Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p16
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 16/24)
Character Range: 984835–987723

reference value (TRV), which is a value representing a dose that will cause no adverse effect over a lifetime of exposure. Note that, as applied here, the TRV means any appropriate measure of tolerable daily intake, and includes doses derived by various bodies for different applications. Reference doses can be tolerable daily intakes (TDI), usually from drinking water guidelines (for example, Australian or WHO), or acceptable daily intakes (ADI) typically used in food and drug guidance, or US EPA reference doses (RfD).

Threshold TRVs are often available for ingestion and inhalation exposure routes, and occasionally for dermal exposure. Since the TRV for different exposure routes can be quite different, each TRV is only applied to the relevant pathway. Consequently, estimated intakes are only summed to the extent that they correspond to the same exposure route (that is, all ingestion pathways added, all inhalation pathways added, but ingestion intake not added to inhalation intake) when estimating risk by comparing intake to the TRV. The relative scarcity of TRVs for the dermal exposure route is usually accommodated by adding the dermal intake to the ingestion intake where a dermal TRV cannot be sourced. Once hazard/risk quotients and indices are calculated, summing of all pathways can and should be conducted as outlined in the risk characterisation discussion in Section 6.

For carcinogens that are considered as non-threshold chemicals (generally genotoxic carcinogens), intakes are estimated on a daily basis, multiplied by the exposure duration (ED) and then divided by the averaging time (AT). AT is typically a value representing a lifetime. This results in a daily intake, which is multiplied by a non-threshold TRV—such as a cancer slope factor (CSF) or unit risk factor (URF)—to produce a measure of excess lifetime cancer risk.
Doing the calculations in this fashion assumes that it is the daily average exposure over the whole lifetime that is relevant to the development of cancer.

    4.7.2          Ingestion intakes
Methodologies and algorithms for estimating ingestion intakes are available for the pathways listed below. Note that the data applied within these methods should be sourced from Australian publications such as enHealth (2012a and 2012b) as far as possible. Details of the data used to generate the HILs are given in Schedule B7 and in Friebel and Nadebaum (2011a) for the HSLs.
    * Incidental ingestion of soil and indoor dust (US EPA 1989)
    * Ingestion of soil attached to home-grown vegetables (DEFRA and EA 2002)
    * Eating home-grown fruit and vegetables (DEFRA and EA 2002)
    * Eating poultry, meat or fish (US EPA 1989)
    * Drinking contaminated water (US EPA 1989)
    * Incidental ingestion of surface water while swimming (US EPA 1989)
    * NHMRC Guidelines for managing risks in recreational water (NHMRC 2008).