BARGE (the Bioaccessibility Research Group of Europe)

Conference archive 2005-2010

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Archive of events at which various members of the BARGE group have presented findings and initiatives concerning both their own and BARGE research activities.

You can view a list of forthcoming conferences on our future conferences page.

Bioaccessibility Special Session at ICOBTE — July 5 2011

Bioaccessibility Special Session at the 11th International Conference on the Biogeochemistry of Trace Elements (ICOBTE) in Florence, Italy.

There will be a special symposium on 'Advances in bioaccessibility methodology to determine human and ecological bioavailability, exposure, and risk from ingestion of trace element contaminated soils' at the 2011 ICOBTE conference in Florence, Italy on 5th July 2011.

The session has been organised by Nick Basta (Ohio State University), Albert Juhasz (University of South Australia), Ken Reimer (Royal Military College of Canada), Joanna Wragg (British Geological Survey) and Karen Bradham (USEPA) and will feature 10 oral and 21 poster presentations by a host of International scientists.

For further information visit www.icobte2011.com

GEOMED 2011 — September 20-25 2011

The 4th International Conference on Medical Geology will be held in Bari, Italy in September 2011 (20-25th).

The theme of the conference is Geological & Medical Sciences for a Safer Environment, and will provide a unique opportunity for mineralogists, physicians, soil scientists, toxicologists, geochemists, veterinarians, biologists, chemists and many other specialists to share ideas and knowledge on the impact of natural environment on health.

The conference includes 35 sessions and workshops covering different aspects of Medical Geology including Environmental Toxicology & Epidemiology, Minerals & Environment, Air, Soil & Water Pollution, and Risk Assessment & Communication.

Medical Geology conference at BGS — March 19th-20th 2009

The BGS held a two day Medical Geology meeting on the 19-21 March at the BGS offices in Nottingham, UK. The meeting was aimed at raising the profile of Medical Geology, with particular emphasis on "Practical Applications". Details of the meeting can be found at http://sites.google.com/site/bgsmedicalgeologymeeting/ . We have agreement to publish original research papers coming from the conference in a special issue of the Environmental Geochemistry and Health Journal. We have a number of high profile keynote speakers including:

Dr Olle Selinus - Geological Survey of Sweden
Professor Paul Nathanail - University of Nottingham and LQM
Professor Roy Harrison - University of Birmingham
Professor Barry Smith - IntelliScience Ltd

12-16 October 2008, ISEE-ISEA Joint Annual Conference, Pasadena Convention Centre, California, USA

Factors Controlling the Absorption of Chemicals from Soil: Emerging Research, Regulations, and Data Gaps.

Requirements for site remediation are frequently based on the potential for contaminants in soil to pose unacceptable health risks following human exposures. It is becoming widely recognized by the international research and regulatory community that site-specific factors may control the bioavailability of chemicals in soil and dust, and therefore adjustments to account for reduced absorption relative to chemicals in other media (e.g., water, food, or dosing media used in research) are becoming more accepted in risk assessment. Both animal models and in vitro bioaccessibility models have been used to estimate relative bioavailability of metals in soil and dust. Although animal models are often held out as the "gold standard," the financial requirements and timeframe for animal testing, as well as ethical issues surrounding the use of animals in research, may preclude wider application of such testing. Routine application of the bioaccessibility models in regulatory settings is being held up by different perceptions of what is required of these models in terms of validation. ISEA 2006 and 2007 provided opportunities for international experts to exchange their research and views on adjustments for relative bioavailability/bioaccessibility, and their application in risk assessments of residential environments and contaminated sites. In 2008, the symposium will build on this base, and the presentations and panel discussions will explore relevant questions, such as:

This symposium will focus on arsenic, summarizing the existing data regarding relative oral bioavailability of arsenic from soils, what is known regarding the geochemical controls on arsenic solubility, scientific and policy issues associated with regulatory approval of site-specific adjustments to arsenic bioavailability, and panel members will be tasked with identifying data gaps that limit broader application of bioavailability adjustments in risk assessment of arsenic in soil.

