Arsenic contamination in groundwater in the Southeast Asia region

Melatonin differentially refines the metabolome to improve seed formation during grain developmental stages and enhances yield in two contrasting rice cultivars, grown in arsenic-contaminated soil

The manuscript revealed the ameliorative effects of exogenous melatonin in two distinct reproductive stages, i.e., developing grains (20 days after pollination) and matured grains (40 days after pollination) in two contrasting indica rice genotypes, viz., Khitish (arsenic-susceptible) and Muktashri (arsenic-tolerant), irrigated with arsenic-contaminated water throughout their life-cycle. Melatonin administration improved yield-related parameters like rachis length, primary and secondary branch length, number of grains per panicle, number of filled and empty grains per panicle, grain length and breadth and 1000-grain per weight. Expression of GW2, which negatively regulates grain development, was suppressed, along with concomitant induction of positive regulators like GIF1, DEP1 and SPL14 in both Khitish and Muktashri. Melatonin lowered arsenic bioaccumulation in grains and tissue biomass, more effectively in Khitish. Unregulated production of reactive oxygen species, leading to cellular necrosis caused by arsenic, was reversed in presence of melatonin. Endogenous melatonin level was stimulated due to up-regulation of the key biosynthetic genes, SNAT and ASMT. Melatonin enhanced the production of diverse antioxidants like anthocyanins, flavonoids, total phenolics and ascorbic acid and also heightened the production of thiol-metabolites (cysteine, reduced glutathione, non-protein thiols and phytochelatin), ensuring effective chelation and arsenic detoxification. Altogether, our observation, supported by principal component analysis, proved that melatonin re-programs the antioxidative metabolome to enhance plant resilience against arsenic stress to mitigate oxidative damages and reduce arsenic translocation from the soil to tissue biomass and edible grains.

Association between arsenic exposure and melanoma: a meta-analysis

BACKGROUND

Melanoma is a highly malignant tumor. Moreover, its prevalence is increasing at a rapid rate year after year. Currently, UV light is the leading cause of melanoma, although numerous other risk factors exist, including arsenic. The link between arsenic and the likelihood of developing melanoma has long been debated. As a result, we conducted a meta-analysis of the available data to investigate the association between arsenic exposure and melanoma.

METHODS

We identified seven non-randomized controlled studies with 41,949 participants by searching the Chinese CNKI, Embase, PubMed, and Cochrane Library databases. We then used random-effects or fixed-effects models to evaluate the pooled odds ratios (OR) and their 95% confidence intervals (CI). Subgroup analyses were also carried out with different included regions.

RESULTS

Participants in the study who were exposed to arsenic had a somewhat higher chance of developing melanoma than those who were not (OR = 1.47, 95% CI 1.01-2.13). A subgroup analysis was also carried out for the US region, and the findings were not statistically significant (OR = 1.40, 95% CI 0.94-2.07).

CONCLUSION

This meta-analysis shows that arsenic exposure relates to an increased risk of melanoma.

Evaluation of Arsenic and Cobalt Levels in Pediatric Patients Receiving Long-Term Parenteral Nutrition

This study continues the research in which we determined the concentration of aluminum in children receiving long-term parenteral nutrition (LPN). Since our results were interesting, we decided to assay arsenic (As) and cobalt (Co) in the collected material, which, like aluminum, constitute contamination in the mixtures used in parenteral nutrition. Excesses of these trace elements in the human body are highly toxic, and deficiencies, particularly in the case of Co, can lead to various complications. The aim of this study was to determine the impact of LPN in children on their serum levels of As and Co, as well as the excretion of these elements in urine, and to compare them with a control group of healthy children. The study group consisted of 83 children receiving home parenteral nutrition from two Polish centers, while the control group included 121 healthy children. In both groups, the levels of As and Co in serum and urine were measured. The elemental compositions of the samples were determined using inductively coupled plasma mass spectrometry (ICP-MS). It was demonstrated that the children receiving LPN did not have increased As exposure compared to the controls. Greater exposure compared to the control group was shown for Co. In conclusion, children receiving LPN are not exposed to As, and even though the concentrations of Co in serum and urine were higher in the LPN group than in the healthy controls, neither trace element poses a health threat to children requiring LPN.

Use of agricultural bio-wastes to remove arsenic from contaminated water

Arsenic (As) is a highly toxic metalloid. High As levels have been recorded in groundwater aquifers at a global scale. This study investigated As level in groundwater of District Vehari and assessed the potential of different agricultural by-products (sugarcane bagasse, cottonseed hulls, soybean hulls, corncobs and rice husk) to remove As from water. The study was carried out in two steps. In the first step, a total of 38 groundwater samples were obtained from Vehari. Groundwater samples were analyzed for total As contents and physicochemical parameters. Results indicated that As content ranged from below detection limit to 49 µg/L in the groundwater samples. The values of hazard quotient and cancer risk were up to 1.5 and 0.0004, respectively, which delineated severe risk of As poisoning. During the second step, six As-contaminated groundwater samples (total As contents: 49, 40, 29, 24, 18, 16 µg/L) were selected to remove As using agricultural by-products. Furthermore, four As solutions (200, 100, 50 and 25 µg/L) were prepared in the laboratory. Results revealed that corncobs and soybean hulls removed, respectively, 98% and 71% As from aqueous mediums after 120 min. Moreover, agricultural by-products were less effective in removing As from groundwater samples than synthetic solutions. The adsorption/removal capacity of by-products was lower at low initial As concentration compared to high initial levels, which needs further studies to explore the underlying mechanisms. Overall, the As removal efficiency of agriculture by-products differed significantly with respect to initial As level, contamination category, type of agricultural by-products and interaction duration. Therefore, these aspects need to be optimized before the possible use of an agricultural by-product as a potential biosorbent.

Risk of urinary tract cancers following arsenic exposure and tobacco smoking: a review

Bladder cancer, prostate cancer, and kidney cancer, due to their high morbidity and mortality rates, result in significant economic and health care costs. Arsenic exposure affects the drinking water of millions of people worldwide. Long-term exposure to arsenic, even in low concentrations, increases the risk of developing various cancers. Smoking is also one of the leading causes of bladder, prostate and kidney cancers. Accordingly, this research reviews the relationship between arsenic exposure and smoking with three kinds of urinary tract cancers (bladder cancer, prostate cancer, and kidney cancer) due to their widespread concern for their negative impact on public health globally. In this review, we have gathered the most current information from scientific databases [PubMed, Scopus, Google Scholar, ISI web of science] regarding the relationship between arsenic exposure and tobacco smoking with the risk of bladder, prostate, and kidney cancer. In several studies, a significant relationship was determined between the incidence and mortality rate of the above-mentioned cancers in humans with arsenic exposure and tobacco smoking. The decrease or cessation of smoking and consumption of arsenic-free water significantly declined the incidence of bladder, prostate, and kidney cancers.

GIS based hotspot analysis and health risk assessment of groundwater arsenic from an unconfined deep aquifer of Lahore, Pakistan

Use of groundwater for drinking purpose poses serious hazards of arsenic contamination particularly in plains of western Himalayan region. Therefore, current study was designed to investigate the level of Arsenic (As) in the water obtained from tubewells in a metropolitan city of Lahore, Pakistan and assess the human health risk. So, a total of 73 tubewells were sampled randomly in the manner that the whole study region was covered without any clustering. The water samples were analyzed for As using atomic absorption spectrophotometer. These samples were also tested for total dissolved solids, chlorides, pH, alkalinity, turbidity, hardness and calcium. GIS based hotspots analysis technique was used to investigate the spatial distribution patterns. Our results revealed that only one sample out of total 73 had arsenic level below the WHO guideline of 10 μg/L. The spatial distribution map of arsenic revealed that the higher concentrations of arsenic are present in the north-western region of Lahore. The cluster and outlier analysis map using Anselin Local Moran's I statistic indicated the presence of an arsenic cluster in the west of River Ravi. Furthermore, the optimized hotspot analysis based on Getis-Ord Gi* statistics confirmed the statistical significance (P < 0.05) and (P < 0.01) of these samples from the vicinity of River Ravi. Regression analysis showed that variables such as turbidity, alkalinity, hardness, chlorides, calcium and total dissolved solids were significantly (all P < 0.05) associated with level of Arsenic in tubewells. Whereas, PH and electrical conductivity and other variables like town, year of installation, depth and diameter of the wells were not significantly associated with Arsenic concentrations in tubewells. Principal component analysis (PCA) exhibited that the random distribution of tubewell samples showed no distinct clustering with towns studied. Health risk assessment based on hazard and Cancer risk index revealed serious risk of developing carcinogenic and non-carcinogenic diseases particularly in children. The health risk due to prevalence of high As concentration in tubewells' water need to be mitigated immediately to avoid worst consequences in future.

