Arsenic speciation in rice, straw, soil, hair and nails samples from the arsenic-affected areas of Middle and Lower Ganga plain

Differential Mechanisms of Microbial As(III) and Sb(III) Oxidation and Their Contribution to Tailings Reclamation

Mine tailings are extremely oligotrophic environments frequently contaminated with elevated As and Sb, making As(III) and Sb(III) oxidation potentially important energy sources for the tailing microbiome. Although they have been proposed to share similar metabolic pathways, a systemic comparison of the As(III) and Sb(III) oxidation mechanisms and energy utilization efficiencies requires further elucidation. In this study, we employed a combination of physicochemical, molecular, and bioinformatic analyses to compare the kinetic and genetic mechanisms of As(III) and Sb(III) oxidation as well as their respective energy efficiencies for fueling the key nutrient acquisition metabolisms. Thiobacillus and Rhizobium spp. were identified as functional populations for both As(III) and Sb(III) oxidation in mine tailings by DNA-stable isotope probing. However, these microorganisms mediated As(III) and Sb(III) oxidation via different metabolic pathways, resulting in preferential oxidation of Sb(III) over As(III). Notably, both As(III) and Sb(III) oxidation can facilitate nitrogen fixation and phosphate solubilization in mine tailings, with Sb(III) oxidation being more efficient in powering these processes. Thus, this study provided novel insights into the microbial As(III) and Sb(III) oxidation mechanisms and their respective nutrient acquisition efficiencies, which may be critical for the reclamation of mine tailings.

Isolation and characterization of rhizobacteria from lentil for arsenic resistance and plant growth promotion

Low-cost microbial remediation strategies serve as a viable and potent weapon for curbing the arsenic menace. In the present study, two arsenic-resistant bacteria were isolated from the contaminated lentil rhizosphere in Gangetic plain of eastern India. LAR-21 (Burkholderia cepacia, MW356875) and LAR-25 (Burkholderia cenocepacia, MW356894) could remove 87.6% and 85.9% of arsenite (10 mM) from the liquid culture medium in laboratory condition. They were highly resistant to arsenate and arsenite and also had a high arsenite oxidase activity. LAR-21 showed the highest level of minimum inhibitory concentration value of 390 mM for arsenate and 31 mM for arsenite. The same strain was found to show highest arsenite oxidase activity, i.e., 5.2 nM min-1 mg-1of protein. These two strains further possess potential plant growth-promoting characteristics like indole acetic acid production (5-15 mM IAA mL-1), 1-aminocyclopropane-1-carboxylate deaminase (8-21 nM α-keto butyrate mg protein-1 h-1), nitrogenase activity (3-8.99 nM ethylene mg cell protein-1 h-1), siderophore production (17-22.1 µM deferoxamine mesylate mL-1), phosphate solubilization (261-453 µg mL-1) under arsenic stress condition. The plant growth promotion of the strains was further validated by pot study of lentil by assessing their agronomic and growth-related traits, and potential to recover from arsenic stress (17.2-21.2% arsenic reduction in root and shoot, 16-19.2% in leaf and pod, and 15-23% reduction in seeds). The LAR-21 strain, thus, emerged as the most suited candidate for bioremediation and plant (lentil) growth promotion in arsenic polluted environment.

Arsenic level in groundwater and biological samples in Khanewal, Pakistan

Groundwater is the most valuable natural source in our earth's planet, being contaminated in various regions worldwide. Despite considerable research, there are scarce data regarding arsenic (As) levels in groundwater and its build-up in biological samples in Pakistan. The current investigation analyzed As contamination in four tehsils of District Khanewal (Kabirwala tehsil, Jahaniyan tehsil, Mian Channu tehsil, and Khanewal tehsil). For that, 123 groundwater samples, 19 animal milk samples, 20 human nails, and 20 human hair samples were collected from the study area. Arsenic concentration in groundwater was up to 51.8 µg/L with an average value of 7.2 µg/L. About 28 water samples (23%) had As contents > WHO limit and 38 samples (31%) > DEP-NJ limit. Low levels of As were detected in biological samples. Average As levels were 23 µg/L in the milk samples and 298 µg/kg in human hair. Arsenic contents were not detected in nail samples, except in one sample from Kabirwala tehsil. The maximum values of hazard quotient and cancer risk in District Khanewal were 4.9 and 0.0022, respectively. It is anticipated that long-term use of As-containing water may led to poisoning of humans in the study area, especially in Kabirwala. Therefore, it is necessary to monitor As contamination in the groundwater of Kabirwala tehsil to reduce the potential health hazards.

Distribution, geochemical behavior, and risk assessment of arsenic in different floodplain aquifers of middle Gangetic basin, India

The present study interprets the distribution and geochemical behavior of As in groundwaters of different regions along the floodplains of Ganga river (Varanasi, Ghazipur, Ballia), Ghaghara river (Lakhimpur Kheri, Gonda, Basti), and Rapti river (Balrampur, Shrawasti) in the middle Gangetic basin, India for risk assessment (non-carcinogenic and carcinogenic). The concentration of As in groundwaters of these floodplains ranged from 0.12 to 348 μg/L (mean 24 μg/L), with around ~ 37% of groundwater samples exceeding the WHO limit of 10 μg/L in drinking water. Highest As concentration (348 μg/L) was recorded in groundwater samples from Ballia (Ganga Floodplains), where 50% of the samples had As > 10 μg/L in groundwater. In the study area, a relatively higher mean concentration was recorded in deep wells (28.5 μg/L) compared to shallow wells (20 μg/L). Most of the high As-groundwaters were associated with the high Fe, bicarbonate and low nitrate and sulfate concentrations indicating the release of As via reductive dissolution of Fe oxyhydroxides. The saturation index values of the Fe minerals such as goethite, hematite, ferrihydrite, and siderite showed the oversaturation to near equilibrium in groundwater, suggesting that these mineral phases may act as source/sink of As in the aquifers of the study area. The health risk assessment results revealed that a large number of people in the study area were prone to carcinogenic and non-carcinogenic health risks due to daily consumption of As-polluted groundwater. The highest risks were estimated for the aquifers of Ganga floodplains, as indicated by their mean HQ (41.47) and CR (0.0142) values.