Speakers included: Dr Yvette Lowney (Exponent, USA), Dr John Drexler (University of Colorado, USA), Professor Ken Reimer (Royal Military College of nada) and Dr Mark Cave (British Geological Survey)

25-29 May 2008, 18th Annual Meeting of the Society of Environmental Toxicology and Chemistry (SETAC), Europe Division, Warsaw, Poland

Remediation of metal polluted soils and evaluation of danger to human health assessed by in vitro oral bioaccessiblity tests

The high contamination level of urban soils by potentially harmful elements increases the sanitary risk for the population, and especially for young children. The risk encountered by this group is increased by the ingestion or the inhalation of contaminated dust or soil via hand-to-mouth transfer. The lead blood level of children around the Metaleurop Nord and the Umicore smelters, situated in Northern France, has previously been considered critical. From 1994 to 2002, 10 to 15 % of children (2 to 4 years old) living near Metaleurop had a level of Pb which exceeded 100 μg L-1 of blood. The environmental assessment performed by the sanitary unit in charge of the Metaleurop area showed a high Pb contamination of the dust present in various living place of the children (home and school). The dust collected on the children's hands and its high metal content (particularly lead) has confirmed the importance of this contamination pathway. In the Metaleurop and the Umicore areas, the remediation of the urban soils is a major environmental and sanitary issue.

This study discusses a multidisciplinary project investigating the incorporation of amendment products to the soil that are able to reduce the metal mobility and bioavailability, with the primary objective of reducing environmental and sanitary risks by long-lasting metal immobilisation and not soil decontamination.

Speaker: Helene Roussel, Laboratoire Sols et Environment

3-6 June 2008, Consoil 2008, Milan, Italy

Advances in the Use of Bioaccessibility Data in Quantitative Risk Assessment through Practical Applications

Proceedings (with links to individual presentations)

Assessment of the risk from contaminated sites is mostly carried out in response to toxicity to humans and in estimating this, the human oral bioavailability of the contaminants is a key parameter. Access to accepted methods for estimating the oral bioavailability of soil contaminants may thus reduce costs of site remediation and soil cleaning, while still maintaining the required protection level. It is generally agreed that it is impractical to measure true human bioavailability. However, an in vitro bioaccessibility test, simple enough to carried out by soil testing laboratories that mimics the amount of harmful substance that becomes solubilised in the human gastrointestinal tract, provides a pragmatic approach to estimating bioavailability. Work on standardising and validating in-vitro bioaccessibility tests are on-going with much discussion among regulators as to what constitutes a validated test. At CONSOIL 2005 the special session organised by the BARGE group concluded that despite these discussions on validation "that bioaccessibility measurements are now reaching a stage where they can be used with confidence in human health risk assessment".

Recent studies show that bioaccessibility research is a very active area with wide-ranging and important applications (Gron and Wragg, 2007). The aim of this special session is to provide an update on the progress of validation of the in-vitro test methods since the last CONSOIL but more importantly to show how bioaccessibility data can be used in the assessment of contaminated sites through case studies. The presentations will show practical applications, which include:

The overall aim is to provide guidance on best practice and to show how bioaccessibility measurement can be an important, if not vital, aid to contaminated land studies.

Speakers include: Dr Chris Collins, Reading University, UK; Dr Christian Gron, DHI, Denmark; Dr Werner Hagens, RIVM, the Netherlands; Prof Paul Nathanail, the University of Nottingham, UK; Prof Ken Reimer, the Royal Military College of Canada; and Drs Mark Cave and Joanna Wragg, the British Geological Survey, UK.

References: Gron C., and Wragg J., Ed., Journal of Environmental Science and Health, Part A Toxic/Hazardous Substances and Environmental Engineering, Special Issue on Bioaccessibility, Volume 42 Issue 9 2007.

