Public Release:  Major symposium on arsenic contamination in food and water supplies

American Chemical Society

NEW ORLEANS, April 10, 2013 -- After virtually eliminating arsenic as a useful tool for homicide, science now faces challenges in doing the same for natural sources of this fabled old "inheritance powder" that contaminates water supplies and food, threatening more than 35 million people worldwide.

The Pulitzer Prize-winning author of a popular book documenting arsenic's horrific history as a poison highlighted that situation at a far-ranging symposium on arsenic here today during the 245th National Meeting & Exposition of the American Chemical Society, the world's largest scientific society. The following topics were among the two dozen presentations at the "Arsenic Contamination in Food and Water" symposium (abstracts appear below):

  • Poisoner's cupboard: The long (and sometimes homicidal) history of arsenic in everyday life.
  • Arsenic in rice and rice products.
  • Remediation of arsenic contamination of groundwater in Asia and USA.
  • Development of a method for assessing perinatal exposures to heavy metals using residual dried blood spots from newborn screening programs.
  • Pick your poison? Arsenic in harvested country foods, edible mushrooms and wine from Canada.
  • Low, slow and Next Gen impact: Arsenic, human health and cancer risks.

"Because of its sinister, homicidal uses, arsenic -- a naturally occurring element found in the Earth's crust -- became world-renowned as the 'inheritance powder,'" explained Deborah Blum, the plenary speaker for the symposium. "What made arsenic such a good homicidal poison is the same thing that makes it dangerous in environmental exposures -- it gives no warning," said Blum, who is at the University of Wisconsin-Madison. "It's mostly tasteless, it's odorless, and it's colorless. The symptoms of arsenic poisoning, especially if given in small doses over a long time, mimic those of natural diseases, so for a long time, people got away with it. Arsenic became one of the great historical poisons in human history."

Blum described how arsenic remained largely the poisoner's first choice until the 19th century, when manufacturers started using it in pesticides, candies, jewelry and even in wallpaper to give it a deep green color. It even found uses in patent remedies and as an additive in certain foods. It was all over the place and easy for anyone to get.

"At the start of the 19th century, scientists started realizing that they had to put a stop to this free-wheeling, murderous situation," she explained. "That's when the big revolution happened -- scientists finally figured out how to detect arsenic in the body. Slowly, people realized they couldn't easily get away with it anymore, and arsenic became more difficult to obtain -- manufacturers stopped adding it to common household products."

Other speakers in the symposium focused on the ongoing problem of arsenic contamination in the 21st century. Arsenic occurs naturally in elevated concentrations in the soil in certain areas of the world. It sometimes leaches into drinking water supplies and food. Recent reports in the news media have drawn attention to its presence in apple juice and rice, and in groundwater in Bangladesh and Chile.

"The goal of the symposium was to bring together experts on many aspects of arsenic, including general insights about arsenic contamination in food and water, regulatory issues, ways to analyze the element and ways to clean up contamination," said Jennifer Maclachlan of PID Analyzers, LLC, who was a co-organizer of the symposium. The other co-organizers were Britt Burton-Freeman, Ph.D., of the Illinois Institute of Technology; Lauren Jackson, Ph.D., of the U.S. Food and Drug Administration (FDA); John Johnston, Ph.D., of the U.S. Department of Agriculture; and Bill Mindak of FDA.

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Abstracts

Poisoner's cupboard: The long (and sometimes homicidal) history of arsenic in everyday life

Deborah Blum1, University of Wisconsin, Madison, WI, United States, 7744135281, dblum@wisc.edu

The story of the element arsenic is a story of human history through a uniquely poisonous lens. One of the earliest realized poisonous elements, homicidal uses of arsenic can easily be traced back to the Middle Ages. But these were notably murders at the upper levels of society. It wasn't until the 19th century -- and the rise of industrial use of elements such as arsenic -- that it became the poison of the everyday citizen, the weapon of choice for serial poisoners. This relates to the fact that arsenic was widely available -- in medicine, in cosmetics, as a pesticide and even as a coloring agent in food. My talk will explore the rise of arsenic for both commercial and homicidal use, the rise of forensic toxicology that grew up as a result and the consequences, even today, of our long and close relationship with history's most important poison.