Arsenic Elevated Groundwater Irrigation: Farmers' Perception of Rice and Vegetable Contamination in a Naturally Arsenic Endemic Area

Arsenic (As) in groundwater and its accumulation in agricultural produces has caused serious threats to human health. The majority of current research on As mainly focuses on the technical aspects while bypassing the social perspectives. Farmers are the prime stakeholders as well as executors of agricultural strategies, and their adaptation largely depends on how they perceive the risk for which a mitigation strategy is proposed. This study aims to explore how rice and vegetable farmers perceive As accumulation in their rice and vegetables as well as explore current crop- and body-loading status, the subsequent health consequences of As, and alleviation possibilities with mitigation strategies and to investigate if there is an association between their socioeconomic status and their level of perception. Results reveal that one-fourth of the farmers gave a positive message regarding the As-contamination scenario in rice and vegetables. Although 10 farmers' socioeconomic characteristics were positively significant, distinctive emphasis should be given to five predictor variables explaining 88% variances: knowledge, direct participation in farming, information sources used, participant education, and organizational participation. Path analysis depicts that direct participation in farming presents the highest positive total effect (0.855) and direct effect (0.503), whereas information sources show the highest positive indirect effect (0.624). The mean As content in all five locations was statistically significant at the 5%, 5%, 0.1%, 1%, and 1% probability levels in scalp hairs, rice, vegetables, soils, and irrigation water, respectively. The first principal component (PC1) explains 92.5% of the variation. Significant variations were primarily explained by As levels in irrigation water, rice grain, and soil. Farmers' perception is far behind the actual field status of As level and its transfer. Therefore, intensified priorities should be administered on the farmers' characteristics contributing to variances in perception. The findings can be utilized for policy formulation in all As-endemic nations. More multidisciplinary research can be undertaken on farmers' attitude towards adopting As-mitigation techniques, with a focus on the socioeconomic position found to influence farmers' perceptions.

Speciation and bioaccessibility of arsenic in rice under different cooking methods and its implication in risk assessment

Numerous studies have studied the health risk assessment of human exposure to As or bioaccessible As via rice intake; however, the bioaccessibility of different As species in rice is seldom reported. In the present study, 31 rice samples were collected from markets or individual growers to investigate the speciation and bioaccessibility of As. Five different species (As^III, As^V, DMA, MMA, and AsB) were detected in rice samples from different regions, among which As^III accounted for the largest proportion (62.95% in average), followed by DMA and As^V. In addition, the cooking method could facilitate the release of As from rice into gastric and intestinal juice, and subsequently increase the bioaccessibility of As. The bioaccessibility of inorganic As in cooked rice ranged from 71.83 to 100%, and that of organic As ranged from 31.69 to 61.04%. Non-carcinogenic and carcinogenic risk assessment of children and adults exposure to As via rice intake considering the bioaccessibility of cooked rice was carried out. The target hazard quotient (THQ) of iAs and total As for children ranged from 0.21 to 1.61 and 0.48 to 2.26, respectively, while those for adults ranged from 0.12 to 0.88 and 0.26 to 1.23, respectively. Incremental lifetime cancer risk (ILCR) for children and adults ranged from 9.57 [Formula: see text] 10^-5 to 7.25 [Formula: see text] 10^-4 and 5.21 [Formula: see text] 10^-5 to 3.95 [Formula: see text] 10^-4, respectively. The results of risk assessment indicated that children would face a higher health risk than adults when they took the same type of rice as their staple food.

Human health impact due to arsenic contaminated rice and vegetables consumption in naturally arsenic endemic regions

Rice and vegetables cultivated in naturally arsenic (As) endemic areas are the substantial source of As body loading for persons using safe drinking water. However, tracing As intake, particularly from rice and vegetables by biomarker analysis, has been poorly addressed. This field investigation was conducted to trace the As transfer pathway and measure health risk associated with consuming As enriched rice and vegetables. Purposively selected 100 farmers from five sub-districts of Chandpur, Bangladesh fulfilling specific requirements constituted the subjects of this study. A total of 100 Irrigation water, soils, rice, and vegetable samples were collected from those farmers' who donated scalp hair. Socio-demographic and food consumption data were collected face to face through questionnaire administration. The mean As level in irrigation water, soils, rice, vegetables, and scalp hairs exceeded the acceptable limit, while As content was significant at 0.1%, 5%, 0.1%, 1%, and 0.1% probability levels, respectively, in all five locations. Arsenic in scalp hair is significantly (p ≤ 0.01) correlated with that in rice and vegetables. The bioconcentration factor (BCF) for rice and vegetables is less than one and significant at a 1% probability level. The average daily intake (ADI) is higher than the RfD limit for As. Both grains and vegetables have an HQ (hazard quotient) > 1. Maximum incremental lifetime cancer risk (ILCR) showed 2.8 per 100 people and 1.6 per 1000 people are at considerable and threshold risk, respectively. However, proteinaceous and nutritious food consumption might have kept the participants asymptomatic. The PCA analysis showed that the first principle component (PC1) explains 91.1% of the total variance dominated by As in irrigation water, grain, and vegetables. The dendrogram shows greater variations in similarity in rice and vegetables As, while the latter has been found to contribute more to human body loading compared to grain As.

Effect of O-substitution in imidazole based Zn(II) dual fluorescent probes in the light of arsenate detection in potable water: a combined experimental and theoretical approach

Efficient detection of arsenate (AsO₄^3-) from contaminated drinking water extracted from underground has become a matter of utmost necessity and an exquisite challenge owing to the growing public health issue due to arsenicosis. In order to combat this we planned to detect arsenate with the naked eye under UV light using a novel chemosensor material whose structure and functioning as a sensor could be certified mechanistically. Hence we were encouraged to synthesize two differently O-substituted imidazole based homologous ligands: C1 (HL¹ = 2-((E)-(3-(1H-imidazole-1-yl)propylimino)methyl)-6-ethoxyphenol) and C2 (HL² = 2-((E)-(3-(1H-imidazole-1-yl)propylimino)methyl)-6-methoxyphenol). To accomplish the purposeful exploration of the luminescent sensor, we considered Chelation Enhanced Fluorescence (CHEF) and kept on searching for a metal cation that would be able to turn on the fluorescence of the ligands. Considering Zn(II) as the most suitable candidate, luminescent complexes D1 and D2 ({[Zn₂(L¹)₂(I)₂](DMF)} and [Zn₂(L²)₂(I)₂](DMF), respectively) were synthesized and characterized by SXRD, UV-Vis, FT-IR, and photoluminescence spectroscopy. In spite of the resemblance in the solid state structures of D1 and D2, the selective response of D1 towards arsenate with high quenching constants (2.13 × 10⁶), unlike D2, has been demonstrated mechanistically with steady state and time resolved fluorescence titration, solution phase ESI-MS spectral analysis and DFT studies. The selectivity and sensitivity of the sensor D1 explicitly make this material a potent candidate for arsenate detection due to its very low detection limit (8.2 ppb), low cost and user friendly characteristics. Real life implementation of this work in a test strip is expected to prove beneficial for public health to identify arsenate polluted water.

