Number: 1999-041-1-600
Title: Bioavailability of Xenobiotics in the Soil Environment
Task Group
Chaiman: Arata
Katayama
Members:
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.
Objective:
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
Description:
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.
Methodology
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.
Clients
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.
Progress:
Last Update: 28 July 2000