Monomethylarsonous acid (MMA(III)) is more toxic than arsenite in Chang human hepatocytes

Density Functional Theory Calculation May Confirm Arsenic-Thiol Adhesion as the Primary Mechanism of Arsenical Toxicity

Previously, it was believed that methylation was the body's primary method to detoxify inorganic arsenic. However, recent research has shown that the metabolized intermediate known as MMAIII is more toxic than arsenite and arsenate, contradicting a previous understanding. Another important question arises: is arsenical toxicity truly caused by arsenic binding to proteins through arsenic thiol adhesion? Based on the toxicity order of the experiment, with MMAIII being the most toxic, followed by arsenite, arsenate, DMAV, and MMAV, density functional theory (DFT) calculations can provide a straightforward assessment of this issue. Our practice captures all the transition states associated with a specific imaginary-frequency vibration mode, including proton transfer and simultaneous departure of leaving group. We have obtained the energy barriers for five arsenicals reacting with thiol, alcohol, and amine separately. In addition to energetic favorability, the following are the energy barriers for arsenic's reaction with thiol ranked from low to high: MMAIII (25.4 kcal/mol), arsenite (27.7 kcal/mol), arsenate (32.8 kcal/mol), DMAV (36.2 kcal/mol), and MMAV (38.3 kcal/mol). Results show that the toxicity of arsenicals is mainly caused by their reaction with thiol rather than with alcohol or amine, as supported by the trend of decreasing toxicity and increasing energy barriers. Thus, this DFT calculation may confirm the paradigm that arsenic-thiol adhesion is the primary cause of arsenic toxicity in the body.

Urine Self-Sampling Kit Combined with an Automated Preparation-Sampler Device for Convenient and Reliable Analysis of Arsenic Metabolites by HPLC-ICPMS

Speciation analysis of arsenic in urine is essential for the studies of arsenic metabolism and biological effects, but the unstable arsenic species represented by MMAIII and DMAIII pose a huge challenge to analytical accuracy. Herein, a novel urine self-sampling (USS) kit combined with an automated preparation-sampler (APS) device is rationally designed and used for convenient analysis of arsenic metabolites by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS). The subject can collect urine into a sampling vial at home and use a homemade syringe to pump argon to displace oxygen in the vial, thereby inhibiting the oxidation of MMAIII and DMAIII. After USS and transportation, the sampling vial is loaded directly onto the APS device, where the urine sample can be automatically mixed with diluent, filtered, and loaded into HPLC-ICPMS for arsenic speciation analysis under anaerobic conditions. For a single sample, the sampling time and the analysis time are <8 and <18 min, respectively. The recoveries of MMAIII and DMAIII in urine over 24 h at 4 °C are 86 and 67%, surpassing the conventional sampling method by 28 and 67%, respectively. When the APS is coupled to HPLC-ICPMS, the detection limits of AsC, iAsIII, MMAIII, DMAV, MMAV, DMAIII, and iAsV are 0.03-0.10 μg L-1 with precisions of <10%. The present method provides a convenient and reliable tool for the storage and analysis of unstable arsenic species in urine and lays the foundation for studying the metabolic and biological effects of methylated trivalent arsenicals.

Bacterial tolerance and detoxification of cyanide, arsenic and heavy metals: Holistic approaches applied to bioremediation of industrial complex wastes

Cyanide is a highly toxic compound that is found in wastewaters generated from different industrial activities, such as mining or jewellery. These residues usually contain high concentrations of other toxic pollutants like arsenic and heavy metals that may form different complexes with cyanide. To develop bioremediation strategies, it is necessary to know the metabolic processes involved in the tolerance and detoxification of these pollutants, but most of the current studies are focused on the characterization of the microbial responses to each one of these environmental hazards individually, and the effect of co-contaminated wastes on microbial metabolism has been hardly addressed. This work summarizes the main strategies developed by bacteria to alleviate the effects of cyanide, arsenic and heavy metals, analysing interactions among these toxic chemicals. Additionally, it is discussed the role of systems biology and synthetic biology as tools for the development of bioremediation strategies of complex industrial wastes and co-contaminated sites, emphasizing the importance and progress derived from meta-omic studies.

Effects of arsenic exposure on trace element levels in the hippocampus and cortex of rats and their gender differences

BACKGROUND

Exposure to arsenic (As) is a major public health challenge worldwide. Chronic exposure to As can cause various human health effects, including skin diseases, cardiovascular disease, neurological disorders, and cancer. Studies have shown that As exposure can lead to disturbances in the balance of trace elements in the body. Moreover, As readily crosses the blood-brain barrier and can be enriched in the hippocampus and cortex, causing neurotoxic damage. At present, there are few reports on the effect of As on trace element levels in the central nervous system (CNS). Therefore, we sought to explore As-induced neurotoxicity and the effects of As on CNS trace element levels.

METHODS

An As-induced neurological injury model in rats was established by feeding As chow for 90 days of continuous exposure, and 19 elements were detected in the hippocampus and cortex of As-exposed rats by inductively coupled plasma mass spectrometry.

RESULTS

The results showed that the As levels in the hippocampus and cortex of As-exposed rats were significantly higher than those in the control group, The As levels in the cortex were significantly higher than in the hippocampus group. The levels of Cd, Ho, and Rb were increased in the hippocampus and decreased in Au, Ba, Ce, Cs, Pd, Se, Sr, and Tl in the As-exposed group, while the levels of Cd and Rb were increased and Se and Au were decreased in the cortex. Significant gender differences in the effects of As on hippocampal Cd, Ba, Rb, and Sr, and cortical Cd and Mo.

CONCLUSION

It is suggested that elemental imbalance may be a risk factor for developing As toxicity plays a synergistic or antagonistic role in As-induced toxicity and is closely related to As-induced CNS damage.

Two-tiered mutualism improves survival and competitiveness of cross-feeding soil bacteria

Metabolic cross-feeding is a pervasive microbial interaction type that affects community stability and functioning and directs carbon and energy flows. The mechanisms that underlie these interactions and their association with metal/metalloid biogeochemistry, however, remain poorly understood. Here, we identified two soil bacteria, Bacillus sp. BP-3 and Delftia sp. DT-2, that engage in a two-tiered mutualism. Strain BP-3 has low utilization ability of pyruvic acid while strain DT-2 lacks hexokinase, lacks a phosphotransferase system, and is defective in glucose utilization. When strain BP-3 is grown in isolation with glucose, it releases pyruvic acid to the environment resulting in acidification and eventual self-killing. However, when strain BP-3 is grown together with strain DT-2, strain DT-2 utilizes the released pyruvic acid to meet its energy requirements, consequently rescuing strain BP-3 from pyruvic acid-induced growth inhibition. The two bacteria further enhance their collective competitiveness against other microbes by using arsenic as a weapon. Strain DT-2 reduces relatively non-toxic methylarsenate [MAs(V)] to highly toxic methylarsenite [MAs(III)], which kills or suppresses competitors, while strain BP-3 detoxifies MAs(III) by methylation to non-toxic dimethylarsenate [DMAs(V)]. These two arsenic transformations are enhanced when strains DT-2 and BP-3 are grown together. The two strains, along with their close relatives, widely co-occur in soils and their abundances increase with the soil arsenic concentration. Our results reveal that these bacterial types employ a two-tiered mutualism to ensure their collective metabolic activity and maintain their ecological competitive against other soil microbes. These findings shed light on the intricateness of bacterial interactions and their roles in ecosystem functioning.

Mechanisms Associated with Cognitive and Behavioral Impairment Induced by Arsenic Exposure

Arsenic (As) is a metalloid naturally present in the environment, in food, water, soil, and air; however, its chronic exposure, even with low doses, represents a public health concern. For a long time, As was used as a pigment, pesticide, wood preservative, and for medical applications; its industrial use has recently decreased or has been discontinued due to its toxicity. Due to its versatile applications and distribution, there is a wide spectrum of human As exposure sources, mainly contaminated drinking water. The fact that As is present in drinking water implies chronic human exposure to this metalloid; it has become a worldwide health problem, since over 200 million people live where As levels exceed safe ranges. Many health problems have been associated with As chronic exposure including cancer, cardiovascular diseases, gastrointestinal disturbances, and brain dysfunctions. Because As can cross the blood-brain barrier (BBB), the brain represents a target organ where this metalloid can exert its long-term toxic effects. Many mechanisms of As neurotoxicity have been described: oxidative stress, inflammation, DNA damage, and mitochondrial dysfunction; all of them can converge, thus leading to impaired cellular functions, cell death, and in consequence, long-term detrimental effects. Here, we provide a current overview of As toxicity and integrated the global mechanisms involved in cognitive and behavioral impairment induced by As exposure show experimental strategies against its neurotoxicity.

Effects of Dietary Intake of Arsenosugars and Other Organic Arsenic Species on Studies of Arsenic Methylation Efficiency in Humans

Extensive research has used dimethylarsinic acid (DMA) in urine as a marker of arsenic methylation. The premise is that humans methylate inorganic arsenicals to monomethylarsonic acid (MMA) and DMA and excrete these arsenic species into the urine. However, DMA in urine not only comes from the methylation of inorganic arsenic but also could be a result of metabolism of other arsenic species, such as arsenosugars and arsenolipids. Most environmental health and epidemiological studies of arsenic methylation might have overlooked confounding factors that contribute to DMA in urine. Here we critically evaluate reported studies that used methylation indexes, concentration ratios of methylated arsenicals, or the percentage of DMA in urine as markers of arsenic methylation efficiency. Dietary intake of arsenosugars potentially confounds the calculation and interpretation of the arsenic methylation efficiencies. Many studies have not considered incidental dietary intake of arsenosugars, arsenolipids, and other organic arsenic species. Future studies should consider the dietary intake of diverse arsenic species and their potential effect on the urinary concentrations of DMA.

