Nitrate contamination in drinking water and colorectal cancer: Exposure assessment and estimated health burden in New Zealand

Tapwater exposures, residential risk, and mitigation in a PFAS-impacted-groundwater community

Tapwater (TW) safety and sustainability are priorities in the United States. Per/polyfluoroalkyl substance(s) (PFAS) contamination is a growing public-health concern due to prolific use, widespread TW exposures, and mounting human-health concerns. Historically-rural, actively-urbanizing communities that rely on surficial-aquifer private wells incur elevated risks of unrecognized TW exposures, including PFAS, due to limited private-well monitoring and contaminant-source proliferation in urbanizing landscapes. Here, a broad-analytical-scope TW-assessment was conducted in a hydrologically-vulnerable, Mississippi River alluvial-island community, where PFAS contamination of the shallow-alluvial drinking-water aquifer has been documented, but more comprehensive contaminant characterization to inform decision-making is currently lacking. In 2021, we analyzed 510 organics, 34 inorganics, and 3 microbial groups in 11 residential and community locations to assess (1) TW risks beyond recognized PFAS issues, (2) day-to-day and year-to-year risk variability, and (3) suitability of the underlying sandstone aquifer as an alternative source to mitigate TW-PFAS exposures. Seventy-six organics and 25 inorganics were detected. Potential human-health risks of detected TW exposures were explored based on cumulative benchmark-based toxicity quotients (∑TQ). Elevated risks (∑TQ ≥ 1) from organic and inorganic contaminants were observed in all alluvial-aquifer-sourced synoptic samples but not in sandstone-aquifer-sourced samples. Repeated sampling at 3 sites over 52-55 h indicated limited variability in risk over the short-term. Comparable PFAS-specific ∑TQ for spatial-synoptic, short-term (3 days) temporal, and long-term (3 years quarterly) temporal samples indicated that synoptic results provided useful insight into the risks of TW-PFAS exposures at French Island over the long-term. No PFAS detections in sandstone-aquifer-sourced samples over a 3 year period indicated no PFAS-associated risk and supported the sandstone aquifer as an alternative drinking-water source to mitigate community TW-PFAS exposures. This study illustrated the importance of expanded contaminant monitoring of private-well TW, beyond known concerns (in this case, PFAS), to reduce the risks of a range of unrecognized contaminant exposures.

A New Zealand freshwater nitrate data quality validation study using commercial laboratories and portable testing instruments

Nitrates are among the most pervasive contaminants in New Zealand freshwaters. Community-based testing such as mail-in programs and town hall events, offers a quick and popular way for residents to understand the extent of nitrate contamination in their region. An essential part of ensuring the robustness of citizen science results is using comparable sample collection, storage and analysis methods. A comparison of seven New Zealand commercial water testing laboratories was undertaken to evaluate their measurement accuracy and precision of a range of nitrate (NO3-N) standards. A further 4 brands of portable nitrate testing instruments were also evaluated. Ten nitrate standards ranging from 0.5 to 25 mg/L NO3-N were analysed by accredited New Zealand commercial laboratories, and 15 nitrate standards ranging from 0.5 to 100 mg/L NO3-N were measured using portable instruments under non-laboratory conditions. All accredited laboratories performed within the expected accuracy criteria between 0 and 5 % of the standards, and the portable instruments had a similar accuracy range for standards between 1 and 10 mg/L NO3-N. The nitrate ion selective electrode probe was found to be the most accurate portable instrument with a wider analytical range than the TriOS NICO, Hydrometrics GW50 and the RQflex, which required sample dilution or optical adjustment. However, from an 'ease of use' perspective, the TriOS NICO and Hydrometrics GW50 performed well for field-based groundwater measurements and required minimum operational training. A further aspect of this study examined the effects of sample storage and holding time on nitrate concentrations. Results showed no significant change in NO3-N concentration over a 1-month period for samples stored in the fridge or at ambient temperature away from sunlight. The outcomes of this comparative study show that the use of portable nitrate measuring instruments for community-driven citizen science is a rapid, cost-efficient method to reveal freshwater nitrate concentration patterns for rural New Zealand. Moreover, when analysing water samples <10 mg/L NO3-N, portable instruments can produce comparative results to commercial laboratory testing.

