Dimethylarsinic Acid Research Articles

Arsenic, polycyclic aromatic hydrocarbons, and metal exposure and risk assessment of stroke.

Globally, stroke is one of the primary causes of morbidity and mortality. In the USA, stroke is a major cause of death and disability. Limited studies assessed the impact of polycyclic aromatic hydrocarbons, arsenic, and other metal exposure and their association with the risk of stroke. This study aimed to assess different arsenic species, including total arsenic; two types of organic arsenic, i.e., arsenobetaine and arsenocholine; four types of inorganic arsenic, i.e., arsenic acid, arsenous acid, dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA); six types of urinary polycyclic aromatic hydrocarbon (PAH) compounds, i.e., 1-hydroxynaphthalene, 1-hydroxyphenanthrene, 1-hydroxypyrene, 2-hydroxynaphthalene, 2-hydroxyfluorene, and 3-hydroxyfluorene; and fourteen types of metals from urine specimen, i.e., manganese, cadmium, lead, mercury, barium, cobalt, strontium, molybdenum, cesium, thallium, antimony, tin, tungsten, and uranium and their association with those who reported having been told they had had a stroke by a medical professional. The National Health and Nutrition Examination Survey (NHANES) data used in this study include three data cycles from 2011-2016. In this study, data from a total of 5537 males and females who are aged 20 years and older were analyzed using logistic modeling of the complex weighted survey design. R version 3.6.3 software was used to conduct the analyses. Four species of urinary PAHs, including the third quantiles of 1-hydroxynaphthalene [odds ratio (OR): 2.327, 95% confidence interval (CI): 0.961-5.632], 2-hydroxynaphthalene [OR: 2.449, 95% CI: 1.067-5.622], and 3-hydroxyfluorene [OR: 2.289, 95% CI: 1.077-4.861] and the second quantiles of 3-hydroxyfluorene [OR: 2.201, 95% CI: 1.115, 4.346] and 1-hydroxypyrene [OR: 2.066, 95% CI: 1.037, 4.114], showed a positive correlation with increased odds of stroke. Among metals, the third (3rd) [OR: 3.566, 95% CI: 1.370, 9.280] and fourth (4th) [OR: 2.844, 95% CI: 0.947, 8.543] quantiles of urinary manganese showed a positive correlation with increased odds of stroke.

Effects of Varied Forms of Arsenic Stress on Seedling Growth and Arsenic Distribution in Honeysuckle Plants

At present, soil arsenic contamination is one of the prominent environmental problems. The arsenic concentration in honeysuckle exceeds the standard levels, thus affecting the quality of traditional Chinese medicine. In this study, the hydroponic method was employed to explore the effect of organic arsenic (dimethyl arsenic) and trivalent inorganic arsenic (NaAsO2) on the growth of honeysuckle plants. The study demonstrated that low concentrations of inorganic arsenic (10–20 mg/L) and 10–50 mg/L organic arsenic had a stimulating effect on the growth of honeysuckle plants. The activities of antioxidant enzymes (peroxidase and catalase) increased correspondingly. However, the antioxidant system in honeysuckle plants was damaged under high concentrations of inorganic arsenic (20–40 mg/L) and 50–70 mg/L organic arsenic. On exposure to 30 mg/L NaAsO2 or 50 mg/L dimethyl arsenic acid for 10 days, the activities of peroxidase and catalase, as well as the malondialdehyde content, increased with prolonged exposure. The micro X-ray fluorescence analysis revealed that the accumulated arsenic in the roots was transported from the central vascular cylinders to the outer part of the root with the increase in concentration and exposure duration of inorganic arsenic. However, organic arsenic stress did not result in significant variations in the distribution of arsenic with increasing concentrations of arsenic. The arsenic element was predominantly located in the middle woody part of the root. The distributions of arsenic in the stems and leaves, in terms of organic and inorganic arsenic stresses, were similar, with accumulation primarily in the cortex of the stem and veins of the leaves. As a commonly used bulk traditional Chinese medicine, honeysuckle has a wide range of product quality issues. Hence, exploring the absorption, distribution, and transport trends of heavy metals such as arsenic in the plant body is of great significance for scientifically evaluating the impact of heavy metal pollution on the quality of medicinal materials and exploring ways to reduce the accumulation of heavy metals in the medicinal parts of plants.

