Human arsenic exposure and risk assessment at the landscape level: a review

Enhanced arsenite removal by superparamagnetic iron oxide nanoparticles in-situ synthesized on a commercial cube-shape sponge: adsorption-oxidation mechanism

HYPOTHESIS

The easy aggregation of superparamagnetic iron oxide nanoparticles (SPION) greatly reduces their adsorption performance for removing arsenic (As) from polluted water. We propose to exploit the porosity and good diffusion properties of a cube-shaped cellulose sponge for loading SPION to reduce the aggregation and to develop a composite adsorbent in the cm-scale that could be used for industrial applications.

EXPERIMENTS

SPION were in-situ synthesized by co-precipitation using a commercial cube-shaped sponge (MetalZorb®) as support. The morphology, iron-oxide phase, adsorption performance and thermodynamic parameters of the composite adsorbent were determined to better understand the adsorption process. X-ray absorption spectroscopy (XAS) was used to investigate the chemical state of the adsorbed As(III).

FINDINGS

The adsorption of the supported SPION outperforms the unsupported SPION (ca. 14 times higher adsorption capacity). The modelling of the adsorption isotherms and the kinetic curves indicated that chemisorption is controlling the adsorption process. The thermodynamic analysis shows that the adsorption retains the spontaneous and endothermic character of the unsupported SPION. The XAS results revealed an adsorption-oxidation mechanism in which the adsorbed As(III) was partially oxidized to less toxic As(V) by the hydroxyl free radical (•OH) generated from Fe(III) species and by the hydroxyl groups.

Arsenic and Human Health: Genotoxicity, Epigenomic Effects, and Cancer Signaling

Arsenic is a well-known element because of its toxicity. Humans as well as plants and animals are negatively affected by its exposure. Some countries suffer from high levels of arsenic in their tap water and soils, which is considered a primary arsenic-linked risk factor for living beings. Humans generally get exposed to arsenic by contaminated drinking waters, resulting in many health problems, ranging from cancer to skin diseases. On the other hand, the FDA-certified drug arsenic trioxide provides solutions for various diseases, including several types of cancers. This issue emphasizes the importance of speciation of the metalloid elements in terms of impacts on health. When species get exposed to arsenic, it affects the cells altering their involvement. It can lead to abnormalities in inflammatory mechanisms and the immune system which contribute to the negative impacts generated on the body. The poisoning originating from arsenic gives rise to various biological signs on the body which can be useful for the diagnosis. It is important to find true biomarkers for the detection of arsenic poisoning. In view of its application in medicine and biology, studies on understanding the biological activity of arsenic have increased. In this review, we aim at summarizing the current state of knowledge of arsenic and the mechanism behind its toxicity including genotoxicity, oxidative insults, epigenomic changes, and alterations in cellular signaling.

Arsenic anomalies in soils and rocks occurring in the southwestern part of the Grand Duchy of Luxembourg

Developing legislation on soil protection, including soil quality standards, is not straightforward for areas with high geogenic metal(loid) concentrations in rocks and soils. Several rock types in southern Luxembourg (laterally continuous into Northern France and Southern Belgium) contain elevated potentially toxic element concentrations. Toarcian and Aalenian Minette ironstones, and soils on top, possess high As concentrations (average of ~100 mg/kg, maximum up to 278 mg/kg). Liassic shales show high Mo concentrations (up to 60 mg/kg). Preliminary health risk assessments suggest increased potential non-carcinogenic and carcinogenic risks. Trace metal and As anomalies, however, do not necessarily pose human and ecotoxicological risks. Petrographic, mineralogical and chemical analyses show a strong association of As to iron oxides present as ooids and rock matrix. Single extractions with CaCl₂ (0.01 mol/l) indicated the low As mobility in the Minettes. The Minette rocks with 10-40 wt% iron oxides, and a clay content of typically 10-30 wt% strongly bind As. As long as Eh and pH do not drastically change in soils, As mobility will remain low. For soils that developed on Minettes, it is advised to consider Fe-content as well as As mobility for risk assessment and development of legislation on soil protection.