3 - 7 August 2008, 5th SETAC World Congress, Sydney Convention and Exhibition Centre, Sydney Australia

Advances in Contaminant Bioaccessibility Methodology for Human Health Risk Assessment from Ingestion of Contaminated Soil

Ingestion of contaminated soil is an important pathway for human exposure. The risk posed from soil ingestion depends on the bioaccessibility of the contaminant (e.g., the amount dissolved in the gastrointestinal tract) and the amount of dissolved metal that is transported across the gut epithelium. Novel research efforts focusing on development and application of methods to measure contaminant bioaccessibility in contaminated soils are ongoing on several continents. Regulatory bodies responsible for human health risk assessment (HHRA) of contaminated soil in the U.S., Canada, E.U., Australia, and other countries are working in tandem with the scientific community to develop risk-based frameworks to account for the effect of contaminant bioaccessibility on HHRA. We are proposing a timely international session that will provide a forum to (i) allow research teams from the U.S., Canada, E.U., Australia, and other countries to present state-of-the-art research findings, and (ii) provide a forum where emerging science and HHRA frameworks will be discussed by scientists, risk assessors, and regulators.

Speakers include: Dr. N.T. Basta, Ohio State University; Dr. M.J. McLaughlin, CSIRO, South Australia; Dr. J. Wragg, British Geological Survey, UK; Dr. K.D. Bradham, U.S. Environmental Protection Agency; and Prof Ken Reimer, Royal Military College of Canada.

14-18 October 2007, International Society of Exposure Analysis, Durham, North Carolina, USA

The 17th Annual conference of the International Society of Exposure Analysis in Durham, North Carolina, a 4 day International event, was attended by over 500 delegates, from thirteen countries. Symposia at the event ranged from 'Exposure sampling methods' to 'Exposure assessment approaches for chemical mixtures'. Information on the conference and the next event, which will be held in Pasadena, California in October 2008, can be found at http://www.iseaweb.org/

A special 1 day symposium was organised by Drs Pat Rasmussen (Health Canada), Mark Cave (British Geological Survey), Karen Bradham (USEPA) and Rosalind Schoof (Integral Consulting Inc), to discuss the use of in vitro bioaccessibility/relative bioavailability estimates in a regulatory setting and the requirements for the use of such data. The audience consisted of interested parties, from a mix of disciplines from the research, regulatory and the risk assessment communities. The symposium was well thought out in its combination of talks concerning the current thinking regarding research issues and policy decisions, providing a balanced view of the latest bioaccessibility and bioavailability information across the international scene and ample time for audience discussions with the panel. Of particular note wer the contributions which discussed how the research community support in vitro data with supplementary information and testing regimes, especially those regarding the source and the geochemistry of the contaminant of concern, were also included. This type of information was shown to be invaluable in the continued development of international collaborative efforts.

The bioaccessibility/bioavailability symposia produced lively debate from both the speaker panel and via audience participation. Debate over the validation status of in vivo relative bioavailability data, with respect to potentially harmful elements and the problems faced by research scientists and the regulatory community alike, have spawned further communication between delegates. The results of which have promoted international collaborative efforts and a new era of information and data sharing which will benefit all involved. Specifically, the arsenic relative bioavailability working group, a cross discipline, international group has been established, which will share information and materials and communicate on a regular basis.

September 2006, ISEE International Conference on Environmental Epidemiology and Exposure, Paris, France

This was special symposium on childhood exposures to bioavailable metals in soil and household dust in residential environments.

The session was chaired by Dr Pat Rasmussen of Health Canada and Dr Mark Cave from the British Geological Survey, UK.

Presentations included;

A Symposium on Childhood Exposures to Bioavailable Metals in Residential Environments, took place at the Paris ISEE/ISEA Conference in September, 2006. The symposium, which was organized by Pat Rasmussen (Health Canada) and Joanna Wragg and Mark Cave (UK Geological Survey), created the opportunity for international experts to exchange their views on adjustments for bioavailability/bioaccessibility, and their application in risk assessments of residential environments and contaminated sites. A variety of sectors and viewpoints were represented, including academic and government researchers and risk assessors, regulators, and private consultants. Some key findings were discussed, from a number of countries (Canada, the UK, the U.S. and parts of the EU) who have started to allow some site-specific bioaccessibility corrections. Most participants expressed discomfort with allowing site-specific methods to be universally applied at this time. There was general agreement that this science was in its infancy, and that a widely-accepted set of criteria were needed to assess both in-vivo and in-vitro methods.