Assessment of disease burden in the arsenic exposed population of Chapar village of Samastipur district, Bihar, India, and related mitigation initiative

Fast growing arsenic menace is causing serious health hazards in Bihar, India, with an estimated 10 million people at risk. The exposed population is often unaware of the problem, which only amplifies the burden of arsenic health effects. In the present study, we have assessed the current situation of arsenic exposure in Chapar village of Samastipur district, Bihar. The health of the inhabitants was assessed and correlated with (1) arsenic concentrations in the groundwater of individual wells and (2) arsenic concentration found in their hair and urine. Altogether, 113 inhabitants were assessed, and 113 hair, urine and groundwater samples were collected. The health study reveals that the exposure to arsenic has caused serious health hazard amongst the exposed population with pronounced skin manifestations, loss of appetite, anaemia, constipation, diarrhoea, general body weakness, raised blood pressure, breathlessness, diabetes, mental disabilities, diabetes, lumps in the body and few cancer incidences. It was found that 52% of the total collected groundwater samples had arsenic levels higher than the WHO limit of 10 µg/l (with a maximum arsenic concentration of 1212 µg/l) and the reduced arsenite was the predominant form in samples tested for speciation (N = 19). In the case of hair samples, 29% of the samples had arsenic concentrations higher than the permissible limit of 0.2 mg/kg, with a maximum arsenic concentration of 46 µg/l, while in 20% exposed population, there was significant arsenic contamination in urine samples > 50 µg/l. In Chapar village, the probability of carcinogenic-related risk in the exposed population consuming arsenic contaminated water is 100% for children, 99.1% for females and 97.3% for male subjects. The assessment report shared to the government enabled the village population to receive two arsenic filter units. These units are currently operational and catering 250 households providing arsenic-free water through piped water scheme. This study therefore identified a significant solution for this arsenic-exposed population.

Application of fingernail samples as a biomarker for human exposure to arsenic-contaminated drinking waters

This study evaluated the relationship between arsenic uptake via drinking water ingestion and arsenic concentration in fingernails as a biomarker for human exposure. For this purpose, we collected fingernail samples from 40 healthy participants of arsenic-affected rural regions of Kaboudrahang County, the west of Iran. A total of 49 fingernail samples were also collected from individuals who lived in areas where contamination of drinking water sources with arsenic had not been reported. It was found that the fingernails arsenic contents in 50 and 4.08% of the samples collected from arsenic-contaminated and reference villages were higher than the normal arsenic values of nails (0.43-1.08 µg/g), respectively. Based on the results of adjusted multiple linear regression, a significant association was found between groundwater and fingernails arsenic concentration (p < 0.001). Moreover, a statistically significant association was shown between arsenic in the fingernail samples and gender (p = 0.037). Fingernails arsenic contents were not significantly affected by other variables including age, smoking habits, and BMI (p > 0.05). In light of the results of this study, the use of biological indicators such as fingernail tissues due to easier sampling and less risk of external contamination is suitable for assessing exposure to heavy metals in contaminated areas.

Usage of Si, P, Se, and Ca Decrease Arsenic Concentration/Toxicity in Rice, a Review

Rice is one of the most important routes for arsenic to enter the human food chain and threatens more than half of the world’s population. In addition, arsenic-contaminated soils and waters increase the concentration of this element in various tissues of rice plants. Thus, direct or indirect—infecting livestock and poultry—increase diseases such as respiratory diseases, gastrointestinal tract, liver, and cardiovascular diseases, cancer, and ultimately death in the long term. Therefore, finding different ways to reduce the uptake and transfer of arsenic by rice would reduce the contamination of rice plants with this dangerous element and improve animal and human nutrition and ultimately disease and mortality. In this article, we aim to take a small step in improving sustainable life on earth by referring to the various methods that researchers have taken to reduce rice contamination by arsenic in recent years. Adding micronutrients and macronutrients as fertilizer for rice is one way to improve this plant’s growth and health. In this study, by examining two types of macronutrients and two types of micronutrients, their role in reducing arsenic toxicity and absorption was investigated. Therefore, both calcium and phosphorus were selected from the macronutrients, and selenium and silicon were selected from the micronutrients, whose roles in previous studies had been investigated.

Bacteria responsible for antimonite oxidation in antimony-contaminated soil revealed by DNA-SIP coupled to metagenomics

Antimony (Sb), the analog of arsenic (As), is a toxic metalloid that poses risks to the environment and human health. Antimonite (Sb(III)) oxidation can decrease Sb toxicity, which contributes to the bioremediation of Sb contamination. Bacteria can oxidize Sb(III), but the current knowledge regarding Sb(III)-oxidizing bacteria (SbOB) is limited to pure culture studies, thus underestimating the diversity of SbOB. In this study, Sb(III)-oxidizing microcosms were set up using Sb-contaminated rice paddies as inocula. Sb(III) oxidation driven by microorganisms was observed in the microcosms. The increasing copies and transcription of the arsenate-oxidizing gene, aioA, in the microcosms during biotic Sb(III) oxidation indicated that microorganisms mediated Sb(III) oxidation via the aioA genes. Furthermore, a novel combination of DNA-SIP and shotgun metagenomic was applied to identify the SbOB and predict their metabolic potential. Several putative SbOB were identified, including Paracoccus, Rhizobium, Achromobacter and Hydrogenophaga. Furthermore, the metagenomic analysis indicated that all of these putative SbOB contained aioA genes, confirming their roles in Sb(III) oxidation. These results suggested the concept of proof of combining DNA-SIP and shotgun metagenomics directly. In addition, the identification of the novel putative SbOB expands the current knowledge regarding the diversity of SbOB.

