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EFFECTS ASSESSMENT
hibernation or migration). Similar to the bw/dfi differences, also this aspect goes beyond the
“normal” interspecies variation.
The AForal should compensate for the above-mentioned specific aspects in the effects
assessment of predators. A factor of 30, accounting for both interspecies variation and lab-tofield
extrapolation, is considered to be appropriate for this purpose. Aditionally,
acute/subchronic to chronic extrapolation needs to be taken into account. The resulting
assessment factors are given in Table 23.
Table 23 Assessment factors for extrapolation of mammalian and bird toxicity data
TOXoral Duration of test AForal
LC50 bird 5 days 3,000
NOECbird chronic 30
NOECmammal, food,chr 28 days
90 days
chronic
If a NOEC for both birds and mammals is given, the lower of the resulting PNECs is used in the
risk assessment.
3.8.3.6 Assessment of secondary poisoning via the aquatic food chain
It should be recognised that the schematic aquatic food chain water → aquatic organism → fish
→ fish-eating bird or mammal is a very simplistic scenario as well as the assessment of risks for
secondary poisoning based on it. Any other information that may improve the input data or the
assessment should therefore be considered as well. For substances where this assessment leads to
the conclusion that there is a risk of secondary poisoning, it may be considered to conduct
additional laboratory tests (e.g. tests of bioaccumulation in fish or feeding studies with
laboratory mammals or birds) in order to obtain better data.
The simplified food chain is only one example of a secondary poisoning pathway. Safe levels for
fish-eating animals do not exclude risks for other birds or mammals feeding on other aquatic
organisms (e.g. mussels and worms). Therefore it is emphasised that the proposed methodology
gives only an indication that secondary poisoning is a critical process in the aquatic risk
characterisation of a chemical.
For a more detailed analysis of secondary poisoning, several factors have to be taken into
account (US EPA, 1993; Jongbloed et al., 1994):
• differences in metabolic rates between animals in the laboratory and animals in the field;
• normal versus extreme environmental conditions: differences in metabolic rate under normal
field conditions and more extreme ones, e.g. breeding period, migration, winter;
• differences in caloric content of different types of food: cereals versus fish, worms or
mussels. As the caloric content of fish is lower than cereals birds or mammals in the field
must consume more fish compared to cereals for the same amount of energy needed leading
to a higher body burden of the pollutant;
• pollutant assimilation efficiency: differences in bioavailability in test animals (surface
application of a test compound) and in the field (compound incorporated in food) and/or;
130
300
90
30