Methods for Deriving Pesticide Aquatic Life Criteria - Reviews of Environmental Contamination and Toxicology - page 84

treated. South Africa utilizes the USEPA methodology (1985). The OECD meth-
odology (OECD 1995) refers users to the USEPA SSD procedures (1985), as well
as those utilized (at the time) by the Netherlands (RIVM 2001) and Denmark
(Samsoe-Petersen and Pedersen 1995).
USEPA (1985) . To calculate the FAV, the GMAVs are ordered from highest to
lowest and assigned ranks from 1 to N . For each GMAV, a cumulative probability
( P ) is calculated as P = R /( N + 1). The four GMAVs nearest to P = 0.05 are selected
(for data sets with fewer than 59 GMAVs, these will always be the four lowest
values in the set). Using the selected GMAVs and P values, the FAV is calculated
as follows (see Erickson and Stephan 1988 for derivation):

∑

(( ) ) ((

∑

))

ln GMAV

2

− ln GMAV

2

/ 4

(2.7)

s

2

=

∑

( (

∑

) ) )

( P ) − ( P

2

/ 4

(

∑ ∑

))) L = (ln GMAV) − s ( ( P / 4 (2.8)

A = s ( 0.05) + L (2.9)

A

FAV = e (2.10)

where
s 2 = variance of lowest four values in the data set
GMAV= genus mean acute value
P = percentile rank of datum
L is as defined in Eq. (8)
A is as defined in Eq. (9)
FAV= final acute value
e = base of the natural logarithm
The acute criterion, called the CMC, is equal to the FAV/2.
The FCV may be derived in the same manner if enough chronic data are avail-
able; however, the FCV is typically derived by application of an ACR to the FAV.
The chronic criterion, called the criterion continuous concentration (CCC), is the
lowest value among the FCV, the FPV, or the FRV.
The Netherlands (RIVM 2001). ERLs are derived using the SSD method of
Aldenberg and Jaworska (2000). That is, HC p values are calculated based on a
log-normal SSD. The HC 5 and HC 50 are calculated as follows:

(2.11)

log HC = x − k s ·

p

where
HC p = Hazardous concentration for p % of species
x = mean of log-transformed NOEC data
k = extrapolation constant depending on percentile, level of certainty, and sample
size (Table 1 in Aldenberg and Jaworska 2000)
s = standard deviation of log-transformed data