Distribution of arsenic in soils of the conterminous United States

David B. Smith1, Dr., Ph.D., U.S. Geological Survey, Denver Federal Center, Box 25046, MS 973, Denver, CO, 80225, United States, 303-236-1849, 303-236-3200, dsmith@usgs.gov

The U.S. Geological Survey recently completed a soil geochemical survey of the conterminous United States. The project was based on sampling of 4,800 sites (1 site per approximately 1,600 km2). At each site a sample from 0 to 5 cm depth was collected along with samples from the soil A and C horizons. Each sample was sieved to <2 mm and then ground to <150 μm prior to chemical analysis for 45 major and trace elements. Arsenic was analyzed by hydride-generation atomic absorption spectrometry following fusion in sodium peroxide and sodium hydroxide. For all three sample types, arsenic varied by approximately three orders of magnitude from less than 0.6 mg/kg to about 1,000 mg/kg, with a median of 5.2 mg/kg for the 0-5-cm and A-horizon soils and 5.7 mg/kg for the C horizon material. Composition of the soil parent material was the primary control on spatial distribution.

Arsenic in rice and rice products

Brian P Jackson1, Dartmouth College, Department of Earth Sciences, HB 6105 Fairchild Bldg, Hanover, NH, 03755, United States, 603-646-1272, bpj@dartmouth.edu

Rice can be a source of both inorganic and organic arsenic to diet. In areas where water exposure is low, food may be the major exposure route for arsenic and rice can be a major source. This talk discusses why rice contains higher levels of arsenic than other grains, the concentration range of arsenic found in rice and rice products, the bioavailability of arsenic from rice and rice products and implications for dietary exposure. The talk also describes the analytical approaches to total and speciated arsenic analysis in rice and rice products.

Using in vitro gastrointestinal bioaccessibility methods to measure arsenic bioavailability and risk from ingestion of food and soil

Nicholas T Basta1, Professor, The Ohio State University, School of Environment and Natural Resources, 2021 Coffey Rd., 210 Kottman Hall, Columbus, Ohio, 43210, United States, 614-292-6282, 614-292-7432, basta.4@osu.edu

Ingestion of As in food and soil ingestion is an important exposure pathway and often is the "risk-driver" for As-contaminated soil and urban gardens. Arsenic exposure from food and soil ingestion depends on its bioaccessibility (e.g., the amount dissolved in the gastrointestinal tract) and the subsequent absorption of the As across the gut epithelium (e.g. bioavailability). Arsenic relative bioavailability in soil and food has been reported to range from <10% to 100%. Phosphate, iron and other chemical constituents in food and soil can greatly increase or decrease As bioavailability. Recently, research effort has been directed toward the development of in vitro gastrointestinal (IVG) methods to simulate human gastrointestinal conditions and estimate bioavailable As. Application of IVG methods to measure As bioavailability in food and soil will be presented. Future directions including application of IVG methods to evaluate practices that reduce As bioavailability in contaminated food and soil will be discussed.

Remediation of arsenic contamination of groundwater in Asia and USA

Satinder Ahuja1, Dr., Ph.D., Ahuja Consulting, Research and Development, 1061 Rutledge Ct, Calabash, NC, 28467, United States, 910-287-7565, sutahuja@atmc.net

Arsenic contamination of groundwater has been reported worldwide, including Asia and the United States. This problem is most pronounced in Bangladesh, where naturally occurring arsenic contaminates millions of wells that were installed to solve the problem of microbial contamination. Arsenicosis, resulting from drinking arsenic-contaminated water, is affecting around 200 million people in Asia; it can lead to a slow and painful death. To seek viable solutions, workshops were held in Bangladesh and India, and several symposia were organized at ACS and UNESCO meetings. Discussion of the problem will focus on how groundwater is contaminated with arsenic, desirable methods for monitoring arsenic contamination at ultratrace levels, and the best options for remediation. Solutions that offer significant improvements in water purification technologies, at reasonable costs, will be highlighted. The talk will encompass how the lessons learned from Asia can help solve the problem in other parts of the world.