Multigenerational effects of co-exposure to dimethylarsinic acid and polystyrene microplastics on the nematode Caenorhabditis elegans.

In the current study, we assessed the impact of DMA (dimethylarsinic acid) and MPs (microplastics) interactions in C. elegans over the course of five generations. We found that the redox state of the organisms changed over generations as a result of exposure to both pollutants. From the third generation onward, exposure to MPs reduced GST activity, indicating reduced detoxifying abilities of these organisms. Additionally, dimethylarsinic exposure decreased the growth of organisms in the second, fourth, and fifth generations. In comparison to isolated pollutants, the cumulative effects of co-exposure to DMA and MPs seem to have been more harmful to the organisms, as demonstrated by correlation analysis. These findings demonstrate that DMA, despite being considered less hazardous than its inorganic equivalents, can still have toxic effects on species at low concentrations and the presence of MPs, can worsen these effects.

Design of a Whole-Cell Biosensor Based on Bacillus subtilis Spores and the Green Fluorescent Protein To Monitor Arsenic.

A green fluorescent protein (GFP)-based whole-cell biosensor (WCB-GFP) for monitoring arsenic (As) was developed in Bacillus subtilis. To this end, we designed a reporter gene fusion carrying the gfpmut3a gene under the control of the promoter/operator region of the arsenic operon (Pars::gfpmut3a) in the extrachromosomal plasmid pAD123. This construct was transformed into B. subtilis 168, and the resultant strain was used as a whole-cell biosensor (BsWCB-GFP) for the detection of As. The BsWCB-GFP was specifically activated by inorganic As(III) and As(V), but not by dimethylarsinic acid [DMA(V)], and exhibited high tolerance to the noxious effects of arsenic. Accordingly, after 12 h exposure, B. subtilis cells carrying the Pars::gfpmut3a fusion exhibited 50 and 90% lethal doses (LD50 and LD90) to As(III) of 0.89 mM and As 1.71 mM, respectively. Notably, dormant spores from the BsWCB-GFP were able to report the presence of As(III) in a concentration range from 0.1 to 1,000 μM 4 h after the onset of germination. In summary, the specificity and high sensitivity for As, as well as its ability to proliferate under concentrations of the metal that are considered toxic in water and soil, makes the B. subtilis biosensor developed here a potentially important tool for monitoring environmental samples contaminated with this pollutant. IMPORTANCE Arsenic (As) contamination of groundwater is associated with serious worldwide health risks. Detection of this pollutant at concentrations that are established as permissible for water consumption by WHO is a matter of significant interest. Here, we report the generation of a whole-cell biosensor for As detection in the Gram-positive spore former B. subtilis. This biosensor reports the presence of inorganic As, activating the expression of the green fluorescent protein (GFP) under the control of the promoter/operator of the ars operon. The biosensor can proliferate under concentrations of As(III) that are considered toxic in water and soil and detect this ion at concentrations as low as 0.1 μM. Of note, spores of the Pars-GFP biosensor exhibited the ability to detect As(III) following germination and outgrowth. Therefore, this novel tool has the potential to be directly applied to monitor As contamination in environmental samples.

