teratogenic and hormone disrupting properties, might affect timing of puberty.

OBJECTIVES

We investigated if prenatal exposure to nitrate from drinking water and diet was associated with timing of puberty.

METHODS

This cohort study included 15,819 children born from 2000 to 2003 within the Danish National Birth Cohort. Self-reported information on current status of various pubertal milestones was provided every six months by a questionnaire from 11 years of age until 18 years or full maturity, whichever came first. Maternal nitrate intake from diet (mg/day) was derived from a mid-pregnancy food frequency questionnaire and individual level nitrate exposure from drinking water (mg/L) was derived using measurements from Danish public waterworks. Adjusted average differences in months in age at attaining several pubertal milestones as well as the average age difference in age at attaining all the milestones were estimated separately for diet and water using a regression model for interval-censored data. C- and E-vitamin, red meat and processed meat intake were explored as potential effect modifiers in sub-analyses.

RESULTS

No strong associations were observed between prenatal exposure to nitrate and timing of puberty in children. However, sons born of mothers with a nitrate concentration in drinking water at their residential address of > 25 mg/L (half of the World Health Organisation (WHO) guideline value) compared with ≤ 1 mg/L showed a tendency towards earlier age at pubertal development with an average age difference of -1.2 months (95 % confidence interval,-3.0;0.6) for all the pubertal milestones combined.

DISCUSSION

Studies including more highly exposed children are needed before the current WHO drinking water guideline value for nitrate can be considered safe concerning pubertal development.

Nitrate in Maternal Drinking Water during Pregnancy and Measures of Male Fecundity in Adult Sons

Animal studies indicate deleterious effects of nitrate exposure on fecundity, but effects in humans are unknown, both for the prenatal and postnatal periods. We aimed to investigate if exposure to nitrate in maternal drinking water during the sensitive period of fetal life is associated with measures of fecundity in the adult sons. In a sub-analysis, the potential effects of nitrate exposure in adulthood were investigated. This cohort included 985 young adult men enrolled in The Fetal Programming of Semen Quality Cohort (FEPOS). Semen characteristics, testes volume and reproductive hormones were analyzed in relation to nitrate concentration in maternal drinking water, using a negative binomial regression model. The nitrate concentration in drinking water was obtained from monitoring data from Danish waterworks that were linked with the mothers' residential address during pregnancy. The median nitrate concentration in maternal drinking water was 2 mg/L. At these low exposure levels, which are far below the World Health Organization's (WHO) guideline value of 50 mg/L, we did not find indications of harmful effects of nitrate on the investigated measures of male fecundity.

Drinking water nitrate and risk of pregnancy loss: a nationwide cohort study

BACKGROUND

Nitrate contamination is seen in drinking water worldwide. Nitrate may pass the placental barrier. Despite suggestive evidence of fetal harm, the potential association between nitrate exposure from drinking water and pregnancy loss remains to be studied. We aimed to investigate if nitrate in drinking water was associated with the risk of pregnancy loss.

METHODS

We conducted a nationwide cohort study of 100,410 pregnancies (enrolled around gestational week 11) in the Danish National Birth Cohort (DNBC) during 1996-2002. Spontaneous pregnancy losses before gestational week 22 were ascertained from the Danish National Patient Registry and DNBC pregnancy interviews. Using the national drinking water quality-monitoring database Jupiter, we estimated the individual and time-specific nitrate exposure by linking geocoded maternal residential addresses with water supply areas. The nitrate exposure was analyzed in spline models using a log-transformed continuous level or classified into five categories. We used Cox proportional hazards models to estimate associations between nitrate and pregnancy loss and used gestational age (days) as the time scale, adjusting for demographic, health, and lifestyle variables.

RESULTS

No consistent associations were found when investigating the exposure as a categorical variable and null findings were also found in trimester specific analyses. In the spline model using the continuous exposure variable, a modestly increased hazard of pregnancy loss was observed for the first trimester at nitrate exposures between 1 and 10 mg/L, with the highest. adjusted hazard ratio at 5 mg/L of nitrate of 1.16 (95% CI: 1.01, 1.34). This trend was attenuated in the higher exposure ranges.

CONCLUSION

No association was seen between drinking water nitrate and the risk of pregnancy loss when investigating the exposure as a categorical variable. When we modelled the exposure as a continuous variable, a dose-dependent association was found between drinking water nitrate exposure in the first trimester and the risk of pregnancy loss. Very early pregnancy losses were not considered in this study, and whether survival bias influenced the results should be further explored.