High geogenic arsenic concentrations in travertines and their spring waters: Assessment of the leachability and estimation of ecological and health risks

Travertines and their springs are rarely investigated as a source of toxicity. Remarkably high contents of As (up to 10 g/kg) have been found in travertine deposits and associated spring waters, nearby Ghorveh city (western Iran). Two types of travertines were distinguished: (i) Fissure ridge travertines, in areas with a carbonate-dominated basement, are characterized by a relatively low content and leaching of As. Their spring waters contain > 150 µg/L of As; (ii) Mound travertines, rich in non-carbonate impurities, occur in areas with volcanic substrates and contain high As concentrations (on average ~1,500 mg/kg) with high leachability. Their spring waters have lower As concentrations than equivalent fissure ridge waters. Principal Component Analyses of the elemental and mineralogical composition show the unstable association of As over a wide range of pH values to non-carbonate related elements, in particular iron, related to clay minerals. The high potential release of As may result in adverse ecotoxicological effects in surrounding agricultural soils and crops. An ecological risk assessment confirms the enrichment and very high potential ecological risk of As around mound carbonates. The human health risk assessment based on calculation via exposure factors suggests adverse non-carcinogenic and high carcinogenic risk with regard to As, both for adults and children.

One-Step Preparation of Chitosan-Based Magnetic Adsorbent and Its Application to the Adsorption of Inorganic Arsenic in Water

Chitosan is a kind of biodegradable natural polysaccharide, and it is a very promising adsorber material for removing metal ions from aqueous solutions. In this study, chitosan-based magnetic adsorbent CMC@Fe₃O₄ was synthesized by a one-step method using carboxymethyl chitosan (CMC) and ferric salts under relatively mild conditions. The Fe₃O₄ microspheres were formed and the core-shell structure of CMC@Fe₃O₄ was synthesized in the meantime, which was well characterized via SEM/TEM, XRD, VSM, FT-IR, thermo gravimetric analysis (TGA), XPS, size distribution, and zeta potential. The effects of initial arsenic concentration, pH, temperature, contact time, and ionic strength on adsorption quantity of inorganic arsenic was studied through batch adsorption experiments. The magnetic adsorbent CMC@Fe₃O₄ displayed satisfactory adsorption performance for arsenic in water samples, up to 20.1 mg/g. The optimal conditions of the adsorption process were pH 3.0, 30-50 °C, and a reaction time of 15 min. The adsorption process can be well described by pseudo-second-order kinetic model, suggesting that chemisorption was main rate-controlling step. The Langmuir adsorption model provided much higher correlation coefficient than that of Freundlich adsorption model, indicating that the adsorption behavior is monolayer adsorption on the surface of the magnetic adsorbents. The above results have demonstrated that chitosan-based magnetic adsorbent CMC@Fe₃O₄ is suitable for the removal of inorganic arsenic in water.

Arsenic in a groundwater environment in Bangladesh: Occurrence and mobilization

Groundwater with an excessive level of Arsenic (As) is a threat to human health. In Bangladesh, out of 64 districts, the groundwater of 50 and 59 districts contains As exceeding the Bangladesh (50 μg/L) and WHO (10 μg/L) standards for potable water. This review focuses on the occurrence, origin, plausible sources, and mobilization mechanisms of As in the groundwater of Bangladesh to better understand its environmental as well as public health consequences. High As concentrations mainly was mainly occur from the natural origin of the Himalayan orogenic tract. Consequently, sedimentary processes transport the As-loaded sediments from the orogenic tract to the marginal foreland of Bangladesh, and under the favorable biogeochemical circumstances, As is discharged from the sediment to the groundwater. Rock weathering, regular floods, volcanic movement, deposition of hydrochemical ore, and leaching of geological formations in the Himalayan range cause As occurrence in the groundwater of Bangladesh. Redox and desorption processes along with microbe-related reduction are the key geochemical processes for As enrichment. Under reducing conditions, both reductive dissolution of Fe-oxides and desorption of As are the root causes of As mobilization. A medium alkaline and reductive environment, resulting from biochemical reactions, is the major factor mobilizing As in groundwater. An elevated pH value along with decoupling of As and HCO₃^- plays a vital role in mobilizing As. The As mobilization process is related to the reductive solution of metal oxides as well as hydroxides that exists in sporadic sediments in Bangladesh. Other mechanisms, such as pyrite oxidation, redox cycling, and competitive ion exchange processes, are also postulated as probable mechanisms of As mobilization. The reductive dissolution of MnOOH adds dissolved As and redox-sensitive components such as SO₄^2- and oxidized pyrite, which act as the major mechanisms to mobilize As. The reductive suspension of Mn(IV)-oxyhydroxides has also accelerated the As mobilization process in the groundwater of Bangladesh. Infiltration from the irrigation return flow and surface-wash water are also potential factors to remobilize As. Over-exploitation of groundwater and the competitive ion exchange process are also responsible for releasing As into the aquifers of Bangladesh.

