Sodium arsenite and cadmium chloride are two widespread environmental toxicants which have deleterious effects on living organisms. At the cellular level, sodium arsenite and cadmium chloride cause oxidative stress, dysregulation of gene expression, apoptosis, and the unfolding of protein. Furthermore, both chemical stressors individually have the ability to induce heat shock protein (HSP) accumulation. HSPs are molecular chaperones that aid in protein folding, translocation and in preventing stress-induced protein aggregation. Previously, our laboratory demonstrated that treatment of A6 kidney epithelial cells of the frog Xenopus laevis, with either cadmium chloride or sodium arsenite plus a concurrent mild heat shock resulted in an enhanced accumulation of HSPs that was greater than found with the sum of the individual stressors. To the best of our knowledge, no information is available to date on the effect that these two chemical stressors have in combination on HSP accumulation in aquatic organisms. The present study examined the effect of simultaneous sodium arsenite and cadmium chloride treatment on the pattern of HSP30 and HSP70 accumulation in Xenopus A6 cells. Immunoblot analysis revealed that the relative levels of HSP30 and HSP70 accumulation in A6 cells treated concurrently with sodium arsenite and cadmium chloride for 12 h were significantly higher than the sum of HSP30 or HSP70 accumulation from cells subjected to the treatments individually. For instance, the combined 10 µM sodium arsenite plus 100 µM cadmium chloride treatment resulted in a 3.5 fold increase in HSP30 accumulation and a 2.5 fold increase in HSP70 accumulation compared to the sum of the stressors individually. This finding suggested a synergistic action between the two stressors. Pretreatment of cells with KNK437, an HSF1 inhibitor, inhibited the combined sodium arsenite- and cadmium chloride-induced accumulation of HSP30 and HSP70 suggesting that this accumulation of HSPs may be regulated, at least in part, at the level of transcription. Immunocytochemical analysis employing the use of laser scanning confocal microscopy (LSCM) revealed that simultaneous treatment of cells with the two stressors induced HSP30 accumulation primarily in the cytoplasm in a punctate pattern with some dysregulation of F-actin structure. Increased ubiquitinated protein accumulation was observed with combined 10 µM sodium arsenite and 10, 50 or 100 µM cadmium chloride treatment compared to individual stressors suggesting an impairment of the ubiquitin-proteasome degradation system. Finally, while incubation of A6 cells with 1 µM sodium arsenite plus 10 µM cadmium chloride did not induce a detectable accumulation of HSPs, the addition of a 30 °C mild heat shock resulted in a strong accumulation of HSP30 and HSP70. This study has demonstrated that concurrent sodium arsenite and cadmium chloride treatment can enhance HSP accumulation. Since HSP accumulation is triggered by proteotoxic stress, these findings are relevant given the fact that aquatic amphibians in their natural habitat may be exposed to multiple chemical stressors simultaneously.

Arsenic (As) is a highly toxic chemical that is widely distributed in groundwater around the world. As-bearing sulfide minerals (ASM) are known to contribute to high background concentrations of As in groundwater in regions where the geochemistry of the parent material is dominated by sulfide minerals. The fate of As in groundwater depends on the activity of microorganisms which can oxidize arsenite (Asᴵᴵᴵ), or reduce arsenate (Asᵛ). In oxidizing environments, Asᵛ is the predominant species, and the accumulation of As is limited by the sorption of As onto iron (Fe) oxides and hydroxides. Under reducing environments, Asᴵᴵᴵ is the predominant specie, and while the sorption strength of Asᴵᴵᴵ on the Fe-surface of Fe (oxy)hydroxides is weaker, the accumulation of As in water can be limited by the precipitation of As as part of an ASM. The main aim of this research is to study the impact of microbial activity on the mobilization and immobilization of As in the environment. The first objective of this research was to characterize the metabolic activity of three Asᴵᴵᴵ-oxidizing bacteria, Azoarcus sp. pb-1 strain EC1, Azoarcus sp. pb-1 strain EC3 and Diaphorobacter sp. pb-1 strain MC, isolated from a non-contaminated, pristine environment. These Asᴵᴵᴵ-oxidizing bacteria demonstrated a great metabolic flexibility to use oxygen and nitrate to oxidize Asᴵᴵᴵ as well as organic and inorganic substrates as alternative