Realgar-Induced Neurotoxicity: Crosstalk Between the Autophagic Flux and the p62-NRF2 Feedback Loop Mediates p62 Accumulation to Promote Apoptosis

Realgar is a traditional Chinese medicine that contains arsenic. It has been reported that the abuse of medicine-containing realgar has potential central nervous system (CNS) toxicity, but the toxicity mechanism has not been elucidated. In this study, we established an in vivo realgar exposure model and selected the end product of realgar metabolism, DMA, to treat SH-SY5Y cells in vitro. Many assays, including behavioral, analytical chemistry, and molecular biology, were used to elucidate the roles of the autophagic flux and the p62-NRF2 feedback loop in realgar-induced neurotoxicity. The results showed that arsenic could accumulate in the brain, causing cognitive impairment and anxiety-like behavior. Realgar impairs the ultrastructure of neurons, promotes apoptosis, perturbs autophagic flux homeostasis, amplifies the p62-NRF2 feedback loop, and leads to p62 accumulation. Further analysis showed that realgar promotes the formation of the Beclin1-Vps34 complex by activating JNK/c-Jun to induce autophagy and recruit p62. Meanwhile, realgar inhibits the activities of CTSB and CTSD and changes the acidity of lysosomes, leading to the inhibition of p62 degradation and p62 accumulation. Moreover, the amplified p62-NRF2 feedback loop is involved in the accumulation of p62. Its accumulation promotes neuronal apoptosis by upregulating the expression levels of Bax and cleaved caspase-9, resulting in neurotoxicity. Taken together, these data suggest that realgar can perturb the crosstalk between the autophagic flux and the p62-NRF2 feedback loop to mediate p62 accumulation, promote apoptosis, and induce neurotoxicity. Realgar promotes p62 accumulation to produce neurotoxicity by perturbing the autophagic flux and p62-NRF2 feedback loop crosstalk.

Chemical transformations of arsenic in the rhizosphere-root interface of Pityrogramma calomelanos and Pteris vittata

Pityrogramma calomelanos and Pteris vittata are cosmopolitan fern species that are the strongest known arsenic (As) hyperaccumulators, with potential to be used in the remediation of arsenic-contaminated mine tailings. However, it is currently unknown what chemical processes lead to uptake of As in the roots. This information is critical to identify As-contaminated soils that can be phytoremediated, or to improve the phytoremediation process. Therefore, this study identified the in situ distribution of As in the root interface leading to uptake in P. calomelanos and P. vittata, using a combination of synchrotron micro-X-ray fluorescence spectroscopy and X-ray absorption near-edge structure imaging to reveal chemical transformations of arsenic in the rhizosphere-root interface of these ferns. The dominant form of As in soils was As(V), even in As(III)-dosed soils, and the major form in P. calomelanos roots was As(III), while it was As(V) in P. vittata roots. Arsenic was cycled from roots growing in As-rich soil to roots growing in control soil. This study combined novel analytical approaches to elucidate the As cycling in the rhizosphere and roots enabling insights for further application in phytotechnologies to remediated As-polluted soils.

Toenail arsenic species and metallome profiles associated with breast, cervical, prostate, and skin cancer prevalence in the Atlantic Partnership for Tomorrow's Health cohort

Introduction

Chronic exposure to arsenic through drinking water has been linked to several cancers. The metabolism of arsenic is thought to play a key role in arsenic-related carcinogenesis as metabolites of varying toxicity are produced and either stored in or excreted from the body. Atlantic Canada has the highest age-standardized incidence rates of all cancers in the country. This may be due to its high levels of environmental arsenic and the prevalence of unregulated private wells for water consumption. Here, we aimed to characterize the profiles of arsenic species and metallome in the toenails of four cancer groups, compare them to healthy participants (N = 338), and assess potential associations between the profiles with cancer prevalence.

Methods

This study employed a case-control design. Toenail samples and questionnaire data from cases (breast, cervical, prostate, and skin cancers) and controls were sourced from the Atlantic Partnership for Tomorrow's Health (PATH) cohort study. The levels of arsenic species were measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) paired with High Performance Liquid Chromatography (HPLC) and total concentrations of metallome (23 metals) were determined by ICP-MS separately. Multivariate analyses were conducted to compare cases with controls within each cancer group.

Results

Arsenic speciation profiles varied by cancer type and were significantly different between cases and controls in the breast (p = 0.0330), cervical (p = 0.0228), and skin (p = 0.0228) cancer groups. In addition, the profiles of metallome (nine metals) were significantly differentiated in the prostate (p = 0.0244) and skin (p = 0.0321) cancer groups, with higher zinc concentrations among cases compared to controls.

Conclusion

History of cancer diagnosis was associated with specific profiles of arsenic species and metallome. Our results indicate that arsenic methylation and zinc levels, as measured in toenails, may be an important biomarker for cancer prevalence. Further research is needed to use toenails as a prognostic measure of arsenic-and other metal-induced cancer.

Association of arsenic exposure and clinical hematological changes during pregnancy: Findings from a prospective Wuhan birth cohort study

BACKGROUND

Animal studies have reported arsenic-induced disturbed erythropoiesis parameters. However, the effects of exposure to arsenic on hematological parameters among pregnant women are unclear.

OBJECTIVES

We aimed to evaluate trimester-specific associations between arsenic metabolites and erythropoietic parameters measured repeatedly during pregnancy.

METHODS

A total of 1945 pregnant women from a birth cohort study were included. We detected arsenic species in urine sampled at each trimester and extracted erythropoietic parameters in different trimesters from the medical records. We used linear regressions with generalized estimating equations (GEEs) to examine the relationship between arsenic metabolites concentrations at different trimesters and erythropoietic parameters. We utilized GEEs to calculate the odds ratio (OR) for anemia during pregnancy.

RESULTS

Adjusted trimester-specific analysis showed that higher monomethylated arsenic (MMA) and %MMA were related to remarkably reduced hemoglobin (Hb) and mean corpuscular hemoglobin (MCH). Additionally, elevated urinary MMA concentration and %MMA in the early trimester were associated with an increased risk of microcytic anemias in the late trimester.

CONCLUSIONS

Our study demonstrated a significant inverse relationship between gestational arsenic exposure and Hb and MCH. Notably, higher MMA and lower methylation capacity to metabolize inorganic arsenic (iAs) in early pregnancy might increase the likelihood of microcytic anemia among pregnant women in late pregnancy.

Negative Impacts of Arsenic on Plants and Mitigation Strategies

Arsenic (As) is a metalloid prevalent mainly in soil and water. The presence of As above permissible levels becomes toxic and detrimental to living organisms, therefore, making it a significant global concern. Humans can absorb As through drinking polluted water and consuming As-contaminated food material grown in soil having As problems. Since human beings are mobile organisms, they can use clean uncontaminated water and food found through various channels or switch from an As-contaminated area to a clean area; but plants are sessile and obtain As along with essential minerals and water through roots that make them more susceptible to arsenic poisoning and consequent stress. Arsenic and phosphorus have many similarities in terms of their physical and chemical characteristics, and they commonly compete to cause physiological anomalies in biological systems that contribute to further stress. Initial indicators of arsenic's propensity to induce toxicity in plants are a decrease in yield and a loss in plant biomass. This is accompanied by considerable physiological alterations; including instant oxidative surge; followed by essential biomolecule oxidation. These variables ultimately result in cell permeability and an electrolyte imbalance. In addition, arsenic disturbs the nucleic acids, the transcription process, and the essential enzymes engaged with the plant system's primary metabolic pathways. To lessen As absorption by plants, a variety of mitigation strategies have been proposed which include agronomic practices, plant breeding, genetic manipulation, computer-aided modeling, biochemical techniques, and the altering of human approaches regarding consumption and pollution, and in these ways, increased awareness may be generated. These mitigation strategies will further help in ensuring good health, food security, and environmental sustainability. This article summarises the nature of the impact of arsenic on plants, the physio-biochemical mechanisms evolved to cope with As stress, and the mitigation measures that can be employed to eliminate the negative effects of As.

Warning system for potential releases of chemical warfare agents from dumped munition in the Baltic Sea

The research aimed to determine the scale of the potential contamination of the southern Baltic by substances from dumped chemical weapons, in the context of applying a strategy for detecting the potential releases of toxic materials. The research included the analysis of total arsenic in sediments, macrophytobenthos, fish, and yperite with derivatives and arsenoorganic compounds in sediments and as an integral part of the warning system the threshold values for arsenic in these matrices were set. Arsenic concentrations in sediments ranged from 11 to 18 mg kg^-1 with an increase to 30 mg kg^-1 in layers dated to 1940-1960, what was accompanied by the detection of triphenylarsine (600 mg kg^-1). The presence of yperite or arsenoorganic-related chemical warfare agents was not confirmed in other areas. Arsenic ranged from 0.14 to 1.46 mg kg^-1 in fish and from 0.8 to 3 mg kg^-1 in macrophytobenthos.

Monomethylarsonous acid binds to Cys-104α and Cys-112β of hemoglobin in acute promyelocytic leukemia patients treated with arsenic trioxide

Arsenic trioxide (As₂O₃) has prominent effect in treating acute promyelocytic leukemia (APL). Identification of arsenic-binding proteins has gained attention for their important biological functions. However, none has been published concerning the binding mechanism of arsenic with hemoglobin (Hb) in APL patients after treatment of As₂O₃. The present study discloses the binding sites of arsenic on Hb in APL patients. Concentrations of inorganic arsenic (iAs), monomethyl arsenic (MMA), and dimethyl arsenic (DMA) in erythrocytes of APL patients were quantified using HPLC-inductively coupled plasma-mass spectroscopy (HPLC-ICP-MS). Hb-bound arsenic was identified by size-exclusion chromatography ICP-MS. The binding sites of arsenic on Hb were determined by mass spectrometry (MS). The concentration trend of arsenic species in erythrocytes of 9 APL patients treated with As₂O₃ was iAs>MMA>DMA, and MMA was the predominant methylated arsenic metabolite. Size-exclusion chromatography separation of free and protein-bound arsenic by simultaneous monitoring of ⁵⁷Fe and ⁷⁵As demonstrated the presence of Hb-bound arsenic. MS information suggested monomethylarsonous (MMA^III) was the dominant arsenic bound to Hb, and further identified that Cys-104α and Cys-112β were two binding sites of MMA^III in Hb. MMA^III binding to Cys-104α and Cys-112β was responsible for arsenic accumulation in erythrocytes of APL patients. This interaction may contribute to understand the therapeutic effect of As₂O₃ as an anticancer drug and its toxicity on APL patients.

