Dimethylarsinate Research Articles

Chemo‐trapping method for determination of volatile arsenic from paddy soil

AbstractThe objective of this study was to develop a technique for collecting and analyzing volatile arsenic species including arsine (AsH3), methyl arsine (CH3AsH2), dimethyl arsine (CH3)2AsH, and trimethyl arsine (CH3)3As emitted from paddy soil. The four volatile arsenic species were captured on AgNO3‐impregnated sand then eluted and quantified. The AgNO3‐impregnated sand was synthesized by crystallizing AgNO3 on 0.5‐1 mm id. sandy particles at 70 oC. The volatile arsenic species were generated by hydride a mixture containing sodium arsenous (NaAsO2), disodium methyl arsenate ((CH3AsO(ONa)2), sodium cacodylate ((CH3)2AsO(ONa)), and trimethyl arsine oxide ((CH3)3AsO) using NaBH4. The formed volatile arsenic species were purged with an Ar stream then retained on a trap packed with the AgNO3‐impregnated sand followed by elution with 2 mL of 2.5% nitric acid and 0.5 mL of 30% H2O2 at 70oC prior to total analysis by ICPMS and speciation analysis by ion exchange chromatography ‐ ICPMS. The total analysis of arsenic revealed that AgNO3‐impregnated sand can efficiently retain the four volatile arsenic with 91‐102% recovery within a range of 20‐2000 ngAs as total amounts. The detection limit for total arsenic species through the trap was 6.5 ngAs. For a trap packed with 300 mg of AgNO3‐impregnated sand, the capture capacity was greater than 2000 ngAs. The speciation of arsenic eluted from the trap was performed by separation on a Hamilton PRP‐X100 anion‐exchange column with gradient elution using 100 mM (NH4)2CO3 mobile phase followed by ICPMS detection. A pot experiment was conducted to evaluate the efficiency of the purge and trapping method for naturally formed volatile arsenic species emitted from flooded paddy soil. Preliminary results showed that methyl arsenic, trimethyl arsenic and arsine were emitted from the studied paddy soil in which arsine contributes 90% of arsenic emission. This method is showing promise to be applied for the emission of volatile arsenic analysis from paddy soil as well as other solid types of samples.

How do different arsenic species affect the joint toxicity of perfluorooctanoic acid and arsenic to earthworm Eisenia fetida: A multi-biomarker approach

Perfluorooctanoic acid (PFOA) and arsenic are widely distributed pollutants and can coexist in the environment. However, no study has been reported about the effects of different arsenic species on the joint toxicity of arsenic and PFOA to soil invertebrates. In this study, four arsenic species were selected, including arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA). Earthworms Eisenia fetida were exposed to soils spiked with sublethal concentrations of PFOA, different arsenic species, and their binary mixtures for 56 days. The bioaccumulation and biotransformation of pollutants, as well as eight biomarkers in organisms, were assayed. The results indicated that the coexistence of PFOA and different arsenic species in soils could enhance the bioavailability of arsenic species while reducing the bioavailability of PFOA, and inhibit the arsenic biotransformation process in earthworms. Responses of most biomarkers in joint treatments of PFOA and As(III)/As(V) showed more significant variations compared with those in single treatments, indicating higher toxicity to the earthworms. The Integrated Biomarker Response (IBR) index was used to integrate the multi-biomarker responses, and the results also exhibited enhanced toxic effects in combined treatments of inorganic arsenic and PFOA. In comparison, both the biomarker variations and IBR values were lower in joint treatments of PFOA and MMA/DMA. Then the toxic interactions in the binary mixture systems were characterized by using a combined method of IBR and Effect Addition Index. The results revealed that the toxic interactions of the PFOA/arsenic mixture in earthworms depended on the different species of arsenic. The combined exposure of PFOA with inorganic arsenic led to a synergistic interaction, while that with organic arsenic resulted in an antagonistic response. Overall, this study provides new insights into the assessment of the joint toxicity of perfluoroalkyl substances and arsenic in soil ecosystems.