Encouraged by the level of enthusiasm and constructive debate at the Paris symposium, Pat and Mark have joined forces with Rosalind Schoof (Integral Consulting Inc.) to propose a similar meeting at the next ISEA Conference to be held in Durham/Research Triangle Park, North Carolina October 14-18, 2007. The next symposium will explore why routine application of metal bioaccessibility models in regulatory settings is being held up. There are different perceptions of what is required of these models in terms of validation. Animal models are often held out as the "gold standard", but animal models may not be reliable for some metals and may not be sensitive enough to test environmentally relevant samples. Is it sufficient to have correlation with animal results or is it necessary to make the models accurate physiologic mimics of human gut dissolution? For regulatory applications such as site clean up decisions, is a model that is predictive adequate even if we don't know why it is predictive, or is it important to know why a model is predictive? The 2007 symposium will explore these questions, as well as presenting new in vitro models and developments for existing models.

Bioavailability of Pollutants and Soil Remediation, 10-13 September 2006, Seville, Spain

Bioavailability of Pollutants and Soil Remediation sponsored by the Fundación BBVA/CRC-CARE.

In the session considering Risk Assessment and Legal aspects Paul Nathanail will be giving the keynote presentation on "Risk Assessment as driving force for bioavailability research" and Sebastien Denys will present work on "Antimony soil speciation related to its bioaccessibility to Man".

14th North American ISSX Meeting, Rio Grande, Puerto Rico, USA, October 22-26, 2006

Esther Brandon will be attending the 14th North American ISSX Meeting entitled "From Drug Biotransformation to Future Innovation" to be held in Rio Grande, Puerto Rico, USA, October 22-26, 2006

Esther will be presenting a paper on the "Human In Vitro Digestion Models: Powerful Tools To Predict Maximum Oral (Relative) Bioavailability"

Download the poster presented by Esther Brandon : Human in vitro digestion models powerful tools to predict maximum oral (relative) bioavailability

SETAC, 5-9 November 2006, Montreal, Canada

At the recent 27th Annual Meeting of the Society of Environmental Toxicology and Chemistry (SETAC) North America, held in Montreal, Canada, Drs Nick Basta, Chris Ollson and Steven Sicilliano organized a series of platform sessions linking Contaminated Soil to Human and Ecosystem Health Impacts'. The session was well attended by interested students and professionals and covered topics concerned with bioavailability and bioaccessibility issues related to soil contamination by inorganic and organic contaminants. The session was attended by members of the BARGE research group and the newly formed BioAccessibility Research Canada (BARC) group, who joined together, with other interested parties for an impromptu meeting of minds.

Invited speakers included;