Metabolomic changes associated with chronic arsenic exposure in a Bangladeshi population

Chronic exposure to arsenic (As) remains a global public health concern and our understanding of the biological mechanisms underlying the adverse effects of As exposure remains incomplete. Here, we used a high-resolution metabolomics approach to examine how As affects metabolic pathways in humans. We selected 60 non-smoking adults from the Folic Acid and Creatine Trial (FACT). Inorganic (AsIII, AsV) and organic (monomethylarsonous acid [MMAs], dimethylarsinous Acid [DMAs]) As species were measured in blood and urine collected at baseline and at 12 weeks. Plasma metabolome profiles were measured using untargeted high-resolution mass spectrometry. Associations of blood and urinary As with 170 confirmed metabolites and >26,000 untargeted spectral features were modeled using a metabolome-wide association study (MWAS) approach. Models were adjusted for age, sex, visit, and BMI and corrected for false discovery rate (FDR). In the MWAS screening of confirmed metabolites, 17 were associated with ≥1 blood As species (FDR<0.05), including fatty acids, neurotransmitter metabolites, and amino acids. These results were consistent across blood As species and between blood and urine As. Untargeted MWAS identified 423 spectral features associated with ≥1 blood As species. Unlike the confirmed metabolites, untargeted model results were not consistent across As species, with AsV and DMAs showing distinct association patterns. Mummichog pathway analysis revealed 12 enriched metabolic pathways that overlapped with the 17 identified metabolites, including one carbon metabolism, tricarboxylic acid cycle, fatty acid metabolism, and purine metabolism. Exposure to As may affect numerous essential pathways that underlie the well-characterized associations of As with multiple chronic diseases.

The Folic Acid and Creatine Trial: Treatment Effects of Supplementation on Arsenic Methylation Indices and Metabolite Concentrations in Blood in a Bangladeshi Population

BACKGROUND

Chronic arsenic (As) exposure is a global environmental health issue. Inorganic As (InAs) undergoes methylation to monomethyl (MMAs) and dimethyl-arsenical species (DMAs); full methylation to DMAs facilitates urinary excretion and is associated with reduced risk for As-related health outcomes. Nutritional factors, including folate and creatine, influence one-carbon metabolism, the biochemical pathway that provides methyl groups for As methylation.

OBJECTIVE

Our aim was to investigate the effects of supplementation with folic acid (FA), creatine, or the two combined on the concentrations of As metabolites and the primary methylation index (PMI: MMAs/InAs) and secondary methylation index (SMI: DMAs/MMAs) in blood in Bangladeshi adults having a wide range of folate status.

METHODS

In a randomized, double-blinded, placebo (PBO)-controlled trial, 622 participants were recruited independent of folate status and assigned to one of five treatment arms: a) PBO (n = 102 ), b) 400 μ g FA/d (400FA; n = 153 ), c) 800 μ g FA/d (800FA; n = 151 ), d) 3 g creatine/d (creatine; n = 101 ), or e) 3 g  creatine + 400 μ g  of FA / d (creatine + 400 FA ; n = 103 ) for 12 wk. For the following 12 wk, half of the FA participants were randomly switched to the PBO while the other half continued FA supplementation. All participants received As-removal water filters at baseline. Blood As (bAs) metabolites were measured at weeks 0, 1, 12, and 24.

RESULTS

At baseline, 80.3% (n = 489 ) of participants were folate sufficient (≥ 9  nmol / L in plasma). In all groups, bAs metabolite concentrations decreased, likely due to filter use; for example, in the PBO group, blood concentrations of MMAs (bMMAs) (geometric mean ± geometric standard deviation ) decreased from 3.55 ± 1.89 μ g / L at baseline to 2.73 ± 1.74 at week 1. After 1 wk, the mean within-person increase in SMI for the creatine + 400 FA group was greater than that of the PBO group (p = 0.05 ). The mean percentage decrease in bMMAs between baseline and week 12 was greater for all treatment groups compared with the PBO group [400FA: - 10.4 (95% CI: - 11.9 , - 8.75 ), 800FA: - 9.54 (95% CI: - 11.1 , - 7.97 ), creatine: - 5.85 (95% CI: - 8.59 , - 3.03 ), creatine + 400 FA : - 8.44 (95% CI: - 9.95 , - 6.90 ), PBO: - 2.02 (95% CI: - 4.03 , 0.04)], and the percentage increase in blood DMAs (bDMAs) concentrations for the FA-treated groups significantly exceeded that of PBO [400FA: 12.8 (95% CI: 10.5, 15.2), 800FA: 11.3 (95% CI: 8.95, 13.8), creatine + 400 FA : 7.45 (95% CI: 5.23, 9.71), PBO: - 0.15 (95% CI: - 2.85 , 2.63)]. The mean decrease in PMI and increase in SMI in all FA groups significantly exceeded PBO (p < 0.05 ). Data from week 24 showed evidence of a reversal of treatment effects on As metabolites from week 12 in those who switched from 800FA to PBO, with significant decreases in SMI [- 9.0 % (95% CI: - 3.5 , - 14.8 )] and bDMAs [- 5.9 % (95% CI: - 1.8 , - 10.2 )], whereas PMI and bMMAs concentrations continued to decline [- 7.16 % (95% CI: - 0.48 , - 14.3 ) and - 3.1 % (95% CI: - 0.1 , - 6.2 ), respectively] for those who remained on 800FA supplementation.

CONCLUSIONS

FA supplementation lowered bMMAs and increased bDMAs in a sample of primarily folate-replete adults, whereas creatine supplementation lowered bMMAs. Evidence of the reversal of treatment effects on As metabolites following FA cessation suggests short-term benefits of supplementation and underscores the importance of long-term interventions, such as FA fortification. https://doi.org/10.1289/EHP11270.

Reduction of Dimethylarsenate to Highly Toxic Dimethylarsenite in Paddy Soil and Rice Plants

Dimethylarsenate [DMAs(V)] is a common methylated As species in soils and plants and can cause the physiological disorder straighthead disease in rice. Because DMAs(V) is relatively noncytotoxic, we hypothesize that phytotoxicity of DMAs(V) may arise from trivalent dimethylarsenite [DMAs(III)]. DMAs(III) has been detected in human urine samples but not in environmental samples, likely due to its instability under oxic conditions. We first established methods for preservation and detections of DMAs(III) in soil and plant samples. We showed that DMAs(III) was a major As species in soil solution from an anoxic paddy soil. Enrichment cultures for fermentative, sulfate-reducing, and denitrifying bacteria from the paddy soil could reduce DMAs(V) to DMAs(III). Twenty-two strains of anaerobic bacteria isolated from the soil showed some ability to reduce DMAs(V). Rice plants grown in hydroponic culture with DMAs(V) also showed the ability to reduce DMAs(V) to DMAs(III). Rice plants and grains grown in a flooded paddy soil contained both DMAs(V) and DMAs(III); their concentrations were higher in the spikelets with straighthead disease than those without. DMAs(III) was much more toxic to the protoplasts isolated from rice plants than DMAs(V). Taken together, the ability to reduce DMAs(V) to highly toxic DMAs(III) is common to soil anaerobes and rice plants.

Nanocurcumin Restores Arsenic-Induced Disturbances in Neuropharmacological Activities in Wistar Rats

The present study was carried out to examine the ameliorative potential of nanocurcumin against arsenic induced (sub-chronic) alterations in central nervous system in male Wistar rats. Nanocurcumin was synthesised and the hydrodynamic diameter, zeta potential and particle size were~76.60 nm, (-) 30 mV and 95nm, respectively. Experimental rats sub-chronically exposed to sodium (meta) arsenite (As; 10 mg.kg-1; 70 days; p.o) induced significant (p<0.05) reduction in superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione and favoured free radical generation and induced lipid peroxidation in brain tissue. The exposure resulted in significant (p<0.05) decrease in voluntary- and involuntary motor activities and enhanced anxiety levels. However, experimental rats receiving nanocurcumin (15 mg.kg-1; p.o) showed significant (p<0.05) recovery in enzymatic - and non-enzymatic antioxidant defence system and restoration of redox balance and overcome arsenic induced depression in motor activities and elevated anxiety levels. Further, Arsenic induced elevation in pro-inflammatory cytokines, cyclooxygenase-2 activity and prostaglandin-E2 in brain and angiotensin-II levels (plasma) was significantly (p<0.05) ameliorated by nanocurcumin. Additionally, quantitative real -time polymerase chain reaction revealed a fivefold decrease in Nox2 expression in brain following nanocurcumin administration. Thus, the study concludes that nanocurcumin can serve as a potential therapeutic candidate to counter arsenic induced redox imbalance and neuropharmacological disturbances and there exists a vast scope to exploit its utility after appropriate clinical modelling.

