Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 5/8)
Character Range: 1043040–1046167

a more detailed treatment of the methodologies applied to assessing cancer risks, refer to the review of cancer risk methodologies in the ASC NEPM Toolbox at http://www.scew.gov.au/archive/site-contamination/asc-nepm.html.

5.4              Other considerations in toxicity assessment

    5.4.1          Absence of information
It will not normally be necessary for risk assessors to derive toxicity reference values for use in site-specific risk assessment. This should only be considered when criteria have not been developed by sources listed in this Schedule and should only be undertaken by a suitably qualified toxicologist.

In cases where the potential site contaminants (that is, known or suspected to be present in the site soil) have no TRVs, but are not detected above the lowest detection limit that can be achieved using available analytical methodology, it is considered acceptable to assume that no additional assessment is necessary. Note that 'available' in this context would include internationally available. The extent of effort expended in procuring a suitable analysis should be proportional to the probability of the contaminant's presence and severity of suspected toxic effects.

Where derivation of new TRVs is required, an extensive and robust literature review undertaken by appropriately qualified toxicologists is expected. The procedure for establishing toxicity reference values is set out in enHealth (2012a) and should be followed. Note that the process requires a high degree of expert judgement.

    5.4.2          Early-life susceptibility
Special consideration has been advocated by the US EPA for assessing risks associated with early-life exposure to mutagenic carcinogens (refer to enHealth 2012a and US EPA 2005a for further information). US legislation also mandates the application of an additional 10x safety/uncertainty factor in the derivation of an RfD for pesticides where studies indicate developmental neurotoxicity or other toxic effects that could be associated with early-life susceptibility.

With respect to non-threshold reference values, the US EPA guidance recommends that individual compounds are assessed to determine whether there is a mutagenic mode of action and whether the potential for early life-time susceptibility should be considered. Where relevant, the following can be applied:
    * If chemical-specific data on susceptibility from early-life exposures is available and incorporated within the derived TRVs (e.g. the oral slope factor for vinyl chloride), then these should be used where appropriate without any further adjustment.
    * If chemical-specific data is not available, then adjustment factors are applied to the calculation of risks associated with early-life exposures. The adjustment factors include a ten-fold adjustment for exposures during the first 2 years of life, a three-fold adjustment for exposures from ages 2 to less than 16 years of life and no adjustment for exposures for ages 16 years and older.
This process should be considered for individual contaminants where there is clear evidence of a mutagenic mode of action.