Carcinogenic effect of arsenic in digestive cancers: a systematic review

BACKGROUND

The carcinogenic effect of arsenic (As) has been documented in lung, bladder and skin cancers but remains unclear for digestive cancers, although metabolic pathways of As and recent data suggest that it may be an important determinant in these malignancies as well.

OBJECTIVE

This study aimed to systematically review the available literature investigating the potential association between As and digestive cancers.

METHODS

An extensive search was conducted in Medline Ovid SP, Cochrane, PubMed, Embase.com, Cochrane Library Wiley, Web of Science and Google Scholar. Studies providing original data in humans, with As measurement and analysis of association with digestive cancers including esogastric cancers (esophagus and stomach), hepato-pancreatico-biliary (HPB) cancers (including biliary tract, liver and pancreas) and colorectal cancers were eligible.

RESULTS

A total of 35 studies were identified, 17 ecological, 13 case-control and 5 cohort studies. Associations between As and digestive cancers were reported for both risks of incidence and cancer-related mortality. Overall, 43% (3/7) and 48% (10/21) studies highlighted an association between As and the incidence or the mortality of digestive cancers, respectively.

CONCLUSIONS

A substantial proportion of studies exploring the potential link between As and digestive cancers suggested an association, particularly in HPB malignancies. These findings emphasize the need to further investigate this topic with dedicated and high-quality studies, as it may have an important impact, including for prevention strategies.

A review on arsenic in the environment: contamination, mobility, sources, and exposure

Arsenic is one of the regulated hazard materials in the environment and a persistent pollutant creating environmental, agricultural and health issues and posing a serious risk to humans. In the present review, sources and mobility of As in various compartments of the environment (air, water, soil and sediment) around the World are comprehensively investigated, along with measures of health hazards. Multiple atomic spectrometric approaches have been applied for total and speciation analysis of As chemical species. The LoD values are basically under 1 μg L-1, which is sufficient for the analysis of As or its chemical species in environmental samples. Both natural and anthropogenic sources contributed to As in air, while fine particulate matter tends to have higher concentrations of arsenic and results in high concentrations of As up to a maximum of 1660 ng m-3 in urban areas. Sources for As in natural waters (as dissolved or in particulate form) can be attributed to natural deposits, agricultural and industrial effluents, for which the maximum concentration of 2000 μg L-1 was found in groundwater. Sources for As in soil can be the initial contents, fossil fuel burning products, industrial effluents, pesticides, and so on, with a maximum reported concentration up to 4600 mg kg-1. Sources for As in sediments can be attributed to their reservoirs, with a maximum reported concentration up to 2500 mg kg-1. It is notable that some reported concentrations of As in the environment are several times higher than permissible limits. However, many aspects of arsenic environmental chemistry including contamination of the environment, quantification, mobility, removal and health hazards are still unclear.

Evolution Mechanism of Arsenic Enrichment in Groundwater and Associated Health Risks in Southern Punjab, Pakistan

Arsenic (As) contamination in groundwater is a worldwide concern for drinking water safety. Environmental changes and anthropogenic activities are making groundwater vulnerable in Pakistan, especially in Southern Punjab. This study explores the distribution, hydrogeochemical behavior, and pathways of As enrichment in groundwater and discusses the corresponding evolution mechanism, mobilization capability, and health risks. In total, 510 groundwater samples were collected from three tehsils in the Punjab province of Pakistan to analyze As and other physiochemical parameters. Arsenic concentration averaged 14.0 μg/L in Vehari, 11.0 μg/L in Burewala, and 13.0 μg/L in Mailsi. Piper-plots indicated the dominance of Na⁺, SO₄^2-, Ca²⁺, and Mg²⁺ ions in the groundwater and the geochemical modeling showed negative saturation indices with calcium carbonate and salt minerals, including aragonite (CaCO₃), calcite (CaCO₃), dolomite (CaMg(CO₃)₂), and halite (NaCl). The dissolution process hinted at their potential roles in As mobilization in groundwater. These results were further validated with an inverse model of the dissolution of calcium-bearing mineral, and the exchange of cations between Ca²⁺ and Na⁺ in the studied area. Risk assessment suggested potential carcinogenic risks (CR > 10^-4) for both children and adults, whereas children had a significant non-carcinogenic risk hazard quotient (HQ > 1). Accordingly, children had higher overall health risks than adults. Groundwater in Vehari and Mailsi was at higher risk than in Burewala. Our findings provide important and baseline information for groundwater As assessment at a provincial level, which is essential for initiating As health risk reduction. The current study also recommends efficient management strategies for As-contaminated groundwater.

Structural, Optical, and Arsenic Removal Properties of Sol-Gel Synthesized Fe-Doped TiO2 Nanoparticles

Pure and Fe-doped TiO₂ nanoparticles were synthesized by the sol-gel method. The samples were characterized by X-ray diffraction, Raman spectroscopy, BET, UV-vis diffuse reflectance spectroscopy, and scanning electron microscopy. The results show a dependence between the crystallite size and the amount of dopant, which decreases from 13.02 to 12.81 nm. The same behavior was observed in the optical properties, where the band gap decreased from 3.2 to 2.86 eV. The arsenic (V) adsorption was tested in aqueous solution containing 5 mg/L of arsenic and 0.5 g/L of adsorbent at pH 7 and in dark conditions. The results indicate that the TiO₂-B sample shows a higher arsenic removal, reaching 88% arsenic removal from the water at pH 7. Thus, it is also shown that the best performance occurs at pH 5, where it reaches an arsenic removal of 94%. Ion competition studies show that arsenic removal capacity is slightly affected by chloride, carbonate, nitrate, and sulfate ions. According to the results, the synthesized samples are a promising material for treating arsenic-contaminated water.

Highly efficient visible light-induced photocatalytic oxidation of arsenite with nanosized WO3 particles in the presence of Cu2+ and CuO

Although WO₃ appears to be one of the extensively studied photocatalysts, the low response of pure WO₃ in aqueous solution under visible light limits its application remarkably. In this work, the enhancement of the efficiency of WO₃ for the visible light-driven photocatalytic oxidation of arsenite was explored using Cu²⁺ ion and CuO as a co-catalyst. While the addition of Cu²⁺ was found effective for the suppression of dissolution of WO₃, the efficiency of CuO appeared to be slightly lower. Significant improvement of the efficiency for the photocatalytic oxidation of As(III) with WO₃ was noted when Cu²⁺ ions and CuO were added. The optimized conditions were WO₃ in the presence of 10 mg L^-1 Cu²⁺ ion and 1 wt% CuO coupled with WO₃, respectively. The As(III) concentration of 10 mg L^-1 could be lowered to less than 0.1 mg L^-1 by the photocatalytic treatment. Acidic pH favours the oxidation of arsenite in the presence of Cu²⁺ whereas basic pH is suitable with CuO. Characterization techniques such as TEM, XPS, XRD and UV-DRS were used to characterize photocatalysts. The reactive species scavenger tests revealed that the photo-induced holes (h⁺) play a key role in the photocatalytic oxidation process while the effect of •OH is negligible. It was found that As(III) oxidation rate was remarkably suppressed in the nitrogen atmosphere. A mechanism for enhanced photocatalytic oxidation has been proposed based on the results of the reactive species scavenger tests. This research may contribute to the large-scale As(III) oxidation treatment in the groundwater.

