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

Part B, Section 7
EC 50
LC 50
UF
= median effective concentration (mg/kg soil)
= median lethal concentration (mg/kg soil)
= uncertainty factor
A minimum of three studies must be considered to select the lowest EC 50 or LC 50 , including one
terrestrial plant, and one soil invertebrate study. If the lowest datum is an EC 50 value, then an
uncertainty factor of five should be initially applied to derive the TEC. If an LC 50 is used as the lowest
datum, then an uncertainty factor of 10 should initially be applied. The selection of these uncertainty
factors is based on median acute/chronic ratios determined for EC 50 and LC 50 data versus NOEC data
for 38 inorganic and organic contaminants for soil-dependent organisms (Bonnell, 1992). Uncertainty
factors of 5 and 10 have also been proposed for use in deriving guidelines for soil from short-term data
(Dennemen and van Gestel, 1990; van de Meent, 1990; van der Berg and Roels, 1991). An additional
uncertainty factor between one and five may be applied if points two, three, or four listed in the LOEC
method for UF selection are incurred.
The TEC should now be compared with the microbial value to determine the SQG SC for agricultural and
residential/parkland land uses (see Appendix A).
7.5.2.5 Insufficient Data for Soil Contact Guidelines Derivation. If minimum data requirements
for the above methods cannot be met, then there is insufficient information to develop a final
environmental soil quality guideline (SQG E ) for agricultural or residential/parkland land uses. Data gaps
will be identified for further research.
7.5.3 Methods for Commercial and Industrial Land Use
7.5.3.1 Overview. A similar level of protection and receptor array is envisioned for commercial and
industrial land use. Accordingly, the following guidelines derivation methods apply to both commercial
and industrial land use. Two methods are described under this procedure. Because guidelines are
derived at a level of effects above the threshold concentration, the effects concentration low (ECL) is
estimated instead of the TEC. Preferably, the weight of evidence method is used to calculate the ECL.
If the minimum data requirements cannot be met for this method, then the ECL may be calculated using
the geometric mean of available LOEC data. If minimum data requirements cannot be met for this
second method, research needs will be identified. An overview of this procedure is presented in Figure
12, and Figure 13 shows graphically where the ECL derived for each method falls in relation to the
distribution of "effects" data for cadmium.
7.5.3.2 Using Microbial (Nutrient and Energy Cycling) Data for Derivation of Soil Contact
Guidelines for Commercial and Industrial Land Use. Once the ECL is calculated, it is compared
with selected microbial process (nutrient and energy cycling) data using the procedure outlined in
Appendix A for commercial and industrial land use. If the microbial value determined in Appendix A is
lower than the ECL calculated using either of the soil contact methods below, then significant adverse
effects may be experienced by microorganisms controlling nutrient and energy cycling processes. In this
case, the geometric mean of the two values is taken and used as the soil quality guideline for soil contact
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