Prenatal exposure to nitrate from drinking water and the risk of preterm birth

Evidence is emerging that preterm birth (PTB, birth before 37 completed weeks of gestation), a risk factor for neonatal mortality and future morbidity, may be induced by maternal nitrate (NO3−) exposure from drinking water. The objective of this study is to assess the association between maternal exposure to nitrate and the risk of PTB in a nationwide study of liveborn singletons.

Towards sustainability: Threat of water quality degradation and eutrophication in Usangu agro-ecosystem Tanzania

The agrochemicals and nutrient losses from farming areas such as paddy farming significantly dictate quality and eutrophication of the freshwater resource. However, how farming and land use pattern affect water qualities and eutrophication remain poorly understood in most African agro-ecosystems. The present study characterized how paddy farming influences water qualities and eutrophication in 10 irrigation schemes in Usangu agro-ecosystem (UA). About 42 water samples were sampled from intakes, channels, paddy fields, and drainages and analyzed for EC, Cl, P, NH₄-N, NO₃-N, TN, Zn, Cu, Ca, and Mg. We observed water pH ranging from 4.89 to 6.76, which was generally below the acceptable range (6.5-8.4) for irrigation water. NH₄-N concentration was in a range of 10.6-70.0 mg/L, NO₃-N (8.4-33.9 mg/L), and TN (19.1-21,104 mg/L). NH₄-N increased along sampling transect (sampling points) from intakes (5.7-29.1 mg/L), channels (19-20 mg/L), fields (12.9-35.8 mg/L), and outflow (10.6-70.0 mg/L), the same trend were found for NO₃-N and TN. The TP determined in water samples were in the range of 0.01 to 1.65 mg/L; where some sites had P > 0.1 mg/L exceeding the allowable P concentration in freshwater resource, thus indicating P enrichment and eutrophication status. The P concentration was observed to increase from intake through paddy fields to drainages, where high P was determined in drainages (0.02-1.65 mg/L) and fields (0.0-0.54 mg/L) compared to channels (0.01-0.13 mg/L) and intakes (0.01-0.04 mg/L). Furthermore, we determined appreciable amount of potentially toxic elements (PTEs) such as Cu, Pb, Cd and Cr in studied water samples. The high N, P, and PTEs in drainages indicate enrichment from agricultural fields leading to water quality degradation and contaminations (eutrophication). The study demonstrates that water quality in UA is degrading potentially due to paddy rice farming and other associated activities in the landscape. Thus, the current study recommends starting initiatives to monitor irrigation water quality in UA for better crop productivity, and improved quality of drainage re-entering downstream through the introduction of mandatory riparian buffer, revising irrigation practices, to include good agronomic practices (GAP) to ensure water quality and sustainability.

Nitrate in Drinking Water and Time to Pregnancy or Medically Assisted Reproduction in Women and Men: A Nationwide Cohort Study in the Danish National Birth Cohort

Purpose

No studies have investigated if drinking water nitrate affects human fecundity. Experimental studies point at detrimental effects on fetal development and on female and male reproduction. This cohort study aimed to explore if female and male preconception and long-term exposure to nitrate in drinking water was associated with fecundability measured as time to pregnancy (TTP) or use of medically assisted reproduction (MAR) treatment.

Methods

The study population consisted of pregnant women recruited in their first trimester in 1996–2002 to the Danish National Birth Cohort. Preconception drinking-water nitrate exposure was estimated for the pregnant women (89,109 pregnancies), and long-term drinking water nitrate exposure was estimated from adolescence to conception for the pregnant women (77,474 pregnancies) and their male partners (62,000 pregnancies) by linkage to the national drinking water quality-monitoring database Jupiter. Difference in risk of TTP >12 months or use of MAR treatment between five exposure categories and log-transformed continuous models of preconception and long-term nitrate in drinking water were estimated. Binominal regression models for risk ratios (RR) were adjusted for age, occupation, education, population density, and lifestyle factors.

Results

Nitrate in drinking water (median preconception exposure: 1.9 mg/L; median long-term exposure: 3.3 mg/L) was not associated with TTP >12 months or use of MAR treatment, neither in the categorical nor in the continuous models.

Conclusion

We found no association between preconception or long-term exposure to drinking water nitrate and fecundability.

Nitrate in drinking water and risk of birth defects: Findings from a cohort study of over one million births in Denmark

Background

A few studies have reported an increased risk of birth defects (BD) with maternal exposure to nitrate in drinking water. We examined this association in a large cohort study with well-characterized exposure.

