Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p11
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 11/15)
Character Range: 1279880–1283045

three biomagnification classes for inorganics should be used: known biomagnifiers, known non-biomagnifiers, and unknown biomagnifiers (which are then treated as biomagnifiers pending further investigation).

     2.3.2.2         Henry's law constant
Henry's law constant (H) is a measure of the volatility of the element, as described previously. Inorganic elements and contaminants in general have very low volatility. Therefore, exposure pathways involving volatility should only be considered for mercury. These have not been included in the method used to determine the important exposure routes for inorganics.

2.3.2.3         Overview of main exposure pathways for inorganic contaminants
Table 6 below presents the two exposure routes for inorganic contaminants that are considered the most important for deriving EILs and/or SQGs, depending on whether the contaminant biomagnifies or not.

For unknown and known biomagnifying inorganics, secondary poisoning should be addressed. For all inorganic contaminants, direct toxicity to relevant species and soil processes should be addressed.

Table 6. The property used to conduct the inorganic contaminant exposure pathway assessment with the corresponding two most important exposure routes
Biomagnifies  Exposure routes to be considered

Primary       Secondary
Yes           Biomagnification                  Direct toxicity
No            Direct toxicity                   
Unknown       Biomagnification                  Direct toxicity

2.4              Derivation of EIL values
A schematic of the methodology to derive EILs for contaminants is given in Figure 2 below. The main steps in the methodology are:
    1. collation and screening of the data
    2. standardisation of the toxicity data
    3. incorporation of an ageing/leaching factor for aged contaminants
    4. calculation of the added contaminant limit (ACL) by either the SSD or assessment factor (AF) approach, depending on the toxicity data
    5. normalisation of the toxicity data to an Australian reference soil. This is only done if the SSD approach is used to calculate the ACL
    6. accounting for secondary poisoning for those contaminants that are considered to biomagnify in the food web
    7. calculation of the ambient background concentration (ABC) of the contaminant in the soil (if appropriate)
    8. calculation of the EIL or SQG by summing the ACL and ABC values
EIL = ABC + ACL        (equation 1)

The separation of naturally occurring concentrations of a contaminant and the added contaminant in deriving EILs and/or SQG is based on the 'added risk approach' (Struijs et al. 1997; Crommentuijn et al. 1997). This approach assumes that the availability of the ABC of a contaminant is zero or sufficiently close that it makes no practical difference. But, more importantly, it assumes that the background 'has resulted in the biodiversity of ecosystems or serves to fulfil the needs for micronutrients for the organisms in the environment' (Traas 2001). Therefore, the approach views only the effect of added contaminants to the environment as adverse. This approach is mostly relevant for ecological risk assessment