Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p17
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 17/21)
Character Range: 1389367–1392434

concepts.

The limitations of the method are that:
    * the resulting limit does not reflect the uncertainty in the toxicity data used in deriving the limit, e.g. a limit based on three acute laboratory-based toxicity data is treated the same as 25 field-based chronic toxicity data—whereas the latter data set is considerably more environmentally relevant than the former
    * the resulting limit is not transparent as it does not state the degree of protection and thus does not permit informed decisions and debate over the level of protection to occur.

3.2.5         Methods for calculating EILs
In deciding which of the above methods would be best to derive EILs, it is important to recognise the role of EILs. They are a concentration above which further investigation should be conducted. Therefore, if the contaminant concentration does not exceed the EIL, then it is assumed that the situation does not warrant further investigation and is, in fact, safe. Therefore, EILs need to be reasonably conservative. Other considerations are scientific validity, ease of use and interpretation and consistency with existing Australian environmental management systems.

3.2.6         Secondary poisoning and biomagnification
Secondary poisoning can occur if a contaminant biomagnifies, that is, it accumulates in organisms' tissue and the concentration increases with each trophic level in a food web (for example, soil—earthworms—birds—predatory birds). The species most at risk are those in the higher trophic levels in a food web, i.e. the predators. Examples of contaminants that biomagnify and have deleterious effects on predators include DDT, Cd and PCBs (Morrissey et al. 2005; Jongbloed et al. 1996).

The vast majority of environmental toxicity data is on direct exposure to contaminants from the ambient environment (that is, soil, water or air) and not from food. Therefore, if contaminants are biomagnified, then normal toxicity data and EILs based on such data may underestimate the impact the contaminant has on the environment and communities. To overcome this problem, contaminants that biomagnify need to be identified and biomagnification needs to be considered in deriving the EIL for those contaminants.

3.2.7         Methods for accounting for secondary poisoning
Secondary poisoning is taken into account in the soil quality guidelines of several countries, including Canada (CCME 2006), USA (US EPA 1996) and the Netherlands (Van de Plassche 1994). However, not all countries consider secondary poisoning in their SQGs, for example, Germany (BBodSchV 1999).

There are three methods for deriving EILs that account for biomagnification:
    1. biomagnification algorithms
    2. default biomagnification factors
    3. increasing the percentage of species to be protected.
These methods are critically assessed below.

3.2.8         Using biomagnification algorithms
There are three slightly different biomagnification algorithms. The main difference between them is whether ingestion of soil is considered (the US EPA and Canadian methods)