electron donors (e-donors) explains their presence in non-As-contaminated environments. The findings suggest that at least some Asᴵᴵᴵ-oxidizing bacteria are flexible with respect to electron-acceptors and e-donors and that they are potentially widespread in low As concentration environments. The second objective of this research was to investigate the stability of orpiment (As₂S₃) and arsenopyrite (FeAsS), at circumneutral pH and 30°C, under aerobic- and or anoxic conditions (nitrate amended as electron acceptor (e-acceptor)), in order to assess the feasibility of immobilizing As by formation of ASM as a long-term option for the bioremediation of As contamination. The percentage of As released from the minerals ranged from zero when FeAsS was biologically incubated to 87% for As₂S₃(s) under anoxic abiotic conditions. While the dissolution of ASM was greater in biological conditions, the presence of inoculum provided as sludge served as a sink for As, limiting the mobilization of As into aqueous phase. Thus, the mobilization of As from ASM can be controlled by altering the environmental conditions such as the redox conditions or by stimulating microbial activity. Further research investigated the formation of ASM catalyzed by biological reduction of Asᵛ and sulfate (SO₄²⁻). In particular, the third objective of this research was to study the effect of the pH on the removal of As due to the biological-mediated formation of ASM in an iron-poor system. A series of batch experiments were performed to study the reduction of SO₄²⁻ and Asᵛ by an anaerobic mixed culture in a range of pH conditions (6.1-7.2), using ethanol as the e-donor. A marked decrease of the total aqueous concentrations of As and S and the formation of a yellow precipitate was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. The fourth objective was to investigate the biomineralization of As through simultaneous Asᵛ and SO₄²⁻ reduction in a minimal iron environment for the As-contaminated groundwater bioremediation. A continuous bioreactor, inoculated with an anaerobic sludge was maintained at circumneutral pH (6.25-6.50) and fed with Asᵛ and SO₄²⁻, utilizing ethanol as an e-donor for over 250 d. A second bioreactor running under the same conditions but lacking SO₄²⁻ was operated as a control to study the fate of As removal. The reactor fed with both Asᵛ and SO₄²⁻ removed on the average 91.2% of the total soluble As, while less than 5% removal was observed in the control bioreactor without S. The biomineralization of As in the bioreactor was also evident from the formation of a yellow precipitate made of a mixture of As₂S₃ and AsS minerals. These results taken as a whole indicate that a bioremediation process relying on the addition of a simple, low-cost e-donor offers potential to promote the removal of As from groundwater by precipitation of ASM. The fifth objective was to evaluate the toxic impact that the exposure to soluble As or the formation of ASM could have on the anaerobic mixed culture used as inocula. The methanogenic community on the reactors was impacted by addition of As. The biogenic ASM inhibited the acetoclastic methanogens causing an accumulation of acetate. In the SO₄²⁻-free bioreactor, the methanogens were initially highly sensitive to Asᴵᴵᴵ (formed from Asᵛ reduction) but quickly adapted to its toxicity. Consequently, the formation of ASM would impact the methanogenic activity of an anaerobic biofilm, while the exposure to Asᴵᴵᴵ would not have a negative impact if the biofilm undergoes adaptation. The sixth and final objective was to study the stability of a biogenic ASM at two different pH values (6.5 and 7.5) and under different redox conditions. The long-term stability was evaluated in three different bioreactors that operated for 145 d: aerobic (R1), anoxic (nitrate as alternative e-acceptor (R2) and anaerobic (R3). The dissolution of ASM was greatly affected by the pH, and slightly by the presence and nature of the e-acceptor. The ASM was very stable at pH 6.5, however, the As mobilization rate was up to 7-fold higher at pH 7.5, likely due to the formation of thioarsenic species. The stability of ASM was also impacted by the e-acceptor present. The As mobilization rate was 77% higher under anaerobic conditions than under aerobic conditions, most likely due to the formation of secondary As-bearing minerals. Therefore, the stability of ASM depends on the conditions of the operation, and it can be controlled by altering the environmental conditions, such as the pH or the presence of the e-acceptor.

