Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 1/18)
Character Range: 2968304–2971305

5                   Exposure assessment
This section provides an overview of the quantitative model used in the derivation of the HILs, including a description of the model algorithms and a summary of the assumptions, including human behavioural characteristics. The information provided is designed to allow risk assessors to gauge the applicability of the HILs at individual sites.

The approach used in the derivation of the HILs is consistent with the Australian quantitative risk assessment framework, as described in Schedule B4. The calculations undertaken combine data on the toxicity of soil contaminants with estimates of potential exposure by adults and children living, working and/or playing on land affected by contamination, over a specified period. By comparing predicted exposure with toxicity reference values, HILs that are protective of human health have been derived.

The equations used to generate the HILs are presented in Appendix B. The values for all input variables used are provided either within the text, or noted in Appendix A. Appendix C presents all the calculations conducted for the derivation of the HILs using the parameters and assumptions presented in Appendices A and B. In general, values presented within the text are those that are considered most significant in terms of understanding the basis of the HILs. Note that input values related to the blood lead model used to derive the lead HIL are presented in Appendix D.

5.1              Exposure pathways
The exposure pathways addressed in the derivation of HILs include:
    * incidental ingestion of surface soil, dust/particulates and soil adhering to home-grown produce
    * indoor and outdoor inhalation of dust particulates
    * consumption of home-grown produce (including vegetables and fruit, but excluding poultry meat and eggs)
    * dermal contact with surface soil and dust/particulates
    * indoor and outdoor inhalation of vapours derived from soil.
The details of the pathways considered for each exposure scenario are presented in Section 3.3.

5.2              General human characteristics applied in the derivation of the HILs
For each standard exposure scenario, full details of the inherent human assumptions (for example, receptor characteristics and behaviour) are summarised in Table 5. In general, exposure settings were selected for consistency with guidance provided in enHealth (2012a). In some cases the assumptions adopted differ slightly (other than simple rounding differences) from those presented in enHealth (2012a). Consideration of these differences does not change the derived HIL, where the underlying principles for the derivation of HILs outlined in Section 1.4 are adopted.

    5.2.1         Body weight
For the assessment of exposures by young children, the average body weight for a child aged 23 years of 15 kg from enHealth (2012a) has been adopted.
Adults have been assessed on the basis of the average lifetime adult body weight of 70 kg from enHealth