Methods

Danish singletons liveborn to Danish-born parents from 1991–2013 were identified using civil and patient registries (n=1,018,914). Exposure to nitrate was estimated using a spatial model based on national data linked with individual addresses. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using logistic regression.

Findings

In total, 33,182 cases of BD were identified. Nitrate concentrations were generally well below US and EU standards. We observed an exposure-response relationship (p=0·004) between nitrate during pregnancy and eye BD, and increased risk in the highest exposure group (≥25 mg/L nitrate) (OR: 1·29; 95% CI: 1·00, 1·66). An interaction was observed between maternal age and continuous nitrate exposure for nervous system BD (p<0·001) indicating an increased risk among mothers <25 years-of-age (OR for 10 mg/L (OR₁₀): 1·20; 95% CI: 1·06, 1·35). An interaction (p<0.01) with maternal age and continuous nitrate exposure was also observed for ear, face, and neck BD indicating an increased risk among babies born to mothers <25 years-of-age (OR₁₀: 1·35; 95% CI: 1·11, 1·66). There was evidence of an inverse exposure-response relationship for any, digestive system, female genital, and urinary BD.

Interpretation

Our study is the first to report an association between nitrate and eye BD and BD of the ear, face, and neck. It also provides support to prior reports of increased risk of nervous system BD.

Funding

This study was supported by a grant from the United States National Institute of Environmental Health Sciences (R01 ES027823-01A1).

Prenatal nitrosatable prescription drug intake, drinking water nitrate, and the risk of stillbirth: a register- and population-based cohort of Danish pregnancies, 1997-2017

BACKGROUND

Nitrosatable drugs commonly prescribed during pregnancy can react with nitrite to form N-nitroso compounds which have been associated with an increased risk of stillbirth. Whether maternal residential drinking water nitrate modifies this association is unknown. We investigated, if household drinking water nitrate was associated with stillbirth, and if it modified the association between nitrosatable prescription drug intake and the risk of stillbirth.

METHODS

We conducted an individual-level register- and population-based cohort study using 652,810 women with the first recorded singleton pregnancy in the Danish Medical Birth Registry between 1997 and 2017. Nitrosatable drug exposure was recorded by use of the Danish National Patient Registry defined as women with a first redeemed prescription of a nitrosatable drug the first 22 weeks of pregnancy. The reference group was women with no redeemed prescription of a nitrosatable drug in this period. The average individual drinking water nitrate concentration level (mg/L) was calculated in the same period. We categorized nitrosatable drugs as secondary amines, tertiary amines, and amides. Cox hazard regression was used to estimate crude and adjusted hazard ratios with 95% confidence intervals for stillbirth stratified into five categories of nitrate concentrations: ≤1 mg/L, > 1- ≤ 2 mg/L, > 2- ≤ 5 mg/L, > 5- ≤ 25 mg/L, and > 25 mg/L.

RESULTS

Drinking water nitrate exposure in the population was not associated with the risk of stillbirth. Among 100,244 women who had a nitrosatable prescription drug redeemed ≤22 weeks of pregnancy of pregnancy, 418 (0.42%) had a stillbirth compared to 1993 stillbirths (0.36%) among 552,566 referent women. Women with any nitrosatable prescription drug intake and > 1- ≤ 2 mg/L nitrate concentration had an increased risk of stillbirth [adjusted hazard ratio 1.55 (95% confidence interval, 1.15-2.09)] compared with referent women. In the stratified analyses, the highest risk of stillbirth was found among women with secondary amine intake and > 25 mg/L nitrate concentrations [adjusted hazard ratio 3.11 (95% CI, 1.08-8.94)].

CONCLUSIONS

The association between nitrosatable prescription drug intake and the risk of stillbirth may depend on the level of nitrate in household drinking water. Evaluations of the effect of nitrosatable drug intake on perinatal outcomes might consider nitrate exposure from drinking water.

Exposure to nitrate from drinking water and the risk of childhood cancer in Denmark

BACKGROUND

There is limited evidence that nitrate, a common contaminant in drinking water, increases the risk of childhood cancers. Our objective was to examine this association in Denmark.

METHODS

We conducted a nationwide case-control study based on all singletons liveborn to Danish-born parents from 1991 to 2015 (N = 1,219,140) that included 596 leukemias, 180 lymphomas, and 310 central nervous system cancers (CNC) who were ≤15 years of age at diagnosis and were identified from the Danish Cancer Registry. Approximately 100 controls were randomly selected and matched to each case on date of birth and sex. Nitrate measurements in public water systems were linked with an address registry to estimate individual average nitrate concentrations during preconception, prenatal, and postnatal periods. Odd ratios (OR) and 95% confidence intervals (95%CI) were estimated using conditional logistic regression controlling for the matching variables, and birth order, birthweight, urbanicity, maternal education, employment, income and smoking, and parental age.