Sodium arsenite and cadmium chloride are two widespread environmental toxicants which have deleterious effects on living organisms. At the cellular level, sodium arsenite and cadmium chloride cause oxidative stress, dysregulation of gene expression, apoptosis, and the unfolding of protein. Furthermore, both chemical stressors individually have the ability to induce heat shock protein (HSP) accumulation. HSPs are molecular chaperones that aid in protein folding, translocation and in preventing stress-induced protein aggregation. Previously, our laboratory demonstrated that treatment of A6 kidney epithelial cells of the frog Xenopus laevis, with either cadmium chloride or sodium arsenite plus a concurrent mild heat shock resulted in an enhanced accumulation of HSPs that was greater than found with the sum of the individual stressors. To the best of our knowledge, no information is available to date on the effect that these two chemical stressors have in combination on HSP accumulation in aquatic organisms. The present study examined the effect of simultaneous sodium arsenite and cadmium chloride treatment on the pattern of HSP30 and HSP70 accumulation in Xenopus A6 cells. Immunoblot analysis revealed that the relative levels of HSP30 and HSP70 accumulation in A6 cells treated concurrently with sodium arsenite and cadmium chloride for 12 h were significantly higher than the sum of HSP30 or HSP70 accumulation from cells subjected to the treatments individually. For instance, the combined 10 µM sodium arsenite plus 100 µM cadmium chloride treatment resulted in a 3.5 fold increase in HSP30 accumulation and a 2.5 fold increase in HSP70 accumulation compared to the sum of the stressors individually. This finding suggested a synergistic action between the two stressors. Pretreatment of cells with KNK437, an HSF1 inhibitor, inhibited the combined sodium arsenite- and cadmium chloride-induced accumulation of HSP30 and HSP70 suggesting that this accumulation of HSPs may be regulated, at least in part, at the level of transcription. Immunocytochemical analysis employing the use of laser scanning confocal microscopy (LSCM) revealed that simultaneous treatment of cells with the two stressors induced HSP30 accumulation primarily in the cytoplasm in a punctate pattern with some dysregulation of F-actin structure. Increased ubiquitinated protein accumulation was observed with combined 10 µM sodium arsenite and 10, 50 or 100 µM cadmium chloride treatment compared to individual stressors suggesting an impairment of the ubiquitin-proteasome degradation system. Finally, while incubation of A6 cells with 1 µM sodium arsenite plus 10 µM cadmium chloride did not induce a detectable accumulation of HSPs, the addition of a 30 °C mild heat shock resulted in a strong accumulation of HSP30 and HSP70. This study has demonstrated that concurrent sodium arsenite and cadmium chloride treatment can enhance HSP accumulation. Since HSP accumulation is triggered by proteotoxic stress, these findings are relevant given the fact that aquatic amphibians in their natural habitat may be exposed to multiple chemical stressors simultaneously.

No description available.

Metabolic syndrome affects approximately 25% of the US population and increases risk for the development of cardiovascular disease, as well as, and Type 2 diabetes. Inorganic arsenite exposure has been associated with cardiovascular disease, insulin resistance and Type 2 diabetes. The mechanisms by which arsenic increases these health risks has not been fully elucidated. In this report we show two pathways by which arsenite may contribute to metabolic syndrome. First through induction of C-Reactive Protein (CRP) and secondly through inhibition of insulin stimulated glucose uptake. CRP is a clinical marker for metabolic syndrome and a predictive clinical marker for cardiovascular disease and type 2 diabetes. Treatment of HepG2 cells with arsenite resulted in elevated CRP production and secretion. In addition, treatment of FvB mice with 100 ppb sodium arsenite via drinking water for six months starting at weaning age resulted in dramatically higher levels of CRP in both the liver and inner medullary region of the kidney. Further, mouse Inner Medullary Collecting Duct cells (mIMCD-3), a mouse kidney cell line, were stimulated with CRP, which resulted in activation of NFkappaB. Pretreatment with Y27632, a Rho kinase inhibitor, prior to CRP stimulation attenuated NFkappaB activation. Additionally, L6 myocytes, an insulin responsive cell line, exposed to arsenite for 4 or 7 days showed decreased insulin-stimulated glucose uptake but no decrease in AKT activation. In addition, we found that ERK activity decreased, while p38 MAPK activity increased, in response to prolonged arsenite treatment. These data support the epidemiological evidence that chronic exposure to low physiologically relevant levels of arsenite can contribute to insulin resistance and type 2 diabetes. These data provide a novel pathway by which arsenic can contribute to metabolic syndrome, cardiovascular disease, insulin resistance and type 2 diabetes.