Impact of green synthesized iron oxide nanoparticles on the distribution and transformation of As species in contaminated soil

Iron nanoparticles (Fe NPs) have often been used for in situ remediation of both groundwater and soil. However, the impact of Fe NPs on the distribution and transformation of As species in contaminated soil is still largely unknown. In this study, green iron oxide nanoparticles synthesized using a euphorbia cochinchinensis leaf extract (GION) were used to stabilize As in a contaminated soil. GION exhibited excellent As stabilization effects, where As in non-specifically-bound and specifically-bound fractions decreased by 27.1% and 67.3% after 120 days incubation. While both arsenate (As (V)) and arsenite (As (III)) decreased after GION application, As (V) remained the dominant species in soil. X-ray photoelectron spectroscopy (XPS) confirmed that As (V) was the dominant species in specifically-bound fractions, while As (III) was the dominant species in amorphous and poorly-crystalline hydrous oxides of Fe and Al. Correlation analysis showed that while highly available As fractions were negatively correlated to oxalate and DCB extractable Fe, they were positively correlated to Fe²⁺ content, which indicated that Fe cycling was the main process influencing changes in As availability. X-ray fluorescence (XRF) spectroscopy also showed that the Fe₂O₃ content increased by 47.9% following GION soil treatments. Overall, this work indicated that As would be transformed to more stable fractions during the cycling of Fe following GION application and that the application of GION, even in small doses, provides a low-cost and ecofriendly method for the stabilization of As in soil.

Risk assessment framework for nitrate contamination in groundwater for regional management

Nitrate pollution in groundwater is now one of the most important environmental problems all over the world. For this purpose, a new framework for risk screening and assessment of groundwater nitrate was proposed according to source-pathway-receptor-response model to provide basic for defining environmental management strategies. The framework is composed of groundwater relative risk model (RRM), groundwater contamination risk assessment (CRA), and human health risk assessment (HHRA). The framework is applied in the lower Liaohe river basin plain, northeast of China. The results showed that the priority area with high groundwater relative risk in study area was successfully screened by RRM. Furthermore, the sites with high human health risk for public by groundwater nitrate were selected as hazardous areas. This framework promotes systematic integration of risk assessment of groundwater nitrate and expands traditional research on groundwater management from a scale-based approach to crucial insights into pollution.

Sensitive determination of As (III) and As (V) by magnetic solid phase extraction with Fe@polyethyleneimine in combination with hydride generation atomic fluorescence spectrometry

The magnetic nanomaterial Fe@polyethyleneimine (Fe@PEI) was successfully synthesized and used as an effective adsorbent material for magnetic solid phase extraction(MSPE) of As(III) and As(V) from water samples. Fe@SiO2 nanoparticles were prepared by one pot synthetic method using a borohydride reduction method, then modified with (3-chloropropyl)trimethoxysilane to obtain Fe@SiO2-Cl by chloropropylation, which was reacted with PEI to achieve Fe@polyethyleneimine (Fe@PEI). The microstructure and morphology of Fe@PEI were characterized by transmission electron microscoscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The experimental results showed that Fe@PEI demonstrated excellent adsorption for As(III) and As(V). Based on this fact, the determination method for these two arsenic species earned good limits of detection (LODs) of 0.002μgL(-1) and wide calibration curves in the concentration range from 0.008 to 0.2μgL(-1). The precisions of As (III) and As (V)were 1.95% and 2.55% (RSD, n=6), respectively. The proposed method was validated with real samples and the spiked recoveries were in the range of 82.7-98.3% and the accuracies were in the range of 2-13.3%. The results demonstrated that the developed MSPE method had good advantages such as simplicity, rapid separation, low cost, easy to reuse and high-quality analytical performances, which made it attractive for rapid and efficient extraction of inorganic arsenic species in the environmental water samples.