RESULTS

There was no evidence of an association of nitrate with leukemia or lymphoma. An association between CNC and the highest category of nitrate exposure (>25 mg/L nitrate) was observed for preconception (OR = 1.82, 95%CI:1.09 to 3.04), prenatal (OR = 1.65, 95%CI:0.97 to 2.81), and postnatal exposure (OR = 1.48, 95%CI:0.82 to 2.68) in fully adjusted models. There was also some evidence of an exposure-response in models of continuous nitrate exposure and CNC.

CONCLUSIONS

Our findings provide some evidence that exposure to nitrate from drinking water may increase the risk of childhood CNC cancer, but not leukemia or lymphoma.

Reed Biochar Addition to Composite Filler Enhances Nitrogen Removal from BDBR Systems in Eutrophic Rivers Channel

With the rapid development of urbanization in China, the eutrophication or black stink of urban rivers has become a critical environmental problem. As a research hotspot in wastewater purification, biofilm technology has shortcomings, such as insufficient carbon sources for denitrification. This study used a Biofilm Denitrification Batch Reactor (BDBR) system constructed using reed biochar as the carbon source required in denitrification, significantly accelerating the biofilm formation. To determine the suitable amount of biochar for water purification from the urban eutrophic rivers by the BDBR system, 0%, 5%, 10%, and 15% reed biochar was added to the viscose fiber combined packing. The combined packing reactor involved in this study had a high removal efficiency of the eutrophication channel COD throughout the experiment. However, adding 5% and 10% biochar in the combined filler effectively increased the number of nitrifying and denitrifying bacteria on the biofilm, improved the dominant bacteria diversity and microbial activity, and enhanced denitrification efficiency in the BDBR system. It provides new ideas and methods for developing and applying in situ denitrification technology for urban polluted rivers.

Microbial Fuel Cell as a Bioelectrochemical Sensor of Nitrite Ions

The deteriorating environmental quality requires a rapid in situ real-time monitoring of toxic compounds in environment including water and wastewater. One of the most toxic nitrogen-containing ions is nitrite ion, therefore, it is particularly important to ensure that nitrite ions are completely absent in surface and ground waters as well as in wastewater or, at least, their concentration does not exceed permissible levels. However, no selective ion electrode, which would enable continuous measurement of nitrite ion concentration in wastewater by bioelectrochemical sensor, is available. Microbial fuel cell (MFC)-based biosensor offers a sustainable low-cost alternative to the monitoring by periodic sampling for laboratory testing. It has been determined, that at low (0.01–0.1 mg·L−1) and moderate (1.0–10 mg·L−1) concentration of nitrite ions in anolyte-model wastewater, the voltage drop in MFC linearly depends on the logarithm of nitrite ion concentration of proving the potential of the application of MFC-based biosensor for the quantitative monitoring of nitrite ion concentration in wastewater and other surface water. Higher concentrations (100–1000 mg·L−1) of nitrite ions in anolyte-model wastewater could not be accurately quantified due to a significant drop in MFC voltage. In this case MFC can potentially serve as a bioelectrochemical early warning device for extremely high nitrite pollution.

Internet of Things Implementation of Nitrate and Ammonium Sensors for Online Water Monitoring

In this work, we proposed a new wireless sensor to contribute to research aimed at continuous monitoring of nitrate and ammonium in water, which as leading agents of water pollution have become the source of a serious problem today. In this research, a well-implemented application of an electroanalytical sensor was achieved by combining it with the internet of things (IoT) concept, which is the most modern technique for wireless data collection. We developed a portable IoT system and ion-selective nitrate and ammonium electrodes and monitored the nitrate and ammonium levels of the water online. The system was produced in a low-cost manner (under $25) and it enabled data acquisition without energy-related problems, thanks to the support of solar energy and mobile power bank. The recovery rates of the sensors were tested with the standard addition method and response was obtained between 101.74 and 147.01%.

The effect of environmental conditions on the occurrence of Campylobacter jejuni and Campylobacter coli in wastewater and surface waters

Aims

The purpose of the study was to evaluate the occurrence of Campylobacter jejuni and Campylobacter coli in the aquatic environment based on the water origin, seasonality and physico‐chemical properties.