O arsênio inorgânico, um contaminante ambiental, produz uma série de respostas de estresse em células de mamíferos, incluindo o comprometimento da função mitocondrial, acompanhado por inibição do crescimento celular e carcinogênese. Como previamente identificamos efeitos deletérios do comprometimento da função mitocondrial e dos radicais livres do oxigênio na oogênese, investigamos os efeitos do arsenito na meiose, no desenvolvimento embrionário pré-implantação e na apoptose embrionária em camundongos. Camundongas com 6 semanas de idade foram tratadas com baixa (0,16 mg) ou média dose de arsenito (0,32 mg), por meio de 7 injeções intraperitoneais, 1 a cada 2 dias, durante 14 dias. Os controles foram injetados com solvente. A incidência de anomalias meióticas, caracterizadas por anormalidades do fuso celular e/ou mal alinhamento cromossômico, foi significantemente aumentada tanto nos oócitos in vivo ovulados, como nos in vitro maturados, oriundos dos animais tratados com arsenito. Foram detectadas reduções significativas das taxas de clivagem (24 horas de cultivo), de formação de mórula (72 h) e de desenvolvimento para blastocisto (96 h), nos embriões dos grupos tratados com arsenito. Apesar do número total de núcleos não ter diferido significativamente entre os blastocistos dos grupos controle e de tratamento, a percentagem de núcleos apoptóticos foi significantivamente maior nos blastocistos derivados dos animais tratados com a dose média de arsenito. Estes dados sugerem que o arsenito causa aberrações meióticas, que podem contribuir tanto para o comprometimento do desenvolvimento embrionário pré-implantação, como para a apoptose embrionária. / Inorganic arsenic, an environmental contaminant, produces a variety of stress responses in mammalian cells, including mitochondrial uncoupling accompanied by growth inhibition and carcinogenesis. Because previously we identified detrimental effects of mitochondrial uncoupling, and reactive oxygen species (ROS) on oogenesis, we investigated effects of arsenite on meiosis, early embryo development, and apoptosis in mice. Six-week-old CD-1 mice were treated with either low (0.16mg) or medium (0.32mg) doses of arsenite every two days by 7 intraperitoneal injections for 14 days, and controls were injected with solvent. The incidence of meiotic anomalies, characterized by spindle disruption and/or chromosomal misalignment or spreading, was significantly increased in both in vivo and in vitro treated oocytes. Further, we found a significant decrease in cleavage rates at 24h, morula formation at 72h, and development to blastocyst at 96h in treated groups. Although the total number of nuclei in developed blastocysts did not significantly differ between the treated and control groups, the percentage of apoptotic nuclei was significantly increased in blastocysts derived from the medium dose treated group. These data suggest that arsenite causes meiotic aberrations, which may contribute to decreased cleavage and preimplantation development, as well as increased apoptosis.

Orientador: Wellerson Rodrigo Scarano / Resumo: O arsênio é um metaloide associado ao desenvolvimento de algumas patologias, como doenças cardiovasculares, lesões dérmicas e diferentes tipos de câncer. Pouco se sabe sobre a ação do arsênio ou compostos de arsênio na próstata durante o período pré-puberal e puberdade, estágios essenciais para a morfogênese tardia da próstata. Nesse sentido, este estudo teve como objetivo estabelecer se a exposição ao arsenito de sódio (NaAsO2) interfere na morfofisiologia da próstata ventral de ratos púberes. Para isso, 30 ratos machos da linhagem Wistar, no dia pós-natal 23 (DPN23), foram distribuídos, aleatoriamente, em 3 grupos experimentais (n =10/grupo). O grupo controle (Ctrl) recebeu água filtrada (veículo); o grupo As1 recebeu 0.01 mg/L de NaAsO2; e o grupo As2 recebeu 10.0 mg/L de NaAsO2. Todas as soluções foram diluídas na água do bebedouro e estiveram disponíveis aos animais do DPN23 ao DPN53. Os hábitos alimentares e a evolução do peso corpóreo dos animais foram acompanhados durante todo o período experimental. Ao final deste período, os animais foram pesados e, em seguida, eutanasiados (DPN53). Coletou-se o sangue para mensurar os níveis de testosterona. O fígado, os rins e a próstata ventral (PV) foram coletados e pesados. Apenas a PV foi dissecada e destinada às análises histológicas (hemilobo esquerdo) e moleculares (hemilobo direito). Os resultados dos parâmetros analisados durante o período experimental revelaram que o NaAsO2 não foi capaz de causar toxicidade sistêmica em... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Arsenic is an endocrine disruptor associated with the development of some pathologies such as cardiovascular diseases, dermal lesions and different types of cancer. Little is known about the action of arsenic or arsenic compounds in the prostate during the prepubertal and puberty period, an essential stage for late morphogenesis of the prostate. Therefore, this study aimed to establish whether exposure to sodium arsenite (NaAsO2) interferes in the morphophysiology of the ventral prostate of pubertal rats. In this study, thirty male Wistar rats, on the postnatal day 23 (PND23), were randomly distributed to 3 experimental groups (n = 10/group). The control group (Ctrl) received only saline solution; the second group (As1) received 0.01 mg/L of NaAsO2; and the third group (As2) received 10.0 mg/L of NaAsO2. All solutions were diluted in drinking water and were available to the animals from DPN23 to DPN53. The eating habits and the evolution of the body weight of the animals were evaluated throughout the experimental period. At the end of this period, the animals were weighed and then euthanized (DPN53). Blood was collected to measure testosterone levels. The liver, kidneys and ventral prostate (VP) were collected and weighed. Only VP was dissected for histological analysis (left hemilobo) and molecular (right hemilobo). The results of the parameters analyzed during the experimental period revealed that NaAsO2 was not able to cause systemic toxicity in both exposed groups nor cha... (Complete abstract click electronic access below) / Mestre

Abstract The object of this study was to investigate the synthesis of a nanoscale zero-valent iron slurry (NZVIS) for use in Fenton-like reactions, and to evaluate its efficiency for As(III) oxidation to As(V) in spiked deionized water and simulated groundwater containing humic acid. Furthermore, this study used injection of the nanoiron slurry combined with electrokinetic processes to remediate As(III) in soil. NZVI was prepared by a chemical reduction process. The efficiency of using 3 wt% soluble starch (SS) to stabilize NZVI was also studied. It was found that the SS could keep the nanoparticles dispersed for over one day. The NZVI was characterized by XRD, FE-SEM, ESEM-EDS, and EDS-mapping, to observe its morphology and crystal structure. In this research the iron species observed took non-crystalline forms. In water batch tests, studies in deionized water were compared with those in simulated groundwater with humic acid, and dissolved oxygen content was adjusted. Injection of NZVIS oxidized As(III) to As(V) in all cases. In both deionized water and simulated groundwater, it was found that when the dissolved oxygen(DO) content was not increased, the NZVIS generated non-selective oxidant OH¡E, thus reducing the As(V) production rate. When dissolved oxygen content was increased, the DO oxidized organic matter present in the simulated groundwater, allowing the OH¡E to react further with As(III) and increasing the As(V) production rate. Finally, a test was performed in actual groundwater under optimal reaction conditions, without increasing the dissolved oxygen content, for comparison of As(V) yield. The concentration of As(V) was found to be higher in this test (As(V) Conc. = 17.55 £gg/L) than when using simulated groundwater (As(V) Conc. = 4.63 £gg/L). This study further examined NZVIS injection combined with electrokinetic (EK) technology for the remediation of soil columns containing a low concentration (initial conc. = 100 mg/kg) and a high concentration (initial conc. = 500 mg/kg) of As(III). EK alone without injection of NZVIS (Test E-1) resulted in a residual soil As(V) concentration of 24 mg/kg in the low-concentration test group. In Test E-2, where NZVIS was injected into the anode reservoir, and Test E-3, where NZVIS was injected into the cathode reservoir, residual soil As(V) concentrations were 2.3 mg/kg and 3.4 mg/kg, respectively. The high-concentration test group was comprised of Test E-4 (EK alone without injection of NZVIS), Test E-5 (NZVIS injected into anode reservoir), and Test E-6 (NZVIS injected into cathode reservoir). In these tests, only soil sections 0.2 and 0.4 (normalized distance from anode reservoir) met soil regulation standards. Residual As(V) concentrations in soil sections 0.6, 0.8, and 1.0 are much higher than the regulatory standard. In soil section 1.0, the residual As(V) concentration was less in Test E-6 than in Test E-5 (116.6 mg/kg and 183.5 mg/kg, respectively). This may be because at high pH values, the iron surface does not corrode, instead arsenic adsorption prevails. Only a fraction of negatively charged As(V) species will migrate towards the anode resulting in a relatively low soil As(V) concentration near the cathode.