Impact of Soil Heavy Metal Pollution on Food Safety in China

Food safety is a major concern for the Chinese public. This study collected 465 published papers on heavy metal pollution rates (the ratio of the samples exceeding the Grade II limits for Chinese soils, the Soil Environmental Quality Standard-1995) in farmland soil throughout China. The results showed that Cd had the highest pollution rate of 7.75%, followed by Hg, Cu, Ni and Zn, Pb and Cr had the lowest pollution rates at lower than 1%. The total pollution rate in Chinese farmland soil was 10.18%, mainly from Cd, Hg, Cu, and Ni. The human activities of mining and smelting, industry, irrigation by sewage, urban development, and fertilizer application released certain amounts of heavy metals into soil, which resulted in the farmland soil being polluted. Considering the spatial variations of grain production, about 13.86% of grain production was affected due to the heavy metal pollution in farmland soil. These results many provide valuable information for agricultural soil management and protection in China.

Vertical distribution of bacterial communities in high arsenic sediments of Hetao Plain, Inner Mongolia

Vertical distribution of bacterial communities was detected in high arsenic (As) sediments in a representative high As area in Inner Mongolia. Nineteen sediment samples were collected from a 30 m borehole and detected by geochemistry and molecular ecological approaches including polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), 16S rRNA gene clone library and 454 pyrosequencing. As contents ranged from 42.1 to 111.3 mg kg(-1) which fluctuated with different depth and significantly high in clay and mild clay sediment samples at depth of 8, 20, 25 and 28 m respectively. The ratios of As(III) to total As generally increased with depth but As(V) dominated in all sediment samples. High concentrations of total As, sulfur, iron and total organic carbon were generally found in clay and low in sand samples. Both DGGE patterns and 454 pyrosequencing results indicated that bacterial communities dynamically diversified with increasing depth and were dominated by Firmicutes, Bacteroidetes, Proteobacteria and Chloroflexi. Most of the sediment samples were dominated by populations including Sporosarcina, Acinetobacter, Pseudomonas, Halomonas, Polaromonas, Paenibacillus and Flavobacterium. These populations were found with high similarities with those microbes capable of denitrification, sulfur oxidation, organic matter degradation and As resistance and reduction. These results implied that microbes might play an important role in As mobilization in the shallow aquifers of Hetao Plain, Inner Mongolia.

Evaluation of the transfer of soil arsenic to maize crops in suburban areas of San Luis Potosi, Mexico

The presence of arsenic (As) in agricultural food products is a matter of concern because it can cause adverse health effects at low concentrations. Agricultural-product intake constitutes a principal source for As exposure in humans. In this study, the contribution of the chemical-soil parameters in As accumulation and translocation in the maize crop from a mining area of San Luis Potosi was evaluated. The total arsenic concentration and arsenic speciation were determined by HG-AFS and IC-HG-AFS, respectively. The data analysis was conducted by cluster analysis (CA) and principal component analysis (PCA). The soil pH presented a negative correlation with the accumulated As in each maize plant part, and parameters such as iron (Fe) and manganese (Mn) presented a higher correlation with the As translocation in maize. Thus, the metabolic stress in maize may induce organic acid exudation leading a higher As bioavailability. A high As inorganic/organic ratio in edible maize plant tissues suggests a substantial risk of poisoning by this metalloid. Careful attention to the chemical changes in the rhizosphere of the agricultural zones that can affect As transfer through the food chain could reduce the As-intoxication risk of maize consumers.