Arsenic species and their health risks in edible seaweeds collected along the Chinese coastline

Edible seaweeds with a relatively high total arsenic concentration have been a global concern. As the largest seaweed producer, China contributes about 60 % of the global seaweed production. The present study investigated 20 seaweed species collected from representative seaweed farming sites in the six provinces along the Chinese coastline, of which Saccharina japonica, Undaria pinnatifida, Neopyropia spp., Gracilaria spp., Sargassum fusiforme were listed as the most consumed seaweeds in Food and Agriculture Organization of the United Nations (FAO). The inorganic arsenic (iAs) concentration in most of the seaweeds was below maximum limits (0.3 mg iAs/kg) as seaweed additives for infant food in the National Food Safety Standard of Pollutants in China (GB2762-2017, 2017), except for the species Sargassum, in which the iAs concentration significantly exceeded the limit and ranged from 15.1 to 83.7 mg/kg. Arsenic speciation in 4 cultivated seaweeds grown in both temperate and subtropical zones is reported for the first time. No significant differences in total As and iAs concentration were identified, except slightly higher total As concentration were found in Saccharina japonica growing in the temperate zone. The estimated daily intake (EDI) of toxic iAs via seaweed consumption was generally below the EFSA CONTAM Panel benchmark dose lower confidence limit (0.3 μg/kg bw/day) except for all Sargassum species where the EDI was significantly higher than 0.3 μg/kg bw/day. Moreover, the first-ever reported data on As speciation indicated very high iAs concentrations in Sargassum hemiphyllum and Sargassum henslowianum. To minimize the food chain iAs exposure, reducing both human intake of Sargassum spp. and the used of Sargassum spp. for animal feed is highly recommended. CAPSULE: This study showed that edible seaweed Sargassum spp. consumption may pose a health risk related to inorganic arsenic (iAs) exposure. The risk of iAs exposure via seaweed consumption or livestock is a concern that needs to be monitored. The arsenic accumulation and speciation may be predominantly species-dependent rather than environmental-dependent.

Thermodynamics, Kinetics, and Mechanisms of the Co-Removal of Arsenate and Arsenite by Sepiolite-Supported Nanoscale Zero-Valent Iron in Aqueous Solution

In this study, a newly synthesized sepiolite-supported nanoscale zero-valent iron (S-nZVI) adsorbent was tested for the efficient removal of As(III) and As(V) in aqueous solution. Compared with ZVI nanoparticles, the As(III) and As(V) adsorption abilities of S-nZVI were substantially enhanced to 165.86 mg/g and 95.76 mg/g, respectively, owing to the good dispersion of nZVI on sepiolite. The results showed that the adsorption kinetics were well fitted with the pseudo-second-order model, and the adsorption isotherms were fitted with the Freundlich model, denoting a multilayer chemical adsorption process. The increase in the initial solution pH of the solution inhibited As(III) and As(V) adsorption, but a weaker influence on As(III) than As(V) adsorption was observed with increasing pH. Additionally, the presence of SO₄^2- and NO₃^- ions had no pronounced effect on As(III) and As(V) removal, while PO₄^3- and humic acid (HA) significantly restrained the As(III) and As(V) adsorption ability, and Mg²⁺/Ca²⁺ promoted the As(V) adsorption efficiency. Spectral analysis showed that As(III) and As(V) formed inner-sphere complexes on S-nZVI. As(III) oxidation and As(V) reduction occurred with the adsorption process on S-nZVI. Overall, the study demonstrated a potential adsorbent, S-nZVI, for the efficient removal of As(III) and As(V) from contaminated water.

Natural Dietary Compounds in the Treatment of Arsenic Toxicity

Chronic exposure to arsenic (As) compounds leads to its accumulation in the body, with skin lesions and cancer being the most typical outcomes. Treating As-induced diseases continues to be challenging as there is no specific, safe, and efficacious therapeutic management. Therapeutic and preventive measures available to combat As toxicity refer to chelation therapy, antioxidant therapy, and the intake of natural dietary compounds. Although chelation therapy is the most commonly used method for detoxifying As, it has several side effects resulting in various toxicities such as hepatotoxicity, neurotoxicity, and other adverse consequences. Drugs of plant origin and natural dietary compounds show efficient and progressive relief from As-mediated toxicity without any particular side effects. These natural compounds have also been found to aid the elimination of As from the body and, therefore, can be more effective than conventional therapeutic agents in ameliorating As toxicity. This review provides an overview of the recently updated knowledge on treating As poisoning through natural dietary compounds. This updated information may serve as a basis for defining novel prophylactic and therapeutic formulations.

Maternal serum concentrations of one-carbon metabolism factors modify the association between biomarkers of arsenic methylation efficiency and birth weight

BACKGROUND

Inorganic arsenic (iAs) is a ubiquitous metalloid and drinking water contaminant. Prenatal exposure is associated with birth outcomes across multiple studies. During metabolism, iAs is sequentially methylated to mono- and di-methylated arsenical species (MMAs and DMAs) to facilitate whole body clearance. Inefficient methylation (e.g., higher urinary % MMAs) is associated with increased risk of certain iAs-associated diseases. One-carbon metabolism factors influence iAs methylation, modifying toxicity in adults, and warrant further study during the prenatal period. The objective of this study was to evaluate folate, vitamin B12, and homocysteine as modifiers of the relationship between biomarkers of iAs methylation efficiency and birth outcomes.

METHODS

Data from the Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort (2011-2012)  with maternal urine and cord serum arsenic biomarkers and maternal serum folate, vitamin B12, and homocysteine concentrations were utilized. One-carbon metabolism factors were dichotomized using clinical cutoffs and median splits. Multivariable linear regression models were fit to evaluate associations between each biomarker and birth outcome overall and within levels of one-carbon metabolism factors. Likelihood ratio tests of full and reduced models were used to test the significance of statistical interactions on the additive scale (α = 0.10).

RESULTS

Among urinary biomarkers, % U-MMAs was most strongly associated with birth weight (β = - 23.09, 95% CI: - 44.54, - 1.64). Larger, more negative mean differences in birth weight were observed among infants born to women who were B12 deficient (β = - 28.69, 95% CI: - 53.97, - 3.42) or experiencing hyperhomocysteinemia (β = - 63.29, 95% CI: - 154.77, 28.19). Generally, mean differences in birth weight were attenuated among infants born to mothers with higher serum concentrations of folate and vitamin B12 (or lower serum concentrations of homocysteine). Effect modification by vitamin B12 and homocysteine was significant on the additive scale for some associations. Results for gestational age were less compelling, with an approximate one-week mean difference associated with C-tAs (β = 0.87, 95% CI: 0, 1.74), but not meaningful otherwise.

CONCLUSIONS

Tissue distributions of iAs and its metabolites (e.g., % MMAs) may vary according to serum concentrations of folate, vitamin B12 and homocysteine during pregnancy. This represents a potential mechanism through which maternal diet may modify the harms of prenatal exposure to iAs.

Arsenic in Caribbean bivalves in the context of Sargassum beachings: A new risk for seafood consumers

Sargassum strandings in the coastal environment can introduce arsenic into food webs. In this context, we assessed the risk of exposure to arsenic for consumers of Caribbean bivalves. In 2019, specimens of Asaphis deflorata and Phacoides pectinatus were collected in an Atlantic coastal zone of Martinique (island) to monitor the presence of arsenic species by LC-ICP-MS. The total arsenic (tAs) concentrations were, on average, 34.4 ± 3.8 and 76.9 ± 22.3 µg.g-1 dry weight for P. pectinatus and A. deflorata, respectively. Seven compounds of arsenic were detected in bivalve soft bodies. In P. pectinatus, monomethylarsonic acid was present at a relatively significant concentration (≈ 29.6%). These results were coupled with survey data collected in 2013 and again in 2019, from the main consumers of bivalves. The tAs intake was up to 6 mg.day-1 for a 240 g (wet weight) meal of bivalves. In addition, we proposed toxicological reference doses also based on detected toxic forms of arsenic and tested their relevance. We concluded that monitoring of total arsenic would be sufficient to ensure the protection of bivalve consumers. Consumption patterns expose consumers to a potential health risk. However, due to a decrease in consumption frequency associated with the depletion of bivalve resources by decomposing Sargassum mats, arsenic exposure has decreased. In the French Caribbean, this is the first study on the risk of human arsenic contamination from the ingestion of bivalves. This study is a contribution to the monitoring of arsenic in the Caribbean coastal environment.

Tocopherol Enhances the Antioxidant Defense System and Histomorphometric Parameters in The Gastrointestinal Tract of Rats Treated with Sodium Arsenite

Arsenic compromises the gastrointestinal integrity and function via the body's anti-oxidative system breakdown.  Hence, this study aimed to investigate the effects of tocopherol on redox imbalance and histoarchitectural alterations in rats' gastrointestinal tract exposed to sodium arsenite. Sodium arsenite and graded doses of tocopherol were administered orally into experimental rats assigned to different groups for four weeks concurrently. Redox status assay was done in homogenized samples by spectrophotometry. Parietal cell mass and mucous cell density (stomach), villus height and crypt depth (ileum), goblet cells count, and crypt depth (colon) were evaluated by histomorphometry. Inflammatory cells infiltration was also assessed using a semi-quantitative procedure. Sodium arsenite caused a significant increase in Malondialdehyde and Myeloperoxidase but, decreased Superoxide dismutase, Catalase, Nitric oxide, Glutathione peroxidase, Glutathione, and Glutathione-S-Transferase. Tocopherol treatment reversed the changes (p<0.05) though not largely dose-dependent. Furthermore, tocopherol annulled sodium arsenite-induced increase in parietal cell mass and decrease in mucous cell density in the stomach, decrease in villus height and villus height/crypt depth ratio in the ileum, and decrease in goblets cells and increase in crypt depth in the colon. Moreover, activated inflammatory cell infiltration by sodium arsenite was mitigated by tocopherol. Sodium arsenite provokes not only marked inflammatory cellular infiltration but a focal loss of glands, hyperplasia of crypts, atrophic villi, and hypertrophy of Peyer's patches in the intestines, which are all lessened with tocopherol treatment.  These findings underscore the anti-oxidative properties of tocopherol as a potent dietary factor against sodium arsenite toxicity in the gastrointestinal tract. Keywords: Tocopherol, arsenic, stomach, ileum, colon.