Arsenic speciation, biotransformation, and toxicity in the environment

Lena Ma1,2, Professor, 2169 McCarty Hall, Gainesville, FL, 32611-0290, United States, 3523921951, lqma@ufl.edu

We will discuss arsenic speciation and toxicity in terrestrial and aquatic environment. While inorganic arsenic dominates terrestrial environment, organic arsenic is more common in marine organisms. Organic arsenic is less toxic, with arsenite being more mobile and toxic than arsenate. We will also cover arsenic biotransformation, which is considered detoxification mechanism for many organisms. While microbial arsenic transformation reduces toxicity for bacteria, it significantly impacts arsenic mobility in the environment. Arsenic is immobile in aerobic environment but it becomes mobile under anaerobic environment upon reduction of Fe and/or arsenate. Though marine organism contains higher level of arsenic compared to terrestrial organisms, it is mostly present as less toxic organic species. However, some may contain high levels of inorganic arsenic, making it unsafe to consume. Arsenic speciation is important not only for determining arsenic mobility and toxicity in the environment but also helps to enhance food safety and minimize human exposure.

Development of a method for assessing perinatal exposures to heavy metals using residual dried blood spots from newborn screening programs

William E. Funk1, Dr., Ph.D., 1810 Hinman Avenue, Evanston, IL, United States, 847-467-6208, w-funk@northwestern.edu

Exposures to heavy metals during fetal and perinatal development are of particular concern. Yet, the health impacts of exposures to toxic metals during these early stages of human development are not well understood due to the paucity of in vivo human data. Dried blood spots, collected by public health departments to screen for inherited metabolic errors and other disorders, are routinely archived and can be used for exposure assessment. Here we report a method for quantifying arsenic in newborn DBS to facilitate epidemiologic research on the health effects of early exposures. Forty-nine randomly selected DBS were obtained from the North Carolina State Laboratory of Public Health with collection dates ranging from 2003-2009, and arsenic was quantified using one-half of a DBS for each sample. The median concentration of arsenic was 1.4 ppb, and the 90th percentile was 6.5 ppb. Arsenic was detectable in 80% of the samples.

Potential for soil amendments to reduce concentrations of As in soils and waters

Darrell Norton1, Ph.D., USDA-ARS (Retired), National Soil Erosion Research Laboratory, 275 South Russell St., Purdue University, West Lafayette, IN, 47907, United States, 765-418-9472, norton@purdue.edu

33As is abundant and variable in soils. Using USGS data on As and geostatistical methods a map for USA shows that As exceeds guidelines for many areas of the USA. As geochemistry requires study to elucidate potential human health risks. The forms are arsenite (ANI) and arsenate (ANA) that are carried in solution. ANI is stable in reducing conditions and ANA in oxidizing. Eh and pH can change forms from ANI and ANA in soils. ANA acts similar to P in soils and methods to reduce mobility are similar. These are: 1) precipitation or 2) absorption onto mineral surfaces. Using soluble P as a surrogate for As we conducted field studies over 4 yr to collect runoff from soil amended with gypsum. Applications of gypsum reduced soluble P in runoff 75% over a control (P>0.01). As would be further reduced because published values for Ksp for various Ca-ANA range from 10-21 to 10-40 when Ca/As was >1.5. Since gypsum produces much soluble Ca then As would be precipitated. Studies were conducted directly on As in soils. Four iron-containing materials: Fe2(SO4)3, FeCl3, zero-valence Fe, and Fe-water treatment residual (WTR) were evaluated for remediation of three As-contaminated soils and one slag waste. Risk from multiple human exposure pathways were evaluated by the following soil chemical methods. The Bray soil test method and pore water was used to evaluate phytoavailable As. Potential exposure via the soil ingestion pathway was determined by measuring bioaccessible As using the OSU IVG method. All amendments were effective in reducing pore water, plant available and bioaccessible As. Reductions were 50 to >90%. Our results show that the Fe-containing amendments may be used as amendments to reduce risks to human health and to the environment of As in As-contaminated soils.

