Environmental Engineering Reference
In-Depth Information
Table 9.3
The assessment factor scheme used uniformly for calculating
PNEC
in aquatic habitats.
Trophic levels and test duration
Assessment factor (AF)
Three trophic levels, at least 1-1 acute toxicity tests
1,000
(3
×
LC50 Daphnia, algae, fish)
Three trophic levels, at least 1 chronic toxicity test
100
(2
×
LC50
+
1
×
NOEC)
Three trophic levels, at least 2 chronic toxicity tests
50
(1
×
LC50
+
2
×
NOEC)
Three trophic levels, 3 chronic toxicity tests
10
(3
×
NOEC)
Mesocosm or field data
1-5
Table 9.4
Calculation of
PNEC
from the results of biotests - an example.
Testing series I
Results I
Testing series II
Results II
Fish acute
EC50
=
7.5mg/L
Fish chronic
NOEC
=
0.05mg/L
Daphnia chronic
NOEC
=
0.1mg/L
Daphnia chronic
NOEC
=
0.1mg/L
Algae
EC50
=
0.5mg/L
Algae chronic
NOEC
=
0.1mg/L
Smallest effective
0.1mg/L
Smallest effective
0.05mg/L
concentration (SC)
concentration (SC)
PNEC (SC/AF)
0.1mg/L/100
=
1
µ
g/L
PNEC (SC/AF)
0.05mg/L/10
=
5
µ
g/L
The example of the establishment of
PNEC
and
DNEL
for human health is shown
below to explain the use of uncertainty factors. Uncertainties are derived from the
following:
-
Interspecies differences;
-
Intraspecies differences;
-
Differences in duration of exposure;
-
Issues related to dose-response;
-
Quality of the database used.
Knowing or estimating the scale of these differences, experts determine the aggre-
gated assessment factor (AF) to be applied both to the ecosystem and to human RA.
One method for the calculation of
PNEC
is the factorial extrapolation, in which,
depending on the quality and uncertainty of data, the uncertainty factor is chosen and
applied in a conservative way. Table 9.3 shows the REACH recommendation for the
AFs of the aquatic ecosystem's
PNEC
(EC TGD, 2003).
Using the recommended assessment factors (uncertainty factors), the
PNEC
of a
contaminant on the aquatic ecosystem will be calculated as shown in Table 9.4.
The establishment of
DNEL
for the calculation of the human no effect level may
use measured data on humans (mainly observational) or animals (mainly experimen-
tal). The dose descriptor (establishing the relationship between dose and effect) is
generally NOAEL (no observable adverse effect level) and LOAEL (lowest observable
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