Abstracts

The Use of In Vitro Methods to Examine Mechanisms of Bioaccessibility.
Beak, D.2,1, Basta, N.1, Scheckel, K.3 and Traina, S.4.
1SENR, Ohio State University, Columbus, OH, USA. 2NRMRL,GWERD,U.S. EPA,Ada, OK, USA. 3NRMRL, LRPCD, U.S. EPA, Cincinnati, OH, USA. 4Sierrra Nevada Research Institute, U.C. Merced, Merced, CA, USA.
The bioavailability of Pb and As to humans and living organisms is important. There have been many proposed in vitro gastrointestinal assays.Most, if not all of these assays, have used as correlation methods between the chemical test and animal feeding studies to determine the bioavailability. This overlooks the importance of reaction mechanisms that occur in the digestive systems of animals and properties of the substrate. Most of these in vitro methods could be useful in providing a better understanding the properties of the substrate and the reactions that occur in the digestive process. In many soils and sediments oxides are major scavengers of As and Pb and were used as a model for the soil system in this research. Oxides have also been used as sorbents for remediation of As and Pb contaminated media. An In Vitro gastrointestinal assay was employed with modifications from that proposed by Rodriguez (1999). A sub-sample was taken prior to the assay and the solids remaining were collected for X-ray Absorption Spectroscopy (XAS) analysis. The bioaccessibility of Arsenate (As(V)) was related to the sorption maximum for corundum and ferrihydrite.Mn bound As(V) showed availability in both the gastric and intestinal phases; however there was no clear relationship to the sorption maximum. XAS analysis conducted demonstrated that the As(V) speciation was the same pre and post in vitro. The bioaccessibility of Pb-sorbed corundum and ferrihydrite only occurred during the gastric phase of the assay. For birnessite, there was no observable bioaccessible Pb. The speciation pre and post in vitro was similar for all oxides. The use of in vitro gastrointestinal assays in conjunction with other analytical tools, such as XAS can be used to help understand the mechanisms of bioaccessibility of As and Pb in environmental media. As was the case with As(V) sorbed oxides, the Pb speciation is important in determining the impacts of Pb bioaccessibility in the soil.

In vitro methods to assess the oral bioavailability of soil-bound hydrophobic organic contaminants (HOCs).
Vasiluk, L.1,2, Pinto, L.2, Gobas, F.3, Eickhoff, C.4 and Moore, M.2.
1Department of Land Resource Science, University of Guelph, Guelph, ON, Canada. 2Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada. 3School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC, Canada. 4Vizon SciTec Inc., Vancouver, BC, Canada.
Ingestion of contaminated soil can be a significant route of chemical exposure in children. At present, the amount of HOCs extractable by chemical solvents is considered the exposure dose. However, the fraction accessible for intestinal absorption can be significantly decreased by sorption to soil/sediment matrices. Currently, matrix effects are not taken into account in human health risk assessment procedures. Therefore, the aim of this study was to evaluate two in vitro models for estimating the oral bioavailability of HOCs bound to soil. Soil, spiked with chrysene (CHR) or benzo[a]pyrene (BaP) was digested in simulated gastrointestinal fluids and incubated with cultured human enterocytes (Caco-2) or a membrane surrogate, ethylene vinyl acetate (EVA). Transport kinetics of partitioning from the aqueous phase were similar for both CHR and BaP, and for both EVA and Caco-2 cells, and best fit a one-compartment model. The lipid-normalized fugacity capacity of Caco-2 cells was higher than EVA for both HOCs. Caco-2 cells and EVA thin film demonstrated similar desorption kinetics. CHR or BaP concentrations in the aqueous phase did not always parallel the amount in the sorptive epithelium; sorbed concentrations were up to 2000-fold higher than the aqueous fraction. These results provide further evidence that the transport of hydrophobic chemicals within the body is fugacity-driven. The EVA and Caco-2 models provide complementary information that could be used to predict the relative oral bioavailability of HOCs.

Lead Distribution in Rats Following Respiratory and Oral Exposure to Lead-Contaminated Soils.
Casteel, S.W.1, Fent, G.M.1, Evans,T.J.1 and Bannon, D.I.2.
1University of Missouri, Columbia, MO, USA. 2U.S. Army Center for Health Promotion & Preventive Medicine,Aberdeen Proving Ground,MD,USA.
Lead (Pb) is an environmental threat to the health of pre-school children. The major route of exposure is believed to be ingestion, though inhalation of airborne Pb also occurs. The purpose of this experiment was to explore the biokinetics of Pb following respiratory exposure to a lead-contaminated soil and to determine the differences in Pb distribution following intratracheal instillation and gastric administration of similar doses of lead-contaminated soil. Intratracheal instillation was used to deliver lead-contaminated soil to the respiratory tract of rats subsequently sacrificed 96 hours later, with tissues collected for analysis. Overall, there was a dose-dependent increase in tissue and blood Pb concentrations in both lead acetate (PbAc) and soil intratracheal instillation groups. In rats exposed via the respiratory tract, nearly 100% of the administered Pb dose from soil or PbAc was cleared from the lung and systemically absorbed during the 96-hour interval between dosing and sacrifice. By comparison there was a much lower mean Pb concentration in tissues from the gastrointestinal exposure groups. Differences were also noted in the tissue distribution between respiratory and oral exposure. In rats exposed via respiratory simulation, kidney lead concentrations were ~20 fold higher than those in the liver, which is the organ of accumulation immediately following oral absorption. Intratracheal instillation proved useful to simulate respiratory exposure in rats and was effective in distinguishing differences in the biokinetics of lead following oral and respiratory exposures.

