Protocol for the Derivation of Environmental and Human ... - CCME

Part B, Section 2
There is consistent use and acceptance of the 7 and 14 day mortality test as a short-term test for
earthworms (e.g., OECD, 1984a; Greene et al. 1989; ISO, 1991) and for the five-day seed
germination/root elongation test as a short-term test for plants (e.g., U.S. EPA, 1982; Porcella, 1983;
Ratsch and Johndro, 1986; Thomas and Cline, 1985; Miller et al., 1985; Wang, 1987; Wang and
Williams, 1988; ASTM, 1990a; ASTM, 1990b). However, short-term toxicological tests for other
soil-dependent organisms (e.g., isopods) are still under development (NISRP, 1991; ISO, 1992).
Long-term standardized toxicity test methods for earthworms have recently been developed and others
are currently being developed for isopods (ISO, 1992; NISRP, 1991). Usually, long-term exposure
tests for soil-dwelling organisms include at least one reproduction stage (in the case of soil
invertebrates), or one growth cycle (in the case of plants). Long-term tests have been proposed for
earthworms (five-week reproduction-ISO, 1991) and some plants {life cycle flowering (ASTM,
1991)}, but there is some uncertainty in the selection of proper endpoints and methodologies for these
tests (OECD, 1990).
The acceptability of short- and long-term tests for general use in this protocol should be determined on
a study-by-study basis using the information cited above as a guide. Data from long-term studies are
preferred for deriving soil quality guidelines. However, given the limited availability of such data, shortterm
toxicity data may be accepted for guidelines derivation.
2.4.2 Short- and Long-term Tests for Mammalian and Avian Species
A considerable number of standardized toxicological tests have been carried out on traditional
laboratory animals using different endpoints for various types of exposure. One of the most common
toxicity tests is the LD 50 (i.e., the lethal dose which results in 50% mortality of the test population). This
test is normally an acute exposure often involving a single administration of various chemical doses to
laboratory animals followed by a 7 to 14 day examination of lethal effects (Klassen, 1986).
Unfortunately, a standardized method for conducting toxicity tests for wildlife and livestock species are
generally lacking, with the exception of the five-day dietary LC 50 test for avian species (Hill and
Hoffman, 1984).
Historically, in mammalian and avian subacute and chronic lethality tests, the number of dose regimes
often do not provide sufficient information to calculate a dose that results in a 50% response. Thus,
endpoints for chronic exposures are often reported as the no observed (adverse) effect level
(NO(A)EL) and the lowest observed (adverse) effect level (LO(A)EL). Chronic adverse effects
endpoints can be related to reproduction, growth, or viability resulting from a continuous exposure over
a significant portion of the organism's lifespan. Subchronic exposures normally involve the same
endpoint as chronic exposures, but are conducted over a shorter time period.
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