Arsenic exposure in Indo Gangetic plains of Bihar causing increased cancer risk

Reportedly, 300 million people worldwide are affected by the consumption of arsenic contaminated groundwater. India prominently figures amongst them and the state of Bihar has shown an upsurge in cases affected by arsenic poisoning. Escalated arsenic content in blood, leaves 1 in every 100 human being highly vulnerable to being affected by the disease. Uncontrolled intake may lead to skin, kidney, liver, bladder, or lung related cancer but even indirect forms of cancer are showing up on a regular basis with abnormal arsenic levels as the probable cause. But despite the apparent relation, the etiology has not been understood clearly. Blood samples of 2000 confirmed cancer patients were collected from pathology department of our institute. For cross-sectional design, 200 blood samples of subjects free from cancer from arsenic free pockets of Patna urban agglomeration, were collected. Blood arsenic levels in carcinoma patients as compared to sarcomas, lymphomas and leukemia were found to be higher. The geospatial map correlates the blood arsenic with cancer types and the demographic area of Gangetic plains. Most of the cancer patients with high blood arsenic concentration were from the districts near the river Ganges. The raised blood arsenic concentration in the 2000 cancer patients strongly correlates the relationship of arsenic with cancer especially the carcinoma type which is more vulnerable. The average arsenic concentration in blood of the cancer patients in the Gangetic plains denotes the significant role of arsenic which is present in endemic proportions. Thus, the study significantly correlates and advocates a strong relation of the deleterious element with the disease. It also underlines the need to address the problem by deciphering the root cause of the elevated cancer incidences in the Gangetic basin of Bihar and its association with arsenic poisoning.

Assessing inorganic arsenic in rice and its health risk to consumers in Ho Chi Minh City, Vietnam

Purpose

The consumption of rice that contains high levels of inorganic arsenic may cause human health risk. This study aims to determine As species concentrations, particularly iAs, in raw rice in Ho Chi Minh (HCM) City and its health risks.

Design/methodology/approach

A total of 60 polished raw composite samples of rice were purchased from traditional markets and supermarkets in HCM City. All samples were analyzed by HPLC-ICPMS for As species determination.

Findings

Mean concentrations of inorganic arsenic in all samples, which were purchased from supermarket and traditional market, were 88.8 µg/kg and 80.6 µg/kg, respectively. Overall, inorganic arsenic level was 84.7 µg/kg and contributed the highest proportion of arsenic species in rice with 67.7%. The proportion profiles for arsenic species were: As (III) (60 %); dimethylarsinic acid (32.2 %); As (V) (7.7 %) and methylarsonic acid (0.1 %). Inorganic arsenic level in raw rice was below the recommendation of World Health Organization. Using the benchmark dose recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), all exposure doses were lower than BMDL05. However, as the doses ranged from 3.0 to 8.6 of Margin of Exposure (MOE), the health risk of iAs from rice consumption remains public health concern.

Originality/value

The study results report on the surveillance data of the presence of inorganic arsenic in raw rice products, which are available in the supermarkets and traditional markets, and its health risk to consumers in a metropolitan city in Vietnam.

Geographical variation of arsenic distribution in paddy soil, rice and rice-based products: A meta-analytic approach and implications to human health

Arsenic is considered as ubiquitous toxic element belonging to the highest health hazard category. Wide ranges of natural as well as anthropogenic activities are subject to create global arsenic distribution in the broad sense. Rice is the major staple food consumed by world's population on the maximum scale. Growing environment of rice typically attributed by geographical origin may influence on arsenic bioavailability in rice grain. Over exploitation of arsenic contaminated, groundwater resources have recognised as major concern in agricultural perspective for rice production. On the other hand, biogeochemical weathering of arsenic bearing rocks as the geogenic origin, mining activities and application arsenical pesticides are recognised to be well known factors responsible to increase the soil arsenic level. Transfer of arsenic into rice is rightly acquainted from these possible sources of contamination in different regions around the world. Consequently, such substantial geographical variation reflects bioavailability as well as speciation of arsenic in rice. In this manuscript, we discuss the contribution of different arsenic entering pathways in soil-rice systems from regional variability. Furthermore, we attempted to apply the meta-analysis in order to predict the comparative risk assessment on distribution pattern of total and inorganic arsenic in rice commercialised from various rice producing regions of Asia, Europe and US by considering a selected number of data set an extensive range of market basket and field survey. In addition, we finally focus on health risk assessment associated by the consumption of rice and rice-based infant products as the dietary intake from the different of origin. Furthermore, we must detect and categorize the possible source of contamination, which may critically enhance the bioavailability of arsenic in rice in order to minimize the risk. These are the major aspects reviewed here.

Acetyl-L-Carnitine Attenuates Arsenic-Induced Oxidative Stress and Hippocampal Mitochondrial Dysfunction

Augmentation of mitochondrial oxidative stress through activating a series of deadly events has implicated as the main culprit of arsenic toxicity and therapeutic approaches based on improving mitochondrial function hold a great promise for attenuating the arsenic-induced toxicity. Acetyl-L-carnitine (ALC) through balancing the coenzyme A (CoA)/acyl-CoA ratio plays an important role in mitochondrial metabolism and thereby can help protect hippocampal neurons from oxidative damage. In the present study, we aimed to explore the effect of arsenic interactions on the mitochondrial function in the hippocampus of rats. Rats were randomly divided into five groups of control (distilled water), sodium arsenite (NaAsO₂, 20 mg/kg), and co-treatment of NaAsO₂ with various doses of ALC in three groups (100, 200, 300 mg/kg) and were treated orally for 21 consecutive days. Our results point out that arsenic exposure caused oxidative stress in rats' hippocampus, which led to the reactive oxygen species (ROS) generation, mitochondrial swelling, the collapse of the mitochondrial membrane potential, and release of cytochrome c. It also altered Bcl-2/Bax expression ratio and increased caspase-3 and caspase-9 activities. Furthermore, arsenic exposure via activation of NF-κB and microglia increased inflammation. ALC could concentration-dependently counteract the arsenic-induced oxidative stress, modulate the antioxidant defense capacity, and improve mitochondrial functions. In addition, ALC decreased the expression of both death-associated proteins and of inflammatory markers. These findings indicate that ALC improved the arsenic-induced hippocampal mitochondrial dysfunction which underlines the importance of ALC in providing a possible therapeutic strategy for the prevention of arsenic-induced neurodegeneration.