Methods and Results

The occurrence of C. jejuni and C. coli was determined in waste (29) or surface (56) waters in four different seasons. The air and water temperatures were measured during sampling and chemical analyses of water samples for ammonium, chloride, chlorine, nitrite, nitrate, phosphate and iron were performed. The thermotolerant Campylobacter spp. were more frequently detected in wastewater (59%; 17 positive samples) compared to surface water (38%; 21 positive samples), with the highest rate in autumn (67% of samples positive) and with a higher C. coli occurrence than C. jejuni (31% vs. 26%). Ammonium (above 0.2 mg/L) and chloride ion concentrations (above 60 mg/L) favour C. jejuni. Similarly, C. coli occurrence in water was supported by ammonium (above 0.2 mg/L), chloride (above 60 mg/L) and in addition by phosphate ion concentrations (below 0.7 mg/L).

Conclusions

Campylobacter presence in water is influenced by physico‐chemical parameters such as concentrations of ammonium and chloride ions.

Significance and Impact of the Study

Water environment is an alternative source of Campylobacter. The concentration of ammonium and chloride ions can be used as a basis for successful prediction of the potential occurrence of C. jejuni and C. coli in wastewater and surface water in future.

Nitrate in Drinking Water during Pregnancy and Spontaneous Preterm Birth: A Retrospective Within-Mother Analysis in California

BACKGROUND

Nitrate is a widespread groundwater contaminant and a leading cause of drinking water quality violations in California. Associations between nitrate exposure and select adverse birth outcomes have been suggested, but few studies have examined gestational exposures to nitrate and risk of preterm birth (before 37 wk gestation).

OBJECTIVE

We investigated the association between elevated nitrate in drinking water and spontaneous preterm birth through a within-mother retrospective cohort study of births in California.

METHODS

We acquired over 6 million birth certificate records linked with Office of Statewide Health Planning and Development hospital discharge data for California births from 2000-2011. We used public water system monitoring records to estimate nitrate concentrations in drinking water for each woman's residence during gestation. After exclusions, we constructed a sample of 1,443,318 consecutive sibling births in order to conduct a within-mother analysis. We used separate conditional logistic regression models to estimate the odds of preterm birth at 20-31 and 32-36 wk, respectively, among women whose nitrate exposure changed between consecutive pregnancies.

RESULTS

Spontaneous preterm birth at 20-31 wk was increased in association with tap water nitrate concentrations during pregnancy of 5 to <10mg/L [odds ratio (OR)=1.47; 95% confidence interval (CI): 1.29, 1.67] and ≥10mg/L (OR=2.52; 95% CI: 1.49, 4.26) compared with <5mg/L (as nitrogen). Corresponding estimates for spontaneous preterm birth at 32-36 wk were positive but close to the null for 5 to <10mg/L nitrate (OR=1.08; 95% CI: 1.02, 1.15) and for ≥10mg/L nitrate (OR=1.05; 95% CI: 0.85, 1.31) vs. <5mg/L nitrate. Our findings were similar in several secondary and sensitivity analyses, including in a conventional individual-level design.

DISCUSSION

The results suggest that nitrate in drinking water is associated with increased odds of spontaneous preterm birth. Notably, we estimated modestly increased odds associated with tap water nitrate concentrations of 5 to <10mg/L (below the federal drinking water standard of 10mg/L) relative to <5mg/L. https://doi.org/10.1289/EHP8205.

Prenatal Exposure to Nitrate from Drinking Water and Markers of Fetal Growth Restriction: A Population-Based Study of Nearly One Million Danish-Born Children

BACKGROUND

High levels of nitrate (NO3-) in drinking water cause methemoglobinemia in infants; however, few studies have examined the potential effects of low-level exposure on fetal growth, and the results have been inconsistent.

OBJECTIVES

We sought to assess the association between maternal exposure to nitrate in drinking water during pregnancy and offspring size at birth in a nationwide study of full-term (≥37 wk gestation) live-born singletons.

METHODS

We estimated maternal nitrate exposure for 898,206 births in Denmark during 1991-2011 by linkage of individual home address(es) with nitrate data from the national monitoring database. Maternal address during pregnancy, infant size at birth [i.e., birth weight, low birth weight (LBW), body length, and birth head circumference] and covariates were compiled from the Danish Civil Registration System, the Danish Medical Birth Register, and The Integrated Database for Longitudinal Labor Market Research. Linear and logistic models with generalized estimating equations were used to account for multiple births to an individual. Nitrate exposure was modeled using five categories and as a log-transformed continuous variable.