ArsZ from Ensifer adhaerens ST2 is a novel methylarsenite oxidase

Trivalent methylarsenite (MAs(III)) produced by biomethylation is more toxic than inorganic arsenite (As(III)). Hence, MAs(III) has been proposed to be a primordial antibiotic. Other bacteria evolved mechanisms to detoxify MAs(III). In this study, the molecular mechanisms of MAs(III) resistance of Ensifer adhaerens ST2 were investigated. In the chromosome of E. adhaerens ST2 is a gene encoding a protein of unknown function. Here we show that this gene, designated arsZ, encodes a novel MAs(III) oxidase that confers resistance by oxidizing highly toxic MAs(III) to relatively nontoxic MAs(V). Two other genes, arsRK, are adjacent to arsZ but are divergently encoded in the opposite direction. Heterologous expression of arsZ in Escherichia coli confers resistance to MAs(III) but not to As(III). Purified ArsZ catalyzes thioredoxin- and NAPD⁺ -dependent oxidation of MAs(III). Mutational analysis of ArsZ suggests that Cys59 and Cys123 are involved in oxidation of MAs(III). Expression of arsZ, arsR and arsK genes is induced by MAs(III) and As(III), and is likely controlled by the ArsR transcriptional repressor. These results demonstrate that ArsZ is a novel MAs(III) oxidase that contributes to E. adhaerens tolerance to environmental organoarsenicals. The arsZRK operon is widely present in bacteria within the Rhizobiaceae family. This article is protected by copyright. All rights reserved.

Arsenic intake-induced gastric toxicity is blocked by grape skin extract by modulating inflammation and oxidative stress in a mouse model

Arsenic (As) is known to induce toxic responses in many organs of human beings and animals. However, research concerning toxicity in the stomach is limited. In this study, arsenic-induced gastric toxicity was investigated in a mouse model, and grape skin extract (GSE) was confirmed to have protective effects against arsenic toxicity. Our experimental results showed that exposure to 10 mg/l arsenic via drinking water for 56 days caused oxidative damage and inflammatory responses. The H₂O₂ and malondialdehyde (MDA) contents were significantly increased, accompanied by significant decreases in total superoxide dismutase (T-SOD) activity and glutathione (GSH) content in the gastric tissue of arsenic-treated mice. Two inflammatory signalling pathways, i.e., TLR2/MyD88/NF-κB and IL-6/STAT-3, were activated, along with inflammatory cell infiltration and the elevated mRNA expression of pro-inflammatory cytokines (TNF-α, IL-1β and IFN-γ) and myeloperoxidase (MPO) in the gastric tissue of mice exposed to arsenic. Meanwhile, the mRNA levels of the ZO-1, ZO-2 and occludin genes, which encode the key components of tight junction (TJ) complexes, were downregulated. However, the application of GSE (300 mg/kg bw) significantly inhibited the arsenic-induced increases in H₂O₂ and MDA contents and the decreases in T-SOD activity and GSH content. The arsenic-mediated gene expression of pro-inflammatory cytokines (TNF-α, IL-1β and IFN-γ), MPO and IL-6/STAT3 and TLR2/MyD88/NF-κB pathways was found down-regulated. Moreover, the arsenic-induced inflammatory cell infiltration and inhibition of TJ genes transcription were markedly attenuated in the As+GSE (300 mg/kg bw) group. Based on the present findings, arsenic intake appears to cause gastric toxicity via oxidative stress and inflammation, and the application of GSE offers significant protection against arsenic toxicity in a mouse model by attenuating the oxidative stress and inflammatory response. Our results suggest that GSE by oral administration might function as a candidate therapeutic supplement to antagonize arsenic toxicity.

Arsenic 3 methyltransferase (AS3MT) automethylates on cysteine residues in vitro

Arsenic toxicity is a global concern to human health causing increased incidences of cancer, bronchopulmonary, and cardiovascular diseases. In human and mouse, inorganic arsenic (iAs) is metabolized in a series of methylation steps catalyzed by arsenic (3) methyltransferase (AS3MT), forming methylated arsenite (MAsIII), dimethylarsenite (DMAIII) and the volatile trimethylarsine (TMA). The methylation of arsenic is coordinated by four conserved cysteines proposed to participate in catalysis, namely C33, C62, C157, and C207 in mouse AS3MT. The current model consists of AS3MT methylating iAs in the presence of the cofactor S-adenosyl-L-methionine (SAM), and the formation of intramolecular disulfide bonds following the reduction of MAsV to MAsIII. In the presence of endogenous reductants, these disulfide bonds are reduced, the enzyme re-generates, and the second round of methylation ensues. Using in vitro methylation assays, we find that AS3MT undergoes an initial automethylation step in the absence of iAs. This automethylation is enhanced by glutathione (GSH) and dithiothreitol (DTT), suggesting that reduced cysteines accept methyl groups from SAM to form S-methylcysteines. Following the addition of iAs, automethylation of AS3MT is decreased. Furthermore, using a Flag-AS3MT immunoprecipitation coupled to MS/MS, we identify both C33 and C62 as acceptors of the methyl group in vivo. Site-directed mutagenesis (C to A) revealed that three of the previously described cysteines were required for AS3MT automethylation. In vitro experiments show that automethylated AS3MT can methylate iAs in the presence of SAM. Thus, we propose that automethylated may represent an active conformation of AS3MT.

Probabilistic health risk assessment of inorganic arsenic and some heavy metals in rice produced from a typical multi-mining county, China

The potential impact of exposure to toxic elements in rice on human health has become a global public health issue. This study analyzed the pollution characteristics and probabilistic health risks of exposure to iAs, Pb, Cd, Cr, and Hg in rice produced in a typical multi-mining county using Monte Carlo simulation, a geographic information system, and bioavailability analysis. The results showed that the enrichment of As and Cd was prominent in rice, with mean tAs, iAs, and Cd contents of 0.34 ± 0.20, 0.15 ± 0.09, and 0.48 ± 0.50 mg·kg^-1, respectively. The probability of non-carcinogenic risk via rice consumption in adults and children exceeding the threshold was 72% and 78%, respectively, and that of carcinogenic risk was as high as 100%. Among toxic elements, Cd and iAs were the main risk factors for health risks. The high-level health-risk areas mainly occurred in the north-eastern and central parts of the study area. Sensitivity analysis highlighted that the top three influential parameters for non-carcinogenic risk in adults were Content(Cd), Content(iAs), and Bioaccessibility(Cd), whereas those in children were ingestion rate of rice, Content(Cd), and Content(iAs). The Content(Cd) was the decisive factor for carcinogenic risk, with a sensitivity coefficient of 78.0% in adults and 64.7% in children. Considering the high risk of ingestion of local rice in this area, it is imperative to place strict supervision and take control measures.

Quantitative benefit and risk assessment of arsenic and nutrient levels in cooked and raw chinese mitten crab (Eriocheir sinensis) using an in vitro digestion model

The safety and quality of aquatic foods are a public concern due to their content of pollutants, such as arsenic. A formula is derived for quantifying the benefit-risk ratio (HQ) of the essential polyunsaturated fatty acids vs. arsenic in Chinses mitten crabs. Among these arsenic species, the proportion of inorganic arsenic, which is extremely harmful to the human body, is<5%, and its level does not exceed the national standard limit. Meanwhile, comparing with the HQ from the original method, the HQs from groups 0 min, 5 min, 15 min are significantly higher(p < 0.05). This suggests the original assessment method could underestimate the risk of eating crabs. Eating steamed crabs is easier to digest essential fatty acids (EFAs) than eating raw crabs, and it also protects consumers against arsenic exposure. To achieve a good balance of dietary benefits and risks, the steaming duration of the crabs should exceed 30 min.

Global genomic analysis of microbial biotransformation of arsenic highlights the importance of arsenic methylation in environmental and human microbiomes

Arsenic is a ubiquitous toxic element, the global cycle of which is highly affected by microbial redox reactions and assimilation into organoarsenic compounds through sequential methylation reactions. While microbial biotransformation of arsenic has been studied for decades, the past years have seen the discovery of multiple new genes related to arsenic metabolism. Still, most studies focus on a small set of key genes or a small set of cultured microorganisms. Here, we leveraged the recently greatly expanded availability of microbial genomes of diverse organisms from lineages lacking cultivated representatives, including those reconstructed from metagenomes, to investigate genetic repertoires of taxonomic and environmental controls on arsenic metabolic capacities. Based on the collection of arsenic-related genes, we identified thirteen distinct metabolic guilds, four of which combine the aio and ars operons. We found that the best studied phyla have very different combinations of capacities than less well-studied phyla, including phyla lacking isolated representatives. We identified a distinct arsenic gene signature in the microbiomes of humans exposed or likely exposed to drinking water contaminated by arsenic and that arsenic methylation is important in soil and in human microbiomes. Thus, the microbiomes of humans exposed to arsenic have the potential to exacerbate arsenic toxicity. Finally, we show that machine learning can predict bacterial arsenic metabolism capacities based on their taxonomy and the environment from which they were sampled.

