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

Part B, Section 2
long-term, sublethal endpoints (EC 50 , NOEC, LOEC) (SECOFASE, 1993). Mortality can be
recognized as the ultimate measurement endpoint in ecotoxicological testing and is most often used in
soil invertebrate and terrestrial avian and mammalian testing. Among sublethal effects, reproduction and
growth are common endpoints for soil invertebrates and plants, and to a lesser degree with avian and
mammalian species.
2.4 Selection of Ecologically Relevant Endpoints for Guidelines Derivation
It is generally accepted that ecotoxicology attempts to prevent local species extinction (SERAS, 1992).
This concept of ecotoxicology should be maintained during the development of "safe" concentrations in
the environment for regulatory purposes. In the development of soil quality guidelines, assessment
endpoints at the community or ecosystem level, such as structure and function, ideally would provide the
best measure of ecological impact. However, as discussed and agreed upon at the OECD workshop
for ecological effects assessment (OECD, 1988), studies at this level are difficult and expensive to
perform. In addition, physicochemical and biological conditions of terrestrial systems are highly variable
in space and time making results of these studies difficult to interpret and limiting their validity for other
areas (van Straalen and van Gestel, 1992; Pederson and Samsoe-Petersen, 1993). Currently, it is not
practical to establish generic soil quality guidelines using endpoints from this level of biological
organization. Further verification of chemical effects on terrestrial ecosystems is needed. Therefore, for
the purposes of generic guidelines derivation assessment, endpoints must be defined by directly
extrapolating measurement endpoints to field populations. The Threshold Effects Concentration (TEC)
(soil-dependent biota) or Daily Threshold Effects Dose (terrestrial animals), provides the measurement
endpoint data, that if exceeded is expected to result in adverse effects on populations in the field.
Therefore, in this protocol, assessment endpoints can be regarded as the biological impairment of a
species ability to survive or reproduce.
For generic guidelines derivation, the protection levels sought in Section 2.1 are determined from
information from laboratory tests, and a suitable extrapolation method. To this end, environmental soil
quality guidelines employ sensitive measurement endpoint data from key receptors that act as "predictive
sentinel species". Extrapolation to assessment endpoints is therefore restricted to the population level
since single species measurement endpoint data are used in guidelines derivation. Information from
laboratory studies should therefore involve endpoints critical to the maintenance of a species.
Specifically, these endpoints include those that are critical for a species to complete a normal lifecycle,
and to produce viable offspring. Traditionally, in soil ecotoxicology, these endpoints have been limited
to mortality, reproduction, and growth.
2.4.1 Short- and Long-term Tests for Soil-dependent Organisms
Current definitions of short- and long-term exposure and endpoints for soil toxicity testing are either
lacking or vary from agency to agency. Whereas numerous short-term tests are available for
earthworms and plants, few long-term tests exist for these or other soil-dependent organisms or
microbial processes (Environment Canada 1994).
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