Removal of Arsenate From Groundwater by Cathode of Bioelectrochemical System Through Microbial Electrosorption, Reduction, and Sulfuration

Arsenate [As(V)] is a toxic metalloid and has been observed at high concentrations in groundwater globally. In this study, a bioelectrochemical system (BES) was used to efficiently remove As(V) from groundwater, and the mechanisms involved were systematically investigated. Our results showed that As(V) can be efficiently removed in the BES cathode chamber. When a constant cell current of 30 mA (I_cell, volume current density = 66.7 A/m³) was applied, 90 ± 3% of total As was removed at neutral pH (7.20–7.50). However, when I_cell was absent, the total As in the effluent, mainly As(V), had increased approximately 2–3 times of the As(V) in influent. In the abiotic control reactor, under the same condition, no significant total As or As(V) removal was observed. These results suggest that As(V) removal was mainly ascribed to microbial electrosorption of As(V) in sludge. Moreover, part of As(V) was bioelectrochemically reduced to As(III), and sulfate was also reduced to sulfides [S(–II)] in sludge. The XANES results revealed that the produced As(III) reacted with S(–II) to form As₂S₃, and the residual As(III) was microbially electroadsorbed in sludge. This BES-based technology requires no organic or chemical additive and has a high As(V) removal efficiency, making it an environment-friendly technique for the remediation of As-contaminated groundwater.

Low-cost electrochemical detection of arsenic in the groundwater of Guanajuato state, central Mexico using an open-source potentiostat

Arsenic is a carcinogenic groundwater contaminant that is toxic even at the parts-per-billion (ppb) level and its on-site determination remains challenging. Colorimetric test strips, though cheap and widely used, often fail to give reliable quantitative data. On the other hand, electrochemical detection is sensitive and accurate but considerably more expensive at the onset. Here, we present a study on arsenic detection in groundwater using a low-cost, open-source potentiostat based on Arduino technology. We tested different types of gold electrodes (screen-printed and microwire) with anodic stripping voltammetry (ASV), achieving low detection limits (0.7 μg L^-1). In a study of arsenic contaminated groundwaters in Mexico, the microwire technique provides greater accuracy than test strips (reducing the median error from -50% to +2.9%) and greater precision (reducing uncertainties from ±25% to ±4.9%). Most importantly, the rate of false negatives versus the World Health Organisation’s 10 μg L^-1 limit was reduced from 50% to 0% (N = 13 samples). Arsenic determination using open-source potentiostats may offer a low-cost option for research groups and NGOs wishing to perform arsenic analysis in-house, yielding superior quantitative data than the more widely used colorimetric test strips.

Association between Arsenic Level, Gene Expression in Asian Population, and In Vitro Carcinogenic Bladder Tumor

The IARC classified arsenic (As) as "carcinogenic to humans." Despite the health consequences of arsenic exposure, there is no molecular signature available yet that can predict when exposure may lead to the development of disease. To understand the molecular processes underlying arsenic exposure and the risk of disease development, this study investigated the functional relationship between high arsenic exposure and disease risk using gene expression derived from human exposure. In this study, a three step analysis was employed: (1) the gene expression profiles obtained from two diverse arsenic-exposed Asian populations were utilized to identify differentially expressed genes associated with arsenic exposure in human subjects, (2) the gene expression profiles induced by arsenic exposure in four different myeloma cancer cell lines were used to define common genes and pathways altered by arsenic exposure, and (3) the genetic profiles of two publicly available human bladder cancer studies were used to test the significance of the common association of genes, identified in step 1 and step 2, to develop and validate a predictive model of primary bladder cancer risk associated with arsenic exposure. Our analysis shows that arsenic exposure to humans is mainly associated with organismal injury and abnormalities, immunological disease, inflammatory disease, gastrointestinal disease, and increased rates of a wide variety of cancers. In addition, arsenic exerts its toxicity by generating reactive oxygen species (ROS) and increasing ROS production causing the imbalance that leads to cell and tissue damage (oxidative stress). Oxidative stress activates inflammatory pathways leading to transformation of a normal cell to tumor cell specifically; there is significant evidence of the advancing changes in oxidative/nitrative stress during the progression of bladder cancer. Therefore, we examined the relation of differentially expressed genes due to exposure of arsenic in human and bladder cancer and developed a bladder cancer risk prediction model. In this study, integrin-linked kinase (ILK) was one of the most significant pathways identified between both arsenic exposed population which plays a key role in eliciting a protective response to oxidative damage in epidermal cells. On the other hand, several studies showed that arsenic trioxide (ATO) is useful for anticancer therapy although the mechanisms underlying its paradoxical effects are still not well understood. ATO has shown remarkable efficacy for the treatment of multiple myeloma; therefore, it will be helpful to understand the underlying cancer biology by which ATO exerts its inhibitory effect on the myeloma cells. Our study found that MAPK is one of the most active network between arsenic gene and ATO cell line which is involved in indicative of oxidative/nitrosative damage and well associated with the development of bladder cancer. The study identified a unique set of 147 genes associated with arsenic exposure and linked to molecular mechanisms of cancer. The risk prediction model shows the highest prediction ability for recurrent bladder tumors based on a very small subset (NKIRAS2, AKTIP, and HLA-DQA1) of the 147 genes resulting in AUC of 0.94 (95% CI: 0.744-0.995) and 0.75 (95% CI: 0.343-0.933) on training and validation data, respectively.

Arsenic in the geo-environment: A review of sources, geochemical processes, toxicity and removal technologies

Impact of arsenic (As) contaminated groundwater on human health, through drinking and irrigation practices, is of grave-concern worldwide. This paper present the review of various sources, processes, health effects and treatment technologies available for the removal of As from arsenic contaminated water. Groundwater with high As concentration is detrimental to human health and incidents of As contamination in groundwater had been reported from different parts of the globe. More serious known As contamination problem as well as largest population at risk are found in Bangladesh, followed by West Bengal state in India along the Indo-Gangetic plains. Large scale natural As contamination of groundwater is found in two types of environment such as strongly reducing alluvial aquifers (ex. Bangladesh, India, China and Hungary) and inland basins in arid or semi-arid areas (ex. Argentina and Mexico). The provisional guideline of 10 ppb (0.0 l mg/l) has been adopted as the drinking water standard by World Health Organization (WHO). In the aquatic environment, the release, distribution and remobilization of As depend on temperature, redox potential, speciation, and interaction between liquid solution and solid phases. As predicaments in the environment is due to its mobilization under natural geogenic conditions as well as anthropogenic activities. Arsenic mineral is not present in As contaminated alluvial aquifer but As occurs adsorbed on hydrated ferric oxide (HFO) generally coat clastic grains derived from Himalayan mountains. As is released to the groundwater mainly by bio-remediated reductive dissolution of HFO with corresponding oxidation of organic matter. The development of strongly reductive dissolution of mineral oxides (Fe and Mn) at near-neutral pH may lead to desorption and ultimately release of As into the groundwater. As release through geochemical process is more important factor in alluvial aquifers causing As contamination rather than sources of arsenic. As is a toxin that dissolves in the bloodstream, rendering the victim susceptible to disease of the skin, bones, and also cancer of liver, kidney, gall bladder and the intestines. It is necessary to adopt highly successful technology to treat As contaminated water into the acceptable limit for human consumption. Universally accepted solutions are not developed/available even after the lapse of almost forty years since slow As poisoning identification in tens of millions of people especially in Bengal delta. The issue poses scientific, technical, health and societal problems even today.

Hydrogeochemical and health risk investigation of potentially toxic elements in groundwater along River Sutlej floodplain in Punjab, Pakistan

Understanding groundwater quality and hydrogeochemical behavior is important because consumption of the potentially toxic elements (PTEs)-contaminated drinking water may induce several health problems for humans and animals. In the current study, we examined the potential groundwater contamination with various PTEs (arsenic, As; cadmium, Cd; copper, Cu; manganese; Mn) and the PTEs-induced health risk. Groundwater (n = 111) was characterized for total As, Cd, Cu, and Mn concentrations and other water quality attributes along the River Sutlej floodplain of Punjab, Pakistan. Results revealed that groundwater, which is used for drinking purpose, contained high concentrations of As and Cd (mean As: 33 µg/L, mean Cd: 3 µg/L), exceeding 100% and 32% than the World Health Organization's safe limits (10 and 3 µg/L, respectively) in drinking water. The other water quality attributes (i.e., EC, HCO₃, Cl and SO₄) were also found above their safe limits in most of the wells. Hydrogeochemical data showed that groundwater was dominated with Na-SO4, Na-Cl, Ca/Mg-CO₃ type saline water. The hazard quotient and cancer risk indices values calculated for As and Cd indicated potential threat (carcinogenic risk > 0.0001 and non-carcinogenic risk > 1.0) of drinking groundwater in the study area. This study shows that the groundwater along River Sutlej floodplain poses a health threat to the communities relying on it for drinking and irrigation due to high concentrations of As and Cd in water. Moreover, it is important to monitor groundwater quality in the adjacent areas along River Sutlej floodplain and initiate suitable mitigation and remediation programs for the safety of people's health in Punjab, Pakistan.