Demethylation of the Antibiotic Methylarsenite is Coupled to Denitrification in Anoxic Paddy Soil

Arsenic (As) biomethylation is an important component of the As biogeochemical cycle, which produces methylarsenite [MAs(III)] as an intermediate product. Its high toxicity is used by some microbes as an antibiotic to kill off other microbes and gain a competitive advantage. Some aerobic microbes have evolved a detoxification mechanism to demethylate MAs(III) via the dioxygenase C-As lyase ArsI. How MAs(III) is demethylated under anoxic conditions is unclear. We found that nitrate addition to a flooded paddy soil enhanced MAs(III) demethylation. A facultative anaerobe Bacillus sp. CZDM1 isolated from the soil was able to demethylate MAs(III) under anoxic nitrate-reducing conditions. A putative C-As lyase gene (BcarsI) was identified in the genome of strain CZDM1. The expression of BcarsI in the As-sensitive Escherichia coli AW3110 conferred the bacterium the ability to demethylate MAs(III) under anoxic nitrate-reducing condition and enhanced its resistance to MAs(III). Both Bacillus sp. CZDM1 and E. coli AW3110 harboring BcarsI could not demethylate MAs(III) under fermentative conditions. Five conserved amino acid resides of cysteine, histidine, and glutamic acid are essential for MAs(III) demethylation under anoxic nitrate-reducing conditions. Putative arsI genes are widely present in denitrifying bacteria, with 75% of the sequenced genomes containing arsI, also possessing dissimilatory nitrate reductase genes narG or napA. These results reveal a novel mechanism in which MAs(III) is demethylated via ArsI by coupling to denitrification, and such a mechanism is likely to be common in an anoxic environment such as paddy soils and wetlands.

Cytogenetic damage in native Baltic Sea fish species: environmental risks associated with chemical munition dumping in the Gotland Basin of the Baltic Sea

This study represents the first attempt to assess genotoxicity and cytotoxicity effects in herring (Clupea harengus membras), flounder (Platichthys flesus), and cod (Gadus morhua callarias) caught at 47 study stations, located close to chemical munition dumpsites in the Gotland Basin, the Baltic Sea. Herring sampled from stations located in the center of chemical munition dumpsites exhibited the highest levels of micronuclei (MN) and total genotoxicity (ΣGentox), which is defined as the sum of frequencies of such nuclear abnormalities as micronuclei, nuclear buds, nuclear buds on the filament, and bi-nucleated erythrocytes with nucleoplasmic bridges. Exceptionally high and high ΣGentox risks were determined for flounder (89.47%), herring (79.31%), and cod (50%) caught at the stations located close to the chemical munition dumpsites.

Arsenite and monomethylarsonous acid disrupt erythropoiesis through combined effects on differentiation and survival pathways in early erythroid progenitors

Strong epidemiological evidence demonstrates an association between chronic arsenic exposure and anemia. We recently found that As+3 impairs erythropoiesis by disrupting the function of GATA-1; however the downstream pathways impacted by the loss of GATA-1 function have not been evaluated. Additionally, our previous findings indicate that the predominant arsenical in the bone marrow of mice exposed to As+3 in their drinking water for 30 days was MMA+3, but the impacts of this arsenical on erythorpoisis also remain largely unknown. The goal of this study was to address these critical knowledge gaps by evaluating the comparative effects of arsenite (As+3) and the As+3 metabolite, monomethyarsonous acid (MMA+3) on two critical regulatory pathways that control the differentiation and survival of early erythroid progenitor cells. We found that 500 nM As+3 and 100 and 500 nM MMA+3 suppress erythropoiesis by impairing the differentiation of early stage erythroid progenitors. The suppression of early erythroid progenitor cell development was attributed to combined effects on differentiation and survival pathways mediated by disruption of GATA-1 and STAT5. Our results show that As+3 primarily disrupted GATA-1 function; whereas, MMA+3 suppressed both GATA-1 and STAT5 activity. Collectively, these findings provide novel mechanistic insights into arsenic-induced dyserythropoiesis and suggest that MMA+3 may be more toxic than As+3 to early developing erythroid cells.

Arsenic: Various species with different effects on cytochrome P450 regulation in humans

Arsenic is well-recognized as one of the most hazardous elements which is characterized by its omnipresence throughout the environment in various chemical forms. From the simple inorganic arsenite (iAsIII) and arsenate (iAsV) molecules, a multitude of more complex organic species are biologically produced through a process of metabolic transformation with biomethylation being the core of this process. Because of their differential toxicity, speciation of arsenic-based compounds is necessary for assessing health risks posed by exposure to individual species or co-exposure to several species. In this regard, exposure assessment is another pivotal factor that includes identification of the potential sources as well as routes of exposure. Identification of arsenic impact on different physiological organ systems, through understanding its behavior in the human body that leads to homeostatic derangements, is the key for developing strategies to mitigate its toxicity. Metabolic machinery is one of the sophisticated body systems targeted by arsenic. The prominent role of cytochrome P450 enzymes (CYPs) in the metabolism of both endobiotics and xenobiotics necessitates paying a great deal of attention to the possible effects of arsenic compounds on this superfamily of enzymes. Here we highlight the toxicologically relevant arsenic species with a detailed description of the different environmental sources as well as the possible routes of human exposure to these species. We also summarize the reported findings of experimental investigations evaluating the influence of various arsenicals on different members of CYP superfamily using human-based models.

Silver nanoparticles protect against arsenic induced genotoxicity via attenuating arsenic bioaccumulation and elevating antioxidation in mammalian cells

Arsenic (As) and its compounds have been classified as Group I carcinogenic agents by the International Agency for Research on Cancer (IARC); however, there is few specific and efficient antidotes used for As detoxification. The present study aimed to investigate the protective effects of silver nanoparticles (AgNPs) at non-toxic concentrations on As(Ⅲ) induced genotoxicity and the underlying mechanism. Our data showed that AgNPs pretreatment significantly inhibited the generation of phosphorylated histone H2AX (γ-H2AX, marker of nuclear DNA double strand breaks) and the mutation frequencies induced by As(Ⅲ) exposure. Atomic fluorescence spectrometer (AFS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis revealed that the intracellular accumulation of As(Ⅲ) in human-hamster hybrid A_L cells was declined by AgNPs via suppressing the expression of specific As(Ⅲ)-binding protein (Gal-1). Moreover, the activities of antioxidant enzymes were greatly up-regulated by AgNPs, which eventually inhibited the generation of reactive oxygen species (ROS) induced by As(Ⅲ) and the downstream stress-activated protein kinases/c-Jun amino-terminal kinases (SAPK/JNK) signaling pathway. These results provided clear evidence that AgNPs dramatically suppressed the genotoxic response of As(Ⅲ) in mammalian cells via decreasing As(Ⅲ) bioaccumulation and elevating intracellular antioxidation, which might provide a new clue for AgNPs applications in As(Ⅲ) detoxification.

Depletion of S-adenosylmethionine pool and promoter hypermethylation of Arsenite methyltransferase in arsenic-induced skin lesion individuals: A case-control study from West Bengal, India

Methylation of arsenic compounds in the human body occurs following a series of biochemical reactions in the presence of methyl donor S-adenosylmethionine (SAM) and catalyzed by arsenite methyltransferase (AS3MT). However, the extent and pattern of methylation differs among the arsenic exposed individuals leading to differential susceptibility. The mechanism for such inter-individual difference is enigmatic. In the present case-control study we recruited exposed individuals with and without arsenic induced skin lesion (WSL and WOSL), and an unexposed cohort, each having 120 individuals. Using ELISA, we observed a reduction in SAM levels (p < 0.05) in WSL compared to WOSL. Linear regression analysis revealed a negative correlation between urinary arsenic concentration and SAM concentration between the study groups. qRT-PCR revealed a significant down-regulation (p < 0.01) of key regulatory genes like MTHFR, MTR, MAT2A and MAT2B of SAM biogenesis pathway in WSL cohort. Methylation-specific PCR revealed significant promoter hypermethylation of AS3MT (WSL vs. WOSL: p < 0.01) which resulted in its subsequent transcriptional repression (WSL vs. WOSL: p < 0.001). Linear regression analysis also showed a negative correlation between SAM concentration and percentage of promoter methylation. Taken together, these results indicate that reduction in SAM biogenesis along with a higher utilization of SAM results in a decreased availability of methyl donor. These along with epigenetic down-regulation of AS3MT may be responsible for higher susceptibility in arsenic exposed individuals.

Recent Advances in Colorimetric Detection of Arsenic Using Metal-Based Nanoparticles

Nowadays, arsenic (III) contamination of drinking water is a global issue. Laboratory and instrument-based techniques are typically used to detect arsenic in water, with an accuracy of 1 ppb. However, such detection methods require a laboratory-based environment, skilled labor, and additional costs for setup. As a result, several metal-based nanoparticles have been studied to prepare a cost-effective and straightforward detector for arsenic (III) ions. Among the developed strategies, colorimetric detection is one of the simplest methods to detect arsenic (III) in water. Several portable digital detection technologies make nanoparticle-based colorimetric detectors useful for on-site arsenic detection. The present review showcases several metal-based nanoparticles that can detect arsenic (III) colorimetrically at a concentration of ~0.12 ppb or lower in water. A literature survey suggests that biomolecule-based metal nanoparticles could serve as low-cost, facile, susceptible, and eco-friendly alternatives for detecting arsenic (III). This review also describes future directions, perspectives and challenges in developing this alternative technology, which will help us reach a new milestone in designing an effective arsenic detector for commercial use.

Nutrition, one-carbon metabolism and arsenic methylation

Exposure to arsenic (As) is a major public health concern globally. Inorganic As (InAs) undergoes hepatic methylation to form monomethyl (MMAs)- and dimethyl (DMAs)-arsenical species, facilitating urinary As elimination. MMAsIII is considerably more toxic than either InAsIII or DMAsV, and a higher proportion of MMAs in urine has been associated with risk for a wide range of adverse health outcomes. Efficiency of As methylation differs substantially between species, between individuals, and across populations. One-carbon metabolism (OCM) is a biochemical pathway that provides methyl groups for the methylation of As, and is influenced by folate and other micronutrients, such as vitamin B12, choline, betaine and creatine. A growing body of evidence has demonstrated that OCM-related micronutrients play a critical role in As methylation. This review will summarize observational epidemiological studies, interventions, and relevant experimental evidence examining the role that OCM-related micronutrients have on As methylation, toxicity of As, and risk for associated adverse health-related outcomes. There is fairly robust evidence supporting the impact of folate on As methylation, and some evidence from case-control studies indicating that folate nutritional status influences risk for As-induced skin lesions and bladder cancer. However, the potential for folate to be protective for other As-related health outcomes, and the potential beneficial effects of other OCM-related micronutrients on As methylation and risk for health outcomes are less well studied and warrant additional research.