Removal of dimethylarsinate from water by robust NU-1000 aerogels: Impact of the aerogel materials

This study compared the effect of three matrices on the dimethylarsinate (DMA) removal from water to NU-1000 (zirconium-based metal–organic framework, Zr-MOF) hybrid aerogels. The porous MOF hybrid aerogels were prepared by grafting NU-1000 into green matrices, i.e., agarose (AG), sodium alginate (SA), and carboxymethyl cellulose (CMC) sodium salt. The adsorption data of DMA can be well described by the pseudo-second-order kinetic model and the Freundlich isotherm model. The maximum adsorption capacity of the NU-1000@AG hybrid aerogel for DMA (119.63 mg/g) was higher than the other two hybrid aerogels due to the negligible interference of AG on the active adsorption sites in NU-1000. However, the functional groups in NU-1000@CMC hybrid aerogel and NU-1000@SA hybrid aerogel occupied the Zr adsorption sites during the cross-linked process and decreased their adsorption capacities. The NU-1000@AG hybrid aerogel demonstrated application potential for removing DMA in a fixed-column dynamic adsorption process. Furthermore, the NU-1000 hybrid aerogels exhibited excellent regeneration performance and ease of solid–liquid separation. The characteristics of various matrices may offer diversified facile and viable strategies for fabricating a blocky adsorbent with superior stability and solid–liquid separation efficiency for water treatment, overcoming the disadvantages of MOF powder and ensuring maximum effectiveness of adsorbent components.

Linking the Low-Density Lipoprotein-Cholesterol (LDL) Level to Arsenic Acid, Dimethylarsinic, and Monomethylarsonic: Results from a National Population-Based Study from the NHANES, 2003-2020.

Arsenic (As) contamination is a global public health problem. Elevated total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) are risk factors for cardiovascular diseases, but data on the association of urinary arsenic species’ level and LDL-C are limited. We performed an association analysis based on urinary arsenic species and blood TC and LDL-C in US adults. Methods: Urinary arsenic, arsenic acid (AA), dimethylarsinic (DMA), monomethylarsonic (MMA), TC, LDL-C, and other key covariates were obtained from the available National Health and Nutrition Examination Survey (NHANES) data from 2003 to 2020. Multiple linear regression analysis and generalized linear model are used to analyze linear and nonlinear relationships, respectively. Results: In total, 6633 adults aged 20 years were enrolled into the analysis. The median total urinary arsenic level was 7.86 µg/L. A positive association of urinary arsenic concentration quartiles was observed with TC (β: 2.42 95% CI 1.48, 3.36). The OR for TC of participants in the 80th versus 20th percentiles of urinary total arsenic was 1.34 (95% CI 1.13, 1.59). The OR for LDL-C of participants in the 80th versus 20th percentiles of urinary total arsenic was 1.36 (95% CI 1.15, 1.62). For speciated arsenics analysis, the OR for arsenic acid and TC was 1.35 (95% CI 1.02, 1.79), whereas the OR for DMA and LDL-L was 1.20 (95% CI 1.03, 1.41), and the OR for MMA and LDL-L was 1.30 (95% CI 1.11, 1.52). Conclusions: Urinary arsenic and arsenic species were positively associated with increased LDL-C concentration. Prevention of exposure to arsenic and arsenic species maybe helpful for the control of TC and LDL-C level in adults.

Association between drinking water arsenic and urinary inorganic arsenic in the US: NHANES 2003-2014

BACKGROUND AND AIM: Important inequalities exist in arsenic (As) in drinking water across US populations. A critical research gap is how water As corresponds to internal dose, measured by urinary biomarkers. We evaluated the association between assigned private well and regulated community water system (CWS) As and urinary As concentrations in the National Health and Nutrition Examination Survey (NHANES). METHODS: We assigned 13,163 NHANES 2003-2014 participants county-level population- weighted CWS concentrations (µg/L) and private well estimates (probability >10 µg/L) using published nationwide estimates from US Environmental Protection Agency and US Geological Survey datasets, respectively. The internal dose of inorganic As related to drinking water was estimated by recalibrating urine dimethylarsinate (DMA) concentrations to adjust for arsenobetaine, seafood, smoking status, and past 24-hour intake of rice and other dietary sources. We evaluated geometric mean ratios (GMRs) of DMA across tertiles of water As, the lowest tertile as reference, for all participants and stratified by census region and quartile of geologic risk of elevated water As. RESULTS: Among CWS users, participants in the highest tertile of CWS As had significantly higher DMA overall (GMR= 1.17, 95% CI 1.09, 1.26) and in the South (GMR =1.23, 95% CI 1.09, 1.38), compared to participants in the lowest tertile. Among private well users, participants in the highest tertile of private well As had significantly higher DMA overall (GMR = 1.23, 95% CI 1.01, 1.50) and in the West (GMR = 1.34, 95% CI 1.18, 1.53). CONCLUSIONS: Arsenic in private wells and CWSs contributes to As exposure, measured in urine, in general US populations. Water As and urine DMA were more strongly associated among private-well users compared to CWS users nationwide, with differences by region. Positive associations were also observed among CWS users in the highest two quartiles of geologic risk. KEYWORDS: arsenic, exposure, water quality