Living with arsenic in the environment: An examination of current awareness of farmers in the Bengal basin using hybrid feature selection and machine learning

High levels of arsenic in drinking water and food materials continue to pose a global health challenge. Over 127 million people alone in Bangladesh (BD) and West Bengal (WB) state of India are exposed to elevated levels of arsenic in drinking water. Despite decades of research and outreach, arsenic awareness in communities continue to be low. Specifically, very few studies reported arsenic awareness among low-income farming communities. A comprehensive approach to assess arsenic awareness is a key step in identifying research and development priorities so that appropriate stakeholder engagement may be designed to tackle arsenic menace. In this study, we developed a comprehensive arsenic awareness index (CAAI) and identified key awareness drivers (KADs) of arsenic to help evaluate farmers' preferences in dealing with arsenic in the environment. The CAAI and KADs were developed using a questionnaire survey in conjunction with ten machine learning (ML) models coupled with a hybrid feature selection approach. Two questionnaire surveys comprising of 73 questions covering health, water and community, and food were conducted in arsenic-affected areas of WB and BD. Comparison of CAAIs showed that the BD farmers were generally more arsenic-aware (CAAI = 7.7) than WB farmers (CAAI = 6.8). Interestingly, the reverse was true for the awareness linked to arsenic in the food chain. Application of hybrid feature selection identified 15 KADs, which included factors related to stakeholder interventions and cropping practices instead of commonly perceived factors such as age, gender and income. Among ML algorithms, classification and regression trees and single C5.0 tree could estimate CAAIs with an average accuracy of 84%. Both communities agreed on policy changes on water testing and clean water supply. The CAAI and KADs combination revealed a contrasting arsenic awareness between the two farming communities, albeit their cultural similarities. Specifically, our study shows the need for increasing awareness of risks through the food chain in BD, whereas awareness campaigns should be strengthened to raise overall awareness in WB possibly through media channels as deemed effective in BD.

A comprehensive review on magnetic carbon nanotubes and carbon nanotube-based buckypaper for removal of heavy metals and dyes

Industrial effluents contain several organic and inorganic contaminants. Among others, dyes and heavy metals introduce a serious threat to drinking waterbodies. These pollutants can be noxious or carcinogenic in nature, and harmful to humans and different aquatic species. Therefore, it is of high importance to remove heavy metals and dyes to reduce their environmental toxicity. This has led to an extensive research for the development of novel materials and techniques for the removal of heavy metals and dyes. One route to the removal of these pollutants is the utilization of magnetic carbon nanotubes (CNT) as adsorbents. Magnetic carbon nanotubes hold remarkable properties such as surface-volume ratio, higher surface area, convenient separation methods, etc. The suitable characteristics of magnetic carbon nanotubes have led them to an extensive search for their utilization in water purification. Along with magnetic carbon nanotubes, the buckypaper (BP) membranes are also favorable due to their unique strength, high porosity, and adsorption capability. However, BP membranes are mostly used for salt removal from the aqueous phase and limited literature shows their applications for removal of heavy metals and dyes. This study focuses on the existence of heavy metal ions and dyes in the aquatic environment, and methods for their removal. Various fabrication approaches for the development of magnetic-CNTs and CNT-based BP membranes are also discussed. With the remarkable separation performance and ultra-high-water flux, magnetic-CNTs, and CNT-based BP membranes have a great potential to be the leading technologies for water treatment in future.

Mitigation of arsenic induced developmental cardiotoxicity by ferulic acid in zebrafish

We investigated whether ferulic acid (FA), a nutraceutical could mitigate the arsenic (As) induced cardiotoxicity. Zebrafish larvae (60 and 72 h post-fertilization [hpf]) were used to study the effect of FA on As at different time points (24 and 48 h after exposure). The FA exposure was given as pre-treatment (60 hpf) and simultaneous treatment (72 hpf) to translate the results for As contaminated areas. To accomplish this, the lethality assay was done, and based on the results, the dosage for As (1 mM) and FA (30 μM) was fixed. The FA intervention (30 μM) as 12 h pre-treatment (60 hpf) and simultaneous treatment along with As (72 hpf) decreased the As content in zebrafish larvae as evidenced by inductively coupled plasma-mass spectrometry. As exposure showed congenital deformities especially cardiac malformations in zebrafish larvae after 24 and 48 h. These teratogenic effects induced by As were reduced by FA supplementation in both groups. Also, o-dianisidine staining demonstrated that As treated larvae encountered abnormal cardiac function with reduced blood circulation, while FA supplementation reversed these effects. The acetylcholinesterase activity, a biomarker of As-induced cardiotoxicity was also found to be decreased in As group, which was rescued by FA. The modulation in the expression of the genes involved in cardiogenesis (nkx2.5, bmp2b, gata4, gata5, myh6, myl7, and tnnt2) further confirmed the ameliorative effect of FA on As induced malformations.

Arsenic geochemistry and mineralogy as a function of particle-size in naturally arsenic-enriched soils

Naturally arsenic (As) enriched agricultural soils represent a significant global human health risk. In this study, As fractionation and mineralogy were investigated in naturally As-enriched agricultural soils and their corresponding sand, silt and clay fractions. Median As increased generally in the order (mg/kg)∶ silt (280) < bulk (314) < sand (323)<clay (484). Sequential extraction showed that amorphous and well-crystalline Fe- and Al-oxide bound and residual As forms accounted 27-42% of total As. Well-crystalline Fe- and Al-oxide bound As was highest (40-42%) in silt and clay fractions, while residual As was generally greatest (41-55%) in bulk and sand fractions. The sand, silt and bulk soils released a consistently higher percentage of non-specifically sorbed As than the clay, but clay released more specifically-sorbed As. Arsenate (As(V)) was the dominant species in soil solutions, although arsenite (As(III)) was significant in a few samples. XRD analysis showed the presence of arsenolite (As₂^IIIO₃) in soils and fractions. SEM/EDS observations revealed that scorodite (FeAs^VO₄·2H₂O) and amorphous Fe-oxides were the main As-bearing minerals in soils and fractions, which were consistent with the geochemical analysis. Outcomes from this research highlight the significant environmental risks of naturally As-enriched soils.

Efficiency of Arsenic and Iron Removal Plants (AIRPs) for Groundwater Treatment in Rural Areas of Southwest Bangladesh

Arsenic (As) removal plants were installed in As-endemic areas of Bangladesh to remove As from well water. In many cases, these removal plants did not perform satisfactorily. This study evaluated the efficiency of 20 As and iron (Fe) removal plants (AIRPs) during pre- and post-monsoon conditions in rural Bangladesh. Results revealed that As removal efficiencies ranged from 67% to 98% and 74 to 93% during the pre- and post-monsoons periods, respectively. In the post-monsoon season As removal at individual AIRP sites was on average (4.01%) greater than in the pre-monsoon season. However, two removal plants were unable to remove As below 50 µg L−1 (Bangladesh drinking water standard) during pre-monsoon, while 11 samples out of 20 were unable to remove As below the WHO provisional guideline value of 10 µg L−1. During post-monsoon, none of the samples exceeded 50 µg L−1, but eight of them exceeded 10 µg L−1. The Fe removal efficiencies of AIRPs were evident in more than 80% samples. Although As removal efficiency was found to be substantial, a cancer risk assessment indicates that hazard quotient (HQ) and carcinogenic risk (CR) of As in treated water for adults and children are above the threshold limits. Thus, additional reductions of As concentrations in treated water are needed to further reduce the excess cancer risk due to As in drinking water. Since 55% and 40% of the AIRPs were unable to remove As < 10 µg L−1 during pre-monsoon and post-monsoon, further improvement including changes in AIRP design, regular cleaning of sludge, and periodic monitoring of water quality are suggested. Future research is needed to determine whether these modifications improve the performance of AIRPs.