Necessity of Assessing Biological Exposure to Arsenic Species by Two Representative Analytical Methods

Arsenic (As) exists as highly toxic chemical species. Chronic exposure to its inorganic form can cause multiple organ failure and skin cancer in humans, warranting the need to determine the toxicity of each chemical species. This study evaluated the proportions of exposure to four chemical species of As (cAs), namely arsenite (AsIII), arsenate (AsV), monomethylarsinic acid (MMA), and dimethylarsenic acid (DMA), and it confirmed the necessity of evaluating biological exposure to cAs. Urine samples were collected from 457 subjects residing near 103 abandoned metal mines. Hydride generation atomic absorption spectroscopy (HG-AAS) was performed to measure the combined concentration of four cAs (hAs_AAS). High-performance liquid chromatography and inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) were performed to determine the concentrations of the individual cAs and the sum of the four cAs (hAs_ICP). The proportions of AsV and MMA were relatively higher in the low-hAs_ICP concentration section. These findings suggest that hAs_AAS, which is mainly used for its cost-efficiency, is limited for evaluating exposure. Though hAs_AAS was found to exist in a low concentration, highly toxic AsV and MMA could be observed in high concentrations. Therefore, HPLC-ICP-MS is recommended for assessing cAs in environmentally vulnerable areas such as abandoned metal mines.

Arsenic compounds: The wide application and mechanisms applied in acute promyelocytic leukemia and carcinogenic toxicology

Arsenic (As), as well as its various compounds have been widely used for nearly 4000 years either as drugs or poisons. These compounds are valuable in the treatment of various diseases ranging from dermatosis to cancer, thereby emphasizing their important roles as therapeutic agents. The ability of As compounds, especially arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL), has fundamentally altered people's understanding of the poison, and has become a major factor in the re-emergence of Western medicine candidates to treat leukemia and other solid tumors. However, long-term exposure to As has been correlated with numerous disadvantageous influences on health, particularly carcinogenesis. Importantly, accumulating evidence suggests that biotransformation of As, as a step to eliminate As from the human body, can induce alterations at the genetic and epigenetic levels, resulting in therapeutic effects or carcinogenesis. In this article, we aimed to provide a systematic overview of the primary contributions associated with As and its compounds, as well as the detailed mechanisms applied in APL cells and carcinogenic toxicology. This review may help to understand the underlying mechanisms and safe wide clinical applications of medicinal As along with its compounds.

Arsenic methylation - Lessons from three decades of research

Between 1990 and 2020, our understanding of the significance of arsenic biomethylation changed in remarkable ways. At the beginning of this period, the conversion of inorganic arsenic into mono- and di-methylated metabolites was viewed primarily as a process that altered the kinetic behavior of arsenic. By increasing the rate of clearance of arsenic, the formation of methylated metabolites reduced exposure to this toxin; that is, methylation was detoxification. By 2020, it was clear that at least some of the toxic effects associated with As exposure depended on formation of methylated metabolites containing trivalent arsenic. Because the trivalent oxidation state of arsenic is associated with increased potency as a cytotoxin and clastogen, these findings were consistent with methylation-related changes in the dynamic behavior of arsenic. That is, methylation was activation. Our current understanding of the role of methylation as a modifier of kinetic and dynamic behaviors of arsenic is the product of research at molecular, cellular, organismic, and population levels. This information provides a basis for refining our estimates of risk associated with long term exposure to inorganic arsenic in environmental media, food, and water. This report summarizes the growth of our knowledge of enzymatically catalyzed methylation of arsenic over this period and considers the prospects for new discoveries.

Microbial reduction of As(V)-loaded Schwertmannite by Desulfosporosinus meridiei

Arsenic-rich schwertmannite may cause arsenic (As) release during phase transition. In this study, microbial sulfidogenesis on As(V)-loaded schwertmannite (As-Sch) and associated As mobility at different SO₄^2- concentrations were investigated under anaerobic conditions by Desulfosporosinus meridiei (D. meridiei). For biotic treatments, the more SO₄^2- was added, the more Fe³⁺ was reduced to Fe²⁺, and the more As(V) was released during the reductive dissolution of As-Sch. The reduction of As(V) to As(III) by D. meridiei resulted in a higher concentration, toxicity, solubility and mobility of As than the corresponding abiotic treatments. However, compared with the abiotic treatments, a variety of new minerals (such as mackinawite, vivianite, sulfur, As₂S₃, and parasymplesite) were generated in the biotic treatments, and the As concentration in aqueous solution was less than 1 μM at the end of the incubation period regardless of the presence of SO₄^2-. The results of continuous extraction of different species of As from secondary minerals showed that the effect of microorganisms decreased As content of amorphous iron oxide-bound phase, while increasing that bound on the surface of iron oxide surface-bound phase, thus increasing As fluidity. Our findings indicated that under anaerobic conditions, D. meridiei sulfidogenesis can trigger significant As mobilization in the early stage and remove As from the aqueous solutions when new minerals are formed at a later stage.

Nutrition, one-carbon metabolism and arsenic methylation in Bangladeshi adolescents

BACKGROUND

Over 57 million people in Bangladesh are chronically exposed to arsenic-contaminated drinking water. Ingested inorganic arsenic (InAs) undergoes hepatic methylation generating monomethyl- (MMAs) and dimethyl- (DMAs) arsenic species in a process that facilitates urinary As (uAs) elimination. One-carbon metabolism (OCM), a biochemical pathway that is influenced by folate and vitamin B12, facilitates the methylation of As. OCM also supports nucleotide and amino acid synthesis, particularly during periods of rapid growth such as adolescence. While folate supplementation increases As methylation and lowers blood As (bAs) in adults, little data is available for adolescents.

OBJECTIVES

To examine the associations between OCM-related micronutrients and As methylation in Bangladeshi adolescents chronically exposed to As-contaminated drinking water.

METHODS

We conducted a cross-sectional study of 679 Bangladeshi adolescents, including 320 boys and 359 girls aged 14-16 years. Nutritional status was assessed by red blood cell (RBC) folate, plasma folate, plasma B12 and homocysteine (Hcys). Arsenic-related outcomes included blood arsenic (bAs), urinary arsenic (uAs), and urinary arsenic metabolites expressed as a percentage of total urinary As: %InAs, %MMAs, %DMAs.

RESULTS

Boys had significantly lower B12, higher Hcys, higher bAs, higher uAs, higher %MMAs, and a trend toward lower RBC folate compared to girls. Therefore, regression analyses controlling for water As and BMI were sex stratified. Among girls, RBC folate was inversely associated with bAs, plasma B12 was inversely associated with uAs, and plasma Hcys was inversely associated with %MMA. Among boys, plasma folate was inversely associated with %InAs and positively associated with %DMA, RBC folate was inversely associated with %InAs and positively associated with %MMA, while Hcys was positively associated with %InAs.

CONCLUSIONS

These findings suggest that associations between OCM nutritional status, bAs, and distribution of As metabolites in adolescents are similar to previously reported observations in adults and in children. The As methylation findings are statistically significant among boys but not among girls; this may be related to estrogen which more strongly influences OCM in females. The inverse association between Hcys and %MMA in girls is somewhat unexpected given that Hcys is known to be an indicator of impaired OCM and low folate/B12 in adults. Overall, these results indicate that the associations between OCM-related micronutrients and arsenic methylation in adolescents are generally similar to prior findings in adults, though these associations may differ by sex. Additionally, these findings suggest that more investigation into the role of Hcys in adolescent physiology is needed, perhaps particularly for girls. Additional studies are needed to evaluate the impact of OCM and As methylation on As-related adverse health outcomes (such as cancer and cardiovascular disease) in people exposed to As during adolescence.

Origins, fate, and actions of methylated trivalent metabolites of inorganic arsenic: progress and prospects

The toxic metalloid inorganic arsenic (iAs) is widely distributed in the environment. Chronic exposure to iAs from environmental sources has been linked to a variety of human diseases. Methylation of iAs is the primary pathway for metabolism of iAs. In humans, methylation of iAs is catalyzed by arsenic (+ 3 oxidation state) methyltransferase (AS3MT). Conversion of iAs to mono- and di-methylated species (MAs and DMAs) detoxifies iAs by increasing the rate of whole body clearance of arsenic. Interindividual differences in iAs metabolism play key roles in pathogenesis of and susceptibility to a range of disease outcomes associated with iAs exposure. These adverse health effects are in part associated with the production of methylated trivalent arsenic species, methylarsonous acid (MAs^III) and dimethylarsinous acid (DMAs^III), during AS3MT-catalyzed methylation of iAs. The formation of these metabolites activates iAs to unique forms that cause disease initiation and progression. Taken together, the current evidence suggests that methylation of iAs is a pathway for detoxification and for activation of the metalloid. Beyond this general understanding of the consequences of iAs methylation, many questions remain unanswered. Our knowledge of metabolic targets for MAs^III and DMAs^III in human cells and mechanisms for interactions between these arsenicals and targets is incomplete. Development of novel analytical methods for quantitation of MAs^III and DMAs^III in biological samples promises to address some of these gaps. Here, we summarize current knowledge of the enzymatic basis of MAs^III and DMAs^III formation, the toxic actions of these metabolites, and methods available for their detection and quantification in biomatrices. Major knowledge gaps and future research directions are also discussed.