The burden of colorectal cancer attributable to high body mass index in China: findings from 1990 to 2021 and prediction to 2035

BACKGROUND

Colorectal cancer (CRC) incidence and mortality are rising in China, with high body mass index (BMI) established as a significant risk factor. However, comprehensive evidence regarding the BMI-attributable CRC burden in the Chinese population remains limited.

OBJECTIVE

This study aims to analyze the trend of CRC burden attributable to high BMI (BMI ≥ 25 kg/m2) in China from 1990 to 2021 and to predict its development from 2022 to 2035, in order to provide a scientific foundation for the formulation of public health policies.

METHODS

We analyzed data from the Global Burden of Disease Study 2021 (GBD 2021) to assess the BMI-attributable CRC burden in China from 1990 to 2021. Temporal trends were analyzed using Joinpoint regression models. Future projections through 2035 were generated using Bayesian age-period-cohort (BAPC) modeling. The Das Gupta method was used to explore the contribution of population growth, aging, and epidemiologic factors to these burden changes.

RESULTS

From 1990 to 2021, China's BMI-attributable CRC burden increased substantially, with ASMR and ASDR rising at annual rates of 2.393% (95% CI 2.306-2.481) and 2.305% (95% CI 2.188-2.422), respectively. The mortality and disability-adjusted life years (DALYs) rate both increased with age. Males showed higher burden rates in most age groups. Projections indicate continued increases in ASMR (2.43% annually) and ASDR (2.44% annually) through 2035. Epidemiological factors were the primary drivers, contributing 99.73% to mortality changes and 44.81% to DALYs changes.

CONCLUSIONS

The BMI-attributable CRC burden in China shows a concerning upward trajectory that is predicted to continue, with epidemiologic factors playing a major role. Urgent public health interventions targeting obesity prevention, lifestyle modification, and expanded CRC screening are needed to mitigate this growing burden.

The association between increases in nitrate in drinking water and colorectal cancer incidence rates in California, USA

PURPOSE

The water resources in California are polluted with nitrate (NO3) due to the ever-increasing application of nitrogen-based fertilizers. Considering the potential connection between NO3 in drinking water and the incidence rate of colorectal cancer, this study aims to investigate the association between long-term exposure to NO3 via drinking water and the incidence of colorectal cancer from 2010 to 2015 in California.

METHODS

A total of 56,631 diagnoses of colorectal cancer were recorded from 2010 to 2015. A generalized linear model was used to obtain the risk ratio (RR) and 95% confidence interval associated with a 1 mg/l-NO3 increase in NO3 concentration across five latency periods. The potential effect modification by sex, race/ethnicity, and age (> 40, 41-64, 65-90, and > 90) was explored through stratification.

RESULTS

The association between increases in the concentration of NO3 at lag 0-1, lag 0-5, lag 0-10, lag 0-15, and lag 0-20 (RRs: 1.056 [1.055, 1.058]; 1.066 [1.063, 1.069]; 1.030 [1.028, 1.031]; 1.017 [1.016, 1.018]; 1.035 [1.034, 1.037], respectively) was positively associated with the RR of colorectal cancer. Sex was not found to be a significant modifier. The RRs for Hispanics, Blacks, and other races were greater than those for Whites; the RRs across different age categories were all significantly positive.

CONCLUSION

This study confirms an association between long-term NO3 exposure in drinking water and the incidence of colorectal cancer in California, emphasizing the need for stringent water quality control and public health strategies to address this risk, particularly in vulnerable populations.