The strategy of arsenic metabolism in an arsenic-resistant bacterium Stenotrophomonas maltophilia SCSIOOM isolated from fish gut

Bacteria are candidates for the biotransformation of environmental arsenic (As), while As metabolism in bacteria is not yet fully understood. In this study, we sequenced the genome of an As-resistant bacterium strain Stenotrophomonas maltophilia SCSIOOM isolated from the fish gut. After arsenate (As(V)) exposure, S. maltophilia transformed As(V) to organoarsenicals, along with the significant change of the expression of 40 genes, including the upregulation of arsH, arsRBC and betIBA. The heterogeneous expression of arsH and arsRBC increased As resistance of E. coli AW3110 by increasing As efflux and transformation. E. coli AW3110 (pET-betIBA) could transform inorganic As into dimethylarsinate (DMA) and nontoxic arsenobetaine (AsB), which suggested that AsB could be synthesized through the synthetic pathway of its analog-glycine betaine. In addition, the existence of arsRBC, betIBA and arsH reduced the reactive oxygen species (ROS) induced by As exposure. In total, these results demonstrated that S. maltophilia adopted an As metabolism strategy by reducing As accumulation and synthesizing less toxic As species. We first reported the production and potential synthetic pathway of AsB in bacteria, which improved our knowledge of As toxicology in microorganisms.

Arsenosugars and arsenolipids are formed simultaneously by the unicellular alga

Environmental context Arsenic is a globally distributed element, occurring in various chemical forms with toxicities ranging from harmless to highly toxic. We conducted 48-h cell culture experiments under batch and continuous conditions using the ubiquitous marine unicellular alga Dunaliella tertiolecta and evaluated the alga’s arsenic metabolome over time. We found that the alga first methylates the inorganic As taken up from the surrounding water, and then further metabolises the intermediate simultaneously into more complex organo-arsenic molecules like sugars and lipids. These time series experiments are valuable pieces in the puzzle of how algae bio-metabolise arsenic, and in our understanding of the global arsenic cycle. Rationale The uptake of arsenate by algae from oceanic waters and its transformation to arsenosugars and arsenolipids is well established, but the biosynthetic pathways remain largely unknown. Methodology We investigated these pathways by using time-series experiments over 48 h to follow the formation of organoarsenic species from arsenate-enriched medium (15 µg As L−1) by the unicellular alga Dunaliella tertiolecta cultured under batch and continuous culture conditions. We used complementary mass spectrometry methods for the determination and quantification of 14 arsenic species; an additional three species could be quantified but remained unidentified. Results The alga rapidly methylated the arsenate to dimethylarsinate (DMA), which then served as the precursor to arsenosugars and arsenolipids; the concentrations of these complex organoarsenicals increased throughout the experiments accompanied by a concomitant reduction in DMA concentrations. The pattern of compounds formed by the alga was similar for both batch and continuous cultures, but the concentrations were 2–3-fold higher in the continuous culture samples and the increases with time were much clearer. Discussion The data suggest that the arsenosugars and the arsenolipids were mostly formed simultaneously from DMA, although there was an indication that the arsenic phospholipids were at least partly also being formed from the arsenosugars. Overall, the data are consistent with a direct biosynthesis of DMA from arsenate by D. tertioleta, and thereafter a non-specific incorporation of DMA into commonly available alga metabolites encompassing various sugars and lipids.

An atlas of metallome and metabolome interactions and associations with incident diabetes in the Strong Heart Family Study.