Fertilization Enhances Grain Inorganic Arsenic Assimilation in Rice

To investigate how soil fertilization/amendments alters arsenic speciation grain off-take in paddy rice, rice was grown to maturity in growth chambers fertilized with standard mineral fertilizer, wood ash (rich in silica), pig slurry (rich in organic matter), and non-amended control. The soil was sourced from a Chinese paddy field. The primary fertilized elements (nitrogen, phosphorus, potassium) were kept constant across treatments. Porewater chemistry and soil microbiology were monitored throughout the experiments. Total grain arsenic, sum of inorganic arsenic and dimethylarsinic acid (DMA), was significantly different between treatments (P = 0.024), with inorganic arsenic varying from 0.025 to 0.08 mg/kg and DMA from 0.08 to 0.16 mg/kg for control compared to fertilized, respectively. Fertilizer source made no difference to arsenic speciation concentration in grain. Porewater analysis found that as anaerobism set in, inorganic arsenic, phosphorus and manganese greatly lowered in concentration. Methylated arsenic species concentrations increased over time, concurrent with an increase in pH, decrease in Eh, and increase in total organic carbon and iron, with no strong treatment effects, except for pig slurry that enhanced pH and decreased Eh. Methanogenic archaea, sulfate-reducing bacteria and Acidobacteria increased with time and some Actinobacteria and Firmicutes increased due to slurry, but then decreased with time (P < 0.01). Methanogenic archaea and sulphate-reducing bacteria correlated positively with porewater DMA and negatively with porewater inorganic arsenic (P < 0.05). Genera within the Actinobacteria and Burkholderiaceae correlated negatively with DMA, while genera with iron-reducing capacity (Clostridiales) correlated positively with porewater inorganic arsenic and DMA (P < 0.05).

Chemical Speciation of Arsenic and Chromium in Seafood by LC-ICP-MS

Two methods were developed for the As and Cr species determination in different kinds of seafood, exploring the LC-ICP-MS potential and chemometric approach to define the extraction conditions. Adequates separation and sensitivity data by LC-ICP-MS were obtained with 0.01 mol L-1 (NH4)2HPO4 in 1% ethanol (pH 8.0) for arsenic, and 0.015 mol L-1 Na2SO4, 0.005 mol L-1 EDTA, and 0.005 mol L-1 NaH2PO4 (pH 7.0) for chromium. The Doehlert matrix and Box-Behnken design defined the ideal extraction conditions for arsenic and chromium species. For As extraction, the optimized conditions employed 0.1 g of sample and 30 mmol L-1 HNO3 at 90°C for 45 min, and Cr, 0.1 g of sample and 0.045 mol L-1 [EDTA] at 90°C for 40 min. Recoveries from 88 to 106% of arsenobetaine (AsB), arsenite [As(III)], dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenate [As(V)], Cr(III) and Cr(VI) were obtained for all evaluated samples. The limits of quantification provided by the proposed methods were 5.3; 52.1; 16.4; 2.8; 83.3; 113.8; 53.9 ng g-1 for AsB, As(III), DMA, MMA, As(V), Cr(III) and Cr(VI) respectively. The trueness was evaluated using certified reference materials and addition and recovery procedures. The sum of the species agreed with the total concentration of arsenic and chromium contents.

In utero arsenic exposure and early childhood motor development in the New Hampshire Birth Cohort Study.

High-level prenatal and childhood arsenic (As) exposure characteristic of several regions in Asia (e.g., Bangladesh), may impact motor function. However, the relationship between lower-level arsenic exposure (characteristic of other regions) and motor development is largely unstudied, despite the potential for deficient motor skills in childhood to have adverse long-term consequences. Thus, we sought to investigate the association between prenatal As exposure and motor function among 395 children in the New Hampshire Birth Cohort Study, a rural cohort from northern New England. Prenatal exposure was estimated by measuring maternal urine speciated As at 24-28 weeks of gestation using high-performance liquid chromatography (HPLC) inductively coupled plasma mass spectrometry (ICP-MS) and summing inorganic As, monomethylarsonic acid, and dimethylarsinic acid to obtain total urinary As (tAs). Motor function was assessed with the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition (BOT-2) at a mean (SD) age of 5.5 (0.4) years. Children who completed this exam were largely reported as white race (97%), born to married mothers (86%) with a college degree or higher (67%). The median (IQR) gestational urine tAs concentration was 4.0 (5.0) µg/L. Mean (SD) BOT-2 scores were 48.6 (8.4) for overall motor proficiency and 48.2 (9.6) for fine manual control [standard score = 50 (10)], and were 16.3 (5.1) for fine motor integration and 12.5 (4.1) for fine motor precision [standard score = 15 (5)]. We found evidence of a non-linear dose response relationship and used a change-point model to assess the association of tAs with overall motor proficiency and indices of fine motor integration, fine motor precision, and their composite, fine manual control, adjusted for age and sex. In models adjusted for potential confounders, each doubling of urine tAs decreased overall motor proficiency by -3.3 points (95% CI: -6.1, -0.4) for tAs concentrations greater than the change point of 9.5 µg/L and decreased fine motor integration by -4.3 points (95% CI: -8.0, -0.6) for tAs concentrations greater than the change point of 17.0 µg/L. In summary, we found that levels of prenatal As exposure above an empirically-derived threshold (i.e., the change point) were associated with decrements in childhood motor development in a US population.