Age-Dependent Metal Bioaccumulation from Smelter-Impacted Soil Ingestion in Deer Mice (Peromyscus maniculatus).
McBride, T.1,Hooper, M.J.1 and Kuhns, K.2
1TIEHH, Texas Tech University, Lubbock, TX, USA. 2HHMI, Texas Tech University, Lubbock, TX, USA.
The bioavailability and bioaccumulation of inorganic metals from contaminated environments present complex challenges for risk assessors. To evaluate the actual risks posed by lifelong exposures to these contaminants, we examined the uptake of soil metals in deer mice as pups raised by dams consuming contaminated soils in food, followed by direct ingestion of the same contaminated food after weaning.We investigated the accumulation of the five contaminants of concern (As, Cd, Pb, Cu and Zn) found in Anaconda Smelter Superfund soils (0.2 mm fraction) through additions into food mimicking 'normal' incidental soil ingestion (3% of diet). Soils originated from three aerial deposition sites with increasing concentrations of the five COCs. Female breeders were exposed to soil-amended food (AIN-76) upon birth of litters. Single individuals of each litter (n=4/dose) were removed and analyzed upon weaning at post-natal day (PND) 21, while the remainder were placed on the same food regimen as the dam, with individuals collected again at PND 50 and 100. Overall, Cd accumulated over time, with significantly increased liver and kidney concentrations. Lactationally exposed pups (PND 21) exhibited substantial uptake of Pb into kidney, liver and blood, with significantly higher tissue concentrations at weaning than following direct ingestion (PND 50 and 100). Erythrocyte ALAD enzyme activity was inhibited by Pb exposure. Blood As was also highest at weaning; further demonstrating that lactational exposure is a significant mode of exposure to young.At the highest exposure level, liver and kidney concentrations accumulated with time, reaching potentially toxic threshold levels. Our investigations illustrate the importance of age-dependent bioaccumulation assessments of soil metals. Profound elevations due to lactational exposure demonstrate that toxic effects may be underestimated using only adult dosing regimes.

Cadmium Bioavailability and Bioaccessibility as Determined by in vitro Digestion, Dialysis and Intestinal Epithelial Monolayers,and Compared to in vivo Data.
Chan, D.1, Black,W.2 and Hale, B.1
1University of Guelph, Guelph, ON,Canada. 2Biomedical Sciences,University of Guelph,Guelph,ON,Canada.
The objective of the study was to compare in vivo estimates of Cd bioavailability in two diet materials (lettuce and durum grain) with bioaccessibility estimates from three in vitro methods (simulated gastric/intestinal digestion, and dialysis or exposure of Caco2 cells). For both diet materials, the Cd was either incorporated during growth or applied topically as a soluble salt just prior to experimentation. Simulated gastric/intestinal digestion using a physiologically based extraction technique (PBET) solubilized less than 3% (lettuce) or 13% (grain) of the Cd that was either incorporated into the plant tissues during growth, or added to the plant tissues before experimentation, as Cd(NO3)2.H2O. Amended diets were not distinguished from incorporated diets. More of the Cd solubilized from amended lettuce than from incorporated lettuce moved to the outside of dialysis sacs (MWCO 10kD and 25kD); no difference between the diets was observed for grain. The per cent of lettuce-Cd solubilized through PBET and sorbed by Caco-2 cells was greater for incorporated than for amended; for Cd in grain, the reverse occurred.While none of the in vitro assays identified the same bioavailability of Cd in the lettuce or grain as was measured in vivo, all of the in vitro assays identified substantially less than 100% bioavailable Cd, as was identified in vivo, and simulating intestinal selectivity improved the comparison to in vivo. Some of the in vitro assays identified subtle differences between the diets (i.e. amended vs. incorporated) that were consistent with the in vivo studies, and with speculated differences in molecular speciation of Cd.