The objective of this research was to investigate the retention of arsenate (iAsV), arsenite (iAsIII), monomethyl arsenate (MMAsV) and dimethyl arsenate (DMAsV) by calcite and assess the impact of dissolved Ca2+, Mg2+, phosphate and sulfate on arsenic solubility, adsorption and precipitation phenomena. Adsorption kinetics of iAsV, evaluated at a low and high concentration, was a relatively rapid process, with a fast initial reaction rate within the first few minutes and a subsequent slower reaction rate as equilibrium was approached. The relative adsorption of arsenicals decreased in the following order: iAsV > iAsIII > DMAV > MMAV. In no case was a clear adsorption maximum observed with increasing dissolved arsenic concentration. Dissolved 0.01 M Ca2+ resulted in an increase in iAsV adsorption; however, in the presence of 0.1 M Ca2+ adsorption of iAsV was decreased. The presence of Mg2+ as 0.01 M Mg(NO3)2 resulted in decreased iAsV adsorption probably the result of a lower iAsV affinity for adsorbed Mg2+ as compared to Ca2+. Phosphate and sulfate were highly competitive with iAsV in adsorption to calcite and both resulted in decreased iAsV adsorption. The total prevention of iAsV adsorption at initial equimolar arsenic/phosphate concentrations > 88 µM each could be from the consumption of available calcite surface sites by the specific adsorption of phosphate. Equilibrium modeling, using the geochemical and mineral speciation of equilibrium model (MINTEQA2), indicated that at low concentrations of arsenate or phosphate solid-phase precipitation was not likely and adsorption processes likely controlled solubility. At high concentrations of arsenate Ca3(AsO4)2 · 3 2/3 H2O and Ca3(AsO4)2 · 4 1/4 H2O solid phases could be controlling arsenate solubility. This study indicates that arsenic adsorption response by calcite was different than that of phosphate suggesting that arsenic may not be specifically adsorbed to calcium at the calcite surface. Reduction and biomethylation of arsenic decreased adsorption, suggesting that processes which could affect the speciation of arsenic in the environment, could increase arsenic mobility in environmental systems where calcite and dissolved aqueous calcium play a predominant role in controlling arsenic solubility. Dissolved aqueous concentrations of magnesium, phosphate and sulfate generally reduced the ability of arsenic to be adsorbed to calcite.

Carcinogenic health concerns over arsenic in drinking water caused the USEPA to reduce the maximum contaminant level (MCL) from 50 to 10 ppb, effective on January 23, 2006. This has forced many smaller utilities into expensive treatment or discontinuation of water distribution. Researchers throughout the world are working to develop an inexpensive method for arsenic removal to meet this MCL. Aluminum silicates, or zeolites, are naturally occurring ionic sorbents. Modification of a zeolite may enhance adsorption capacities and ion selectivity. This research investigates the arsenic adsorption capacities of a modified Chabazite. This adsorption, coupled with a hollow fiber, microfiltration membrane substrate, allows for the use of finer zeolite particles. Powdered zeolite creates a cake layer on the filtration surface through which the arsenic solution must filter. The research goal was to develop an overall mathematical model for the adsorption of arsenic through the adsorption equilibrium isotherms, the cake layer, and the microfiltration operational settings. Baseline adsorption isotherms where performed in distilled water. Solutions containing counter ions were then used to determine any counter-effects. The final isotherms were found using dechlorinated tap water, which is similar to many groundwaters found in the United States. Various runs were used to determine the most efficient modification and loading rate.Initial characterization of the membrane system defined membrane permeability and inherent arsenic rejection. Variable mass loading in both deadend and crossflow filtration determined that the cake layer was not compressible due to linear pressure increases. This process also determined the maximum cake layer permissible hydraulically on the membrane surface. Membrane system operational characteristics and arsenic dosing were chosen to adhere to these parameters as well as the adsorption isotherms. Adsorption runs were conducted which varied the flux through the membrane, the arsenic feed concentration, and the cake layer thickness. Through the data collected, a mathematical model based on irreversible adsorption was developed. This novel approach to arsenic removal and the predictive mathematical model can be used as an effective method for removal of aqueous arsenic, and may provide small water utilities with a cost effective way to meet the recommended new MCL.