A REVIEW ON COMPREHENSION AND ACCRETION OF ARSENIC IN RICE (ORYZA SATIVA L.) PLANT

Consuming rice exposes you to arsenic (As), which is dangerous for your health. The buildup of As in rice was investigated in this study. According to research, Bangladesh and Taiwan have higher levels of As buildup in their rice than other nations. Furthermore, the key elements affecting the uptake of As into rice crops are described. Additionally, it was investigated if it would be possible to use efficient methods to lessen the buildup of As in rice. Arsenic is a hazardous element that has the ability to harm peoples health. In addition to being a source of both amino acids (AAs) and mineral elements, rice is an unwelcome supply of As for the billions of people who eat it as their main source of nutrition. A necessary metalloid called selenium (Se) has the ability to reduce As toxicity by enhancing antioxidant capacity. Through phosphate transporters and intrinsic channels that resemble nodulin 26, As(V) and As(III) are delivered to the root. The entry of methylated As, dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA), into the root may be significantly influenced by the silicic acid transporter. DMA(V) is very mobile in plants and is quickly translocated from root to shoot among As species. The use of microalgae and bacteria is the most effective agronomic strategy for reducing the uptake and accumulation of As in rice.

Arsenic Uptake, Transport, Accumulation in Rice and Prospective Abatement Strategies - A Review

Recent reports claim that arsenic (As) toxicity affects millions of individuals worldwide. A significant problem for rice output and quality as well as for human health is the high content of arsenic (As), a non-essential poisonous metalloid, in rice grains. Therefore, substantial research has been done on the interactions between rice and As in recent years. As rice plants uptake at the root surface is impacted by factors like radical oxygen loss and iron plaque. The absorption and movement of various As species as well as the transfer to sub cellular compartments include a multitude of transporters, including phosphate transporters and aquaglyceroporins. As III and AsV are transported into the root by phosphate transporters and intrinsic channels that mimic nodulin 26. The silicic acid transporter may have a substantial impact on how methylated As, dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA), enter the root. The issue of As contamination in rice is being addressed by researchers and practitioners to the best of their abilities. Making better plans may be aided by recent research on rice that explains the processes of arsenic ingestion, transportation, and metabolism at the rhizosphere. Common agronomic techniques, such as collecting rainwater for agricultural irrigation, using natural substances that aid in the methylation of arsenic, and biotechnology methods, may be investigated in an effort to lessen the uptake of arsenic by food crops. Innovative agronomic techniques and recent research findings on arsenic contamination in rice crops will be included in this review.

Reproductive-Toxicity-Related Endpoints in C. elegans Are Consistent with Reduced Concern for Dimethylarsinic Acid Exposure Relative to Inorganic Arsenic.