Nitrate pollution in urban runoff: A comprehensive risk assessment for human and ecological health

Nitrate pollution in urban runoff poses significant environmental and public health risks, with its impact varying across different land use types. This study investigates nitrate concentrations in runoff from residential, commercial, industrial, and traffic zones in Tehran, Iran, using Event Mean Concentration (EMC) analysis and Monte Carlo simulations to assess both ecological and human health risks. The results indicate that industrial and traffic zones exhibit the highest nitrate concentrations, reaching 58.13 mg/L, significantly exceeding regulatory thresholds. Ecological risk assessments highlight the potential for aquatic system degradation, while health risk evaluations reveal hazard index (HI) values surpassing the safe limit (HI > 4), particularly in industrial and high-traffic areas. These findings underscore the need for targeted mitigation strategies, including the implementation of green infrastructure and stricter pollution control measures, to improve urban water quality and reduce associated risks.

Social-Environmental Burden Is Associated with Increased Colorectal Cancer Mortality in Metropolitan Detroit

SIGNIFICANCE

Understanding the role of environmental justice in cancer survivorship could influence policy decisions, aiding intervention practices.

Identifying the spatial pattern and driving factors of nitrate in groundwater using a novel framework of interpretable stacking ensemble learning

Groundwater nitrate contamination poses a potential threat to human health and environmental safety globally. This study proposes an interpretable stacking ensemble learning (SEL) framework for enhancing and interpreting groundwater nitrate spatial predictions by integrating the two-level heterogeneous SEL model and SHapley Additive exPlanations (SHAP). In the SEL model, five commonly used machine learning models were utilized as base models (gradient boosting decision tree, extreme gradient boosting, random forest, extremely randomized trees, and k-nearest neighbor), whose outputs were taken as input data for the meta-model. When applied to the agricultural intensive area, the Eden Valley in the UK, the SEL model outperformed the individual models in predictive performance and generalization ability. It reveals a mean groundwater nitrate level of 2.22 mg/L-N, with 2.46% of sandstone aquifers exceeding the drinking standard of 11.3 mg/L-N. Alarmingly, 8.74% of areas with high groundwater nitrate remain outside the designated nitrate vulnerable zones. Moreover, SHAP identified that transmissivity, baseflow index, hydraulic conductivity, the percentage of arable land, and the C:N ratio in the soil were the top five key driving factors of groundwater nitrate. With nitrate threatening groundwater globally, this study presents a high-accuracy, interpretable, and flexible modeling framework that enhances our understanding of the mechanisms behind groundwater nitrate contamination. It implies that the interpretable SEL framework has great promise for providing valuable evidence for environmental management, water resource protection, and sustainable development, particularly in the data-scarce area.

A review of drinking water quality issues in remote and indigenous communities in rich nations with special emphasis on Australia

This review paper examines the drinking water quality issues in remote and Indigenous communities, with a specific emphasis on Australia. Access to clean and safe drinking water is vital for the well-being of Indigenous communities worldwide, yet numerous challenges hinder their ability to obtain and maintain water security. This review focuses on the drinking water-related issues faced by Indigenous populations in countries such as the United States, Canada, New Zealand, and Australia. In the Australian context, remote and Indigenous communities encounter complex challenges related to water quality, including microbial and chemical contamination, exacerbated by climate change effects. Analysis of water quality trends in Queensland, New South Wales, Western Australia, and the Northern Territory reveals concerns regarding various pollutants with very high concentrations in the source water leading to levels exceeding recommended drinking water limits such as hardness, turbidity, fluoride, iron, and manganese levels after limited treatment facilities available in these communities. Inadequate water quality and quantity contribute to adverse health effects, particularly among Indigenous populations who may resort to sugary beverages. Addressing these challenges requires comprehensive approaches encompassing testing, funding, governance, appropriate and sustainable treatment technologies, and cultural considerations. Collaborative efforts, risk-based approaches, and improved infrastructure are essential to ensure equitable access to clean and safe drinking water for remote and Indigenous communities, ultimately improving health outcomes and promoting social equity.