Comparison of sensitive methods for the measurement of inorganic arsenic in apple juice: Photoionization (PID) and ICP-MS

Jack Driscoll1, Ph.D., PID Analyzers, LLC, 2 Washington Circle #4, Sandwich, MA, 02563, United States, 7744135281, United States, pidguy@aol.com

In January of 2012, Consumer Reports found 10% of apple juice samples tested from five brands had total arsenic levels above the drinking water standard of 10 parts per billion. Most of that arsenic was inorganic arsenic, a known carcinogen. American apple juice is made from apple concentrate, a majority of which is imported from China. Inorganic Arsenic has been detected as AsH3 following reduction via AA or ICP MS. The cost of these types of spectrometers is in the $60-200K price range. Many labs would have to choose the older colorimetric methods but we have developed and modified the hydride generation-PID method for arsenic in water analysis at ppb levels (1) to work with food and juice. The system cost is a fraction of the $200K spectrometer price. We will describe the modifications of the new method for arsenic in apple juice as well as the comparison results with ICP-MS. (1) Driscoll, JN and GA Cutter, "Total and Speciated Arsenic Compounds in Water by Photoionization and Gas Chromatography/PID" in "Toxic Trace Metal Remobilization & Remediation - A Geochemical Body of Work" to be published by the ACS (2012).

Pick your poison? Arsenic in harvested country foods, edible mushrooms, and wine from Canada

K. Reimer1, Royal Military College of Canada, Environmental Sciences Group, 17000 Station Forces, Kingston, ON, K7K 7B4, Canada, 613 541-6000 x6161, reimer-k@rmc.ca

The toxicity of arsenic in foods depends on its chemical form as well as the fraction that is soluble for absorption into the blood stream after ingestion (bioaccessibility). Arsenic bioaccessibility was measured in country foods from historic mining areas in Yellowknife, NT, and Seal Harbour, NS, both in Canada. Country foods including berries, edible mushrooms, Labrador tea, and hare meat were studied, and percent bioaccessibilities were generally less than 50%, although some mushroom species were extracted more efficiently. Arsenic species in bioaccessibility extracts were also determined and varied widely depending on the sample, although generally plants (berries and Labrador tea) contained predominantly inorganic arsenic, some mushrooms contained predominantly arsenobetaine (a non-toxic form), and other samples contained a mixture of compounds, including inorganic arsenic, dimethylarsinic acid (DMA) and other organoarsenicals. Arsenic species were also measured in mushrooms from uncontaminated locations and grocery stores, and in juice and wine purchased in Canada, representing the first Canadian survey of these samples. Concentrations in juice and wine were generally less than 20 ug/L and in most cases less than the drinking water standard of 10 ug/L, with predominantly inorganic arsenic and DMA. The actual, rather than perceived risk of arsenic in foods will be reviewed.

Water remediation as a method to reduce exposure to arsenic

Allen Apblett1, Oklahoma State University, Department of Chemistry, Physical Sciences 107, Stillwater, OK, United States, 405-744-5943, allen.apblett@okstate.edu

Arsenic occurs in water in many parts of the world mainly as a result of natural sources but also as a consequence of anthropogenic activities. Consuming water contaminated by arsenic can cause skin and bladder cancer and cardiovascular disease. Therefore, the US and WHO maximum contaminant level (MCL) for arsenic in drinking water is 10 ppb but concentrations higher than this occur throughout the world leading to a tremendous need for development of cost efficient methods for arsenic removal. There are currently many methods for remediating arsenic-containing water that could be utilized not only to purify water for drinking but potentially could be used to prevent contamination of food by treatment of agricultural water. The various methods for removal of arsenic and their benefits and drawbacks will be reviewed in this presentation, culminating with a discussion of novel high capacity sorbents for removal of arsenic from water.