RESULTS

There was evidence of a decreasing trend in models for term birth weight using categorical or continuous measures of exposure. Modeling exposure continuously, a difference of -9.71 g (95% confidence interval: -14.60, -4.81) was predicted at 25 mg/L (half the value of the European Union drinking water standard) compared with 0 mg/L NO3-. Body length also decreased as nitrate concentrations increased in categorical and continuous models. There was little evidence of an association between NO3- and head circumference or LBW.

DISCUSSION

Although the estimated effects were small, our findings for live singleton births to Danish-born parents suggest that maternal intake of nitrate from drinking water may reduce term birth weight and length, which are markers of intrauterine growth. However, there was little evidence for an association between nitrate and head circumference or LBW. Future studies in other populations and with data on dietary sources of nitrate are encouraged to confirm or refute these findings. https://doi.org/10.1289/EHP7331.

Source to Tap Risk Assessment for Intermittent Water Supply Systems in Arid Regions: An Integrated FTA-Fuzzy FMEA Methodology

Water utilities in arid regions deal with multifaceted issues of natural groundwater contamination, high treatment costs, and low water rates. These utilities rely on intermittent supplies resulting in numerous water quality failures at source, treatment, distribution, and in-house plumbing systems. The present research presents an inclusive risk assessment methodology for managing water quality from source to tap. Three-year monitoring data for turbidity, TDS, pH, iron, ammonia, nitrates, residual chlorine, Coliform group, E. coli, and Fecal Streptococci identified the root causes of failures. The cause-effect relationships in the form of a fault tree were solved using multiple failure modes and effect analysis (FMEA) to handle both the Boolean operations. The fuzzy sets addressed the uncertainties associated with data limitations in calculating exceedance probabilities (P_e) and vagueness in expert opinion for subjective evaluation of severity and detectability. The methodology was applied on a smaller system serving 18,000 consumers in Qassim, Saudi Arabia. Potable supplied water underwent reoccurrence of TDS (P_e = 20%), turbidity (P_e = 10%), and Fe (P_e = 2%) failures in distribution that further increased up to 44%, 33%, and 11% at the consumer end. The P_e for residual chlorine failure soared up to 89%. Economic controls reduced the cumulative risk to 50%, while the shift to continuous supply can limit the remaining failures under the acceptable risk. The framework will help utilities manage water quality in intermittent systems from source to tap in Saudi Arabia, the Gulf, and elsewhere.

Decreased natural organic matter in water distribution decreases nitrite formation in non-disinfected conditions, via enhanced nitrite oxidation

Nitrite in drinking water is a potentially harmful substance for humans, and controlling nitrite formation in drinking water distribution systems (DWDSs) is highly important. The effect of natural organic matter (NOM) on the formation of nitrite in simulated distribution systems was studied. The objective was to inspect how a reduced NOM concentration affected nitrite development via nitrification, separated from the effects of disinfection. We observed that nitrite formation was noticeably sensitive to the changes in the NOM concentrations. Nitrite declined with reduced NOM (TOC 1.0 mg L^-1) but increased with the normal NOM concentration of tap water (TOC 1.6 mg L^-1). Ammonium oxidation was not altered by the reduced NOM, however, nitrite oxidation was enhanced significantly according to the pseudo-first order reaction rate model interpretation. The enhanced nitrite oxidation was observed with both ammonium and nitrite as the initial nitrogen source. The theoretical maximum nitrite concentrations were higher with the normal concentration of NOM than with reduced NOM. The results suggest that the role of nitrite oxidation may be quite important in nitrite formation in DWDSs and worth further studies. As a practical result, our study supported enhanced NOM removal in non-disinfected DWDSs.

Selective Recovery of Ammonia Nitrogen from Wastewaters with Transition Metal-Loaded Polymeric Cation Exchange Adsorbents

Extracting valuable products from wastewaters with nitrogen-selective adsorbents can offset energy-intensive ammonia production, rebalance the nitrogen cycle, and incentivize environmental remediation. Separating nitrogen (N) as ammonium from other wastewater cations (e.g., K⁺ , Ca²⁺ ) presents a major challenge to N removal from wastewater and N recovery as high-purity products. High selectivity and capacity were achieved through ligand exchange of ammonia with ammine-complexing transition metals loaded onto polymeric cation exchange resins. Compared to commercial resins, metal-ligand exchange adsorbents exhibited higher ammonia removal capacity (8 mequiv g^-1 ) and selectivity (N/K⁺ equilibrium selectivity of 10.1) in binary equimolar solutions. Considering optimal ammonia concentrations (200-300 mequiv L^-1 ) and pH (9-10) for metal-ligand exchange, hydrolyzed urine was identified as a promising candidate for selective TAN recovery. However, divalent cation exchange increased transition metal elution and reduced ammonia adsorption. Ultimately, metal-ligand exchange adsorbents can advance nitrogen-selective separations from wastewaters.

