Closing the gap between exposure and effects in monitoring studies
D. E. Tillitt and D. M. Papoulias
Columbia Environmental Research Center, U.S.Department
of Interior, Geological Survey, 4200 New Haven Road, Columbia, MO 65201,
USA
Abstract: A major challenge to contaminant monitoring programs
is the selection of an appropriate suite of measurements for assessing
exposure and effects. Early monitoring programs relied solely on residue
analysis to detect the organochlorine compounds that were in use at
that time. A shift to the use of more transient, less persistent chemicals
required that a new set of tools be developed to determine if an organism
had been exposed. This led to the development of cellular and biochemical
assays that could indicate the presence of these types of chemicals
in biota and the environment. However, it was recognized that measures
of contaminant presence alone were insufficient to assess the health
of biota. As a result, considerable research began to be directed toward
development of diagnostic tools for measuring chemical effects in fish
and wildlife. Today, contaminant monitoring programs follow a paradigm
for study design that emphasizes not only the use of measures of exposure,
but also measures of effect.
Using data from our monitoring and research studies for hormonally
active substances, we discuss a variety of metrics of exposure and effects
and their application to specific chemicals, and the current information
gaps. We conclude that although several bioindicators of exposure and
effect have been promoted and used, to date there continues to be a
poor association between cause and effect for endocrine active substances.
In part, this is due to the limited number of diagnostic tools that
are available and to a lack of basic toxicological information concerning
toxicokinetics and mechanisms of action of hormonally active chemicals
in fish and wildlife species. In the foreseeable future, both tissue
and environmental residue data, despite the many limitations, will continue
to be an important component of monitoring programs for hormonally active
chemicals as we continue to develop and validate more specific bioindicators
of exposure and effects.
*Report from a SCOPE/IUPAC project: Implication of
Endocrine Active Substances for Human and Wildlife (J. Miyamoto and
J.Burger, editors). Other reports are published in this issue,
pp. 1617-2615.
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