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ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts

Health Canada Approaches and Activities With Respect to Bioavailability of Contaminants in Soil

Petrovic, Sanya A.; Richardson, G Mark

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Under the Canadian Federal Contaminated Sites Action Plan (FCSAP), Health Canada is responsible for the provision of guidance, training, and advice on human health risk assessment (and related topics) to federal departments with custodial responsibilities for contaminated sites. This presentation provides an overview of Health Canada-funded research into the relevance and applicability of in vitro simulated lung fluid solubility assays, in vitro dermal penetration of various soil-borne contaminants using viable human skin, and factors affecting oral bioavailability. One way to improve human health exposure estimates is to apply an increasingly realistic understanding of the fate of particulates and the substances they carry. A review of in vitro studies for the pulmonary tract indicated that given the complexity of particulate distribution, clearance, dissolution, and interaction with macrophages in the pulmonary tract, there is insufficient experimental evidence for other types of solubility assessments to allow for the confident use of in vitro assays as estimates of in vivo contaminant bioavailability. Based on the currently available studies, any arguments for decreased bioavailability of substances derived from inhaled particulates are necessarily accompanied by a very low level of confidence. Ongoing in vitro studies are being conducted at Health Canada to examine bioavailability through viable excised skin. It is anticipated that this will provide more relevant data for human exposures than studies with cadaver skin or animal studies. Contaminated soils are applied to the tissue for various durations as well as soils spiked with chemicals. A database of these results will be compiled for a variety of chemicals that are commonly found at contaminated sites. With regard to oral bioavailability, Health Canada has funded numerous studies to evaluate oral bioavailability of soil-borne contaminants. Health Canada is working toward having a standardized in vitro test that can be used to evaluate site-specific bioaccessibility of metals in soils because the soil characteristics and chemical speciation can have a significant impact on the bioavailability. Each of these pathways can have significant influence in the estimates of exposures in human health risk assessment, including childhood exposures to metals in soils and house dust in residential environments. This presentation provides information on these studies and recommendations toward regulatory approaches with respect to bioavailability of contaminants in soils and housedust.

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