Origin and assessment of groundwater pollution and associated health risk: a case study in an industrial park, northwest China

Groundwater quality which relates closely to human health has become as important as its quantity due to the demand for safe water. In the present study, an entropy-weighted fuzzy water quality index (WQI) has been proposed for performing groundwater quality assessment in and around an industrial park, northwest China, where domestic water requirements are solely met by groundwater. The human health risk was assessed with the model recommended by the United States Environmental Protection Agency. In addition, the sources of major ions and main contaminants were also analyzed. The study shows that groundwater in the study area has been contaminated conjunctively by natural processes and industrial and agricultural activities. Nitrate, manganese (Mn), fluoride, total dissolved solids, total hardness and sulfate are major contaminants influencing groundwater quality. Nitrate and heavy metals such as Mn are mainly affected by human agricultural activities and industrial production, while other contaminants are mainly originated from mineral weathering and water-rock interactions. The results of water quality assessment suggest that half of the groundwater samples collected are of medium quality thus require pretreatment before human consumption. The mean health risk caused by the consumption of contaminated groundwater in the area is 8.42 × 10(-5) per year which surpasses the maximum acceptable level (5 × 10(-5) per year) recommended by the International Commission on Radiologic Protection. The entropy-weighted fuzzy WQI proposed in this study can not only assign proper weights to parameters but also treat uncertainties associated with water quality classification. This study will be of interest to international environmentalists and hydrogeologists. It will also be useful in regional groundwater management and protection.

Arsenic mitigation in Bangladesh: an analysis of institutional stakeholders' opinions

While Bangladesh made significant achievements in safe water coverage via installation of shallow tubewells (STWs) nationwide, this success was shattered by the discovery of arsenic (As) in the STWs. The extent and severity of As groundwater contamination throughout Bangladesh and its detrimental effects on human health are well known and demand long-term sustainable mitigation. It is an immensely complex and expensive task to bring tens of millions of arsenic exposed people under safe water coverage. While various mitigation measures have been undertaken by various organizations, most have not achieved their expected outcomes due to technical, spatial and socio-economic challenges. Better understanding of these challenges by institutional stakeholders is crucial for sustainable arsenic mitigation in Bangladesh. In this study, institutional stakeholders' opinions on various aspects of As mitigation were elicited to identify their preferences for and reservations of specific mitigation measures. The current status of As mitigation activities and the factors influencing the success of As mitigation were also explored. Institutional weakness, lack of accountability and a latency period were the major factors hindering sustainable As mitigation. The results also suggested that the stakeholders' understanding of the As problem and their preferences for the different mitigation measures have a significant impact on the effectiveness of As mitigation. Mitigation of As contamination is a complex issue that requires a coordinated effort from various levels of stakeholders. The concept of "paying for water", which is currently potentially unknown in the rural areas of Bangladesh, also needs to be developed as this will create a stronger sense of user ownership of As safe water and thus better water management.

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

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

Evaluating the potential for environmental pollution from chromated copper arsenate (CCA)-treated wood waste: a new mass balance approach

The potential for pollution from arsenic, chromium and copper in chromated copper arsenate (CCA) treated wood waste was assessed using two lysimeter studies. The first utilised lysimeters containing soil and CCA wood waste mulch exposed to natural conditions over a five month period. The second study used the same lysimeter setup in a regulated greenhouse setting with a manual watering regime. Woodchip, soil and leachate samples were evaluated for arsenic, chromium and copper concentrations. Resultant concentration data were used to produce mass balances, an approach thus far unused in such studies. This novel analysis revealed new patterns of mobility and distribution of the elements in the system. The results suggest that CCA wood waste tends to leach on initial exposure to a leachant and during weathering of the wood. When in contact with soil, metal(loid) transport is reduced due to complexation reactions. With higher water application or where the adsorption capacity of the soil is exceeded, the metal(loid)s are transported through the soil column as leachate. Overall, there was an unexplained loss of metal(loid)s from the system that might be attributed to volatilisation of arsenic and plant uptake. This suggests a hitherto unidentified risk to both the environment and human health.