Chronic exposure to certain metals plays a role in disease development. Integrating untargeted metabolomics with urinary metallome data may contribute to better understanding the pathophysiology of diseases and complex molecular interactions related to environmental metal exposures. To discover novel associations between urinary metal biomarkers and metabolism networks, we conducted an integrative metallome-metabolome analysis using a panel of urinary metals and untargeted blood metabolomic data from the Strong Heart Family Study (SHFS). The SHFS is a prospective family-based cohort study comprised of American Indian men and women recruited in 2001-2003. This nested case-control analysis of 145 participants of which 50 developed incident diabetes at follow up in 2006-2009, included participants with urinary metal and untargeted metabolomic data. Concentrations of 8 creatinine-adjusted urine metals/metalloids [antimony (Sb), cadmium (Cd), lead (Pb), molybdenum (Mo), selenium (Se), tungsten (W), uranium (U) and zinc (Zn)], and 4 arsenic species [inorganic arsenic (iAs), monomethylarsonate (MMA), dimethylarsinate (DMA), and arsenobetaine (AsB)] were measured. Global metabolomics was performed on plasma samples using high-resolution Orbitrap mass spectrometry. We performed an integrative network analysis using xMWAS and a metabolic pathway analysis using Mummichog. 8,810 metabolic features and 12 metal species were included in the integrative network analysis. Most metal species were associated with distinct subsets of metabolites, forming single-metal-multiple-metabolite clusters (|r|>0.28, p-value<0.001). DMA (clustering with W), iAs (clustering with U), together with Mo and Se showed modest interactions through associations with common metabolites. Pathway enrichment analysis of associated metabolites (|r|>0.17, p-value<0.1) showed effects in amino acid metabolism (AsB, Sb, Se and U), fatty acid and lipid metabolism (iAs, Mo, W, Sb, Pb, Cd and Zn). In stratified analyses among participants who went on to develop diabetes, iAs and U clustered together through shared metabolites, and both were associated with the phosphatidylinositol phosphate metabolism pathway; metals were also associated with metabolites in energy metabolism (iAs, MMA, DMA, U, W) and xenobiotic degradation and metabolism (DMA, Pb) pathways. In this integrative analysis of multiple metals and untargeted metabolomics, results show common associations with fatty acid, energy and amino acid metabolism pathways. Results for individual metabolite associations differed for different metals, indicating that larger populations will be needed to confirm the metal-metal interactions detected here, such as the strong interaction of uranium and inorganic arsenic. Understanding the biochemical networks underlying metabolic homeostasis and their association with exposure to multiple metals may help identify novel biomarkers, pathways of disease, potential signatures of environmental metal exposure.

Water as a relevant source of inorganic arsenic exposure in U.S. cities

BACKGROUND AND AIM: Water arsenic represents a health concern for US residents served by community water systems (CWS) exceeding the Environmental Protection Agency (EPA) Maximum Contaminant Level (MCL) of 10 µg/L, and for residents reliant on unregulated private wells. Little is known on the contribution of CWS arsenic exposures below the MCL, particularly in urban areas. We evaluated whether water arsenic is a relevant source of urinary arsenic in urban settings in the Multi-Ethnic Study of Atherosclerosis (MESA). METHODS: We examined the association of CWS arsenic with urinary arsenic concentrations (µg/L) for 910 MESA participants from Baltimore, Chicago, Los Angeles, New York City, St. Paul, MN, and Winston-Salem, NC. We assigned three-year population weighted averages of CWS arsenic concentrations using 2006-2008 EPA data (before MCL implementation) to participants by zip code. Dietary information and urinary samples were collected in 2000-2002. Urinary arsenic species were measured using HPLC-ICPMS. We accounted for seafood intake using a residual based method. Linear models adjusted for race/ethnicity, income, smoking status, diet (rice) and urinary creatinine to account for urine dilution. RESULTS:CWS arsenic levels ranged from 0.5 µg/L (LOD) in several cities to 3.05 µg/L in Chicago (median 0.44 µg/L). CWS arsenic was positively correlated (p 0.05) with urinary inorganic arsenic (Spearman’s rho 0.11), dimethylarsinate (DMA) (0.09), monomethylarsonate (MMA) (0.16) and their sum (0.10). In adjusted models, a 1 µg/L change in CWS arsenic was associated with 1.29 (95%CI 1.01, 1.64) higher inorganic arsenic and 1.19 (1.03, 1.38) higher MMA. The association with DMA, sum of inorganic and methylated species was not statistically significant. CONCLUSIONS:Drinking water arsenic is a relevant source of exposure and internal dose in US urban areas, determined by urinary arsenic biomarkers. Research is needed to determine health implications of chronic exposure to water arsenic below the MCL, including vulnerable subpopulations. KEYWORDS: arsenic, drinking water, exposure assessment, environmental epidemiology

Effects of kinetin on arsenic speciation and antioxidative enzymes in fronds of the arsenic hyperaccumulator Pteris cretica var. nervosa and non-hyperaccumulator Pteris ensiformis