Selection of priority emerging contaminants in surface waters of India, Pakistan, Bangladesh, and Sri Lanka

The challenge of emerging contaminants (ECs) in global surface water bodies and particularly in low- and middle-income countries such as India, Pakistan, Bangladesh, and Sri Lanka, is evident from the literature. The complexity arises from the high costs involved in EC analysis and the extensive list of ECs, which complicates the selection of essential compounds for scientific and regulatory investigations. Consequently, monitoring programs often include ECs that may have minimal significance within a region and do not pose known or suspected ecological or human health risks. This study aims to address this issue by employing a multi-risk assessment approach to identify priority ECs in the surface waters of the aforementioned countries. Through an analysis of occurrence levels and frequency data gathered from published literature, an optimized risk quotient (RQ) was derived. The findings reveal a priority list of 38 compounds that exhibit potential environmental risks and merit consideration in future water quality monitoring programs. Furthermore, the majority of antibiotics in India (12 out of 17) and Pakistan (7 out of 17) exhibit a risk quotient for antimicrobial resistance selection (RQAMR) greater than 1, highlighting the need for devising effective strategies to mitigate the escalation of antibiotic resistance in the environment.

Effects of recharge process on groundwater nitrate concentration in an oasis of Tengger Desert hinterland, China

Groundwater nitrate concentrations cannot be effectively diluted in an oasis of desert hinterland without direct recharge from external rivers. Therefore, there is an urgent need to understand the relationship between groundwater nitrate concentration and the groundwater recharge process. Using hydrochemicals, stable isotopes, LUCC, and combining these with the MixSIAR model, the distributions of groundwater nitrate concentration in the Dengmaying Basin (DMYB) in 2006 and 2020 were obtained. The contributions of groundwater recharge and nitrate sources were also quantified. With the development of agriculture in the DMYB, groundwater irrigation leakage has gradually become a crucial recharge source of groundwater, with a recharge proportion reaching 30.3%. From 2006 to 2020, under the influence of well irrigation and agricultural fertilization, the groundwater nitrate concentration in the DMYB increased significantly, with an increased range of 1.3 ~ 14.3 mg L-1. Moreover, the δ15N-NO3- and δ18O-NO3- values of nitrate in cultivated soil water were similar to those in groundwater, which also proves the process of carrying nitrate from the vadose zone into groundwater by irrigation water. The contribution of anthropogenic sources (54.9%) to groundwater nitrate exceeded that of natural sources (45.1%) to groundwater nitrate in the DMYB. These results indicate that the potential for nitrate pollution in groundwater must be considered, even in desert oases.

The development and validation of a nationwide dataset of water distribution zones in Aotearoa New Zealand: A cross-sectional geospatial study

The reliable supply of safe drinking water is vital for the health of human populations. Despite this, there is no consistent nationwide spatial dataset of water distribution zones (WDZ) for Aotearoa New Zealand (A-NZ). The purpose of this data article is to describe the development and validation of a consistent nationwide dataset of WDZ across A-NZ. We obtained spatial data from all 67 district and city councils through: 1) information requests between 2021 and 2023; 2) the Ministry of Health and; 3) the Institute of Environmental Science and Research. Data were modified to improve the spatial accuracy of the WDZ using auxiliary data on the building footprints (Land Information New Zealand) and the drinking water reticulation (WSP & councils). We estimated the population served by each WDZ through spatial linking to meshblock-level data provided by Statistics New Zealand (meshblocks are the smallest administrative geographic unit in A-NZ). The dataset will be useful to provide insights into the extent of the publicly-owned drinking water assets in A-NZ and is essential for the accurate exposure assessment in epidemiological research investigating the impact of drinking water quality on human health.

An integrated approach using multi-source data for effective pollution risk monitoring of urban rivers: a case study of Hangzhou

With the rapid urbanization of cities, water pollution has emerged as a major challenge to their sustainable development. To tackle this problem, we developed a river pollution risk management system that integrates multi-source data and includes risk identification, early warning, and control. We applied this system to a case study of urban rivers in Hangzhou, China. The results indicated that the measured and effect values of urban river water quality in Hangzhou were 1.01 and 1.14, respectively, indicating mild pollution levels. NH₃-N is the main risk factor, with poor supervision and land use being the main risk sources. River pollution risk in different drainage zones demonstrated stratification. Since 2012, the measured risk of water quality in Hangzhou has been decreasing, mainly concentrated in the built-up area; however, the effect risk has been increasing, especially in the new center and sub-center of the city. Based on these findings, three strategies for urban river pollution control are suggested: water ecology source rehabilitation, water environment process supervision, and water pollution end management. The results of this study extend the understanding of urban water environment risk and provide implications for sustainable urban planning.