Hydrogeochemical investigation of arsenic in drinking water of schools and age dependent risk assessment in Vehari District, Punjab Pakistan: a multivariate analysis

Globally, a large number of school-aged children is suffering from water-borne diseases, particularly in low-income countries. Arsenic (As) is a hazardous and potentially carcinogenic metal(loid) in drinking water. Nowadays, alarming levels of As have been reported in the groundwater of Vehari District, Punjab Pakistan. In this study, drinking water supplies for high and higher secondary schools were examined in Vehari District. A total of 164 water samples were collected from schools and subjected to heavy metal(loid) analysis (As) and basic water physicochemical parameters. The results were analyzed with respect to sampling area, school type, school education level, sources of sample collection, and the depth of the source. The results revealed that As concentration of water samples in boys' and girls' schools was 12.8 μg/L and 9.2 μg/L, respectively. However, when the As concentration in drinking water was evaluated at the school education level, a notable higher concentration of As was observed in the higher secondary schools than the high schools with an average of 19.5 and 9.7 μg/L, respectively. The risk assessment indices were calculated based on education level and different age groups of the children (primary, elementary, high, and higher secondary). High carcinogenic (cancer risk = 0.001) and non-carcinogenic (hazard quotient = 2.0) risks were noted for the children in higher secondary school. The current findings anticipated that the drinking water of schools in Vehari District did not meet the requirement of the World Health Organization (WHO) drinking water quality guidelines. Safe drinking water is crucial for the development and growth of children. Therefore, it is important for educational authorities to take steps for provision of As free safe drinking water to students and local inhabitants.

Compositional and health risk assessment of drinking water from health facilities of District Vehari, Pakistan

Arsenic (As) is a potentially toxic and carcinogenic metalloid. It has gained considerable attention owing to its high ecotoxic nature. High As contamination of groundwater in scattered areas is the current status of Pakistan. A number of assessments exist for the As contamination of the drinking water in District Vehari, Pakistan. However, there is scarcity of data about As contents in drinking water of health facilities and healthcare centers in District Vehari. The current study, therefore, was carried out to assess As concentration and associated health risk in the drinking water of three health facilities (district head quarter, rural health center and basic health unit) of District Vehari. In total, 75 drinking water samples were collected and examined for As contents in addition to physicochemical characteristics such as electrical conductivity, pH, total soluble salts, chloride, carbonates, bicarbonates, fluoride, nitrate, nitrite, calcium, magnesium and iron. Results indicated that the groundwater samples are not fully fit for drinking purposes with respect to several parameters, especially the alarming levels of As. It was found that 52% of drinking water samples of Vehari have As concentration greater than WHO permissible limit (10 µg/L) and 17% have As concentration greater than Pak-EPA permissible limit (50 µg/L). The risk assessment parameters (average daily dose, hazard quotient and carcinogenic risk) showed possible carcinogenic and non-carcinogenic risks associated with ingestion of As-contaminated drinking water in the healthcare facilities. Based on the results of the present study, it is anticipated that hospitals and health centers in Vehari are in need of safe drinking water. The implementation of national/international standards for drinking water in healthcare facilities is a necessary measure to improve the services and increase local access to safe drinking water. The same may be applied to other public offices and organizations such as educational institutes and district government offices.

Nanofiltration for Arsenic Removal: Challenges, Recent Developments, and Perspectives

Arsenic (As) removal is of major significance because inorganic arsenic is highly toxic to all life forms, is a confirmed carcinogen, and is of significant environmental concern. As contamination in drinking water alone threatens more than 150 million people all over the world. Therefore, several conventional methods such as oxidation, coagulation, adsorption, etc., have been implemented for As removal, but due to their cost-maintenance limitations; there is a drive for advanced, low cost nanofiltration membrane-based technology. Thus, in order to address the increasing demand of fresh and drinking water, this review focuses on advanced nanofiltration (NF) strategy for As removal to safeguard water security. The review concentrates on different types of NF membranes, membrane fabrication processes, and their mechanism and efficiency of performance for removing As from contaminated water. The article provides an overview of the current status of polymer-, polymer composite-, and polymer nanocomposite-based NF membranes, to assess the status of nanomaterial-facilitated NF membranes and to incite progress in this area. Finally, future perspectives and future trends are highlighted.

Association between chronic arsenic exposure and the characteristic features of asthma

Widespread contamination of arsenic (As) has become a global public health concern. Exposure to As causes respiratory complications. Asthma, a major respiratory complication, is increasing worldwide. However, the effect of chronic As exposure on the risk of asthma remains to be clarified. This study aims to examine the associations between As exposure (water, hair and nail As) and the risk of asthma among 842 individuals exposed to a wide range of As concentrations through drinking water in Bangladesh. Subjects' As exposure levels were measured with ICP-MS. Lung function was examined by a handheld spirometer. Characteristic features of asthma were evaluated by bronchodilator-mediated reversibility in airway obstruction and asthma-like symptoms through a structured questionnaire. Total serum immunoglobulin E (sIgE) levels were measured by immunoassay. As exposure metrics showed inverse associations with lung function measures (FEV1, FEV6, and FEV1/FEV6 ratio) and positive associations with the risks of airway obstruction (AO), reversible airway obstruction (RAO), and asthma-like symptoms. The majority of AO patients (70 of 97) were RAO with one or more characteristic symptoms of asthma. Intriguingly, subjects' As exposure levels showed positive associations with total sIgE levels. Total sIgE in RAO patients was significantly (p < 0.001) higher than that in the control group. Thus the results revealed that chronic As exposure was associated with the risk of the characteristic features of asthma. Additionally the association between As exposure and subjects' total sIgE levels and an elevated level of total sIgE in RAO group suggested that As exposure-related asthma might be allergic in nature.

The in situ technique of aqueous binding concentration and diffusion for measurements of arsenate concentrations in lake waters

Arsenic contaminations in waters are concerned worldwide. This research was to examine an in situ method of aqueous binding concentration and diffusion (ABCD) technique with an aqueous solution of metal immobilized polycationic polymer (MIP) as a binding phase and a dialysis membrane as a diffusive layer to pre-concentrate trace arsenate in lake waters. Although the maximum binding capacity of arsenate to MIP was influenced by the presence of anions in water, the binding phase was capable of pre-concentrating arsenate in lake water. This in situ pre-concentration technique was combined with light emitting diodes (LED) for semi-on line detection of trace arsenate in waters. The system was eventually validated in lake waters in lab and in natural lake waters in China. In this work, new colorimetric method for detection of arsenate in the binding phase has been developed to minimize the potential spectra interferences of silicates, phosphates and other oxyanions. Potassium iodide was used to reduce arsenate to arsenite before the solution was mixed with the colour generation reagent of RhodamineB.

Arsenic Toxicity: Molecular Targets and Therapeutic Agents

High arsenic (As) levels in food and drinking water, or under some occupational conditions, can precipitate chronic toxicity and in some cases cancer. Millions of people are exposed to unacceptable amounts of As through drinking water and food. Highly exposed individuals may develop acute, subacute, or chronic signs of poisoning, characterized by skin lesions, cardiovascular symptoms, and in some cases, multi-organ failure. Inorganic arsenite(III) and organic arsenicals with the general formula R-As²⁺ are bound tightly to thiol groups, particularly to vicinal dithiols such as dihydrolipoic acid (DHLA), which together with some seleno-enzymes constitute vulnerable targets for the toxic action of As. In addition, R-As²⁺-compounds have even higher affinity to selenol groups, e.g., in thioredoxin reductase that also possesses a thiol group vicinal to the selenol. Inhibition of this and other ROS scavenging seleno-enzymes explain the oxidative stress associated with arsenic poisoning. The development of chelating agents, such as the dithiols BAL (dimercaptopropanol), DMPS (dimercapto-propanesulfonate) and DMSA (dimercaptosuccinic acid), took advantage of the fact that As had high affinity towards vicinal dithiols. Primary prevention by reducing exposure of the millions of people exposed to unacceptable As levels should be the prioritized strategy. However, in acute and subacute and even some cases with chronic As poisonings chelation treatment with therapeutic dithiols, in particular DMPS appears promising as regards alleviation of symptoms. In acute cases, initial treatment with BAL combined with DMPS should be considered.