An alternative analytical method for determining arsenic species in rice by using ion chromatography and inductively coupled plasma-mass spectrometry

Qualitative and quantitative determination of total arsenic content and arsenic species in rice is very important because rice is one of the main sources of human arsenic intake. However, extraction and determination of arsenic species in rice has been very difficult due to severe matrix interference. An alternative analytical method was developed in this study to determine arsenic species in rice by using ion chromatography coupled to inductively coupled plasma-mass spectrometry. Two internal standards were used. The first internal standard was injected before sample introduction to correct signal change with time. The second internal standard was spiked into the sample to reduce matrix interference. Using the developed method, recoveries of dimethylarsinic acid, monomethylarsonic acid, and inorganic arsenic compared to certified values (NIST SRM 1568b rice flour) were 116%, 107%, and 92%, respectively.

Thiolated arsenic in natural systems: What is current, what is new and what needs to be known

Thiolated arsenic compounds are the sulfur analogous substructures of oxo-arsenicals as the arsinoyl (As = O) is substituted by an arsinothioyl (As = S) group. Relatively brief history of thioarsenic research, mostly in the current decade has endeavored to understand their consequences in the natural environment. However, thioarsenic related aspects have by far not attached much research concern on global scale compared to other arsenic species. This review attempts to provide a critical overview for the first time on formation mechanisms of thioarsenicals, their chemistry, speciation and analytical methodologies in order to provide a rational assessment of what is new, what is current, what needs to be known or what should be done in future research. Thioarsenic compounds play a vital role in determining the biogeochemistry of arsenic in sulfidic environments under reducing conditions. Thioarsenic species are widely immobilized by naturally occurring processes such as the adsorption on iron (oxyhydr)oxides and precipitation on iron sulfide minerals. Accurate measurement of thioarsenic species is a challenging task due to their instability upon pH, temperature, redox potential, and concentrations of oxygen, sulfur and iron. Assessment of direct and indirect effects of toxic thioarsenic species on global population those who frequently get exposed to high levels of arsenic is an urgent necessity. Dimethylmonothioarsinic acid (DMMTA^V) is the most cytotoxic arsenic metabolite having similar toxicological effects as dimethylarsinous acid (DMA^III) in human and animal tissues. The formation and chemical analysis of thioarsenicals in soil and sediments are highly unknown. Therefore, future research needs to be more inclined towards in determining the molecular structure of unknown thioarsenic complexes in various environmental suites. Contemporary approaches hyphenated to existing technologies would pave the way to overcome critical challenges of thioarsenic speciation such as standards synthesis, structural determination, quantification and sample preservation in future research.

Review of interactions between phosphorus and arsenic in soils from four case studies

Arsenic is a non-essential element that poses risks in many environments, including soil, groundwater, and surface water. Insights into the environmental biogeochemistry of As can be gained by comparing As and P reaction processes. Arsenic and P are chemical analogues, and it is proposed that they have similar chemical behaviors in environmental systems. However some chemical properties of As and P are distinct, such as redox reactions, causing the biogeochemical behavior of the two elements to differ. In the environment, As occurs as either As(V) or As(III) oxyanions (e.g., AsO₄^3- or AsO₃^3-). In contrast, P occurs predominantly as oxidation state five plus; most commonly as the orthophosphate ion (PO₄^3-). In this paper, data from four published case studies are presented with a focus on P and As distribution and speciation in soil. The goal is show how analyzing P chemistry in soils can provide greater insights into As reaction processes in soils. The case studies discussed include: (1) soil developed from shale parent material, (2) mine-waste impacted wetland soils, (3) phosphate-amended contaminated soil, and (4) plants grown in biochar-amended, mine-contaminated soil. Data show that while P and As have competitive reactions in soils, in most natural systems they have distinct biogeochemical processes that create differing mobility and bioavailability. These processes include redox reactions and rhizosphere processes that affect As bioavailability. Results from these case studies are used as examples to illustrate how studying P and As together allows for enhanced interpretation of As biogeochemical processes in soils.

Concentrations of inorganic arsenic in groundwater, agricultural soils and subsurface sediments from the middle Gangetic plain of Bihar, India

Concentrations of inorganic forms [arsenite, As(III) and arsenate, As(V) of arsenic (As) present in groundwater, agricultural soils and subsurface sediments located in the middle Gangetic plain of Bihar, India were determined. Approximately 73% of the groundwater samples (n=19) show As(III) as the dominant species while 27% reveals As(V) was the dominant species. The concentration of As(III) in agricultural soil samples varies from not detectable to 40μg/kg and As(V) was observed as the major species (ranging from 1050 to 6835μg/kg) while the total As concentration varied from 3528 to 14,690μg/kg. Total extracted concentration of As was higher in the subsurface sediments (range 9119-20,056μg/kg in Methrapur and 4788-19,681μg/kg in Harail Chapar) than the agricultural soil, indicating the subsurface sediment as a source of As. Results of X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) revealed the presence of hematite and goethite throughout the vertical section below while magnetite was observed only in the upper oxidized layer at Methrapur and Harail Chapar. Alteration of Fe-oxides and presence of fibrous goethite indicating presence of diagenetic sediment. Siderite plays a crucial role as sinks to the As in subsurface sediments. The study also concluded that decomposition of organic matter present in dark and grey sections promote the redox conditions and trigger mobilization of As into groundwater.

