Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p8
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 8/16)
Character Range: 2071348–2074230

scientific investigation.'

On the basis of the above the use of a threshold doseresponse approach for the assessment of carcinogenic effects associated with arsenic exposure is considered appropriate and has been adopted in the derivation of soil HILs.

The review of arsenic by the New Zealand Ministry for the Environment (MfE 2011) noted that, while there is general consensus that arsenic is likely to act indirectly on DNA in a sub-linear or threshold manner, it is considered that there is insufficient data available to determine a 'well-defined non-linear doseresponse'. For this reason the derivation of the New Zealand soil guideline values has adopted a non-threshold (linear) approach for arsenic (i.e. adopting a default non-threshold approach similar to that adopted by default by the US EPA). This differs from the approach adopted in Australia.

    1.4.3         Assessment of End Points – Oral Exposures

1.4.3.1         Existing Oral DoseResponse Approaches  Australia
Arsenic intakes (oral) have been considered in Australia in the derivation of the current HIL (Langley 1991) and the Australian Drinking Water Guidelines (ADWG) (NHMRC 2011). The following can be noted from these guidelines:
    * The derivation of the HIL for arsenic is dated (Langley 1991) and considers all intakes of arsenic on the basis of a threshold PTWI established by WHO in 1983, and reconfirmed in 1988 (WHO 1989). The PTWI adopted is 15 μg/kg/week. In setting the PTWI it was noted that there is 'a narrow margin between the PTWI and intakes reported to have toxic effects in epidemiological studies' (WHO 1989). The PTWI was withdrawn by JECFA (WHO 2011a) following further review (refer to discussion below).
    * The previous ADWG (NHMRC 2004) derived criteria of 7 μg/L for inorganic arsenic in drinking water, based on the former WHO PTWI (noted above) converted to a daily intake (provisional maximum tolerable daily intake) of 2 μg/kg/day. The current ADWG (NHMRC 2011) has adopted a guideline of 10 μg/L based on a 'practicable achievable' approach supported by contemporary epidemiological studies in which elevated cancer risks and other adverse effects are not demonstrable at arsenic concentrations around 10 µg/L. It is noted that this level is equivalent to an adult (70 kg) intake of 0.28 μg/kg/day.
A review of arsenic toxicity was conducted by APVMA (2005) where a threshold approach was considered appropriate (noted above). A threshold value of 3 μg/kg/day was derived by the Australian and New Zealand Food Authority (ANZFA, now Food Standards Australia New Zealand (FSANZ)) in 1999, and considered in the APVMA (2005) review. The review considered that skin cancers appear to be the most sensitive indicator of carcinogenicity of inorganic arsenic in humans and, based on epidemiological studies, a threshold of 2.9 μg/kg/day (rounded to 3 μg/kg/day) can