Low, slow, and Next Gen impact: Arsenic, human health, and cancer risks

Janet M Hock1, Sr. Investigator, Ph.D., Maine Institute for Human Genetics and Health, 8215 River Bay Dr East, Indianapolis, IN, 46240, United States, 207-951-2717, janethock@gmail.com

Arsenic exposure contributes to human health risks of cardiovascular disease, diabetes, and cancer. Arsenic's mechanisms of action and threshold for disease risk remain controversial. While arsenic exposure via water has been more studied, relatively little is known about arsenic in food. This review discusses current concepts of low dose and time responses to arsenic and consequences of exposure on the next generation. While short-term effects of arsenic in immortalized human lung cells appear reversible, longer-term in vitro exposure promoted malignant transformation, essential for lung carcinogenesis. Drosophila, mouse and zebrafish studies suggest that early-life exposure to arsenic exacerbate health risks. Detrimental health effects in offspring occur when pregnant mice are exposed to arsenic during gestation. The underlying mechanisms were linked to epigenetic effects. Cell and animal models link in vitro and epidemiology studies, and will likely translate as human health risks, with pregnant mothers and their children being especially susceptible.

Analysis for arsenic species in food

William R Mindak1, U.S. Food and Drug Administration, CFSAN, 5100 Paint Branch PKY, College Park, MD, 20740, United States, 240-402-2005, william.mindak@fda.hhs.gov

The issue of arsenic in rice and rice products has been in the news recently. The FDA and other organizations have released reports that list the levels of various arsenic species present in these products. This attention suddenly increased the demand for analysis of rice and rice products for arsenic. However, due to the difference in toxicity of the chemical forms of arsenic, there is a need to determine the various arsenic species especially the more highly toxic inorganic arsenic forms. Most laboratories involved with trace element analysis do not have experience with arsenic speciation. Several methodologies can be used for arsenic speciation including hydride generation-cryogenic trapping followed by either ICP-AES or AA and chromatography coupled to ICP-MS. The presentation will discuss various approaches to determine arsenic species and give details of the HPLC-ICP-MS methods that the FDA uses to analyze juice, rice and various rice products.

Overview of the toxicological properties of arsenic and arsenic-containing compounds

Paul B Tchounwou1, Dr., Sc.D., Jackson State University, Department of Biology, 1400 Lynch Street, Box 18750, Jackson, Mississippi, 39217, United States, 601-979-0777, 601-979-2058, paul.b.tchounwou@jsums.edu

Arsenic and arsenic containing compounds are considered human carcinogens. Exposure to arsenic occurs occupationally in several industries, including mining, pesticide, glass and microelectronics, as well as environmentally from both industrial and natural sources. Cardiovascular diseases, developmental abnormalities, neurologic and neurobehavioral disorders, diabetes, hearing loss, hematologic disorders (anemia, leukopenia and eosinophilia), and various types of cancer, have all been associated with human exposure to arsenic. Research has also pointed out significantly higher standardized mortality rates and cumulative mortality rates for cancers of the bladder, kidney, skin, liver and colon in many areas of arsenic pollution. Both acute and chronic exposures have been reported in several countries of the world, where a large proportion of drinking water is contaminated with high concentrations of arsenic. Recent epidemiologic studies have demonstrated a strong correlation between arsenic exposure and the increase in incidence of human cancers. There is therefore a great need for developing a comprehensive risk assessment model, to be used in the management of health risks associated with arsenic exposure. This paper discusses the toxicological properties and the potential mechanisms of the toxic action of arsenic and arsenic-containing compounds. Such information is critical for understanding the magnitude of health effects associated with arsenic exposure throughout the world.

