Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 4/24)
Character Range: 951278–954396

should be made to the physical setting assumptions outlined in Schedule B7 for guidance on values likely to be suitable for Australian sites. Site-specific data from site investigations should be used wherever possible.

    4.2.3          Exposed population input values
The purpose of this part of the risk assessment is to determine the characteristics and behaviour of the critical exposed populations. Exposed populations may relate to the current or proposed future use of the site, and it should be made clear which land use assumptions are being made. Exposed populations may be located at some distance from the site, with pathways involving transport via groundwater, surface water or wind. Exposed populations may also be linked to the site via the food chain, for example, consumers of fish, meat or agricultural products that may be affected by site contaminants.

The physical characteristics and behaviour patterns representative of the exposed population should be selected for modelling. This is essentially a common sense exercise, which does not normally require any specific assessment methodology or data.

The main considerations are described below.

Physical characteristics  selection of representative values for physical aspects such as age, life expectancy, body weight and respiration rate need to be applied. It is not expected that risk assessors will be generally required to generate these assumptions (refer to those listed in B7 and/or enHealth (2012a and 2012b) where relevant)—considerable uncertainty is involved and variations in assumptions can have a significant impact on the risk assessment outcome. Exposed population physical characteristics should be sourced from applicable Australian guidance on exposure assessment (i.e. enHealth 2012b). Schedule B7 provides the values that have been selected to derive the HILs, which are primarily sourced from enHealth (2012a and 2012b).

Exposed population behaviour  exposure assessment requires the development of a model behaviour pattern that is judged to represent an exposed population. Some data on Australian behaviour patterns is available (for example, see EPHC 2004, enHealth 2012b). Important considerations in contaminated land risk assessment include factors such as the distribution of hours spent indoors and outdoors, amount of time spent in the location where exposure is predicted, level of physical activity, the nature of work or leisure activities, and the exposure duration. In selecting values to represent exposed population behaviour, it is important to consider the following:
    * Plausible high-end exposure — is the recommended approach to judging receptor population behaviour. The likelihood of the modelled scenario should be considered, and behaviours which might reasonably apply to real people should be selected for modelling.
    * Consistency— Schedule B7 provides behavioural and exposure duration assumptions for four standard exposure scenarios. Where site-specific assessments are essentially considering the same exposed populations in similar circumstances to the standard scenarios,