Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p14
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 14/15)
Character Range: 1288081–1291013

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 for soil organisms is the soil pore water concentration (Van Gestel 1992; ECB 2003). Therefore the EqP is not suitable for:
    * contaminants with log Kow values >4 (as they partition to soil rather than soil pore water)
    * contaminants with a specific mode of action (e.g. endocrine disruptors)
    * species that are exposed primarily through food
    * aquatic species that have no direct terrestrial equivalent (e.g. fish)
    * species where the main exposure pathway in terrestrial systems is dissimilar to that in water.

Therefore, the EqP method should only be used to assess the toxicity of the following taxonomic groups, as they meet the above criteria: annelida, bacteria, fungi, hexapoda (larvae only), nematoda, protozoa and tardigrades.

The EqP estimate of a NOEC for a contaminant in soil (NOECsoil) is calculated from the NOEC of aquatic species as indicated below:
     (equation 4)
where RHOsoil is the bulk density of the saturated soil and Kd is the soilwater partitioning coefficient (L/kg) (ECB 2003).
While there has been work done overseas to assess the validity of the EqP method (Van Beelen et al. 2003), there has been no such work undertaken in Australia. This is not a preferred method as Australian soils are relatively old, have low concentrations of nutrients, low organic carbon contents and different clay mineralogy (Taylor 1983), and are thus quite different from European and North American soils.

2.4.1.5         Screening and selection of toxicity data
The next step in the methodology is to determine the suitability of the available toxicity data. Toxicity data is considered acceptable when the:
    * difference between tested concentrations was not greater than five-fold
    * exposure duration was greater than or equal to 24 hours
    * toxicity end point measured was growth, seedling emergence, lethality, immobilisation, reproduction, population growth or the equivalent
    * measured toxic effect was a given percentage effect concentration (e.g. LC10, EC50) or were NOEC, LOEC or MATC (see the Glossary) values.

Biomarker end points, like enzyme production, lysosomal damage and avoidance responses, are considered to be less ecologically relevant and therefore they should not be used for the derivation of EILs unless data is limited and the predictive methods discussed in the previous section are not suitable. Biomarker tests are very sensitive and are therefore considered as early warning tests. However, if such data is used to derive EILs, this should be clearly stated. Biomarker data can be highly relevant for site-specific ecological risk assessment.

Once the unsuitable toxicity data has