Transforming ICP-MS technology: Advances in interference removal for accurate arsenic analysis in food and beverages

Amir Liba1, Ph.D., Agilent Technologies, 2850 Centerville Rd, Wilmington, DE, 19808, United States, 302-636-1530, amir_liba@agilent.com

Arsenic contamination of food and beverages has become a heated topic of discussion in media outlets and many households across the globe. Arsenic, like many other toxic analytes, exists in many forms, some of which are very toxic (As3+, As5+) while many others are inert. It has thus become very critical to identify the levels and types of species that exists in a particular sample in order to differentiate between the non-toxic and toxic species. Since arsenic is monoisotopic and possesses a large number of polyatomic interferences, it is necessary to use a collision/reaction cell for accurate unbiased analysis. Two main methods exist for interference removal, collision mode and reaction mode. Collision mode, using kinetic energy discrimination (KED), allows for matrix-independent analysis achieving relatively low detection limits, ppt-ppb. Reaction mode of operation is highly dependent on the sample matrix. Collision/reaction cells allow for the entire ionized sample (matrix and analytes) to enter the cell. Since no control exists to what enters the cell, chemical reactions are largely uncontrolled and lead to side reactions and the formation of cluster ions, ultimately biasing the results. Controlling what enters the cell is key to controlled chemical reactions thus allowing for accurate, precise and unbiased data in reaction mode. Triple Quad ICP-MS (ICP-QQQ) provides the capability of controlling what enters the cell using MS/MS technology by selecting a particular mass (single AMU) or a mass range via the control of the first quadrupole (Q1) located upstream from the collision/reaction cell. This mechanism gives the operator valuable information on what enters the cell. With this critical piece of information, it is then possible to perform controlled chemical reactions. Here we will discuss the theory and operation of the ICP-QQQ with MS/MS technology and its relevance to analyses of toxic analytes in food and beverages.

Sources and perspectives of arsenic in the environment

Kevin L. Armbrust1, Ph.D., Office of the State Chemist - Mississippi, Mississippi State Chemical Laboratory, PO Box CR, Mississippi State, MS, 39762, United States, 662-325-3324, 662-325-7807, armbrust@mscl.msstate.edu

Arsenic has a long history and engenders a picture of poison in the minds of the general public, however it is important to realize it is a naturally occurring element with varied sources. Unlike organic compounds like chlorinated hydrocarbons such as PCBs and DDT, metals such as arsenic are not man-made. All arsenic comes from nature however its varied forms and distribution within environmental systems can be manipulated by man's activities. By far the major inputs are from biogeochemical distribution from sources in soil or atmospheric inputs from volcanism. Distribution and biotransformation in marine ecosystems result in the presence of arsenic in seafood. Transformation processes within soil and sediment can result in forms that are bioavailable for plant uptake and allow it to enter the food supply. Such processes are not static. They are dynamic and can dramatically impact the amount, form, and ultimately the toxicity of arsenical compounds in food or water. These dynamic processes must be considered in any risk assessment for arsenic, and aggregate sources should be factored into any assessment of overall exposure.

Multi-faceted approach to arsenic speciation analysis for characterization of food products using selective extraction followed by IC/RP/GC-ICP-MS

Russell Gerads1, Vice President, 18804 Northcreek Parkway, Suite 100, Bothell, WA, 98011, United States, 425-483-3300, russ@appliedspeciation.com

A multi-faceted approach to the speciation of arsenic present in food products was applied for the quantitation of: arsenite, arsenate, monomethylarsonic acid, dimethylarsenic acid, trimethylarsine oxide, tetramethylarsonium ion, arsenocholine, arsenobetaine, thio-dimethylarsenite, roxarsone, arsenolipids, arsenosugars, p-arsinilic acid, and phenylarsonic acid. The extraction and analytical methods were specific to the target molecules and substrate. Comparison between various extraction methods was performed including, but not limited to: neutral pH, phosphate based extractions, enzymes, organic acids, polar solvent, and non-polar solvents. Certain extraction methods were proven to quantitatively decompose organic arsenic species to arsenate which can produce false positives when assessing the consumption risk for humans. The findings from this research conclusively identified that the applied extraction and analytical methods must be specific to the substrate components and the target arsenic species. Analytical method used for quantitation of arsenic species included different chromatographic separation techniques (GC, IC, RP) coupled to an inductively coupled plasma collision reaction cell mass spectrometer.

