Grantee Research Project Results
1999 Progress Report: Development of Chemical Methods to Assess the Bioavailability of Arsenic in Contaminated Media
EPA Grant Number: R825410Title: Development of Chemical Methods to Assess the Bioavailability of Arsenic in Contaminated Media
Investigators: Basta, Nicholas T. , Rodriguez, Robin R. , Casteel, Stan W.
Institution: Oklahoma State University , University of Missouri - Columbia
EPA Project Officer: Hahn, Intaek
Project Period: November 1, 1996 through October 31, 1999 (Extended to October 31, 2000)
Project Period Covered by this Report: November 1, 1998 through October 31, 1999
Project Amount: $431,677
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Objective:
Soil ingestion from incidental hand-to-mouth activity by children is an important issue in assessing the public health risks associated with exposure to arsenic-contaminated soils and media. Use of the swine model for bioavailability determinations has been thoroughly validated for lead and arsenic-contaminated materials. Several disadvantages using animal models to measure contaminant bioavailability include expense, specialized facilities, and personnel. Chemical methods (chemical fractionation, in vitro gastrointestinal) that provide a reasonable estimate of the bioavailable arsenic in contaminated media may provide rapid and inexpensive information needed to characterize risk at Superfund sites.The objectives of the proposed research are to provide answers to the following questions: Can chemical fractionation and in vitro gastrointestinal (IVG) laboratory methods provide accurate assessments of bioavailable arsenic in contaminated media? Can an IVG method that simulates gastrointestinal (GI) absorption provide a more accurate estimate of arsenic bioavailability than an IVG method that does not simulate GI absorption? Is arsenic bioavailability a function of arsenic concentration where soil may serve as a sink and decrease arsenic bioavailability? To answer these questions, arsenic measured by chemical methods (chemical fractionation and in vitro gastrointestinal methods) are compared with arsenic uptake by immature pigs for contaminated media (soil and slag) collected from smelter sites.
Progress Summary:
A laboratory in vitro method that simulates the human GI environment by estimating the bioavailability of arsenic in contaminated soil and solid media was developed (Rodriguez, et al., 1999). In this IVG method, arsenic is sequentially extracted from contaminated soil with simulated gastric and intestinal solutions. Across all contaminated media, the IVG method provides an estimate of bioavailable arsenic; however, results are matrix-dependent. The IVG method provides an accurate estimate of arsenic in noncalcinated slags and soils, but not calcinated wastes. The ability of standard soil chemical fractionation laboratory methods to measure bioavailable arsenic was evaluated. Arsenic extracted by hydroxylamine hydrochloride soil extractant was strongly correlated with in vivo bioavailable arsenic. This relationship was even stronger when results were sorted by contaminated media type.Dissolved metal contaminants are continuously removed from the GI tract by absorption. An in vitro method that accounts for absorption and mimics in vivo GI absorption may improve the ability of the IVG method to estimate bioavailable arsenic. A modified IVG method, in which iron hydroxide gel is used as an arsenic sink to simulate the GI absorption of arsenic, was evaluated; however, the IVG method that simulated the GI absorption was not more accurate than the IVG method that did not address GI absorption.
Soils not only have the capacity to be a source of contaminants but also a sink for contaminants. At low levels of contamination, arsenic may strongly be adsorbed by soil and not be bioavailable; however, solubility and bioavailability may increase as the capacity of soil to adsorb arsenic is exceeded. Therefore, bioavailability may be a function of the amount of arsenic in contaminated media. Results from this study show that bioavailable arsenic does change with arsenic concentration; however, the relationship is a complex one and is under study.
The IVG and hydroxylamine hydrochloride extraction methods may serve as inexpensive methods of obtaining estimates of the site-specific bioavailability, thereby lowering the degree of uncertainty in risk assessment. These rapid, inexpensive tests can serve as screening methods to select remediation treatments that reduce arsenic bioavailability and risk; and are cost effective and protective of human health.
Future Activities:
The project objectives and goals are almost complete. Laboratory and in vivo swine studies will be completed by June 2000. Research publications will be prepared and submitted to scientific journals.Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 20 publications | 1 publications in selected types | All 1 journal articles |
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Rodriguez RR, Basta NT, Casteel SW, Pace LW. An in vitro gastrointestinal method to estimate bioavailable arsenic in contaminated soils and solid media. Environmental Science & Technology 1999;33:642-649. |
R825410 (1999) |
not available |
Supplemental Keywords:
risk assessment, cleanup levels, remediation endpoints, site-specific bioavailability, oral bioavailability, human health, exposure, children, health effects., RFA, Health, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Contaminated Sediments, Environmental Chemistry, Chemistry, Epidemiology, Arsenic, Risk Assessments, Fate & Transport, Susceptibility/Sensitive Population/Genetic Susceptibility, Children's Health, genetic susceptability, fate and transport, health effects, risk assessment, fate, contaminated mines, ingestion, soil ingestion, Superfund sites, contaminant transport, risk characterization, soil sediment, human health effects, contaminated sediment, dermal contact, sediment transport, transport contaminants, chemical speciation, adverse human health affects, chemical contaminants, kinetic studies, soils, hazardous waste, children, toxicity, human exposure, superfund site, chronic health effects, environmental toxicant, mobility, arsenic mobility, animal research, ecology assessment models, arsenic exposure, hazardous waste sites, exposure assessmentRelevant Websites:
http://www.agr.okstate.edu/soilchem/Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.