The bioaccessibility of lead, arsenic, and mercury in soils and edible berries from Northern Canada using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME).
Laird, B.1,Van De Wiele,T.2 and Siciliano, S.D.1
1Department of Toxicology, University of Saskatchewan, Saskatoon, SK, Canada. 2Laboratory of Microbial Ecology and Technology, University of Ghent, Ghent, Belgium.
The ingestion of metal contaminated soils and foods have been identified as potential health risk to Northern communities that live in proximity to metal hotspots. Current practice in risk assessment is to assume that the bioaccessibility of the ingested compound is one hundred percent, or at least equal to the material used to derive the Toxicological Reference Value. However, the validity of this practice is questionable since recent work has demonstrated that there are large differences in metal bioaccessibility between different foods and soils. Blueberries (Vaccinium uliginosum) and crowberries (Empetrum nigrum), both edible berries consumed in traditional Northern diets, and adjacent soil samples were collected from sites of known metal contamination in Iqaluit, NV. In addition, berry and soil samples were collected from pristine sites in a nearby Territorial Park. The transport of soil metal contaminants into fruit was investigated to allow the comparison of the metal exposure of Northern people's through diet and incidental soil ingestion. Subsequently, the percent bioaccessibility of arsenic, mercury, and lead from berries and soils was evaluated using the SHIME (Simulator of the Human Intestinal Microbial Ecosystem), an in vitro human gastrointestinal model incubated with a microbial community representative of that found in the human gut. The roles of contaminant concentration, gastrointestinal stage residence time, and gastrointestinal microorganisms on bioaccessibility were examined for berries and soils. Analysis of the metal bioaccessibility of these samples will allow researchers to provide Northern communities with precise exposure mitigation strategies.

Bioaccessibility of Metals and Metalloids in Soil Matrices.
Reimer, K.1, Koch, I.1, Ollson, C.2,1, Wragg, J.1, Brewis, M.1, Lord-Hoyle, M.1 and Meunier, L.1
1Environmental Sciences Group, Royal Military College of Canada, Kingston, ON, Canada. 2Risk Assessment, Jacques Whitford Limited, Ottawa, ON, Canada.
Evaluating the health impacts associated with soil contaminants is a complex task. As a starting point, the contaminants must be identified, and their concentrations must be determined for a given soil matrix. The bioavailability of these soil contaminants must then be assessed to give a measure of the amount of contaminant that can be absorbed into the body; these measurements carry substantial experimental and analytical costs. Alternatively, the bioaccessibility of these contaminants can be used as a conservative surrogate for bioavailability. Bioaccessibility is concerned with the fraction of a substance that is soluble in the gastro-intestinal (GI) environment and is thus available for absorption in systemic circulation. Several laboratory methods have been developed and published in the literature to study the bioaccessibility of metals from soil matrices. A review of research currently carried out at RMC will be presented, some of which examines the impacts of buffer, soil:liquid ratio and soil matrix components used in simulated gastric and gastro-intestinal fluids. Initial experiments indicate that a high concentration of amino acid buffer can have an effect on arsenic bioaccessibility and also solubilise greater concentrations of certain divalent metal contaminants than those predicted with bioavailability tests. The results presented will include the hypothesized chemical reasons for the variations in extraction, together with experiments systematically designed to test these hypotheses. This information is crucial in understanding the bioaccessibility of contaminants and is a step towards predicting how contaminants behave under known conditions.