Exposures to arsenic and mercury are known to pose significant threats to human health; however, the effects specific to organic vs. inorganic forms are not fully understood. Caenorhabditis elegans' (C. elegans) transparent cuticle, along with the conservation of key genetic pathways regulating developmental and reproductive toxicology (DART)-related processes such as germ stem cell renewal and differentiation, meiosis, and embryonic tissue differentiation and growth, support this model's potential to address the need for quicker and more dependable testing methods for DART hazard identification. Organic and inorganic forms of mercury and arsenic had different effects on reproductive-related endpoints in C. elegans, with methylmercury (meHgCl) having effects at lower concentrations than mercury chloride (HgCl2), and sodium arsenite (NaAsO2) having effects at lower concentrations than dimethylarsinic acid (DMA). Progeny to adult ratio changes and germline apoptosis were seen at concentrations that also affected gravid adult gross morphology. For both forms of arsenic tested, germline histone regulation was altered at concentrations below those that affected progeny/adult ratios, while concentrations for these two endpoints were similar for the mercury compounds. These C. elegans findings are consistent with corresponding mammalian data, where available, suggesting that small animal model test systems may help to fill critical data gaps by contributing to weight of evidence assessments.

Stability of monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) in human urineand mouse tissues

Urine samples were collected from 75 subjects in theLagunera area of Mexico. There were four groups, based on totalarsenic concentrations in their drinking water(9-100μg/L).After collection,the samples were immediately put in a portable iceboxcontaining dry ice, and they were kept frozen while beingtransported to the University of Arizona, Tucson where theywerestored at -70°C before analysis.Arsenic metabolites,including MMA(III) and DMA(III),were measured in urine samples by usingHPLC-ICP-MS.

Construction of algal-bacterial consortia using green microalgae Chlorella vulgaris and As(III)-oxidizing bacteria: As tolerance and metabolomic profiling

Bioremediation became a promising technology to resolve arsenic (As) contamination in aquatic environment. Since monoculture such as microalgae or bacteria was sensitive to environmental disturbance and vulnerable to contamination, green microalgae Chlorella vulgaris and arsenite (As(III)) - oxidizing bacteria Pseudomonas sp. SMS11 were co-cultured to construct algal-bacterial consortia in the current study. The effects of algae-bacteria (A:B) ratio and exposure As(III) concentration on algal growth, As speciation and metabolomic profile were investigated. Algal growth arrested when treated with 100 mg/L As(III) without the co-cultured bacteria. By contrast, co-cultured with strain SMS11 significantly enhanced As tolerance in C. vulgaris especially with A:B ratio of 1:10. All the As(III) in culture media of the consortia were oxidized into As(V) on day 7. Methylation of As was observed on day 14. Over 1% and 0.5% of total As were converted into dimethylarsinic acid (DMA) after 21 days cultivation when the initial concentrations of As(III) were 1 and 10 mg/L, respectively. Metabolomic analysis was further performed to reveal the response of consortia metabolites to external As(III). The enriched metabolomic pathways were associated with carbohydrate, amino acid and energy metabolisms. Tricarboxylic acid cycle and glyoxylate and dicarboxylate metabolism were upregulated under As stress due to their biological functions on alleviating oxidative stress and protecting cells. Both carbohydrate and amino acid metabolisms provided precursors and potential substrates for energy production and cell protection under abiotic stress. Alterations of the pathways relevant to carbohydrate or amino acid metabolism were triggered by energy requirement.

Prenatal arsenic exposure, arsenic metabolism and neurocognitive development of 2-year-old children in low-arsenic areas