Arsenic in rice and rice products: FDA activities

Philip C Spiller1, US FDA, 5100 Paint Branch PKY, College Park, MD, 20740, United States, 240-402-1428, philip.spiller@fda.hhs.gov

Several organizations, including the FDA, have released reports about the level of total and inorganic arsenic in rice and various rice products during the past year. The FDA launched an initiative to address the concerns about this issue. Consumer information, Q&As and results for over 1000 samples have been posted on the Internet. Products tested included rice, cereals, rice beverages, rice based snacks and rice cakes. A comprehensive assessment of potential health risks is in progress. The agency will evaluate strategies designed to limit arsenic exposure from rice and rice products and is working with other government agencies, industry, scientists, consumer groups and others to study the issue and assess risks. The talk will review FDA's past activities, highlight the current risk assessment and discuss possible future efforts to limit arsenic exposure which may include consumer guidance and regulation.

Genetic and field management strategies for limiting accumulation of arsenic in rice grains

Shannon R.M. Pinson1,2 , USDA-ARS, Dale Bumpers National Rice Research Center, 2890 Hwy130 E, Stuttgart, AR, United States, 870-672-9300 x 228, shannon.pinson@ars.usda.gov

In 2002, disturbingly high levels of arsenic were reported in rice produced in Bangladesh using soil and water naturally high in arsenic. Study of arsenic in rice produced in additional countries, including the USA, soon followed. Grain-arsenic is higher in rice than other crops because the flooding of rice paddies converts soil arsenic into forms more readily absorbed by plants. Rice offers unique opportunity to study the genes and physiological mechanisms controlling arsenic-uptake and accumulation because the same varieties can be grown either flooded or flush-irrigated. In our multi-year, multi-location evaluation of several diverse rice populations, flooding increased grain-arsenic 10-fold. Of the 13 genetic loci identified as affecting grain-arsenic, 9 were effective in flooded rice, 6 in unflooded rice. Nine of the 13 loci also affected accumulation of phosphorus, silica and/or sulfur, elements known to impact arsenic accumulation. Grain-arsenic was not driven by plant height or grain shape, but maximum-arsenic increased with days-to-heading.

Arsenic species in seaweed harvested for consumption and for fertilizer

Vivien F Taylor1, Dr., Dartmouth College, Trace Element Analysis Core, HB 6105 Fairchild Hall, Dartmouth College, Hanover, NH, 03755, United States, 603-646-3318, vivien.f.taylor@dartmouth.edu

Seaweed is a hyper-accumulator of arsenic, having concentrations in the 10-150 mg/kg range. Arsenic is present primarily in the form of a variety of arsenosugars, as well as dimethyl As and inorganic As. The toxicity of As is highest for inorganic As, and varies between organic species, necessitating complete speciation analyses. There has been recent growth of the seaweed harvesting industry in New England, both for consumption and for use as an organic fertilizer. In some of the seaweed products we have analyzed, the amount of inorganic As in a single gram of sample exceeds daily tolerable dose guidelines. The use of seaweed as a fertilizer has also been shown to significantly increase bioaccessible As in soils. A survey of As speciation seaweeds and seaweed products from New England was conducted to understand how to minimize As exposure from this source.

Extension of a method for speciation of arsenic in rice to other rice-based products, and propagation of the method to other laboratories

Sean Conklin1, Ph.D., 5100 Paint Branch Parkway, College Park, MD, United States, 240-402-2204, sean.conklin@fda.hhs.gov

Over the past year FDA scientists have been working on developing, validating and propagating to cooperating laboratories a method for speciation of arsenic in rice-based food products. Rice and rice-derivatives are ingredients in a wide variety of products such as rice cakes, cereals, granola/snack bars, chips, noodles, pudding, and infant formula. Each product represents a novel matrix which may or may not be compatible with the method as written. This talk will address the process of extending the scope of a method developed for rice to include other rice-based products. The difficulties of bringing new laboratories up to speed on a new method and, in some cases, new analytical techniques, will also be discussed.