Application of water quality index, synthetic pollution index, and geospatial tools for the assessment of drinking water quality in the Indus Delta, Pakistan

Seawater intrusion into the Indus Delta, Pakistan, has spoiled groundwater aquifers in the area. In the delta, the groundwater is widely used by residents for drinking. Considering the gravity of the problem, and concerns expressed by affected communities, the present study was conducted to assess and map the quality of groundwater, based on the physico-chemical properties of 180 samples, using two standard numerical indices, geospatial and statistical techniques. The analysis of water samples revealed that several parameters exceeded the drinking water quality guidelines suggested by the World Health Organization (WHO). The water quality index (WQI) identified that about 1.7%, 1.1%, 27.8%, 42.8%, and 26.6% of the water samples were excellent, good, poor, very poor, and unsuitable for drinking purposes, respectively. However, the synthetic pollution index (SPI) ranked the quality of 2.8%, 2.2%, 23.9%, 41.7%, and 29.4% as suitable, slightly polluted, moderately polluted, highly polluted, and unsuitable, respectively. Though the numerical model's input is different, the proportionate ranking revealed a fair correlation (R² = 0.75) between the outcomes of both indices. The results of the numerical indices and the interpolated geographical information system (GIS) mapping revealed that the quality of groundwater in most of the delta does not meet WHO guidelines for potable water. Hence, it is recommended that the groundwater of the delta should be properly treated before its use for domestic purposes. The study highlights the significance of using numerical indices and geospatial techniques for water quality evaluation in the Indus Delta and similar deltaic regions throughout the world.

Arsenic contamination, subsequent water toxicity, and associated public health risks in the lower Indus plain, Sindh province, Pakistan

Arsenic (As) contamination in drinking water is a global public health risk. The present study highlighted the geological and anthropogenic causes of As contamination in groundwater (GW) and surface water (SW) and assessment of their potential health risks in Sindh province of Pakistan. Upon analyzing 720 GW and SW samples from 18 different sites, the estimates of As in groundwater and surface water was observed in the range of 0 to 125 and 0 to 35 μg/L with mean values of 46.8 and 15.43 μg/L respectively. Majority of the samples exceeded WHO permissible limit of As (10 μg/L) with higher concentration detected in groundwater samples compared to surface water. Moreover, both of these sample sources were found not potable based on physicochemical characteristics. The results of statistical analysis (correlation analysis, principal component analysis (PCA), and hierarchy cluster analysis (HCA)) indicate that natural mobilization of As in groundwater is believed to be enhanced by the pH-based reductive dissolution of iron hydroxide (FeOH) and competitive sorption of bicarbonate minerals in the presence of microorganisms along with evaporative enrichment while water logging, coal mining, and excessive use of pesticides are believed to be the anthropogenic causes of As enrichment. Furthermore, enormous health risk was associated with As in terms of chronic daily intake (CRI), hazard quotient (HQ), and cancer risk probability (CR) in GW and SW. Mean HQ values in GW were 4.47 mg/kg/day in adults and 3.89 mg/kg/day in children (standard HQ ≤ 1) and was 1.43 and 1.28 mg/kg/day in SW. Mean CR value in both GW and SW was found higher than the safe limit (10^-6) having a mean of 2 × 10^-3 in GW and 7 × 10^-4 (mg/kg/day) in SW. These findings suggest that majority of the sampling sites carry serious public health risk due to high As values and hence demands exigent remedial and management measures.

Unraveling prevalence and public health risks of arsenic, uranium and co-occurring trace metals in groundwater along riverine ecosystem in Sindh and Punjab, Pakistan

The current study focuses on the understanding of contamination status, distribution, source apportionment and health perspectives of arsenic (As), uranium (U) and other co-occurring trace metals in the groundwater samples collected along the major rivers in Sindh and Punjab provinces, Pakistan. ICP-MS analysis revealed that the concentrations of As in the groundwater in Sindh and Punjab ranged from 0.2 to 81.1 µg/L (n = 38) and 1.1 to 501.1 µg/L (n = 110), respectively. Importantly, this study is the first evidence of U contamination in the groundwater samples in Pakistan, which revealed the concentrations of U at from 0.8 to 59.0 and 0.1 to 556.0 µg/L respectively, in Sindh and Punjab. Moreover, the concentrations of Sr and Mn exceeded the WHO limits in the current study area. Anthropogenic activities such as urbanization, direct dispose of industrial, agricultural waste into waterways and extensive use of pesticides and fertilizers might be the main sources of elevated levels of total dissolved solids and electrical conductivity, which increased the mobilization of As, U and Sr in the groundwater samples. Human health risk assessment parameters such as average daily dose, hazard quotient (HQ) and cancer risk indicated severe risks of As and U in the study area. The HQ values of As and U in Punjab were observed at 69.6 and 7.7, respectively, implying the severity of the health risks associated with consumption of contaminated groundwater for drinking purposes. In a nutshell, proactive control and rehabilitation measures are recommended to eradicate trace metals associated groundwater contamination in the targeted areas to avoid future worst scenarios.

Ultra-structure alteration via enhanced silicon uptake in arsenic stressed rice cultivars under intermittent irrigation practices in Bengal delta basin

The study implements a periodical intermittent water cycle during rice cultivation providing insight potential in minimizing soil bio-available arsenic. Soil As concentrations were 34 ± 0.49 and 72.03 ± 0.54 mg kg-1 As respectively in two selected fields with rice cultivars gosai and satabdi, in comparison to 42.26 ± 0.37 and 83.69 ± 0.48 mg kg-1 in continuously flooded field soil, determined through ICP-MS. The study found higher translocation of silicon from soil to rice plant parts under intermittent irrigation having pH range of 7.6-9.4 and greater availability of soil organic content that in turn release more labile silicon from soil to aqueous phase for plant accumulation. This increased uptake of silicon strengthens rice shoots, nodes and leaf xylem-phloem integrity compared to conventional continuously flooded rice cultivation approach, suppressing the arsenic translocation, as observed under FE-SEM real-time imaging. Fresh plants were analysed for bioaccumulation and translocation factors of arsenic and silicon to justify the enhanced silicon uptake under proposed practice. Plant stress regulator enzymes viz. malondialdehyde (MDA), total protein, superoxide dismutase (SOD), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) from both conditions and found to be better in intermittent method over conventional practice with higher productivity.

Removal of heavy metals from water sources in the developing world using low-cost materials: A review

Heavy metal contamination is a growing concern in the developing world. Inadequate water and wastewater treatment, coupled with increased industrial activity, have led to increased heavy metal contamination in rivers, lakes, and other water sources in developing countries. However, common methods for removing heavy metals from water sources, including membrane filtration, activated carbon adsorption, and electrocoagulation, are not feasible for developing countries. As a result, a significant amount of research has been conducted on low-cost adsorbents to evaluate their ability to remove heavy metals. In this review article, we summarize the current state of research on the removal of heavy metals with an emphasis on low-cost adsorbents that are feasible in the context of the developing world. This review evaluates the use of adsorbents from four major categories: agricultural waste; naturally-occurring soil and mineral deposits; aquatic and terrestrial biomass; and other locally-available waste materials. Along with a summary of the use of these adsorbents in the removal of heavy metals, this article provides a summary of the influence of various water-quality parameters on heavy metals and these adsorbents. The proposed adsorption mechanisms for heavy metal removal are also discussed.