Cytokinins (CTKs) enhance plant tolerance to heavy metals, but the associated mechanisms are not yet fully understood. Here, we investigated the effects of kinetin (KT, a type of CTKs) on arsenic (As) speciation and antioxidative enzymes in plant fronds, by comparing Pteris cretica var. nervosa (As hyperaccumulator) and Pteris ensiformis (non-hyperaccumulator). A hydroponic test was carried out and the two plant species were treated with 2 mg L−1 arsenite [As(III)], arsenate [As(V)] or dimethylarsinate (DMA), and then 0–1.0 mg L−1 KT was exogenously applied for 14 days. The maximum As uptake of the two experimental plants was 0.5 mg L−1 KT. Fresh plant biomass was also significantly increased, except in P. cretica var. nervosa under DMA stress. The frond superoxide dismutase (SOD) and catalase (CAT) activity in the two plant species was significantly increased by 0.5 mg L−1 KT. Additionally, a significant decline in frond peroxidase (POD) activity was observed in P. ensiformis at 1.0 mg L−1 KT under As(III) stress. However, POD activity was significantly increased in P. cretica var. nervosa, at 0.1 mg L−1 KT, under As(III) or DMA stress, and at 1.0 mg L−1 KT, under As(V) stress. Therefore, KT promoted As transport and increased frond POD activity in P. cretica var. nervosa, which contributed to its As tolerance under stress from different As species.

Associations between rice consumption, arsenic metabolism, and insulin resistance in adults without diabetes.

Rice consumption is an important source of arsenic exposure. Little has known about the impact of rice consumption on arsenic metabolism, which is related to insulin resistance. In this study, we examined the associations between rice consumption and arsenic metabolism, and between arsenic metabolism and insulin resistance in non-diabetic U.S adults who participated in the National Health and Nutrition Examination Survey (NHANES) 2003-2016. Rice consumer was defined as ≥0.25 cups of cooked rice/day. HOMA2-IR was calculated using HOMA2 Calculator software based on participant's fasting glucose and insulin values. Urinary arsenic concentrations below limits of detection were imputed first, and then arsenic metabolism (the proportions of inorganic arsenic (iAs), monomethylarsonate (MMA), and dimethylarsinate (DMA) to their sum) were calculated (expressed as iAs%, MMA%, and DMA%). Using the leave-one-out approach, rice consumers compared with non-consumers had a 1.71% (95% CI: 1.12%, 2.29%) higher DMA% and lower MMA% when iAs% fixed; a 1.55% (95% CI: 0.45%, 2.66%) higher DMA% and lower iAs% when MMA% fixed; and a 1.62% (95% CI: 0.95%, 2.28%) higher iAs% and lower MMA% when DMA% fixed, in multivariable adjustment models. With every 10% decrease in MMA%, the geometric mean ratio of HOMA2-IR was 1.06 (95% CI:1.03,1.08) and 1.05 (95% CI:1.02, 1.09) when DMA% and iAs% was fixed, respectively; however, the associations were attenuated after adjusting for body mass index. In stratified analysis, we found that lower MMA% was associated with higher HOMA2-IR in participants with obesity: a 10% increase in iAs% with a 10% decrease in MMA% was associated with higher HOMA2-IR with the geometric mean ratio of 1.05 (95% CI: 1.01, 1.09). Our findings suggest that rice consumption may contribute to lower MMA% that was further associated with higher insulin resistance, especially in individuals with obesity. Future prospective studies are needed to confirm our results in different populations.

Variations of arsenic forms and the role of arsenate reductase in three hydrophytes exposed to different arsenic species

In order to understand the mechanisms of arsenic (As) accumulation and detoxification in aquatic plants exposed to different As species, a hydroponic experiment was conducted and the three aquatic plants (Hydrilla verticillata, Pistia stratiotes and Eichhornia crassipes) were exposed to different concentrations of As(III), As(V) and dimethylarsinate (DMA) for 10 days. The biomass, the surface As adsorption and total As adsorption of three plants were determined. Furthermore, As speciation in the culture solution and plant body, as well as the arsenate reductase (AR) activities of roots and shoots, were also analyzed. The results showed that the surface As adsorption of plants was far less than total As absorption. Compared to As(V), the plants showed a lower DMA accumulation. P. stratiotes showed the highest accumulation of inorganic arsenic but E. crassipes showed the lowest at the same As treatment. E. crassipes showed a strong ability to accumulate DMA. Results from As speciation analysis in culture solution showed that As(III) was transformed to As(V) in all As(III) treatments, and the oxidation rates followed as the sequence of H. verticillata>P. stratiotes>E. crassipes>no plant. As(III) was the predominant species in both roots (39.4–88.3%) and shoots (39–86%) of As(III)-exposed plants. As(V) and As(III) were the predominant species in roots (37–94%) and shoots (31.1–85.6%) in As(V)-exposed plants, respectively. DMA was the predominant species in both roots (23.46–100%) and shoots (72.6–100%) in DMA-exposed plants. The As(III) contents and AR activities in the roots of P. stratiotes and in the shoots of H. verticillata were significantly increased when exposed to 1 mg·L-1 or 3 mg·L-1 As(V). Therefore, As accumulation mainly occurred via biological uptake rather than physicochemical adsorption, and AR played an important role in As detoxification in aquatic plants. In the case of As(V)-exposed plants, their As tolerance was attributed to the increase of AR activities.