Comparative analysis of patients with upper urinary tract urothelial carcinoma in black-foot disease endemic and non-endemic area

BACKGROUND

A high incidence of upper urinary tract urothelial carcinoma has been reported in the southwestern area of Taiwan, where arsenic water contamination was considered the main cause. However, there is no definite proof to show a correlation between arsenic water contamination and upper urinary tract urothelial carcinoma. To investigate the clinical and epidemiological features of patients with upper urinary tract urothelial carcinoma between arsenic water endemic and non-endemic areas, we analyzed patients in terms of characteristics, stratified overall survival, disease-free survival, and cancer-specific survival.

METHODS

The records of a total of 1194 patients diagnosed with upper urinary tract urothelial carcinoma were retrospectively reviewed. Clinical data and current medical status were collected from the medical records. Statistical analyses were performed to determine the clinical variables and stratified survival curves between endemic and non-endemic groups.

RESULTS

Female predominance was revealed in both endemic and non-endemic groups (male:female ratio = 1:1.2-1.4). No statistical differences were found in histological types, staging, and tumor size between the two groups. Nonetheless, patients with characteristics of aging and having end-stage renal disease were outnumbered in the non-endemic group, while a higher prevalence of previous bladder tumors and more ureteral tumors were found in the endemic group. Adjusted stratified cumulative survival curves suggested a poorer prognosis in endemic patients, especially in disease-free survival of early stage disease.

CONCLUSIONS

A higher mortality rate with more previous bladder cancer history and ureteral tumors was seen in patients with upper urinary tract urothelial carcinoma residing in the arsenic water contamination area. This may be attributed to the long-term carcinogenic effect of arsenic underground water.

Advances in Nutritional Epigenetics-A Fresh Perspective for an Old Idea. Lessons Learned, Limitations, and Future Directions

Nutritional epigenetics is a rapidly expanding field of research, and the natural modulation of the genome is a non-invasive, sustainable, and personalized alternative to gene-editing for chronic disease management. Genetic differences and epigenetic inflexibility resulting in abnormal gene expression, differential or aberrant methylation patterns account for the vast majority of diseases. The expanding understanding of biological evolution and the environmental influence on epigenetics and natural selection requires relearning of once thought to be well-understood concepts. This research explores the potential for natural modulation by the less understood epigenetic modifications such as ubiquitination, nitrosylation, glycosylation, phosphorylation, and serotonylation concluding that the under-appreciated acetylation and mitochondrial dependant downstream epigenetic post-translational modifications may be the pinnacle of the epigenomic hierarchy, essential for optimal health, including sustainable cellular energy production. With an emphasis on lessons learned, this conceptional exploration provides a fresh perspective on methylation, demonstrating how increases in environmental methane drive an evolutionary down regulation of endogenous methyl groups synthesis and demonstrates how epigenetic mechanisms are cell-specific, making supplementation with methyl cofactors throughout differentiation unpredictable. Interference with the epigenomic hierarchy may result in epigenetic inflexibility, symptom relief and disease concomitantly and may be responsible for the increased incidence of neurological disease such as autism spectrum disorder.

Arsenal of Phytochemicals to Combat Against Arsenic-Induced Mitochondrial Stress and Cancer

Significance: Phytochemicals are important dietary constituents with antioxidant properties. They affect various signaling pathways involved in the overall maintenance of interior milieu of the cell. Arsenic, an environmental toxicant, is well known for its deleterious consequences, such as various diseases, including cancers in humans. Mitochondria are the cell's powerhouse that fuel all metabolic energy requirements. Dysfunctional mitochondria due to stressors may lead to abnormal functioning of the organelle, hampering the crucial cellular cross talks and ultimately leading to cancer. Application of phytochemicals against arsenic-induced mitochondrial disorders may be a preventive measure to counteract the ruinous impacts of the metalloid. Recent Advances: In recent years, extensive research on the role of mitochondria in cancer gives a better understanding of the areas the organelle covers in maintaining a healthy cell or in inducing carcinogenicity. Detailed knowledge of the mitochondrial governances would enable researchers to administer numerous phytochemicals to ameliorate altered oxidative phosphorylation, mitochondrial membrane potential (MMP), mitochondrial oxidative stress, unfolded protein response, glycolysis, or even apoptosis. Critical Issues: In this review, we have addressed how various phytochemicals belonging to diverse classes combat against arsenic-induced mitochondrial oxidative stress, depletion of MMP, cell cycle abrogation, apoptosis, glycolytic damages, oncogenic regulations, chaperones, mitochondrial complexes, and mitochondrial membrane pore formation in both in vitro and in vivo models. Future Directions: Insightful application of mitoprotective phytochemicals against arsenic-induced mitochondrial oxidative stress and carcinogenesis may guide researchers to develop preclinical chemopreventive agents to fight arsenic toxicity in humans.

Arsenite oxidation and arsenic adsorption on birnessite in the absence and the presence of citrate or EDTA

Birnessite not only oxidizes arsenite into arsenate but also interacts with organic matter in various ways. However, effects of organic matter on interaction between As and birnessite remain unclear. This study investigated effects of citrate and EDTA (3.12 and 2.05 mM, respectively) on oxidation of As(III) (1.07 mM) and adsorption of As(V) (0.67 mM) on birnessite (5.19 mM as Mn) at near-neutral pH. We found that As(V) adsorption on birnessite was enhanced by citrate and EDTA, which resulted from the increase in active adsorption sites via dissolution of birnessite. In comparison with citrate batches, more As was adsorbed on birnessite in EDTA batches, where dissolved Mn was mainly presented as Mn(III)-EDTA complex. Citrate or EDTA-induced dissolution of birnessite did not decrease the As(III) oxidation rate in the initial stage where As(III) oxidation rate was rapid. Afterwards, As(III) oxidation was conspicuously suppressed in citrate-amended batches, which was mainly attributed to the decrease in adsorption sites by adsorption of citrate/Mn(II)-citrate complex. This suppression was enhanced by the increase in concentrations of dissolved Mn(II). Citrate inhibited As adsorption after As(III) oxidation due to the strong competitive adsorption of citrate/Mn(II)-citrate complex. However, the As(III) oxidation rate was increased in EDTA-amended batches in the late stage, which mainly derived from the increase in the active sites via birnessite dissolution. The strong complexation ability of EDTA led to formation of Mn(III)-EDTA complex. Arsenic adsorption was not affected due to the limited competitive adsorption of the complex on the solid. This work reveals the critical role of low molecular weight organic acids in geochemical behaviors of As and Mn in aqueous environment.

Review: Efficiently performing periodic elements with modern adsorption technologies for arsenic removal

Arsenic (As) toxicity is a global phenomenon, and it is continuously threatening human life. Arsenic remains in the Earth's crust in the forms of rocks and minerals, which can be released into water. In addition, anthropogenic activity also contributes to increase of As concentration in water. Arsenic-contaminated water is used as a raw water for drinking water treatment plants in many parts of the world especially Bangladesh and India. Based on extensive literature study, adsorption is the superior method of arsenic removal from water and Fe is the most researched periodic element in different adsorbent. Oxides and hydroxides of Fe-based adsorbents have been reported to have excellent adsorptive capacity to reduce As concentration to below recommended level. In addition, Fe-based adsorbents were found less expensive and not to have any toxicity after treatment. Most of the available commercial adsorbents were also found to be Fe based. Nanoparticles of Fe-, Ti-, Cu-, and Zr-based adsorbents have been found superior As removal capacity. Mixed element-based adsorbents (Fe-Mn, Fe-Ti, Fe-Cu, Fe-Zr, Fe-Cu-Y, Fe-Mg, etc.) removed As efficiently from water. Oxidation of AsO₃^3- to AsO₄^3-and adsorption of oxidized As on the mixed element-based adsorbent occurred by different adsorbents. Metal organic frameworks have also been confirmed as good performance adsorbents for As but had a limited application due to nano-crystallinity. However, using porous materials having extended surface area as carrier for nano-sized adsorbents could alleviate the separation problem of the used adsorbent after treatment and displayed outstanding removal performances.

Interactions of arsenic metabolism with arsenic exposure and individual factors on diabetes occurrence: Baseline findings from Arsenic and Non-Communicable disease cohort (AsNCD) in China

The interaction between arsenic metabolism and potential modifiers on the risk of diabetes is unclear. This research aimed to investigate arsenic metabolism and diabetes prevalence and to identify the interactive effects of arsenic metabolism with some risk factors on diabetes in a Chinese population. A baseline cross-sectional survey was performed in two areas with groundwater arsenic contamination in China. Arsenic levels in water and arsenic metabolites in urine were analyzed. The proportions of each arsenic metabolite (inorganic arsenic [iAs%], monomethylarsonic acid [MMA%], and dimethylarsinic acid [DMA%]) were computed to evaluate arsenic metabolism. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the association between arsenic and diabetes. Interaction on the additive scale between arsenic methylation index and effect modifier was evaluated by calculating the relative excess risk due to interaction (RERI). Compared with participants in the lower tertile of MMA%, participants in the middle and upper tertiles of MMA% were less prone to diabetes (OR: 0.47 and 0.31, respectively). However, participants in the upper tertiles of urinary DMA% (OR: 3.18) were more likely to have diabetes than those participants in the lower tertiles. The stratified analyses revealed that a one-unit increase in DMA% was associated with higher odds of diabetes in females (OR: 1.06, 95% CI: 1.01, 1.11), older people (OR: 1.05, 95% CI: 1.00, 1.10), and subjects with body mass index (BMI) under 25 kg/m² (OR: 1.07, 95% CI: 1.01, 1.14). The additive interactions between DMA% and female gender (RERI: 0.40, 95% CI: 0.01, 11.88), DMA% and age (RERI: 0.02, 95% CI: 0.01, 8.85), as well as DMA% and BMI (RERI: 0.49, 95% CI: 0.01, 9.62), were statistically significant. In conclusion, efficient arsenic metabolism is associated with higher odds of diabetes. Urinary DMA% and individual factors interact to synergistically influence diabetes occurrence in the Chinese population.