Methods for Deriving Pesticide Aquatic Life Criteria - Reviews of Environmental Contamination and Toxicology - page 49

life-cycle tests (those ranging from just over 7 d, for mysids, to 15 mon for salmonids);
partial life-cycle tests (those with all major life stages exposed, but less than 15
mon in duration; specifically for fish that require more than 1 yr to reach sexual
maturity), or those that test early life stages (those that range from 28 d to 60 d;
particularly applies to fish). Chronic data (reported as an MATC value or deter-
mined by regression analysis) are used to derive an FCV. The FCV may also be
calculated by applying an ACR to the FAV. The South African methodology (Roux
et al. 1996) generally follows that of the USEPA (1985), in terms of using LC 50 /
EC 50 and MATC data, but does not contain explicit descriptions of acute versus
chronic data.
The German guidelines (Irmer et al. 1995) use NOECs derived from studies of
long-term toxicant exposure. If no chronic data are available, acute data may be
multiplied by a factor, and used instead. No guidance is given on how to classify
tests as either acute or chronic.
For derivation of full guidelines, in Canada (CCME 1999), the results of at least
two of three fish toxicity studies must be from full or partial life-cycle (chronic)
studies, and both invertebrate studies must be from full or partial life-cycle exposures.
Rather than using NOEC values, as most methodologies do, the Canadian method-
ology uses the lowest observable effect level (LOEL; equivalent to LOEC), to
derive guidelines. ACRs may be used to convert acute data to chronic values. A study
on plants, of unspecified duration, is required for most substances. However, for
highly phytotoxic substances, four acute and/or chronic studies are required (dura-
tion of acute vs chronic is not defined for plants).
The UK guidelines (Zabel and Cole 1999) use both acute and chronic data for
derivation of annual average (AA) concentrations, but use only acute data for deri-
vation of maximum allowable concentrations (MAC). Chronic values may constitute
chronic or subchronic NOECs, MATCs, or chronic EC 50 s. No guidance is given on
how to distinguish between acute and chronic data for nonplants, although the
guidelines specify that algal growth tests lasting 48-72 hr represent chronic expo-
sures, and should not be used to derive an MAC. However, they state that tests
measuring algicidal effects in a 48-72 hr exposure would be appropriate for deri-
vation of an MAC. If, however, algae are the most sensitive of species tested for a
substance, then a growth inhibition EC 50 may be used to derive an MAC.
Both acute LC 50 and chronic NOEC data may be used according to the EU
methodology (Bro-Rasmussen 1994), but definitions for what constitutes acute or
chronic are not given. The EU risk assessment TGD (ECB 2003) avoids the use of
the terms “acute” and “chronic” and, instead, refers to short- and long-term tests.
Short-term results are in the form of LC 50 s/EC 50 s, and long-term results are in the
form of NOECs, which may be estimated from LOECs, EC 10 s, or MATCs. The only
guidance given, regarding what duration constitutes a short- versus long-term exposure
is for algae studies; such studies are considered to be short-term if they are less than
72 hr, and long-term if they are 72 hr or longer.
The Danish, French, and German guidelines (Samsoe-Petersen and Pedersen
1995; Lepper 2002) all utilize both LC 50 and NOEC data to derive criteria, but none
of them specifically define acute versus chronic tests.