Arsenic exposure through drinking Water and oxidative stress Status: A cross-sectional study in the Ayeyarwady region, Myanmar

Arsenic is a well-known toxic heavy metal that is naturally dispersed in groundwater. Whereas arsenic is widely accepted to be involved in oxidative stress damage, little is known about arsenic-induced oxidative damage in relationship to contaminated drinking water as a source. The aim of this study was to determine the association between arsenic exposure through drinking water and oxidative stress status by measuring levels of urinary 8-hydroxydeoxyguanosine (8-OHdG) as a biomarker of oxidative stress damage in a Myanmar population. A questionnaire-based survey and drinking water and urine sampling (n = 198) were performed to assess the association between arsenic exposure and urinary 8-OHdG concentration in the Ayeyarwady Region, Myanmar. Urinary arsenic concentrations were significantly correlated with drinking water arsenic concentrations (Spearman's rho = 0.32, p < 0.001). Multivariate linear regression analysis showed that higher urinary arsenic concentrations were significantly associated with higher 8-OHdG concentrations (coefficient = 0.09, 95% confidence interval, 0.03 - 0.15; p =  0.002). The present study identified that exposure to arsenic through drinking water could induce an increase in the urinary 8-OHdG concentration, reflecting increased oxidative DNA damage. These findings provide evidence that may explain the role of arsenic-induced oxidative stress in the pathophysiology of arsenic-induced diseases including cancers.

Phytoextraction of arsenic forms in selected tree species growing in As-polluted mining sludge

The aim of this study was to determine the phytoextraction of inorganic (As(III), As(V)) and organic arsenic (As_org) forms in six tree species: Acer platanoides, Acer pseudoplatanus, Betula pendula, Quercus robur, Tilia cordata and Ulmus laevis. Plants were grown in a pot experiment using As-polluted mining sludge for 90 days. Arsenic (As_total) was accumulated mainly in the roots of all six tree species, which were generally thinner, shorter and/or black after the experiment. The highest concentration of As(III) and As(V) was determined in the roots of A. pseudoplatanus and A. platanoides (174 and 420 mg kg^-1, respectively). High concentrations of As(III) were also recorded in the shoots of B. pendula (11.9 mg kg^-1) and As(V) in the aerial parts of U. laevis and A. pseudoplatanus (77.4 and 70.1 mg kg^-1). With some exceptions, the dominant form in the tree organs was As_org, present in mining sludge in low concentration. This form has a decisive influence on As phytoextraction by young tree seedlings even though its BCF value was the only one lower than 1. The obtained results highlight the important role of speciation studies in assessing the response of plants growing in heavily polluted mining sludge.

Controls on high and low groundwater arsenic on the opposite banks of the lower reaches of River Ganges, Bengal basin, India

Understanding the controls on spatial variability of groundwater arsenic (As) is critical for mitigating As contamination. The objective of this study is to determine controls on previously unexplained differences in groundwater As concentrations, which are high along the east bank and low along the west bank of the River Bhagirathi-Hoogly (B-H), the primary Indian distributary of the River Ganges, on the western margin of the Bengal basin. A total of 54 wells were sampled after the monsoon season at four sites (two each east and west of the B-H) in Murshidabad district, West Bengal, for field parameters, major and minor solutes, and stable isotopes of water. An additional four boreholes were drilled for analyses of sediment texture, mineralogy, total organic and inorganic carbon, and total As and other metal(loid)s. Results show that higher As in east-bank groundwater (median 0.031 mg/L) is associated with generally more anoxic conditions (higher median total Fe and lower median E_H and NO₃^-) relative to west-bank groundwater (median As < 0.001 mg/L), consistent with previous studies. In contrast, concentrations of Mn in the study area are highest in west-bank wells near the B-H. Carbonate and silicate weathering appear to be more important in east- and west-bank groundwater, respectively, which may reflect differences in sediment sources. Ranges of total As are similar in east- and west-bank sediments. Relatively depleted values of δ¹⁸O and δ²H in the east-bank aquifer and streams appear to reflect focused recharge through paleochannels, while relatively enriched west-bank values suggest diffuse recharge to upland aquifers. We speculate that water infiltrating through erosional, stratigraphic "windows" carries organic matter capable of mobilizing As in east-bank groundwater. This comprehensive evaluation of groundwater chemistry provides a more detailed understanding of controls on As variability within the basin.

Arsenic-rich shallow groundwater in sandy aquifer systems buffered by rising carbonate waters: A geochemical case study from Mannar Island, Sri Lanka

Major ion, trace elements, and stable isotope analyses were performed on groundwater samples collected from Mannar Island in the northern Indian Ocean. Arsenic concentrations up to 34μg/L have been observed in groundwater samples from the island. In addition, 23% of extensively used shallow drinking water wells showed higher arsenic contents than the recommended value by the World Health Organization (10μg/L). Groundwater in the island showed pH values between 6.9 and 8.9 and was dominated by Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO₃^-, Cl^- and SO₄^2-. The δ¹⁸O_H2O and δ²H_H2O composition of most groundwater plotted very close to the local meteoric waterline, however, some wells showed enriched isotope compositions that are most likely due to evaporation. Sea water intrusion in this island was likely of minor importance as indicated by the major ion composition. An approximated mass balance calculation using chloride concentrations indicated that out of the 35 investigated wells only 6 near-shore wells were influenced by sea water intrusion up to about 15%. Even though this is a sandy aquifer, groundwaters were characterized with higher contents of dissolved inorganic carbon (DIC) (2.11-10.9mmol/L). The corresponding δ¹³C_DIC values varied from -19.4‰ to -6.5‰. Except for a few samples with values approaching -20‰, these isotope values are more typical for carbonate dissolution and equilibration of CO₂ in the aquifer. This study shows that the underlying carbonate system may buffer the aqueous geochemistry of the groundwater on the island. The high arsenic content in groundwater may have been mobilized through reductive dissolution of Fe-Mn oxides and oxy-hydroxides that are coated on sandy aquifer materials. The lower content of DOC (0.2-1.5mmol/L) provides evidence for the restricted formation of pyrite in the aquifer.

Spatial analysis of groundwater suitability for drinking and irrigation in Lahore, Pakistan

This study used a total of 474 groundwater samples analyzed from 2014 data to evaluate the distribution of groundwater quality in the Water and Sanitation Agency (WASA) jurisdiction of Lahore city, Pakistan. The study further assessed the variations in suitability of groundwater for drinking (emphasis on arsenic and fluoride) and irrigation using spatial correlation technique in GIS. The hydrochemical analysis revealed a predominance of Mg-Ca-HCO₃-SO₄ and Ca-Mg-HCO₃-SO₄ type. Distribution analysis indicated relatively higher salinity (TDS_max = 1667 mg/L), total hardness (TH_max = 558 mg/L), and alkalinity (HCO₃^-_max = 584 mg/L) in the south-eastern region of the city, while the central part displayed the highest levels of SO₄ and NO₃. Also, the eastern region (north-south) of Lahore had significantly elevated As concentrations (up to 86 μg/L). The order of exceedance in terms of arsenic was Gunj Bakhsh town (17.4%), Nishter town (16.4%), Iqbal town (9.8%), Aziz Batti and Shalimar town (8.1%), and Ravi town (3%). The groundwater was classified as average saline to highly saline, except few samples in Aziz Batti/Shalimar town that were in non-saline group. Otherwise, the various indices classified the groundwater for irrigation as generally acceptable. With the various irrigation quality indices displaying discernible variations for the entire study area, it was observed from the distribution maps that the groundwater suitability for irrigation is relatively excellent in the areas away from industries and landfill locations. Also, the chloride analysis shows 98.7% of the groundwater samples belong to the very fresh and fresh water class. Thus, continued monitoring and studying the changes in groundwater quality in Lahore is imperative.

