Methods for Deriving Pesticide Aquatic Life Criteria - Reviews of Environmental Contamination and Toxicology - page 92

compiled data showing that average efficiency of absorption of hydrophobic
organic chemicals from food for salmon and rainbow trout was 0.45 ± 0.06, for
chemicals with log K ow s < 7.0, and was 0.18 ± 0.04 for chemicals with log K ow s ≥
7.0. Thus, dietary uptake may be less important for extremely hydrophobic chemicals,
but it is prospectively important as an exposure route. The OECD guidelines use
toxicity data to derive a maximum concentration in food that will minimize risk for
fish-eating wildlife (other than fish). This maximum concentration is divided by the
BCF, for fish, to give the MTC for water (based on a method presented by Romijn
et al. 1993). If the water MTC, derived in this manner, is lower than the MTC
derived for protection of aquatic life, then secondary poisoning must be considered
in setting criteria.
The EU risk assessment TGD (ECB 2003) describes potentially bioaccumulative
chemicals as those that have a log K ow > 3, or are highly adsorptive, or belong to a
class of chemicals known to be bioaccumulative, or have a structure that indicates
bioaccumulative potential, and have no features that might mitigate bioaccumulative
potential (e.g., short half-life). The TGD provides guidance for assessment of sec-
ondary poisoning, but from the perspective of assessing risk to predators from
dietary uptake, rather than for setting water quality criteria. That is, BCFs and
BMFs (relative concentration in predator compared to prey) are used to predict
concentrations of contaminants in prey, based on concentrations measured in water,
using the following equation:

PEC = PEC × BCF × BMF (2.18)

oral,predator water fish

where
PEC oral,predator = predicted environmental concentration in food
PEC water = predicted environmental concentration in water (from exposure
assessment)
BCF fish = BCF for fish on wet weight basis
BMF= biomagnification factor in fish
By substituting NOEC values for the PEC values in Eq. (18), one could solve for
NOEC water given a NOEC oral,predator , BCF and BMF values:

NOEC

oral-predator

NOEC = (2.19)

water

BCF BMF

fish

Inclusion of the BMF value accounts for residues in fish, which result both from
direct water uptake and dietary intake of contaminated organisms from lower
trophic levels. If experimentally determined BMF values are not available, default
values taken from other studies are used in the TGD. As noted, the USEPA (1985),
the OECD (1995) and the RIVM (2001) guidelines discuss BAFs (which include
dietary uptake), but use BCFs (no dietary component) in their calculations, because
BCFs are normally available. However, these methodologies make no attempt to
correct the calculated water concentrations for the dietary uptake component. This
results in water concentration values (e.g., FRVs in the case of USEPA) that are