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Current Project

Chemistry and the Environment Division (VI)


Number: 1999-041-1-600

Title: Bioavailability of Xenobiotics in the Soil Environment

Task Group
Arata Katayama

C. Bellin, A. Felsot, E. Carazo, C. Harris, J. Linders, H.-G. Nolting, K. Racke, B. Rubin, G. Stephenson, J. Unsworth, D. Wauchope, H. Egli, W. Koerdel, J. Lintelman, W.J.G.M. Peijnenburg.

Remarks: The task group is comprised of scientists from two commissions of the IUPAC Division of Chemistry and the Environment, Agrochemicals and the Environment (VI.4), and Soil and Water Chemistry (VI.3), who are experts on interactions between chemicals and biota in the soil environment.

To clarify the scientific basis for bioavailability and to recommend rules for estimating the ecotoxicity or efficacy of xenobiotics, including agrochemicals, based on residue and metabolite profiles in soil

Problem Statement
In the IUPAC Conference of Pesticide Chemistry in London in 1998, there was a controversial discussion on the topic whether agrochemicals in the environment are really hazardous. The conventional wisdom is that chemicals in soil are available to microorganisms, plant roots, and soil fauna like earthworms and animals via dermal exposure. Then bioaccumulation through the food web may induce indirect exposure to higher organisms. National governments are simply reducing the threshold levels of chemicals in the environments for larger safety margins in their guidelines. However, the question raised at the Congress was that chemical residues in the environment are not always bioavailable, so that the actual exposure of biota to chemicals is rather different from the amount (concentration) present in the environment. In addition, the persistence and efficacy of agrochemicals are affected by their bioavailability in soil. There is a lack of comprehensive understanding of the bioavailability of chemicals with different chemical characteristics, such as non-polar organochlorines, polar agrochemicals and etc. Thus, there is a strong needs to clarify the scientific basis for bioavailability: definition, estimation methods and affecting factors.

The project will examine available data on the bioavailability of chemicals in soil. Attention will be focused on organic chemicals such as agrochemicals and organochlorine pollutants, which will be classified based on their chemical properties affecting bioavailability. Data sources will include the peer-reviewed published literature, reports from government monitoring programs, and proprietary data generated by agrochemical manufacturers and industry associations. Information on bioavailability will be critically reviewed. Data requirements will be examined for the determination of bioavailability. The final work product will provide a solid scientific basis to the question of bioavailability in the risk assessment of xenobiotic pollutants.

The following clients will be interested in the results and recommendations of this project on regulatory limits of xenobiotic pollutants in soil: International agencies such as OECD and FAO, health authorities, soil authorities, agrochemical companies, environmental agencies, regulatory authorities, analytical laboratories.



Last Update: 28 July 2000


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