Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p15
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 15/24)
Character Range: 982049–985077

a minimum:
    * an understanding of the diet of the exposed population
    * an estimation of contaminant concentrations in the food source consumed by the livestock or fish
    * an estimation of the relative percentage of time spent roaming and feeding in the contaminated area
    * an accounting for assimilation rates of the contaminant into the food source and bioaccumulation within the higher organism.
Data is scarce for each element and there is currently no generic methodology available for estimating contaminant levels in animals resulting from their exposure to contaminated soil or water.

If the exposure of farm livestock has already occurred, direct measurement of the contaminant levels in the meat would be the most practical means to estimate intakes of potentially exposed populations. Some studies have been conducted on fish and shellfish and equations for estimating contaminant concentrations in fish from water concentrations are available in ANZECC and ARMCANZ (2000) and Arnot and Gobas (2003). Additional algorithms on uptake in humans from consumption of contaminated fish are also provided in the ANZECC and ARMCANZ (2000) guidelines.

In the absence of directly measured contaminant concentrations in fish, the ANZECC and ARMCANZ method is recommended to estimate the likely concentration of contaminant uptake into fish tissues and subsequently the mean daily intake dose from human consumption. Implementing the ANZECC and ARMCANZ methodology involves:
    * measuring the contaminant concentrations in the water environment that the fish inhabit
    * estimating the uptake of contaminant into the edible portion of the fish tissue (allowing for the percentage of time the fish may spend in the contaminated section of the environment)
    * estimating potential human consumption of fish caught within the contaminated area.

4.7              Estimation of contaminant intake

    4.7.1          Introduction
Contaminant intake is estimated for each chemical and pathway separately. The recommended methodology generally follows US EPA (1989). There are two basic approaches that have been developed on the basis of the way in which chemicals cause toxicity:
    * Threshold toxicity is exhibited by chemicals where there is an exposure level below which no toxic effect is thought to occur. Threshold substances are generally considered to include most non-carcinogenic chemicals and non-genotoxic carcinogens.
    * Non-threshold toxicity is exhibited by chemicals where there is considered to be no dose below which no adverse effect will occur. In theory, any level of exposure could result in a response. Genotoxic carcinogens comprise this group.
For threshold chemicals, the estimated daily intake can be compared with a threshold toxicity 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