Thiolated arsenicals in arsenic metabolism: Occurrence, formation, and biological implications

Arsenic (As) is a notoriously toxic pollutant of health concern worldwide with potential risk of cancer induction, but meanwhile it is used as medicines for the treatment of different conditions including hematological cancers. Arsenic can undergo extensive metabolism in biological systems, and both toxicological and therapeutic effects of arsenic compounds are closely related to their metabolism. Recent studies have identified methylated thioarsenicals as a new class of arsenic metabolites in biological systems after exposure of inorganic and organic arsenicals, including arsenite, dimethylarsinic acid (DMA^V), dimethylarsinous glutathione (DMA^IIIGS), and arsenosugars. The increasing detection of thiolated arsenicals, including monomethylmonothioarsonic acid (MMMTA^V), dimethylmonothioarsinic acid (DMMTA^V) and its glutathione conjugate (DMMTA^VGS), and dimethyldithioarsinic acid (DMDTA^V) suggests that thioarsenicals may be important metabolites and play important roles in arsenic toxicity and therapeutic effects. Here we summarized the reported occurrence of thioarsenicals in biological systems, the possible formation pathways of thioarsenicals, and their toxicity, and discussed the biological implications of thioarsenicals on arsenic metabolism, toxicity, and therapeutic effects.

Arsenic groundwater contamination and its health effects in Patna district (capital of Bihar) in the middle Ganga plain, India

We investigated the extent and severity of groundwater arsenic (As) contamination in five blocks in Patna district, Bihar, India along with As in biological samples and its health effects such as dermatological, neurological and obstetric outcome in some villages. We collected 1365 hand tube-well water samples and analyzed for As by the flow injection hydride generation atomic absorption spectrometer (FI-HG-AAS). We found 61% and 44% of the tube-wells had As above 10 and 50 μg/l, respectively, with maximum concentration of 1466 μg/l. Our medical team examined 712 villagers and registered 69 (9.7%) with arsenical skin lesions. Arsenical skin lesions were also observed in 9 children of 312 screened. We analyzed 176 biological samples (hair, nail and urine). Out of these, 69 people had arsenical skin lesions and rest without skin lesions. We found 100% of the biological samples had As above the normal levels (concentrations of As in hair, nail and urine of unexposed individuals usually ranges from 20 to 200 μg/kg, 20-500 μg/kg and <100 μg/l, respectively), indicating many people are sub-clinically affected. Arsenical neuropathy was observed in 40.5% of 37 arsenicosis patients with 73.3% prevalence for predominant sensory neuropathy and 26.7% for sensor-motor. Among patients, different clinical and electrophysiological neurological features and abnormal quantitative sensory perception thresholds were also noted. The study also found that As exposed women with severe skin lesions had adversely affected their pregnancies. People including children in the affected areas are in danger. To combat As situation in affected areas, villagers urgently need (a) provision of As-safe water for drinking and cooking, (b) awareness about the danger of As toxicity, and (c) nutritious food.

Arsenic contamination of groundwater and its induced health effects in Shahpur block, Bhojpur district, Bihar state, India: risk evaluation

The objective of this study was to determine the magnitude of groundwater arsenic contamination in Shahpur block of Bhojpur district, Bihar state, India and its health effects such as dermal, neurological, obstetric effects, and cancer risk. The School of Environmental Studies (SOES) collected 4704 tube-well water samples from all 88 villages of Shahpur, which were analyzed for arsenic. We found 40.3 and 21.1 % of the tube-wells had arsenic above 10 and 50 μg/l, respectively, with maximum concentration of 1805 μg/l. The study shows that 75,000, 39,000, and 10,000 people could be exposed to arsenic-contaminated water greater than 10, 50, and 300 μg/l, respectively. Our medical team examined 1422 villagers from Shahpur and registered 161 (prevalence rate, 11.3 %) with arsenical skin lesions. Arsenical skin lesions were also observed in 29 children of 525 screened. We analyzed 579 biological samples (hair, nail, and urine) from Shahpur and found that 82, 89, and 91 % of hair, nail, and urine, respectively, had arsenic above the normal levels, indicating many people in the study area are sub-clinically affected. Arsenical neuropathy was observed in 48 % of 102 arsenicosis patients. The study also found that arsenic exposed women with severe skin lesions had adversely affected their pregnancies. The carcinogenic and non-carcinogenic risks were also estimated based on the generated data. Safe drinking water supply is urgently required to combat arsenic situation in affected villages of Shahpur.

Arsenic speciation in rice and risk assessment of inorganic arsenic in Taiwan population

This study assessed the total arsenic content and arsenic speciation in rice to determine the health risks associated with rice consumption in various age-gender subgroups in Taiwan. The average total arsenic levels in white rice and brown rice were 116.6 ± 39.2 and 215.5 ± 63.5 ng/g weight (n = 51 and 13), respectively. The cumulative cancer risk among males was 10.4/100,000. The highest fraction of inorganic/total arsenic content in white rice ranged from 76.9 to 88.2 % and from 81.0 to 96.5 % in brown rice. The current study found different arsenic speciation of rice in southern Taiwan, where the famous blackfoot disease has been reported compared with arsenic speciation from other Taiwan areas. Therefore, rice and other grains should be further monitored in southern Taiwan to evaluate whether arsenic contamination is well controlled in this area.

Arsenic and other elements in drinking water and dietary components from the middle Gangetic plain of Bihar, India: Health risk index

This study investigates the level of contamination and health risk assessment for arsenic (As) and other elements in drinking water, vegetables and other food components in two blocks (Mohiuddinagar and Mohanpur) from the Samastipur district, Bihar, India. Groundwater (80%) samples exceeded the World Health Organization (WHO) guideline value (10μg/L) of As while Mn exceeded the previous WHO limit of 400μg/L in 28% samples. The estimated daily intake of As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn from drinking water and food components were 169, 19, 26, 882, 4645, 14582, 474, 1449 and 12,955μg, respectively (estimated exposure 3.70, 0.41, 0.57, 19.61, 103.22, 324.05, 10.53, 32.21 and 287.90μg per kg bw, respectively). Twelve of 15 cooked rice contained high As concentration compared to uncooked rice. Water contributes (67%) considerable As to daily exposure followed by rice and vegetables. Whereas food is the major contributor of other elements to the dietary exposure. Correlation and principal component analysis (PCA) indicated natural source for As but for other elements, presence of diffused anthropogenic activities were responsible. The chronic daily intake (CDI) and health risk index (HRI) were also estimated from the generated data. The HRI were >1 for As in drinking water, vegetables and rice, for Mn in drinking water, vegetables, rice and wheat, for Pb in rice and wheat indicated the potential health risk to the local population. An assessment of As and other elements of other food components should be conducted to understand the actual health hazards caused by ingestion of food in people residing in the middle Gangetic plain.