Speciation analysis of organoarsenic species in marine samples: method optimization using fractional factorial design and method validation

Organoarsenic species in marine matrices have been studied for many years but knowledge gaps still exist. Most literature focuses on monitoring of arsenic (As) species using previously published methods based on anion- and cation-exchange high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). These studies are often limited to few As species and/or only specific method performance characteristics are described. Most marine certified reference materials (CRMs) are only certified for arsenobetaine (AB) and dimethylarsinate (DMA), making it difficult to evaluate the accuracy of analytical methods for other organoarsenic species. To address these gaps, the main objective of this work was to develop and validate a method for speciation analysis of a broad range of organoarsenic species in marine matrices. Optimum extraction conditions were identified through a 27–3 fractional factorial design using blue mussel as test sample. The effects of sample weight, type and volume of extraction solution, addition of H2O2 to the extraction solution, extraction time and temperature, and use of ultrasonication were investigated. The highest As recoveries were obtained by using 0.2 g as sample weight, 5 mL of aqueous methanol (MeOH:H2O, 50% v/v) as extractant, extraction carried out at 90 °C for 30 min, and without ultrasonication. Anion- and cation-exchange HPLC-ICP-MS settings were subsequently optimized. The method detected a total of 33 known and unknown As species within a run time of 23 and 20 min for cation-exchange and anion-exchange, respectively. A single-laboratory validation was conducted using several marine CRMs: BCR 627 (tuna fish tissue), ERM-CE278k (mussel tissue), DORM-4 (fish protein), DOLT-5 (dogfish liver), SQID-1 (cuttlefish), TORT-3 (lobster hepatopancreas), and CRM 7405-b (hijiki seaweed). Method performance characteristics were evaluated based on selectivity, limits of detection and quantification, linearity, trueness, precision, and measurement uncertainty. This work proposes an extraction procedure which allowed satisfactory quantification of As species with low solvent and energy consumption, supporting “Green Chemistry” principles. The study also presents a new set of As speciation data, including methylated arsenic species and arsenosugars, in recently issued marine CRMs, which will be valuable for future speciation studies on As. This work is the first to report a total of 33 different As species in marine CRMs.Graphical abstract

Distribution and chemical speciation of arsenic in different sized atmospheric particulate matters

The distribution and chemical speciation of arsenic (As) in different sized atmospheric particulate matters (PMs), including total suspended particles (TSP), PM10, and PM2.5, collected from Baoding, China were analyzed. The average total mass concentrations of As in TSP, PM10, and PM2.5 were 31.5, 35.3, and 54.1 µg/g, respectively, with an order of PM2.5 >PM 10 > TSP, revealing that As is prone to accumulate on fine particles. Due to the divergent toxicities of different As species, speciation analysis of As in PMs is further conducted. Most of previous studies mainly focused on inorganic arsenite (iAsIII), inorganic arsenate (iAsV), monomethylarsonate (MMA), and dimethylarsinate (DMA) in PMs, while the identification and sensitive quantification of trimethylarsine oxide (TMAO) were rarely reported. In this study, a high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry system was optimized for As speciation including TMAO in PMs. An anion exchange column was used to separate MMA, DMA and iAsV, while a cation exchange column to separate TMAO and iAsIII. Results showed that iAsV was the dominate component in all the samples, corresponding to a portion of 79.2% ± 9.3% of the total extractable species, while iAsIII, TMAO and DMA made up the remaining 21%. Our study demonstrated that iAsIII accounted for about 14.4% ± 11.4% of the total extracted species, with an average concentration of 1.7 ± 1.6 ng/m3. It is worth noting that TMAO was widely present in the samples (84 out of 97 samples), which supported the assumption that TMAO was ubiquitous in atmospheric particles.