BackgroundThere is limited evidence on the effects of arsenic species and metabolic capacity on child neurodevelopment, particularly at low levels. Further, little is known about the critical window of exposure. ObjectiveTo estimate the associations of arsenic exposure and arsenic metabolism in different pregnancy periods with neurodevelopment of two-year-old children. MethodsConcentrations of arsenobetaine (AsB), arsenite, arsenate, monomethyl arsenic acid (MMA), and dimethyl arsenic acid (DMA) in urine samples collected in three trimesters from 1006 mothers were measured using HPLC − ICPMS. Inorganic arsenic (iAs) was calculated as the sum of arsenite and arsenate. Total arsenic (tAs) was calculated as the sum of iAs, MMA and DMA. Child neurodevelopment was assessed with the Bayley Scales of Infant Development. ResultsThe geometric mean (GM) of SG-adjusted tAs in the first, second, third trimester was 16.37, 12.94, 13.04 μg/L, respectively. The mental development index (MDI) score was inversely associated with iAs and tAs. Compared to the 1st quartile, the MDI score decreased 0.43 (95%CI: −4.22, 3.36) for the 2nd, 6.50 (95%CI: −11.73, −1.27) for the 3rd, 5.42 (95%CI: −10.74, −0.10) for the 4th quartiles of iAs, and decreased 4.03 (95%CI: −7.90, −0.15) in the 4th quartile of tAs. In trimester-specific models, negative associations of DMA [−1.94 (95%CI: −3.18, −0.71)] and tAs [−1.61 (95%CI: −3.02, −0.20)] with the psychomotor development index (PDI) were only observed in 1st trimester. ConclusionsOur study found inverse associations between prenatal arsenic exposure, especially in early pregnancy, and neurodevelopment of children at two years old, even at low exposure levels.

Individual, Independent, and Joint Associations of Toxic Metals and Manganese on Hypertensive Disorders of Pregnancy: Results from the MIREC Canadian Pregnancy Cohort.

Toxic metals, such as lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg), may be associated with a higher risk of gestational hypertension and preeclampsia, whereas manganese (Mn) is an essential metal that may be protective. We estimated the individual, independent, and joint associations of Pb, Cd, As, Hg, and Mn on the risk of developing gestational hypertension and preeclampsia in a cohort of Canadian women. Metal concentrations were analyzed in first and third trimester maternal blood (). We measured blood pressure after 20 wk gestation to diagnose gestational hypertension, whereas proteinuria and other complications defined preeclampsia. We estimated individual and independent (adjusted for coexposure) relative risks (RRs) for each doubling of metal concentrations and examined interactions between toxic metals and Mn. We used quantile g-computation to estimate the joint effect of trimester-specific exposures. Each doubling of third trimester Pb (; 95% CI: 1.06, 2.22) and first trimester blood As (; 95% CI: 1.01, 1.58) was independently associated with a higher risk of developing preeclampsia. First trimester blood As (; 95% CI: 1.40, 8.28) and Mn (; 95% CI: 0.42, 0.94) concentrations were associated with a higher and lower risk, respectively, of developing gestational hypertension. Mn modified the association with As such that the deleterious association with As was stronger at lower concentrations of Mn. First trimester urinary dimethylarsinic acid concentrations were not associated with gestational hypertension (; 95% CI: 0.60, 2.85) or preeclampsia (; 95% CI: 0.68, 1.24). We did not observe overall joint effects for blood metals. Our results confirm that even low blood Pb concentrations are a risk factor for preeclampsia. Women with higher blood As concentrations combined with lower Mn in early pregnancy were more likely to develop gestational hypertension. These pregnancy complications impact maternal and neonatal health. Understanding the contribution of toxic metals and Mn is of public health importance. https://doi.org/10.1289/EHP10825.

Arsenic, cadmium, and lead in rice and rice products on the Austrian market

ABSTRACT Fifty-one rice samples, i.e. 25 rice varieties, 8 rice products, and 18 rice containing baby foods from the Austrian market were surveyed for arsenic, cadmium, and lead. Inorganic arsenic (iAs) is most toxic to human health, and its mean concentrations in rice were 120 µg kg−1, 191 µg kg−1 in rice products, and 77 µg kg−1 in baby foods. The average dimethylarsinic acid and methylarsonic acid concentrations were 56 µg kg−1 and 2 µg kg−1, respectively. The highest iAs concentration was found in rice flakes (237 ± 15 µg kg−1), close to the Maximum Level (ML) set by the EU regulation for husked rice (250 µg kg−1). The levels of cadmium (12 to 182 µg kg−1) and lead (6 to 30 µg kg−1) in the majority of rice samples were below the European ML. Upland grown rice from Austria showed both, low inorganic arsenic (<19 µg kg−1) and cadmium (<38 µg kg−1) concentrations.