Environmental Impact of High Concentration Nitrate Migration in Soil System Using HYDRUS Simulation

Nitrate is a promising heat transfer fluid in solar thermal power and nuclear power systems, but its leakage can cause serious environmental problems. The present paper investigates the deep and prolonged migration of high concentrations of nitrate into the soil system, and the associated diffusion range is studied to estimate and reduce the environmental pollution caused by nitrate leaks. The vertical nitrate contaminated range is mainly impacted by annual precipitation, soil properties and groundwater depth, while the horizontal contaminated range is mainly affected by the initial leakage area. During the process, the vertical contaminated range first continuously enlarges, and then decreases after a long time. The nitrate contaminant can exist and affect the environment for as long as 115-625 years, and the nitrate contamination time can be even longer in dry regions. Since nitrate diffuses more quickly in unsaturated regions rather than in saturated regions, the migration region and contaminated range both decrease as the groundwater depth is increased.

TiO2-based catalysts for photocatalytic reduction of aqueous oxyanions: State-of-the-art and future prospects

Nowadays, an increasing discharge of oxyanions to the natural environment has been attracting worldwide attention. TiO₂-based photocatalysis is regarded as one of the most promising technologies for the conversion of toxic oxyanions (such as chromate, nitrate, nitrite, bromate, perchlorate and selenate) to harmless and/or less toxic substances in contaminated waters. Various types of TiO₂-based catalysts have been developed, and each of them exhibits its own advantages in catalytic reduction of oxyanions. However, the application of these nanostructured TiO₂ in real water bodies remains a challenge, with limitations associated with sunlight harvesting abilities, production costs, reuse stability and exposure risks. Herein, we aim to present a critical review on reported TiO₂-based photocatalytic reduction of aqueous oxyanions, provide a comprehensive understanding of the possible reaction pathways of formed active species, and evaluate the reduction performance of different types of TiO₂-based catalysts. In addition, the impact of operating parameters (such as solution pH, temperature, dissolved oxygen and coexisting substances) on catalytic reduction performance is discussed. Furthermore, the perspectives of TiO₂-based photocatalytic reduction of oxyanions are also proposed.

Effects of environmental variables on abundance of ammonia-oxidizing communities in sediments of Luotian River, China

Ammonia-oxidizing communities play important functional roles in the nitrification. However, environmental stresses can significantly affect this process by controlling the abundant communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) communities. In this study, we examined the abundance variations of ammonia-oxidizing communities using quantitative polymerase chain reaction (qPCR) and terminal-restriction fragment length polymorphism (T-RFLP) in a typical subtropical river, Luotian County, South Dabie Mountains, China. Clone libraries were conducted to evaluate the community structure and abundance of AOA and AOB in sediments. Results showed that Nitrososphaera sp and Nitrosopumilus sp were the most dominant AOA. The abundance of the AOA and AOB amoA gene ranged from 5.28 × 10⁸ gene copies (g-soil⁻¹) to 2.23 × 10⁸ gene copies (g-soil⁻¹) and 5.45 × 10⁸ gene copies (g-soil⁻¹) to 3.30 × 10⁷ gene copies (g-soil⁻¹), respectively. Five environmental variables, namely, ORP, DO, NO\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${}_{3}^{-}$\end{document}3−, Temp, and NH\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${}_{4}^{+}$\end{document}4+ were played a major function in microbial communities of AOA and AOB in sediments. The T-RFLP profiles of AOA showed that 488 and 116 bp T-RFs were dominated. Overall, the results of this study showed that anthropogenic activities andenvironmental stress in rivers can alter the structure and function of microbes in their variable environment.

