EU-SICHERHEITSDATENBLATT Dieselkraftstoff ... - Schmierstoffe

(see Appendix 2). Since BCF predictions derived from this model are based on a default
lipid content of 10.7%, predictions were adjusted to 5% lipid content as recommended in
REACH Guidance Chapter R.7c (ECHA, 2008a). Default values for particulate and
dissolved organic carbon concentrations of 0.5 mg/l that are assumed in the BCFBAF
model were also used as conservative defaults in these calculations. The marked
influence that fish biotransformation exerts on the predicted BCFs derived from this
model is evident (see second figure in each of the sections below). BAF predictions
included in the BCFBAF model were judged to be inappropriate for hydrocarbons since
metabolism in the gut (which effectively reduces the default dietary assimilation
efficiency assumed in food chain model calculations) is ignored. The decision to exclude
BAF model predictions in this analysis is supported by experimental dietary BMF data
(see below) demonstrating the critical role of gut metabolism in limiting biomagnification
of hydrocarbons via the diet.
Experimental data
Aqueous and dietary bioaccumulation data are reported in tables in each hydrocarbon
class section. Dietary bioaccumulation tests (Anon, 2004) offer a number of practical
advantages over traditional aqueous BCF tests, particularly for more hydrophobic test
substances. These data may be used to calculate a biomagnification factor (BMF) which
is defined as the concentration ratio of test substance in fish tissue at steady-state to that
in the administered diet. If expressed on a lipid normalized basis, substances that exhibit
a BMF significantly above one may undergo biomagnification while substances with a
BMF well below one may exhibit trophic dilution in the food chain. Experimental
elimination rate data derived from these studies can also be combined with allometric
equations for estimating the uptake clearance (k 1 ) to estimate a BCF for the test substance
(Parkerton et al. 2008):
The BCF, normalized to 5% lipid content is calculated with the following equation:
BCF
C
C
fish
water
ku
t
0.693
1
2
5
x
L
fish
where k u is the uptake rate constant (520·W -0.32 ) (Sijm et al. 1995), t 1/2 is the growthcorrected
half-life, derived from the slope of the depuration plot and the fish growth rate
during the dietary test, and L fish
a correction for bioavailability which limits uptake for more hydrophobic substances. For
such substances, complexation to low concentrations of organic carbon in dilution water
is unavoidable. As a result, the ratio of chemical to oxygen gill transfer efficiencies
declines as predicted by the following relationship (Gobas and Arnot 2003):
1
, X poc = 0, X doc = 2×10 -6
(1 (0.35
X K ) (0.08
X K )
poc
OW
doc
OW
29