Fate of 14 C-MSMA in a soil column study simulating herbicide use environments.

Monosodium methanearsonate (MSMA), a selective contact herbicide, is a sodium salt of monomethyl arsenic acid (MMA or MAA). This paper focuses on the environmental fate of MMA. Decades of research have shown that a significant portion of applied MSMA drips to soil and is sorbed quickly. The fraction available for leaching or biological uptake decreases at a biphasic rate, first rapidly and then at a slower rate. A soil column study was designed to obtain quantitative information about MMA sorption and transformation and the effects of different environmental variables on these processes, in conditions simulating the environment of MSMA use on cotton and turf. Using 14 C-MSMA, this study quantified MSMA-derived arsenic species and differentiated between added arsenic and soil background levels. Similar behavior of MSMA was observed across all test systems with respect to sorption, transformation, and mobility, despite differences in soil type and rainfall treatment. All soil columns exhibited a rapid sorption of added MMA followed by continual sorption of residues into the soil matrix. Within the first 2 days, only 20%-25% of radioactivity was extracted by water. On day 90, less than 3.1% of added MMA was in a water extractable phase. MMA sorption was most rapid in the soil with the higher clay content. Dominant extractable arsenic species were MMA, dimethylarsinic acid, and arsenate, indicating that methylation and demethylation occurred. In all MSMA-treated columns, arsenite concentrations were negligible and indiscernible from those in untreated columns.

Speciated and Total Urinary Arsenic Levels in Belo Horizonte, the Largest Brazilian City within the Mineral-Rich Region “Iron Quadrangle”

The “Quadrilátero Ferrífero” (Iron Quadrangle) is a mineral-rich province in Brazil, where arsenic anomalies are associated with gold mining and tailings dam failures. Urine samples were randomly collected from residents of Belo Horizonte (BH) city (N = 506 total/138 speciation) and the metropolitan area (N = 35 total/10 speciation), with stratifications in age, female-male and geopolitical regions. Creatinine, acid-digested total arsenic (TAs), and five inorganic and organic arsenic species were measured: arsenobetaine (AsB); arsenous (AsIII) and arsenic (AsV) acids and their dissociation products; monomethylarsonic acid (MMA); and dimethylarsinic acid DMA). Overall, the TAs GM (μg/g creat) of all stratification groups indicated no statistical difference. The TAs geometric mean (GM) of BH was 9.68 [9.17–10.2] μg/g creat, being AsB (43.8%) and DMA (20.7%) the major components. The toxic arsenic (ToxAs) fraction (i.e., AsIII + AsV + MMA + DMA) was 5.23 [4.45–6.15] μg/L. These TAs and ToxAs values are lower than international benchmarks and the Brazilian legislated standard of 35 μg/L for ToxAs. The TAs GM (μg/L) and creatinine were 36% higher for males than for females (p < 0.0001), making TAs GMs comparable, after creatinine correction. Similarly, though the 10–19 age group showed significantly higher ToxAs GM (12.7 [6.49–24.8] μg/L) (p = 0.048) and creatinine (p < 0.001), the ToxAs GM (7.22 [2.92–17.9] μg/g creat), was not statistically different than those from the other age groups. The study, the first one in Brazil, identifies the relative contribution of inorganic and organic arsenic and provides a baseline level for clinical reference and bio-monitoring studies, particularly applicable to both occupational and non-occupational populations in a mineral-rich region.Graphical abstract

Evaluation of the long-term stability of arsenic species in certified reference materials: certification of arsenobetaine, As(V), and dimethylarsinic acid in NMIJ CRMs 7901-a, 7912-a, and 7913-a.