Assessment of a unified in-vitro bioaccessibility method for Arsenic, Cadmium and Lead in soils.
Cave, M.1, Wragg, J.1, Klinck, B.1, Gron, C.2, Oomen, A.3, van de Wiele, T.4, Ollson, C.5, Koch, I.5, Reimer, K.5, Basta, N.6, Casteel, C.7, Denys, S.8, Tack, K.8
1British Geological Survey, Nottingham, United Kingdom. 2DHI, Copenhagen, Denmark. 3RIVM, Utrecht, Netherlands. 4University of Ghent, Ghent, Belgium. 5Royal Military College of Canada 6Ohio State University, Ohio, OH, USA. 7University of Missouri, Missouri, MO, USA. 8INERIS, Paris, France.
When considering the direct ingestion of soil in the risk assessment, total concentrations of potentially harmful substances (PHS) are often considered to be a gross overestimate of the amount of PHS entering the body. The human gastrointestinal tract only makes a fraction of the PHS accessible for absorption. UK technical guidance, however, permits the use of site-specific estimates of oral bioaccessibility. This presentation describes two initiatives being undertaken by the BGS and the Bioaccessibility Research Group of Europe (BARGE) to standardised and validated procedures for measuring bioaccessibility by: 1 Preparation of a reference soil to allow testing laboratories to monitor the QA of bioaccessibility measurement; 2 Development of a Unified and Validated in-vitro bioaccessibility test. The Reference material consists of 0.5 tonne of soil, which was dried ground, homogenised and characterised and the total As concentration was found to be 87.1 ± 4.7 mg kg-1 with the bioaccessible As c.5 mg kg-1. The proposed unified procedure has been derived from the RIVM physiologically based in-vitro extraction test (Oomen, 2000). The performance of the method has been tested on nine soils for which in-vivo arsenic bioavailability data has been obtained using a swine model (Rodriguez et al, 2003). The soils have been provided by Professor Nick Basta of the Ohio State University, Columbus, Ohio, USA and Professor Stan Casteel, University of Missouri, USA. The soils are calcine and iron slag soils with total As concentrations ranging from c. 400 - 18000 mg kg-1 and relative bioavailabilities from c. 4-40%.

References
Oomen, A.G. (2000).Bioavailability of soil borne contaminants.University of Utrecht. Rodriguez, R.R., Basta, N.T., Casteel, S.W., Armstrong, F.P and Ward, D.C. (2003). Chemical Extraction Methods to Assess Bioavailable Arsenic in Soil and Solid Media. Journal of Environmental Quality, 32, 876-884.

Linking Arsenic Speciation in Smelter Contaminated Soil to Oral Bioavailability.
Basta, N.T.1, Foster, J.N.1, Scheckel, K.G.2 and Casteel, S.W.3
1School of Environment and Natural Resources, Ohio State University, Columbus, OH, USA. 2NRMRL, U.S. Environmental Protection Agency, Cincinnati, OH, USA. 3College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.
Arsenic speciation, bioaccessibility and oral relative bioavailability (RBA) was determined for smelter contaminated soils. Arsenic speciation was performed by chemical extractions and extended X-ray absorption fine structure (EXAFS). The only chemical extraction that was significantly, positively, and linearly correlated to RBA As was the hydroxylamine hydrochloride extraction (r = 0.95**). The Ohio State University in vitro gastrointestinal method was also highly correlated with RBA As. Water (r = 0.93**), sodium acetate (r = 0.94**), and phosphate (r = 0.95**) extractable As all were strongly related to RBA As but these relationships were nonlinear. Arsenic strongly bound to the Fe and Al oxide fraction and in the mineral form of scorodite, an oxidation product of arsenopyrite, produced significant negative relationships with RBA As and BA. Thus, these fractions represented the unavailable As in these contaminated soils. The EXAFS analysis determined a large fraction of As was associated as scorodite (67.9 % and 54.0 %) for the calcine and slag contaminated soils, respectively. This study supports the finding that soils with As associated with Fe and Al oxides and/or scorodite-like mineral forms have low As oral bioavailability.

CONSOIL 2005