Analytical Strategies for the Determination of Arsenic in Rice

Arsenic is an element of concern given its toxicological significance, even at low concentrations. Food is a potential route of exposure to inorganic arsenic and in this regard arsenic in rice is associated with soil contamination, fertilizer application, and the use of arsenic-containing irrigation water. Therefore, there is a need to investigate the regional rice crops with a view to future discussions on the need for possible regulatory measures. Several studies have reported high concentrations of arsenic in rice grown in soils irrigated with contaminated water; however, procedures used, including sample pretreatment and preconcentration steps, have to be followed to ensure sensitivity, accuracy, and reproducibility. Arsenic is a difficult element to measure in complex matrices, such as foods, because the matrix must be destroyed at an elevated temperature without the loss of the analyte or contamination. This review summarizes the major methods for the determination of arsenic in rice samples. The main purpose of this review is to provide an update on the recent literature concerning the strategies for the determination of arsenic and to critically discuss their advantages and weaknesses. These difficulties are described along with recent developments aimed at overcoming these potential issues.

Arsenic levels from different land-use settings in Pakistan: Bio-accumulation and estimation of potential human health risk via dust exposure

The present study aims at assessing arsenic (As) levels in outdoor dust and human exposure risks at different land use setting (i.e., rural, industrial, urban) from Punjab, Pakistan. The results showed higher As concentrations (mg/kg) in all the sample types ( i.e., dust, hair and nail) collected from industrial sites (9.78, 2.36, 2.5) followed by urban (7.59, 0.38, 0.88) and rural sites (6.95, 0.52, 1.12), respectively. In the current study, we also carried out human risk assessment via contaminated dust exposure, which suggested that dust ingestion is the major route of As contamination for the associated population, followed by the inhalation and dermal contact, at all studied land use settings. Hazard Index (HI) calculated for non-carcinogenic health risks for adults showed higher values at industrial (0.65) and urban (0.53) sites, which reflected that dust exposure is the major contributing source of human arsenic burden and may pose several adverse health effects. Carcinogenic risk values showed that at industrial areas the risk of carcinogenesis to the associated population is mainly due to As contaminated dust exposure. Hair (60%) and nail samples (70%) collected from industrial land use were found above the WHO threshold limit of 1mg/kg, suggested high risks for human health in the studied area. The results of the present study would be useful for assessing the human health risks due to arsenic contamination via dust exposure in different parts of country.

Arsenic toxicity in rice with special reference to speciation in Indian grain and its implication on human health

BACKGROUND

Rice is a potentially important route of human exposure to arsenic, especially in populations with rice-based diets. However, arsenic toxicity varies greatly with species. The initial purpose of the present study was to evaluate arsenic speciation in rice.

RESULTS

It appeared very clear from the present study that inorganic arsenic shared maximum arsenic load in rice straw while in grains it is considerably low. As species recovered from rice grain and straw are principally As(III) and As(V) with a small amount of dimethylarsenic acid (DMA) and almost non-detectable monomethylarsonic acid (MMA) and arsenobetain (AsB). Discussion of the health risk of As in rice has largely been based on its inorganic arsenic content because these species have generally been considered to be more toxic than MMA and DMA and can be directly compared to As in drinking water, assuming equal bioavailability of inorganic As in the rice matrix and in water. The maximum dietary risk of exposure to inorganic arsenic through transplanted boro paddy in the present experiment was calculated to be almost 1706% of the provisional tolerable weekly intake for an adult of 60 kg body weight.

CONCLUSION

As species recovered from boro rice grain and straw are principally As(III) and As(V) with a small amount of DMA and almost non-detectable MMA and AsB. Reductions in total As load through organic amendments in boro rice grain and straw samples were manifested predominately through reduced accumulations of inorganic As species [As(III) and As(V)], between which As(V) accounted for the larger share.

Di-oxime based selective fluorescent probe for arsenate and arsenite ions in a purely aqueous medium with living cell imaging applications and H-bonding induced microstructure formation

A 2-hydroxy-5-methyl-benzene-1,3-dicarboxaldehyde di-oxime based turn-on blue emission fluorescent probe was found to recognize both AsO₂⁻ and H₂AsO₄⁻ in a purely aqueous medium in intra and extra-cellular conditions.

Westernized diets lower arsenic gastrointestinal bioaccessibility but increase microbial arsenic speciation changes in the colon

Arsenic (As) is an important contaminant present in food and water. Several studies have indicated that the occurrence of As based skin lesions is significantly different when root and gourd rich diets are consumed compared to meat rich diets. Additionally, urinary As speciation from orally exposed individuals appears to depend on the composition of the diet. These observations imply that diet composition can affect both the bioavailable As fraction as the As speciation in the body. In this study, we used the in vitro gastrointestinal method (IVG) to evaluate how an Asian type diet (fiber rich) and a Western type diet (fat and protein rich), differ in their capability to release inorganic As (iAs(V)) and dimethyl arsinate (DMA(V)) from a rice matrix following gastrointestinal digestion. Moreover, we used a validated dynamic gut simulator to investigate whether diet background affects As metabolism by gut microbiota in a colon environment. An Asian diet background resulted in a larger As bioaccessibility (81.2%) than a Western diet background (63.4%). On the other hand, incubation of As contaminated rice with human colon microbiota in the presence of a Western type diet resulted in a larger amount of hazardous As species - monomethyl arsonite and monomethylmonothio arsonate - to be formed after 48 h. The permeability of these As species (60.5% and 50.5% resp.) across a Caco-2 cell line was significantly higher compared to iAs(V) and DMA(V) (46.5% and 28% resp.). We conclude that dietary background is a crucial parameter to incorporate when predicting bioavailability with bioaccessibility measurements and when assessing health risks from As following oral exposure.