The potential human health hazard of nitrates in drinking water: a media discourse analysis in a high-income country

BACKGROUND

Recent studies linking low levels of nitrate in drinking water to colorectal cancer have raised public concerns over nitrate contamination. The aim of this study was to analyze the media discourse on the potential human health hazard of nitrates in drinking water in a high-income country with a large livestock industry: New Zealand (NZ).

METHODS

Searches of media sources ("major newspapers") held by the Factiva database for the NZ setting in the five-year period 17 December 2016 to 20 December 2021.

RESULTS

The largest number of media items was observed for 2017 (n = 108), the year of a NZ general election, with a notable decrease in 2020 (n = 20) that was likely due to the Covid-19 pandemic, which dominated health media. However, the percentage of these media items with a health focus steadily increased over time, from 11.1% of all articles in 2017 to 51.2% in 2021. The most commonly mentioned health hazard was colorectal cancer, followed by methemoglobinemia. The temporal pattern of media items suggests that the release of scientific studies and scholarly blogs was associated with the publication of subsequent media items. Major stakeholders involved in the discourse included representatives of local and central government, environmental and recreational interest groups, researchers, local residents, agricultural interest groups, and health organizations. Māori (Indigenous New Zealanders) values or perspectives were rarely mentioned.

CONCLUSIONS

Analysis of major newspapers for a five-year period indicated that a wide range of expert comment and opinions were made available to the public and policy makers on the issue of nitrates in water. While many different stakeholder views were captured in the media discourse, there is scope for the media to better report the views of Māori on this topic. There is also a need for articles detailing the health issues to also refer to the environmental, recreational, and cultural aspects of protecting water quality to ensure that the public, policy makers, and regulators are aware of co-benefits.

Nitrate contamination in drinking water and adverse reproductive and birth outcomes: a systematic review and meta-analysis

Exposure to low levels of nitrate in drinking water may have adverse reproductive effects. We reviewed evidence about the association between nitrate in drinking water and adverse reproductive outcomes published to November 2022. Randomized trials, cohort or case-control studies published in English that reported the relationship between nitrate intake from drinking water and the risk of perinatal outcomes were included. Random-effect models were used to pool data. Three cohort studies showed nitrate in drinking water is associated with an increased risk of preterm birth (odds ratio for 1 mg/L NO3-N increased (OR1) = 1.01, 95% CI 1.00, 1.01, I2 = 23.9%, 5,014,487 participants; comparing the highest versus the lowest nitrate exposure groups pooled OR (ORp) = 1.05, 95% CI 1.01, 1.10, I2 = 0%, 4,152,348 participants). Case-control studies showed nitrate in drinking water may be associated with the increased risk of neural tube defects OR1 = 1.06, 95% CI 1.02, 1.10; 2 studies, 2196 participants; I2 = 0%; and ORp = 1.51, 95% CI 1.12, 2.05; 3 studies, 1501 participants; I2 = 0%). The evidence for an association between nitrate in drinking water and risk of small for gestational age infants, any birth defects, or any congenital heart defects was inconsistent. Increased nitrate in drinking water may be associated with an increased risk of preterm birth and some specific congenital anomalies. These findings warrant regular review as new evidence becomes available.

