Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p13
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 13/15)
Character Range: 1285484–1288347

insufficient data. If QSARs or QAARs are not available, the equilibrium partitioning method (Van Gestel 1992; ECB 2003) can be used if toxicity data is available for aquatic species.

Figure 2. Schematic of the methodology for deriving ecological investigation levels (EILs) for Australian soils.

2.4.1.2         Quantitative structureactivity relationships
QSARs are empirical relationships between the toxicity of contaminants to a particular test organism and one or more physicochemical properties of the contaminant. QSARs are derived for contaminants with either the same mechanism of action or similar contaminant structures. The most widely used physicochemical property is log Kow. An example of a typical QSAR is presented below:
    log EC 50  = -0.72 log Kow + 3.37   (equation 2)

where log EC50 (μmol/L) is the concentration at which 50% growth inhibition of lettuce (Lactuca sativa) was observed (Hulzebos et al. 1991).

The toxicity of contaminants with the same mechanism of action or chemical structure as those in the QSAR can be predicted based on their physicochemical properties. The prediction is made by substituting the value of the contaminant into the QSAR. If equation 2 was being used, the log Kow of a contaminant would be substituted into the equation.

QSARs have been developed for terrestrial plants (Hulzebos et al. 1991) and invertebrates (Van Gestel et al. 1991); however, they are not as widely available as for aquatic species (Posthumus & Slooff 2001). Only QSARs derived using terrestrial species should be used to derive EILs and other SQGs.

2.4.1.3         Quantitative activityactivity relationships
The simplest forms of QAARs are empirical relationships that model the toxicity of contaminants with the same mechanism of action to one species using toxicity data of another species. These are termed binary relationships. An example (Westbury et al. 2004) is provided below:
    log EC50 (C. d.) = 0.848 log LC50 (P. r.) + 0.047 (equation 3)

where log EC50 (C. d.) is the log of the concentration that causes a 50% immobilisation of the cladoceran Ceriodaphnia dubia, and log LC50 (P. r.) is the log of the concentration that kills 50% of the fish Poecilia reticulata.

More complex QAARs have been developed that relate the toxicity of contaminants simultaneously to multiple species (Raimondo et al. 2007; Morton et al. 2008). Both the simple and more complex QAARs allow toxicity data for one or more species to be used to estimate the toxicity to another species. Thus they can fill some of the data gaps that often occur in deriving EILs or their equivalents.

2.4.1.4         Equilibrium partitioning method
The equilibrium partitioning method (EqP) is used to predict the toxicity of a contaminant in soils based on aquatic toxicity data. The EqP is based on the assumption that the main route of exposure