Arsenic accumulation in maize crop (Zea mays): a review

Arsenic (As) is a metalloid that may represent a serious environmental threat, due to its wide abundance and the high toxicity particularly of its inorganic forms. The use of arsenic-contaminated groundwater for irrigation purposes in crop fields elevates the arsenic concentration in topsoil and its phytoavailability for crops. The transfer of arsenic through the crops-soil-water system is one of the more important pathways of human exposure. According to the Food and Agriculture Organization of the United Nations, maize (Zea mays L.) is the most cultivated cereal in the world. This cereal constitutes a staple food for humans in the most of the developing countries in Latin America, Africa, and Asia. Thus, this review summarizes the existing literature concerning the conditions involved in agricultural soil that leads to As influx into maize crops and the uptake mechanisms, metabolism and phytotoxicity of As in corn plants. Additionally, the studies of the As accumulation in raw corn grain and corn food are summarized, and the As biotransfer into the human diet is highlighted. Due to high As levels found in editable plant part for livestock and humans, the As uptake by corn crop through water-soil-maize system may represent an important pathway of As exposure in countries with high maize consumption.

A simple spectrophotometric method for the determination of arsenic in industrial and environmental samples using 2,4-Dihydroxy benzophenone-2-amino thiophenol

2,4-Dihydroxy benzophenone-2-amino thiophenol (BPBT) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of arsenic. The reagent reacts with arsenic in acidic medium (pH=6.0, sodium acetate-acetic acid buffer) to form light greenish yellow colored 1:1 (M:L) complex. Maximum absorbance was obtained at 343 nm and remains constant for over 24 h. The molar absorptivity and Sandell's sensitivity of BPBT are found to be 6.01×10(4) L mol(-1)cm(-1) and 0.0016 μg cm(-2) respectively. The system obeys Beer's law in the range of 0.125-2.637 μg/ml of As (III). Since BPBT method is more sensitive, it was applied for the determination of arsenic in some environmental water samples.

Efficacy of indigenous soil microbes in arsenic mitigation from contaminated alluvial soil of India

Selected arsenic-volatilizing indigenous soil bacteria were isolated and their ability to form volatile arsenicals from toxic inorganic arsenic was assessed. Approximately 37 % of AsIII (under aerobic conditions) and 30 % AsV (under anaerobic conditions) were volatilized by new bacterial isolates in 3 days. In contrast to genetically modified organism, indigenous soil bacteria was capable of removing 16 % of arsenic from contaminated soil during 60 days incubation period while applied with a low-cost organic nutrient supplement (farm yard manure).

Fluorescence sensing of arsenate at nanomolar level in a greener way: naphthalene based probe for living cell imaging

Naphthalene-salisaldehyde conjugate (NAPSAL) is established as a novel arsenate (H2AsO4(-)) selective 'turn-on' fluorescence probe. It can detect as low as 5 × 10(-9) M H2AsO4(-) in HEPES buffered EtOH : water (0.1 M, 1 : 9, v/v, pH 7.4). Trace level H2AsO4(-) in drinking water samples is measured using standard addition method. Intracellular arsenate in Candida albicans, grown in arsenic contaminated water of Purbasthali has successfully been detected under fluorescence microscope.

The Determination of Arsenic Compounds: A Critical Review

A large number of publications describe the determination of arsenic in “environmental” samples in the broadest sense, a substantial subset of which focus on plant-based foodstuffs. There is a considerable interest in the inorganic arsenic content of food, especially rice, as there is recent evidence that concentrations may be high enough to exceed acceptable risk thresholds. The methodology for the determination of arsenic in rice is critically evaluated and results (a) for a rice flour reference material (National Institute of Standards SRM 1568a, certified only for total arsenic) and (b) a recent proficiency test (run by the European Commission's Joint Research Centre Institute for Reference Materials and Measurement) are examined. Difficulties with this particular analysis may lie in the sample preparation stages, over which there is still disagreement with regard to species stability, though a simple, hot-water extraction may be sufficient. High performance liquid chromatography separations with plasma-source mass spectrometry detection are popular; however, chromatographic separations are often not adequately described, the enhancement effect of carbon-containing species is often overlooked, and the fate of chlorine-containing species, responsible for an isobaric overlap interference, often obscure. Compound-dependent responses, for which there is a plenty of evidence, are almost never acknowledged or discussed.

Application of hyphenated techniques in speciation analysis of arsenic, antimony, and thallium

Due to the fact that metals and metalloids have a strong impact on the environment, the methods of their determination and speciation have received special attention in recent years. Arsenic, antimony, and thallium are important examples of such toxic elements. Their speciation is especially important in the environmental and biomedical fields because of their toxicity, bioavailability, and reactivity. Recently, speciation analytics has been playing a unique role in the studies of biogeochemical cycles of chemical compounds, determination of toxicity and ecotoxicity of selected elements, quality control of food products, control of medicines and pharmaceutical products, technological process control, research on the impact of technological installation on the environment, examination of occupational exposure, and clinical analysis. Conventional methods are usually labor intensive, time consuming, and susceptible to interferences. The hyphenated techniques, in which separation method is coupled with multidimensional detectors, have become useful alternatives. The main advantages of those techniques consist in extremely low detection and quantification limits, insignificant interference, influence as well as high precision and repeatability of the determinations. In view of their importance, the present work overviews and discusses different hyphenated techniques used for arsenic, antimony, and thallium species analysis, in different clinical, environmental and food matrices.

Arsenic in cooked rice: effect of chemical, enzymatic and microbial processes on bioaccessibility and speciation in the human gastrointestinal tract

Rice, used as staple food for half of the world population, can easily accumulate arsenic (As) into its grain, which often leads to As contamination. The health risk induced by presence of As in food depends on its release from the food matrix, i.e., its bioaccessibility. Using an in vitro gastrointestinal simulator, we incubated two types of cooked rice (total As: 0.389 and 0.314 mg/kg). Arsenic bioaccessibility and speciation changes were determined upon gastrointestinal digestion. Washing with deionized water and cooking did not result in changes of As speciation in the rice although the arsenic content dropped by 7.1-20.6%. Arsenic bioaccessibility of the cooked rice in the small intestine ranged between 38 and 57%. Bioaccessibility slightly increased during digestion in the simulated small intestine and decreased with time in the simulated colon. Significant speciation changes were noted in the simulated colon, with trivalent monomethylarsonate (MMA(III)) becoming an important species.