The long-term stabilities of arsenobetaine (AsB), arsenate (As(V)), and dimethylarsinic acid (DMA), which are arsenic (As) compounds in certified reference materials (CRMs), namely, NMIJ CRMs 7901-a, 7912-a, and 7913-a, were monitored. The CRMs were developed and certified by the National Metrology Institute of Japan (NMIJ) and the National Institute of Advanced Industrial Science and Technology (AIST) in 2009 to prepare a calibrant for the speciation analysis of As species. The CRMs were prepared from high-purity reagent powders as raw materials, and each reagent was dissolved in water or diluted acid. The certification of the CRMs for AsB, As(V), and DMA was conducted by NMIJ. The concentration of total As was determined by more than three independent analytical techniques. Then, the obtained As concentrations were converted into the concentration of each chemical species, and the mass fractions of each certified value were certificated. The long-term stability of As species in the CRMs under storage was performed by liquid chromatography-inductively coupled plasma-mass spectrometry, and this report presents data on long-term stability that occurred approximately 13years. The obtained monitoring results were evaluated using both measurement results with uncertainty and a statistical parameter method, complying with ISO Guide 35. According to the results, the long-term stability of all mass fractions was confirmed.

Synchronous response of arsenic methylation and methanogenesis in paddy soils with rice straw amendment.

Rice straw (RS) amendment promotes arsenic (As) methylation and methane (CH4) emissions from paddy soils, which can cause straighthead disease and climate warming. Although methanogens have been identified as critical regulators of methylated As concentrations in flooded soils, the mechanism of these microbial groups on As methylation in paddy soils with RS amendment remains unknown. In this study, paddy soil was incubated to test the response in As methylation and methanogenesis in flooded soil with RS amendment. Our results showed that RS amendment increased the accumulation of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) whether methanogenesis was inhibited or not. The methanogens inthe genera ofMethanocella probably played critical role in promoting As methylation in flooded soil with RS amendment. With the RS amendment, inhibition of methanogenesis led to the accumulation MMA and DMA by suppressing DMA demethylation. The demethylation of DMA was driven by methanogens possibly belonging to the genera of Methanobacterium. This study revealed a wealth of methanogens that dominate As methylation with RS amendment. It will provide guidance to RS amendment in As contaminated paddy soil and has important implications for rice quality and global climate change.

Abstract P171: Associations Between Metals and Allostatic Load Among Non-Hispanic Asians and Non-Hispanic Whites From the National Health and Nutrition Examination Survey: 2015-2020

Introduction: Environmental metal exposure has been linked with multi-system toxicity and elevated stress hormones, and high metal concentrations have been observed among Asian Americans. Metal exposure may also increase Allostatic Load (AL), or physiologic “wear-and-tear” on the body. Hypothesis: Metal biomarker concentration is associated with high AL among non-Hispanic Asian (NHA) and non-Hispanic White (NHW) adults. Methods: AL scores were calculated based on 9 biomarkers representing cardiovascular, metabolic, and immune system function using data from the National Health and Nutrition Examination Survey (2015-2020). High AL was defined as having ≥3 high-risk biomarkers based on empirically defined thresholds. Lead, cadmium, and mercury were quantified in blood while arsenic, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured in urine. Metal concentrations were categorized into empirically-defined sample tertiles. Survey-weighted logistic regression analyses controlled for demographic, socioeconomic, and health behavior variables. Analyses were also stratified by NHA and NHW. Results: The study sample consisted of 5,012 adults [mean age: 50.4, SE: 0.5] (21.6% foreign-born NHA, 2.7% US-born NHA, and 75.7% NHW). Prevalence of high AL was 38.2% among NHW, 32.4% among foreign-born NHA, and 19.3% among US-born NHA. Metal exposure demonstrated heterogenous relationships with AL ( Table ). Individuals in the highest tertile of cadmium exposure had 38% greater odds of having high AL than those in the lowest tertile, however this association was attenuated after controlling for socioeconomic status and health behaviors. Lead, mercury, arsenic, DMA, and MMA were associated with lower odds of high AL. Relationships were similar when stratified by NHW and NHA. Conclusion: The association between metals and AL differs by metal type in our study population. Future studies should explore the mechanistic pathways between high metal exposure and AL.