Determination of four arsenic species in environmental water samples by liquid chromatography- inductively coupled plasma - tandem mass spectrometry

Robust and sensitive methods for monitoring inorganic and organic As species As(III), As(V), dimethylarsinate (DMA), and monomethylarsonate (MMA) in environmental water are necessary to understand the toxicity and redox processes of As in a specific environment. The method is sufficiently sensitive and selective to ensure accurate and precise quantitation of As(III), As(V), DMA, and MMA in surface water and groundwater samples with As species concentrations from tens of nanograms per liter to 50 µg/L without dilution of the sample. Mean recoveries of the four species spiked into reagent water, surface water and groundwater and measured periodically over three months ranged from 87.2 % to 108.7 % and relative standard deviation of replicates of all analytes ranged from 1.1 % to 9.0 %.•A PRP-X100 column and nitrate/phosphate mobile phase was used to separate As(III), As(V), DMA, and MMA in 0.45 µm filtered surface water and groundwater matrices.•Oxygen was used in the collision cell of the inductively coupled plasma-mass spectrometer with MS/MS mode to shift the measured As mass from 75 to 91.•The analytical performance of the method and figures of merit including detection limits, precision, accuracy, and interferences when applied to surface water and groundwater matrices were investigated.

Stability of inorganic and methylated arsenic species in laboratory standards, surface water and groundwater under three different preservation regimes

Geogenic arsenic (As) adversely affects drinking water quality in geologically diverse aquifers across the globe. Although the species of As significantly affects its fate, transport, toxicity, and As treatment technology efficacy, reported effectiveness of As species preservation methods varies widely with preservation methods and natural water geochemistry. Our study 1) evaluates the shelf life of As(III), As(V), dimethylarsinate (DMA), and monomethylarsonate (MMA) in standards prepared with ultrapure water; 2) establishes a hold time for these As species in low-iron (Fe) groundwater and surface water samples preserved with a concentration of EDTA that exceeded the sum of the molar concentrations of Al, Fe, Mn, Ca, Mg, and Sr (molar excess of EDTA); and 3) evaluates As(III) species stability in groundwater samples with detectable SO4 and up to 6.5 mg/L Fe concentrations preserved in 3 ways: less than molar excess EDTA, molar excess EDTA, and Vacuette® tubes with an unknown (proprietary) amount of EDTA. Arsenic species standards prepared with 2.5 mM EDTA in ultrapure water and stored at 4 °C had a shelf life of at least 180 days. As(III) was stable for at least 15 days and DMA and MMA were stable for at least 90 days in environmental samples with Fe less than 1 mg/L that were preserved with a molar excess of EDTA and stored in opaque containers at 4 °C. As(III) species were not stable for any holding time in samples with Fe greater than 1 mg/L and detectable SO4 when preserved with a molar excess of EDTA and stored in white high density polyethylene bottles at room temperature, or when preserved by storage in EDTA containing Vacuette® tubes at 4 °C. For geochemical or water quality studies where the distribution of As(III) and As(V) is a critical factor, an understanding of the sample chemistry, rapid As speciation analysis after sample collection, and collecting a field spike with the sample can be helpful for collecting accurate inorganic As species data.

Arsenic methylation capacity is associated with locus-specific DNA methylation: an epigenome-wide association study among adults with low-to-moderate arsenic exposure in the United States

Background/Aims: Chronic Arsenic (As) exposure remains a global health problem. Adverse health effects persist decades after arsenic exposure has ended, suggesting a role for epigenetic dysregulation. Methylation of inorganic arsenic (iAs) to monomethylarsonate (MMA) and dimethylarsinate (DMA) by arsenic(III) methyltransferase (AS3MT) decreases toxicity and facilitates urinary excretion. Whether arsenic methylation is associated with DNA methylation is unknown. Methods: We measured DNA methylation at &gt;850,000 loci in 2,325 participants in the Strong Heart Study, a population-based study of American Indian adults exposed to low-moderate levels of arsenic in drinking water. Arsenic methylation was measured as the proportion of arsenic metabolites in urine: iAs%, MMA%, and DMA%. Blood DNA differentially methylated positions (DMPs) associated with each arsenic metabolite were tested using linear models. Gene ontology (GO) analysis was conducted using GOmeth adjusting for array coverage. Models were adjusted for estimated cell type proportions, age, sex, BMI, smoking, education, estimated glomerular filtration rate, and study site. Results: In adjusted models, we identified 84 and 13, 46 and 22, and 112 and 25 CpGs associated with iAs%, MMA%, and DMA% at PFDR &lt; 0.05 / PBonferroni &lt; 0.05, respectively. Seventeen FDR-significant CpGs were common between arsenic metabolites, including 4 CpGs annotated to AS3MT and 13 CpGs located within 650 kilobase pairs up- or downstream of the AS3MT gene and annotated to CNNM2, WBP1L, C10orf95, NT5C2, CALHM1, and TRIM8. Top GO terms overrepresented among genes containing iAs% DMPs were related to muscle hypertrophy; top GO terms associated with MMA% and %DMA% were related to response to tumor cells and regulation of protein catabolic processes. Conclusions: In an epigenome-wide association study, we identified CpGs associated with % arsenic metabolites within a gene region covering AS3MT. Further research is needed to understand the relationship between DNA methylation of AS3MT, gene expression, arsenic methylation capacity and health.