Ongoing arsenic mitigation research in the U.S. rice industry

Steven Hensley1, U.S. Rice Federation, 2101 Wilson Blvd., Ste. 610, Arlington, VA, 22201, United States, 703-236-1445, shensley@usarice.com; Reece Langley1 , U.S. Rice Federation, 2101 Wilson Blvd., Ste. 610, Arlington, VA, 22201, United States, 703-236-1471, rlangley@usarice.com

The USA Rice Federation will address ongoing cooperative research between the rice industry and government to address the ongoing issue of arsenic in rice. Specifically we will touch on research into lower arsenic-accumulating cultivars that are adaptable to the various rice growing regions of the U.S. We will also discuss research into water management techniques thought to reduce arsenic uptake and their effect on yield, GHG emissions, disease and other metal and nutrient uptake. We will touch on the public perception of the contributions of fertilizer and pesticides and, depending upon research schedules, possibly the issue of consumer mitigation of arsenic content.

Arsenic behavior in flooded rice soils

Philip A. Moore, Jr.1, Ph.D., USDA/ARS, University of Arkansas, Plant Sciences 115, Fayetteville, AR, 72701, United States, 479-575-5724, philipm@uark.edu

Recent reports indicate that arsenic (As) levels in rice are relatively high compared to other grains. This results because rice is grown under flooded conditions and As is a redox element. Arsenic behavior in soils is also influenced by iron (Fe) and manganese (Mn), both of which are also redox elements. When soils are flooded, the lack of oxygen forces microorganisms to use alternate electron acceptors for respiration, such as Fe and Mn. This causes the soil redox potential (Eh) to decrease following flooding. This reduction not only causes an increase in dissolved Fe and Mn in solution, it results in an increase in dissolved phosphorus (P), because P is adsorbed on Fe and Mn oxides and hydroxides. Arsenic has four oxidation states: arsenate (5+), arsenite (3+), arsenic (0), and arsine (3-), although arsenic and arsine are unstable in soils. Under oxidized soil conditions As is present as arsenate (As5+); under reducing conditions As5+ is reduced to As3+ (arsenite). Under very reducing conditions As can be methylated by bacteria to form monomethylarsonic acid or dimethylarsinic acid. Hence, soil solution As concentrations initially increase when a soil is flooded due to release from Fe and Mn compounds that are reduced. As soils become more reducing, As solubility increases further when As5+ is reduced to As3+. Arsenic concentrations have been shown to be lower in soil solution and grain of rice grown in fields that are intermittently flooded compared to continuously flooded, which is likely due to higher Eh.

Dietary arsenic: Forms, hazards, and risks

P. Michael Bolger1, Exponent, 1150 Connecticut Ave., NW, Washington, DC, 20036, United States, 410-279-4956, pmbolger33@gmail.com

Arsenic which originates from both anthropogenic and natural sources is a well known and ubiquitous. environmental contaminant, particularly in drinking water. Inorganic arsenic (iAs) demonstrates a myriad of toxicological effects across a broad spectrum of organ systems. It has generally been believed that arsenic in food occurs in organic forms that demonstrate minimal, if any toxicological activity. This is particularly the case with the forms found in seafood (e.g., arsenosugars). However, there has been concern for some time that organic forms may not be the predominant forms in certain foods, like rice, where concentrations of inorganic forms in certain cultivars may be significant. In addition, other organic forms, like tri- and penta- forms of mono- and dimethyl arsenic, maybe found at levels that are not insignificant and could potentially pose a health hazard. These organic forms may not be as innocuous as the organic forms found in seafood. This presentation will explore the current state of knowledge regarding the occurrence of various forms of arsenic found in foods, as well as their potential exposures, hazards (e.g., toxicological, epidemiological) and risks to public health.

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