Copper induces nitrification by ammonia-oxidizing bacteria and archaea in pastoral soils

Copper (Cu) is the main co-factor in the functioning of the ammonia monooxygenase (AMO) enzyme, which is responsible for the first step of ammonia oxidation. We report a greenhouse-based pot experiment that examines the response of ammonia-oxidizing bacteria and archaea (AOB and AOA) to different bioavailable Cu concentrations in three pastoral soils (Recent, Pallic, and Pumice soils) planted with ryegrass (Lolium perenne L.). Five treatments were used: control (no urine and Cu), urine only at 300 mg N kg^-1 soil (Cu0), urine + 1 mg Cu kg^-1 soil (Cu1), urine + 10 mg Cu kg^-1 soil (Cu10), and urine + 100 mg Cu kg^-1 soil (Cu100). Pots were destructively sampled at Day 0, 1, 7, 15, and 25 after urine application. The AOB/AOA amoA gene abundance was analyzed by real-time quantitative polymerase chain reaction at Days 1 and 15. The AOB amoA gene abundance increased 10.0- and 22.6-fold in the Recent soil and 2.1- and 2.5-fold in the Pallic soil for the Cu10 compared with Cu0 on Days 1 and 15, respectively. In contrast, the Cu100 was associated with a reduction in AOB amoA gene abundance in the Recent and Pallic soils but not in the Pumice soil. This may be due to the influence of soil cation exchange capacity differences on the bioavailable Cu. Bioavailable Cu in the Recent and Pallic soils influenced nitrification and AOB amoA gene abundance, as evidenced by the strong positive correlation between bioavailable Cu, nitrification, and AOB amoA. However, bioavailable Cu did not influence the nitrification and AOA amoA gene abundance increase.

The Nitrogen Dynamics of Newly Developed Lignite-Based Controlled-Release Fertilisers in the Soil-Plant Cycle

The effect of newly developed controlled-release fertilisers (CRFs); Epox5 and Ver-1 and two levels of Fe2+ applications (478 and 239 kg-FeSO4 ha−1) on controlling nitrogen (N) losses, were tested on ryegrass, in a climate-controlled lysimeter system. The Epox5 and Ver-1 effectively decreased the total N losses by 37 and 47%, respectively, compared to urea. Nitrous oxide (N2O) emissions by Ver-1 were comparable to urea. However, Epox5 showed significantly higher (p < 0.05) N2O emissions (0.5 kg-N ha−1), compared to other treatments, possibly due to the lock-off nitrogen in Epox5. The application of Fe2+ did not show a significant effect in controlling the N leaching loss and N2O emission. Therefore, a dissimilatory nitrate reduction and chemodenitrification pathways were not pronounced in this study. The total dry matter yield, N accumulation, N use efficiency and soil residual N were not significantly different among any N treatments. Nevertheless, the N accumulation of CRFs was lower in the first month, possibly due to the slow release of urea. The total root biomass was significantly (p < 0.05) lower for Epox5 (35%), compared to urea. The hierarchical clustering of all treatments revealed that Ver-1 outperformed other treatments, followed by Epox5. Further studies are merited to identify the potential of Fe2+ as a controlling agent for N losses.

An assessment of compliance with optimal fluoride levels for oral health benefit by New Zealand drinking water suppliers

OBJECTIVES

Community water fluoridation (CWF) has proven oral health benefits. We investigated whether drinking water suppliers are meeting New Zealand CWF targets (0.7-1.0 ppm) to ensure these benefits.

METHODS

We retrieved fluoride testing data from 25 supplies serving 2,059,000 people (82% of people on a fluoridated supply), for the years 1992-2022 (22,220 weekly observations). We descriptively assessed compliance with fluoride targets in this convenience sample.

RESULTS

The mean fluoride level was 0.66 ppm (SD 0.28). Water suppliers achieved fluoride targets 54.1% of the time (range 4.2%-77.9%). Fluoride concentration fell short of the target in 42.2% of observations, exceeded but under the maximum acceptable value (MAV) in 3.6%, and in excess of the MAV in 0.1%. The percentage of compliant observations was greater in larger than smaller supplies.

CONCLUSIONS

Noncompliance with CWF targets was common. Epidemiological studies that rely on fluoridation status as their exposure may underestimate the oral health benefits of CWF. Our results highlight future challenges with the feasibility of expanding CWF under new legislation as well as the weaknesses in drinking water surveillance.