Modeling spatial patterns in soil arsenic to estimate natural baseline concentrations

Arsenic in soil is an important public health concern, but risk-based toxicity regulatory standards derived from laboratory studies should also consider concentrations measured away from obvious contamination (i.e., baseline concentrations that approximate natural background) to avoid unnecessary remediation burdens on society. We used soil and stream sediment samples from the USGS National Geochemical Survey to assess the spatial distribution of As over a 1.16 × 10 km area corresponding to the state of Ohio. Samples were collected at 348 soil and 144 stream sites at locations selected to minimize anthropogenic inputs. Total As was measured by sodium peroxide fusion with subsequent dissolution using concentrated HCl and analysis using hydride-generation atomic absorption spectrometry. Arsenic in the soil and streambed samples ranged from 2.0 to 45.6 mg kg. Sequential Gaussian simulation was used to map the expected concentration of As and its uncertainty. Five areas of elevated concentration, greater than the median of 10 mg kg, were identified, and relationships to geologic parent materials, glacial sedimentation, and soil conditions interpreted. Arsenic concentrations <4 mg kg were rare, >10 mg kg common, and >20 mg kg not unusual for the central and west central portions of Ohio. Concentrations typically exceeded the soil As human generic screening level of 0.39 mg kg, a value corresponding to an increase in cancer risk of 1 in 1,000,000 for soil ingestion. Such results call into question the utility of the USEPA and similarly low soil screening levels. The contrast between laboratory screens and concentrations occurring in nature argue for risk assessment on the basis of baseline concentrations.

Regional specific groundwater arsenic levels and neuropsychological functioning: a cross-sectional study

BACKGROUND

The purpose of the study was to examine the link between geographic information system (GIS)-estimated regional specific groundwater levels and neuropsychological functioning in a sample of individuals with and without cognitive impairment.

METHODS

This cross-sectional study design analyzed data from 1390 participants (733 Alzheimer's disease, 127 Mild Cognitive Impairment, and 530 with normal cognition) enrolled in the Texas Alzheimer's Research and Care Consortium. GISs analyses were used to estimate regional specific groundwater arsenic concentrations using the Environmental Systems Research Institute and arsenic concentrations from the Texas Water Development Board.

RESULTS

In the full cohort, regional specific arsenic concentrations were positively associated with language abilities (p = 0.008), but associated with poorer verbal memory, immediate (p = 0.008), and delayed (p < 0.001), as well as poorer visual memory, immediate (p = 0.02), and delayed (p < 0.001). The findings varied by diagnostic category with arsenic being related with cognition most prominently among mild cognitive impairment cases.

CONCLUSIONS

Overall, estimated regional specific groundwater arsenic levels were negatively associated with neuropsychological performance.

Arsenic waste management: a critical review of testing and disposal of arsenic-bearing solid wastes generated during arsenic removal from drinking water

Water treatment technologies for arsenic removal from groundwater have been extensively studied due to widespread arsenic contamination of drinking water sources. Central to the successful application of arsenic water treatment systems is the consideration of appropriate disposal methods for arsenic-bearing wastes generated during treatment. However, specific recommendations for arsenic waste disposal are often lacking or mentioned as an area for future research and the proper disposal and stabilization of arsenic-bearing waste remains a barrier to the successful implementation of arsenic removal technologies. This review summarizes current disposal options for arsenic-bearing wastes, including landfilling, stabilization, cow dung mixing, passive aeration, pond disposal, and soil disposal. The findings from studies that simulate these disposal conditions are included and compared to results from shorter, regulatory tests. In many instances, short-term leaching tests do not adequately address the range of conditions encountered in disposal environments. Future research directions are highlighted and include establishing regulatory test conditions that align with actual disposal conditions and evaluating nonlandfill disposal options for developing countries.

The Determination of Arsenic Compounds: A Critical Review

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

The impact of GPX1 on the association of groundwater selenium and depression: a Project FRONTIER study

BACKGROUND

Prior animal model and human-based studies have linked selenium concentrations to decreased risk for depression; however, this work has not focused on household groundwater levels or specific depressive symptoms. The current study evaluated the link between groundwater selenium levels and depression. We also sought to determine if a functional polymorphism in the glutathione peroxidase 1 (GPX1) gene impacted this link.

METHODS

We used a cross-sectional design to analyze data from 585 participants (183 men and 402 women) from Project FRONTIER, a study of rural health in West Texas. Residential selenium concentrations were estimated using Geospatial Information System (GIS) analyses. Linear regression models were created using Geriatric Depression Scale (GDS-30) total and subfactor scores as outcome variables and selenium concentrations as predictor variables. Analyses were re-run after stratification of the sample on GPX1 Pro198Leu genotype (rs1050454).