Urine Arsenic and All-cause and Cancer Mortality among U.S. Adults: the 2003-2014 National Health and Nutrition Examination Survey (NHANES)

Background: Inorganic arsenic (iAs) is an established human carcinogen. Studies on the relationship of low to moderate exposure to iAs with all-cause and cancer mortality are limited. We investigated the association of exposure to iAs, measured by urinary dimethylarsinate (DMA), with all-cause and cancer mortality in U.S. adults.Methods: We studied 9,244 adults aged ≥20 years who participated in NHANES 2003-2014 and were assessed for urine arsenic analysis. Participants were followed for mortality through December 31, 2015. We estimated adjusted hazard ratios (HR) for all-cause and cancer mortality endpoints comparing tertiles of urinary DMA concentrations.Results: The median (IQR) urinary DMA concentration was 2.5 µg/L (1.4-4.1). After a mean of 6.7 years of follow-up, there were 876 deaths (203 cancer deaths). The HR (95% CI) comparing the highest DMA tertile (&gt;3.42 µg/L) to the lowest tertile (&lt;1.08 µg/L) were 1.09 (0.59, 2.02) for cancer mortality and 1.04 (0.82, 1.34) for all-cause mortality. For cancer mortality, urine DMA concentration was associated with increased risk among female participants (HR: 2.49, 95% CI: 1.07, 5.79). There was increased risk for cancer mortality among participants who were non-Black or White race/ethnicities, never and former smokers, overweight and without a history of cancer at baseline, although these findings were not statistically significant. For all-cause mortality, urine DMA concentration was associated with increased risk among non-Black or White race/ethnicities (HR: 2.24, 95% CI: 1.09, 4.60). There was a non-statistically significant increased risk for all-cause mortality among females, never and former smokers and overweight participants.Conclusions: In this representative sample of the U.S. population exposed to low-moderate arsenic levels, urinary DMA concentrations were not associated with all-cause or cancer mortality in the overall population. There was evidence of increased risk for all-cause mortality among participants of non-Black or White race/ethnicities and for cancer mortality among female participants.

Non-Chromatographic Speciation of As by HG Technique—Analysis of Samples with Different Matrices

The applicability of the hydride generation (HG) sample introduction technique combined with different spectrochemical detection methods for non-chromatographic speciation of toxic As species, i.e., As(III), As(V), dimethylarsinate (DMA) and monomethylarsonate (MMA), in waters and other environmental, food and biological matrices is presented as a promising tool to speciate As by obviating chromatographic separation. Different non-chromatographic procedures along with speciation protocols reported in the literature over the past 20 year are summarized. Basic rules ensuring species selective generation of the corresponding hydrides are presented in detail. Common strategies and alternative approaches are highlighted. Aspects of proper sample preparation before analysis and the selection of adequate strategies for speciation purposes are emphasized.

Arsenic transformation behavior mediated by arsenic functional genes in landfills

Landfill arsenic pollution is a complicated problem because of the sophisticated species and transformation of fractions involved. This study investigated arsenic transformation behavior from the viewpoint of arsenic functional genes based on analysis of 29 aged refuse samples collected from 11 sanitary landfills in 10 cities in Zhejiang Province, China. Arsenic species distribution varied significantly with landfill process. Landfill contains rich arsenic resistant microbes. arrA genes were the key factor responsible for arsenic transformation and migration in landfill. Although the abundance of aioA genes was the lowest among the four tested arsenic functional genes, it was the second important genes for arsenic distribution. Microbial metabolic activity was the main cause of arsenic transformation, and arsenate reduction by microbes was a key driver of arsenic mobilization in landfills. Moreover, arsenate was reduced to arsenite and further methylated to monomethylarsine (MMA) and dimethylarsine (DMA), decreasing the total arsenic content during the landfill process, but also inducing a new risk because of the arsenic effluent will be more easily as the state of arsenite, MMA, and DMA in the liquid phase. Overall, this study provides a picture of arsenic species transformation and insight into key roles involved in arsenic pollution during landfill processes.