Methods for Deriving Pesticide Aquatic Life Criteria - Reviews of Environmental Contamination and Toxicology - page 72

of 10. If only acute data are available, then the lowest LC 50 /EC 50 value is divided by
an ACR, if one is available. The resulting estimated chronic value is then divided
by 10 to derive the criterion. If no ACR is available, then the criterion is derived directly
from the lowest LC 50 /EC 50 by dividing it by either 20 (for nonpersistent chemicals)
or 100 (for persistent chemicals).
The Netherlands methodology (RIVM 2001) utilizes the AF method for deriva-
tion of MPC and SRC ECO values, through a process called “preliminary effect
assessment.” This is not the preferred derivation method, and is used only where
results of four chronic toxicity studies, from four different taxonomic groups, are
not available. Assessment factors range from 1 to 1000, and are applied according
to the amounts and kinds of data available. Similarly, the OECD recommends use
of an AF method for limited data sets (OECD 1995), with factors ranging from 1 to
1000, depending on available data. A factor of 10 is applied to the lowest NOEC or
QSAR estimate of chronic toxicity, from a data set that includes at least algae,
crustaceans, and fish. If only acute data or QSAR estimates of acute data are avail-
able, then a factor of 100 is applied, if the data set includes algae, crustaceans, and
fish; a factor of 1000 is applied only if one or two species are represented.
Although the USEPA (1985) does not derive criteria when data sets are inade-
quate, the state of North Carolina and the Great Lakes region utilize the AF method
to derive criteria when data are lacking. In addition, for derivation of criteria in
California, Lillebo et al. (1988) developed an AF method that uses LOEC values. For
pesticides, this method involves finding the geometric mean of the three lowest
LOEC values from acceptable tests, and multiplying them by a factor of 0.1. This
criterion is intended to protect all species in an ecosystem from the effects of long-
term exposure. In the state of North Carolina, if adequate data are not available for
derivation of a FAV, using the USEPA methodology (1985), then a factor of 3 is
applied to the lowest available LC 50 value to render an acceptable acute value. North
Carolina uses chronic toxicity values to set aquatic life standards. In the absence of a
chronic value, a measured ACR may be applied to an acute value. If no ACR is avail-
able, then the acute value is divided by 100 (for t 1/2 > 96 hr), or 20 (for t 1/2 < 96 hr;
North Carolina Department of Environment and Natural Resources 2003).
For derivation of Tier I aquatic life values, the Great Lakes methodology
(USEPA 2003a) follows the USEPA guidelines (1985). However, when not enough
data are available for derivation of Tier I values, Tier II values are derived using an
AF method. Secondary acute values (SAVs) are derived by dividing the lowest
available GMAV by a factor ranging from 4.3 (if seven GMAVs are available) to
21.9 (if only one GMAV is available). The secondary maximum concentration
(SMC) is the SAV divided by 2. The secondary chronic value (SCV) is derived in
one of three ways: (1) the FAV (from a Tier I procedure) is divided by a secondary
ACR(derivation is described below); (2) the SAV is divided by the final ACR (from
Tier I); or (3) the SAV is divided by the SACR. The secondary chronic concentra-
tion (SCC) is equal to the lower of the SCV or the Final Plant Value (FPV).
In practice, all of the current Australia/New Zealand TVs that were derived from
single-species toxicity tests were calculated by the SSD method, but the ANZECC
and ARMCANZ guidelines (2000) include an AF method where data are lacking.