RESULTS

Selenium levels were significantly and negatively related to all GDS and subfactor scores accounting for up to 17% of the variance beyond covariates. Selenium was most strongly protective against depression among homozygous carriers of the C allele at the Pro198Leu polymorphism of the GPX1 gene. Analyses also point towards a gene-environmental interaction between selenium exposure and GPX1 polymorphism.

CONCLUSION

Our results support the link between groundwater selenium levels and decreased depression symptoms. These findings also highlight the need to consider the genetics of the glutathione peroxidase system when examining this relationship, as variation in the GPX1 gene is related to depression risk and significantly influences the protective impact of selenium, which is indicative of a gene-environment interaction.

Geographical information systems and health: current state and future directions

This paper provides an introduction to Geographical Information Systems (GIS) and how they can be used. It reviews the current state of GIS use in health care before identifying the barriers to more pervasive use of GIS in health. Finally, it makes recommendations for the direction of health GIS research over the next decade and concludes with a call to action to health informatics researchers to stop ignoring a tool and methodology that has such immense potential for improving the health of our communities.

Low-level arsenic exposure, AS3MT gene polymorphism and cardiovascular diseases in rural Texas counties

Most Americans living in rural areas use groundwater for drinking. Exposure to low-level (around the current U.S. standard 10 μg/L) arsenic in drinking water is associated with increased mortality of cardiovascular diseases. The current study was to determine if coronary heart disease, hypertension, and hyperlipidemia were associated with low-level arsenic exposure and AS3MT gene single nucleotide polymorphism (SNP) A35991G (rs10748835) in rural Texas. Subjects (156 men, 343 women, 40-96 years of age with a mean of 61) were residents from rural counties Cochran, Palmer, and Bailey, Texas. Groundwater arsenic concentration at each subject's home was estimated with ArcGIS inverse distance weighted interpolation based on the residential location's distances to surrounding wells with known water arsenic concentrations. The estimated groundwater arsenic concentration ranged from 2.2 to 15.3 (mean 6.2) μg/L in this cohort. Logistic regression analysis showed that coronary heart disease was associated with higher arsenic exposure (p<0.05) and with AS3MT genotype GG vs. AA (p<0.05) after adjustments for age, ethnicity, gender, education, smoking status, alcoholism, and anti-hyperlipidemia medication. Hypertension was associated with higher arsenic exposure, while hyperlipidemia was associated with genotype AG vs. AA of the AS3MT gene (p<0.05). Thus, coronary heart disease and its main risk factors were associated with low-level arsenic exposure, AS3MT polymorphism or both.

Total and inorganic arsenic in marketed food and associated health risks for the Catalan (Spain) population

Inorganic arsenic (iAs) is considered to be a human carcinogen. In this paper, total (As) and iAs contents of 215 food products and drinks (i.e., seafood, fruits and vegetables, meat products, oils and fats, rice and rice products, seasonings, and alcoholic drinks) marketed in Catalonia (Spain) were quantified by inductively coupled plasma-mass spectrometry. The analytical method described was used for different food products, obtaining feasible results without the need to couple LC-ICP-MS for iAs. Daily As and iAs intakes for the average adult Catalan consumer were estimated at 354 and 6.1 μg/day/person, respectively, using consumption data from the Catalan Nutrition Survey (ENCAT). The highest As content was found in seafood, contributing 96% of dietary As intake, whereas rice presented the highest iAs values, corresponding to 67% of dietary iAs intake. As cooking process may affect iAs content, boiled rice was evaluated, showing an iAs reduction (up to 86%) when using higher water volumes (30:1 water/rice ratio) than those used in previous studies. This iAs exposure was slightly below the exposure risk range stated by the European Food Safety Authority (0.3-8 μg/kg of body weight/day), although the possibility of a risk to the population with high rice consumption cannot be excluded.

