technical guidance documents - Institute for Health and Consumer ...

TESTING STRATEGIES
Care must be taken, when attempting to revise the effects assessment by conducting additional
aquatic toxicity testing, to ensure that species sensitivity is fully taken into account. Although the
choice of tests is necessarily limited, it must reflect the anticipated exposure conditions and the
chemical properties of the substance.
In determining whether additional testing is required, the following guidelines should be
followed:
• additional testing should lead to a revision of the estimated PNECwater which, when based on
long-term ecotoxicity data, is more reliable than the PNECwater when based on short-term
data;
• the species with the lowest L(E)C50 in short-term studies should normally be examined first
for the purposes of long-term testing. Differences in L(E)C50s can be determined by
comparing their values: one value is considered to be significantly lower than another if it is
more than ten times lower. However, these definitions can only provide a guide to the
relative sensitivities of taxonomic groups. Expert judgement must therefore be used to
determine whether they are sufficient in any given case;
• further testing would not normally be required on a species for which no short-term toxicity
has been demonstrated (L(E)C50 > 100 mg/l). This may not apply to poorly water-soluble
substances (water solubility < 1 mg/l) for which no short-term toxicity may have been
demonstrated (see Section 5.6). In other cases, expert judgement should be used to
determine whether further testing of a species is necessary.
For substances that have a potential to bioaccumulate, it should be recognised that long-term or
delayed effects are possible. These effects might not have been apparent or predicted from the
results of short-term studies or long-term tests appropriate for non-bioaccumulating substances.
This is considered to be of particular importance when considering long-term fish and Daphnia
toxicity since several sensitive stages of their development can be affected because of their high
lipid content in the early stages of their life-cycles. Care needs to be taken, therefore, to ensure
that the appropriate long-term test is selected and that steady state concentrations are achieved in
the organisms for a period that is sufficient to allow the potential effects of bioaccumulation to
be investigated. Normally a Fish Early Life Stage test (OECD 210, 1984g) would be considered
appropriate for examining fish toxicity. However, the fish, juvenile growth test (EU Annex V
C.14) (for substances with log Kow < 5) or egg and sac-fry stage test (EU Annex V C.15) (for
substances with log Kow < 4) may also be considered.
The results from these long-term toxicity tests cannot exclude the possibility of delayed effects.
When such effects are suspected, it may be appropriate to consider full life-cycle tests for fish
according to the US EPA guidelines 670/4-73-001 (US EPA, 1973) or 600/9-78-010 (US EPA,
1978) and/or Daphnia (A guideline for a full life-cycle test for Daphnia is not available yet).
Such testing would not be regarded as normal and should be necessary only in exceptional
circumstances.
Not all endpoints (such as multi-generation effects or behavioural disturbances) are assessed
using these tests and biomagnification processes can hardly be reproduced in laboratory scale
experiments. Consequently, even with this information, delayed effects in the ecosystems cannot
be ruled out.
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