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MARINE RISK ASSESSMENT
and most no-effect levels are expressed in term of concentrations of the food that the organisms
consume (i.e. in mg .kg -1 food). Therefore, the actual assessment is normally based on a
comparison of the (predicted) concentration in the food of the top predator and the (predicted)
no-effect concentration which is based on studies with laboratory animals. A distinction is made
between the methodology used to assess the effects of substances whose effects can be related
directly to bioconcentration (direct uptake via water) and those where also indirect uptake via the
food may contribute significantly to the bioaccumulation.
Highly bioaccumulative substances have both a very high bioconcentration potential (log Kow
typically >4.5 or BCF > 500) and are also resistant to biotransformation in animals.
Biomagnification of such chemicals (increased food chain accumulation) is a major risk to the
top predators of food webs, as the consumption of contaminated food is a major source of
contaminants in predatory marine birds and mammals. In contrast the direct uptake of substances
from the environment (that is from water and sediment) is only of minor relevance (Biddinger
and Gloss, 1984; Opperhuizen, 1991). Factors that make these very hydrophobic substances of
particular concern to the marine environment include longer food chains, migratory and
reproductive aspects that may cause especially high exposure of progeny of marine species
likely, long-life of many marine predators, and a higher fat content. However, whilst steady state
levels in birds may be reached within weeks depending on the biological half-life of the
chemical (Pearce et al., 1989), contamination levels in mammals may continually increase with
age, with a plateau only being evident after several years (Thompson, 1990; Teigen et al., 1993).
No distinction can effectively be made between the spatial scales in the approach to the
assessment since the predators will take food from sources spread across local and regional
marine scenarios, as well as from the open sea. In the assessment it is therefore proposed to use a
PECsaltwater based on the mean of the local and regional concentrations for the assessment of the
local situation, and for the regional situation to apply a spatially broader scale. Given that marine
predators may have a wider range of foraging and that the regional sea concentrations will
normally be lower, this is considered as a reasonable worst-case assumption.
Bioaccumulation of metallic species is not considered explicitly in this section.
4.3.3.2 Assessment of bioaccumulation and secondary poisoning
The assessment scheme
The principal endpoints for the secondary poisoning assessment are the predators and top
predators that prey on organisms that are in direct contact with the marine aqueous phase and
receive the substances from this source. A relatively simple food chain is modelled which
consists of the marine water phase, marine food, marine fish and two separate levels of
predators. This food chain is visualised in Figure 16. As can be seen from this scheme risks for
three different trophic levels need to be assessed:
1. risks to marine fish: No specific calculation needs to be performed for estimating the risk to
marine fish as this is covered by the risk assessment for aquatic organisms.
2. risks to marine predators: The risk to marine predators is calculated as the ratio between the
concentration in their food (marine fish) and the no-effect concentration for oral intake
(PNECoralpredator). The concentration in the marine fish (Cfish) is obtained from
bioconcentration of the substance from the aqueous phase and (for very hydrophobic
substances) as a result of bioaccumulation from the food the fish consumes (which consists
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