Long-term low-level arsenic exposure is associated with poorer neuropsychological functioning: a Project FRONTIER study

Exposure to elements in groundwater (toxic or beneficial) is commonplace yet, outside of lead and mercury, little research has examined the impact of many commonly occurring environmental exposures on mental abilities during the aging process. Inorganic arsenic is a known neurotoxin that has both neurodevelopmental and neurocognitive consequences. The aim of this study was to examine the potential association between current and long-term arsenic exposure and detailed neuropsychological functioning in a sample of rural-dwelling adults and elders. Data were analyzed from 434 participants (133 men and 301 women) of Project FRONTIER, a community-based participatory research study of the epidemiology of health issues of rural-dwelling adults and elders. The results of the study showed that GIS-based groundwater arsenic exposure (current and long-term) was significantly related to poorer scores in language, visuospatial skills, and executive functioning. Additionally, long-term low-level exposure to arsenic was significantly correlated to poorer scores in global cognition, processing speed and immediate memory. The finding of a correlation between arsenic and the domains of executive functioning and memory is of critical importance as these are cognitive domains that reflect the earliest manifestations of Alzheimer's disease. Additional work is warranted given the population health implications associated with long-term low-level arsenic exposure.

Does arsenic in soil contribute to arsenic urinary concentrations in a French population living in a naturally arsenic contaminated area?

A cross sectional study using environmental and biological samples was implemented to assess the association between arsenic (As) concentrations in the environment and urinary As levels of residents living in an area where the soil is naturally As rich. As was measured in drinking water, atmospheric particulate matter, and soil and a geographic information system was used to assign environmental concentrations closest to the participants' dwellings and the sum of inorganic As and metabolites in urine samples. The only potential source of As environmental contamination was from soil with a range of 13-131 mg As/kg of dry matter. As(V) was the only species present among As extracted from the analyzed soil samples. The chemical extraction showed a poor mobility of As soil. There was no difference between child and teenager, and adult urinary As concentrations, though men had higher urinary As concentrations than women (p<0.001). Given the important differences in lifestyle between 7-18 year olds, men, and women, these groups were analyzed separately. Whilst we were unable to find a stable model for the 7-18 year old group, for the adult men group we found that seafood consumption in the 3 days prior to the investigation (p=0.02), and beer (p=0.03) and wine consumption in the 4 days before the study, were associated with As urinary levels (μg/L). In adult women, creatinine was the only variable significantly associated with As urinary concentration (μg/L). The concentrations we measured in soils were variable and although high, only moderately so and no link between As concentrations in the soil and urinary As concentrations could be found for either men or women. Some individual factors explained half of the variability of adult men urinary As levels. The unexplained part of the variability should be searched notably in As mobility in soil and uncharacterized human behavior.

Urinary arsenic concentrations and speciation in residents living in an area with naturally contaminated soils

A cross sectional study was carried out to evaluate arsenic exposure of residents living in an area with a soil naturally rich in arsenic (As), through urinary measurements. During the summer of 2007, 322 people aged over 7 years and resident in the study area for at least 4 days prior to the investigation were recruited. The sum of urinary inorganic arsenic and metabolites (iAs+MMA+DMA) and speciation were determined by graphite furnace atomic absorption spectrometry and high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry, respectively. Geometric means levels of iAs+MMA+DMA were 3.6 microg/L or 4.4 microg/g creatinine. The percent of DMA, As(III) and MMA contribution to urinary arsenic concentrations was respectively 84.2%, 12% and 3.7%. We found significant associations between urinary arsenic concentrations and the consumption of seafood (p=0.03), the consumption of wine (p=0.03) and beer (p=0.001), respectively 3 and 4 days before the investigation. When we focus on the various species, As(V) was rarely detected and DMA is the predominant metabolite composing the majority of measurable inorganic-related As in the urine. Considering the percent of DMA contribution to iAs+MMA+DMA urinary concentrations, almost half of the subjects had 100% of DMA contribution whatever the concentration of urinary As whereas the others had a lower DMA contribution, between 39 and 90%. Arsenic levels reported in this original study in France were between 2 and 4 times lower than in other studies dealing with iAs+MMA+DMA levels associated with soil arsenic exposure. Arsenic levels were similar to those observed in unexposed individuals in European countries, although 10% were above the French guideline values for the general population.