Spatiotemporal Water Quality Variations in Smaller Water Supply Systems: Using Modified CCME WQI from Groundwater Source to Distribution Networks

Original Canadian Council of Minster of the Environment Water Quality Index (CCME WQI) is being used for assessing the water quality of surface water sources and distribution systems on a case by case basis. Its full potential as a management tool for complete water supply systems (WSSs) has yet to be recognized at the global level. A framework is developed using the modified CCME WQI to assess spatiotemporal water quality from groundwater source to treatment and distribution networks in smaller systems. The modified index resolves a limitation of the original index by also evaluating the microbiological water quality parameters which have to be completely absent for meeting desired drinking water quality standards. The framework divides the distribution network in different zones, which are further segregated into districts, to improve the decision-making process. Temporal assessment identifies the seasons with higher probabilities of failures, while the spatial assessment provides an insight on the performance (i.e., Excellent to Poor) of each district in a distribution network. In addition to failure probability, risk mapping gives appropriate attention to the number of consumers in different districts. Application of the framework on two smaller WSSs (population less than 50,000) in Qassim region revealed that the remotely located districts from the treatment facility underperform in comparison to the closely situated districts. Managers can effectively apply the proposed framework to identify the locations and periods of water quality failures in each component (i.e., source, treatment, and distribution) of a smaller WSS for effective utilization of their resources in Saudi Arabia and elsewhere with similar conditions.

The Seasonality of Nitrite Concentrations in a Chloraminated Drinking Water Distribution System

We studied the seasonal variation of nitrite exposure in a drinking water distribution system (DWDS) with monochloramine disinfection in the Helsinki Metropolitan Area. In Finland, tap water is the main source of drinking water, and thus the nitrite in tap water increases nitrite exposure. Our data included both the obligatory monitoring and a sampling campaign data from a sampling campaign. Seasonality was evaluated by comparing a nitrite time series to temperature and by calculating the seasonal indices of the nitrite time series. The main drivers of nitrite seasonality were the temperature and the water age. We observed that with low water ages (median: 6.7 h) the highest nitrite exposure occurred during the summer months, and with higher water ages (median: 31 h) during the winter months. With the highest water age (190 h), nitrite concentrations were the lowest. At a low temperature, the high nitrite concentrations in the winter were caused by the decelerated ammonium oxidation. The dominant reaction at low water ages was ammonium oxidation into nitrite and, at high water ages, it was nitrite oxidation into nitrate. These results help to direct monitoring appropriately to gain exact knowledge of nitrite exposure. Also, possible future process changes and additional disinfection measures can be designed appropriately to minimize extra nitrite exposure.

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.

Does nitrite and nitrate levels in drinking water impact the health of people in Dakahlia governorate, Egypt?

A total of 1291 drinking water samples were examined for nitrite and nitrate during 6 months from December, 2015 to May, 2016 at 17 cities of Dakahlia governorate (Nile Delta, north of Egypt), and the results were utilized for assessment of health risk of the exposure from drinking water by calculating average daily intake (ADI), hazard quotient (HQ), and the hazard index (HI). The nitrite and nitrate in drinking water had a concentration range of 0.030-0.113 and 2.41-8.70 mg L^-1, with mean values of 0.059 ± 0.014 and 5.25 ± 1.61 mg L^-1, respectively. Nitrite and nitrate levels in rural areas and ground water samples were significantly higher than that in the urban ones. None of the analyzed samples exceeded WHO guideline values that set out to prevent methemoglobinemia. The values of HQ and HI for all age groups do not exceed unity indicating a low risk of methaemoglobinaemia for the population in this area. Results of the present study indicate that there is no health risk of residents from nitrite and nitrate through drinking water in the studied area. However, the other sources of exposure to nitrite and nitrate should be investigated in further studies.

Nitrate in drinking water and colorectal cancer risk: A nationwide population-based cohort study

Nitrate in drinking water may increase risk of colorectal cancer due to endogenous transformation into carcinogenic N-nitroso compounds. Epidemiological studies are few and often challenged by their limited ability of estimating long-term exposure on a detailed individual level. We exploited population-based health register data, linked in time and space with longitudinal drinking water quality data, on an individual level to study the association between long-term drinking water nitrate exposure and colorectal cancer (CRC) risk. Individual nitrate exposure was calculated for 2.7 million adults based on drinking water quality analyses at public waterworks and private wells between 1978 and 2011. For the main analyses, 1.7 million individuals with highest exposure assessment quality were included. Follow-up started at age 35. We identified 5,944 incident CRC cases during 23 million person-years at risk. We used Cox proportional hazards models to estimate hazard ratios (HRs) of nitrate exposure on the risk of CRC, colon and rectal cancer. Persons exposed to the highest level of drinking water nitrate had an HR of 1.16 (95% CI: 1.08-1.25) for CRC compared with persons exposed to the lowest level. We found statistically significant increased risks at drinking water levels above 3.87 mg/L, well below the current drinking water standard of 50 mg/L. Our results add to the existing evidence suggesting increased CRC risk at drinking water nitrate concentrations below the current drinking water standard. A discussion on the adequacy of the drinking water standard in regards to chronic effects is warranted.