Carcinogenic and non-carcinogenic health risks of metal(oid)s in tap water from Ilam city, Iran

One of the most important pathways for exposure to metals is drinking water ingestion. Chronic or acute exposure to metals can endanger the health of the exposed population, and hence, estimation of human health risks is crucial. In the current study for the first time, the concentrations of Mercury (Hg), Arsenic (As), Zinc (Zn), Lead (Pb) and Cobalt (Co) in 120 collected tap water samples (2015, July-November) from Ilam city, Iran were investigated using flame atomic absorption spectrophotometer. Also, the metal-induced carcinogenic and non-carcinogenic risks for consumers exposed to tap drinking water were calculated. The average (range) concentrations of Hg, Zn, As, Pb and Co were defined as 0.40 ± 0.10 μg/L (ND-0.9 μg/L), 5014 ± 5707 μg/L (2900.00-5668.33 μg/L), 21.008 ± 2.876 μg/L (3.5-62 μg/L), 30.38 ± 5.56 μg/L (6-87 μg/L), and 11.34 ± 1.61 μg/L (0.1-50 μg/L), respectively. Average concentrations of all examined metals were significantly higher than WHO and national standard recommended limits. The ranking order of metals concentrations in the tap drinking water was Zn > Pb > As > Co > Hg. Except for Hg and Co, at least one age group consumers were at considerable non-carcinogenic risks induced by Zn, As and Pb [Target Hazard Quotient (THQ > 1)]. The rank order of age groups consumers based on THQ and Incremental lifetime cancer risk (ILCR) was <1 years >1-9 years > 20 + years > 10-19 years. The calculated ILCR for As in all age groups were higher than 10^-3 value. All age groups of consumers in Ilam city, especially infants (<1 years) and children (1-10 years), are at considerable non-carcinogenic and carcinogenesis risk.

Human health risks and socio-economic perspectives of arsenic exposure in Bangladesh: A scoping review

Arsenic contamination of drinking water, which can occur naturally or because of human activities such as mining, is the single most important public health issue in Bangladesh. Fifty out of the 64 districts in the country have arsenic concentration of groundwater exceeding 50µgL^-1, the Bangladeshi threshold, affecting 35-77 million people or 21-48% of the total population. Chronic arsenic exposure through drinking water and other dietary sources is an important public health issue worldwide affecting hundreds of millions of people. Consequently, arsenic poisoning has attracted the attention of researchers and has been profiled extensively in the literature. Most of the literature has focused on characterising arsenic poisoning and factors associated with it. However, studies examining the socio-economic aspects of chronic exposure of arsenic through either drinking water or foods remain underexplored. The objectives of this paper are (i) to review arsenic exposure pathways to humans; (ii) to summarise public health impacts of chronic arsenic exposure; and (iii) to examine socio-economic implications and consequences of arsenicosis with a focus on Bangladesh. This scoping review evaluates the contributions of different exposure pathways by analysing arsenic concentrations in dietary and non-dietary sources. The socio-economic consequences of arsenicosis disease in Bangladesh are discussed in this review by considering food habits, nutritional status, socio-economic conditions, and socio-cultural behaviours of the people of the country. The pathways of arsenic exposure in Bangladesh include drinking water, various plant foods and non-dietary sources such as soil. Arsenic affected people are often abandoned by the society, lose their jobs and get divorced and are forced to live a sub-standard life. The fragile public health system in Bangladesh has been burdened by the management of thousands of arsenicosis victims in Bangladesh.

Using urine as a biomarker in human exposure risk associated with arsenic and other heavy metals contaminating drinking groundwater in intensively agricultural areas of Thailand

Urine used as a biomarker was collected and compared between two groups of participants: (1) a groundwater-drinking group and (2) a non-groundwater-drinking group in intensively agricultural areas in Ubon Ratchathani province, Thailand. The statistical relationship with the metal concentration in shallow groundwater wells was established with urine data. According to the groundwater data, the health risk assessment results for four metals appeared to be higher for participants who drank groundwater than for the other group. The carcinogenic risk and non-carcinogenic risk of arsenic (As) were found in 25.86 and 31.03% of participants, respectively. For lead (Pb), 13.79% of the participants had a non-carcinogenic risk. Moreover, 30 of the 58 participants in the groundwater-drinking group had As urine higher than the standard, and 26, 2 and 9 of the 58 participants had above-standard levels for cadmium (Cd), Pb and mercury (Hg) in urine, respectively. Both the risk assessment and biomarker level of groundwater-drinking participants were higher than in the other group. The results showed an average drinking rate of approximately 4.21 ± 2.73 L/day, which is twice as high as the standard. Interestingly, the As levels in the groundwater correlated with those in the urine of the groundwater-drinking participants, but not in the non-groundwater-drinking participants, as well as with the As-related cancer and non-carcinogenic risks. The hazard index (HI) of the 100 participants ranged from 0.00 to 25.86, with an average of 1.51 ± 3.63 higher than the acceptable level, revealing that 28 people appeared to have non-carcinogenic risk levels (24 and 4 people for groundwater-drinking participants and non-groundwater-drinking participants, respectively). Finally, the associated factors of heavy metals in urine were the drinking water source, body weight, smoking, sex and use of personal protective equipment.

A millimeter-scale observation of the competitive effect of phosphate on promotion of arsenic mobilization in sediments

A millimeter-scale investigation is key to the understanding of the competitive effects of phosphate(P) on arsenic(As) mobility in sediments by taking the great biogeochemical heterogeneity of the sediments into consideration. In this study, a microcosm experiment was performed in this aspect using high-resolution dialysis and diffusive gradients in thin films (DGT) to simultaneously measure dissolved and labile P, As, and iron (Fe) in sediments, respectively. With the increase of P content in water from 0.02 mg L^-1 to 0.20 and 2.4 mg L^-1, consistent release of As from sediments was observed. The concentrations of DGT-labile As increased significantly especially in the upper sediment layer (up to 12 times of the 0.02 mg P L^-1 treatment) due to the competition of phosphate, which corresponded well to the increase in DGT-labile P. There was limited increase in dissolved P and As contents due to the buffering provided by sediment solids, while the concentrations of both dissolved and DGT-labile Fe in sediments decreased. A stoichiometric calculation showed that 47% and 8% of the added P were removed through Fe(II) precipitation for the 0.20 and 2.4 mg P L^-1 treatments, respectively, which greatly suppressed the release of As induced by P competition for the 0.20 mg P L^-1 treatment. The DGT-induced fluxes in sediments (DIFS) modeling showed an increase in solid resupply to pore water As from elevation of water P through the increases of the desorption rate constant from 5.4 to 31( × 10^-7) s^-1 and the sorption rate constant from 1.8 to 22( × 10^-4) s^-1.

A Review of the Effects of Chronic Arsenic Exposure on Adverse Pregnancy Outcomes

Exposure to arsenic has a number of known detrimental health effects but impact on pregnancy outcomes is not as widely recognized. This narrative review examines existing epidemiological evidence investigating the association between arsenic exposure via drinking water and adverse pregnancy outcomes. We reviewed published epidemiological studies from around the world on impact of chronic arsenic exposure on spontaneous abortion, stillbirth, neonatal death, post neonatal death, low birth weight and preterm baby. Plausible mechanisms of arsenic toxicity causing adverse pregnancy outcomes were also determined through literature review. There is convincing evidence to support the association between high inorganic arsenic exposure (>50 ppb) and spontaneous abortion, stillbirth and low birth weight. Limitations of certain studies include study design, small sample size, recall constraints and exposure assessment. There needs to be further research investigating the dose metered impact of arsenic exposure on pregnancy outcomes. Further research on impact of low-moderate arsenic concentration exposure on pregnancy outcomes will allow for appropriate public health policy recommendations.

Risk assessment for arsenic-contaminated groundwater along River Indus in Pakistan

The study determined the risk zone and estimated the population at risk of adverse health effects for arsenic exposure along the bank of River Indus in Pakistan. A cross-sectional survey was conducted in 216 randomly selected villages of one of the districts along River Indus. Wells of ten households from each village were selected to measure arsenic levels. The location of wells was identified using global positioning system device, and spatial variations of the groundwater contamination were assessed using geographical information system tools. Using layers of contaminated drinking water wells according to arsenic levels and population with major landmarks, a risk zone and estimated population at risk were determined, which were exposed to arsenic level ≥10 µg/L. Drinking wells with arsenic levels of ≥10 µg/L were concentrated within 18 km near the river bank. Based on these estimates, a total of 13 million people were exposed to ≥10 µg/L arsenic concentration along the course of River Indus traversing through 27 districts in Pakistan. This information would help the researchers in designing health effect studies on arsenic and policy makers in allocating resources for designing focused interventions for arsenic mitigation in Pakistan. The study methods have implication on similar populations which are affected along rivers due to arsenic contamination.