D10: Impact of Contaminants - Hydromod

Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas
EUROLAKES
D10: Impact of Contaminants
FP5_Contract No.: EVK1-CT1999-00004
Version: 4.0
Date: 25/07/01
File: D10-vers.4.0.doc
Page 28 of 136
• from multi-species effects to the protection of the structure and function of ecosystems.
Typical examples of this approach are the derivation of:
• the EU Water Quality Objectives [BRO-RASMUSSEN et al., 1994].
• the Predicted No Effect Concentrations in the TGD for risk assessment of industrial
chemicals [EC, 1996c].
• the OSPAR Ecotoxicological Assessment Criteria [OSPAR, 1994]
• the proposed Environmental Quality Standards in the Water Framework Directive
(which follow the TGD estimation for PNECs)
Summaries of the application factors employed by the different methods can be found
in [ECETOC, 1993; OSPAR, 1994; TARAZONA, 1998]. The probabilistic approach use
the available information to produce a probabilistic distribution for the species sensitivity
for each chemical. Obviously, the uncertainty in the estimation will depend on the
amount and quality of the information employed to create the distribution. The ecotoxicological
threshold is then calculated as the concentration which is safe for a predetermined
percentage (e.g., 95%) of the species (or other levels of taxonomic organisation).
A classical example for this procedure is the Dutch Maximum Tolerable Concentration
procedure [i.e, VAN STRAALEN AND DENNEMAN, 1989]. Combination of deterministic
and probabilistic approaches are possible in different ways, i.e. by applying a safety
factor to the concentration which protect a certain percentage of the species [i.e., for
the USEPA Water Quality Criteria, USEPA, 1995].
Nowadays, the tendency is to considered probabilistic approaches as a higher tier step
in the tiered scheme. Several proposals for the incorporation of probabilistic methods in
the EU Ecological Risk Assessment programmes for industrial chemicals and for pesticides
have been presented.
It must be pointed out that in any case this approach tries to protect individuals or even
species. If there is a concern for the effects on single species or even for the protection
of individuals within a species (e.g. relevant for certain endangered species) then, the
ecotoxicological approach is not valid and environmental (e.g. wildlife) toxicological
methods are required. The outcome of this approach can be either more or less severe
than the ecotoxicological method (e.g. requiring either higher or lower threshold values
to obtain acceptable margins of safety), but in any case it can be assumed that individuals
are protected by ecotoxicological thresholds.
The role of single-species ecotoxicity tests in the assessment of endocrine disrupters:
In theory the basic concepts discussed above are general and not related to the mode
of action of the chemical. Therefore any mechanism is expected to be covered in the
extrapolation from laboratory data to the ecotoxicological threshold. This conceptual
approach can be justified unless:
• due to technical problems the toxicity test/endpoints can be regarded as unable
to detect the effects related to this mechanisms