Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 3/16)
Character Range: 2057820–2060654

the comprehensive monkey study conducted by Roberts et al. (2002) as the study of choice. This study was conducted on behalf of the Florida Department of Environmental Protection (DEP) in order to specifically establish a gastrointestinal absorption efficiency factor for arsenic in soil that could be applied to soil risk assessments. The Roberts et al. (2002) study identified the maximum of the arithmetic mean value of 24.7% (for five animals and for relative bioavailability for each of five soil types) as a 'conservative, upper bound case for any particular soil type'. While the maximum individual value reported in the study was 32.4%, the authors did not recommend this value for use as a reasonable maximum exposure (RME) value for risk assessment on the basis that 'only under highly specific, rare circumstances is the maximum value for a particular parameter used in environmental characterisation, exposure assessment and risk assessment' (Roberts et al. 2002). The US EPA agreed with the Florida DEP and selected 25% as an RME value for relative bioavailability for health risk assessments of arsenic in soil (US EPA 2001) and both agencies currently endorse the value of 25%. While the Roberts et al. (2002) study used five soil types typical of Florida soils, another monkey study (using a difference species) was conducted by Freeman et al. (1995) using soil near a smelter in Anaconda, Montana. The mean absolute percentage bioavailabilities, based on urinary excretion data, were 68, 19, and 14% for the gavage (soluble sodium arsenate in oral solution), house dust, and soil treatments, respectively. The values for house dust and soil are consistent with those reported by Roberts et al. (2002) for soil.

Available data from Bendigo in Victoria suggests that the bioavailability of arsenic in soil derived from mine tailings in this region commonly ranges from 1020% and is generally less than 30%. The value of 25% that is adopted by the US EPA would be appropriate in these areas.

With consideration of the above, a range of 2570% bioavailability may be appropriate for the assessment of arsenic in soil. The range of bioavailabilities considered would need to be based on suitable data in relation to source and site-specific bioavailability (where lower bioavailability values were considered appropriate).

    1.3.2         Dermal Absorption
Review of dermal absorption by the New Zealand Ministry for the Environment (MfE 2011) has noted that 'despite the fact that skin cancer is a primary toxicological effect of concern as a result of exposure to arsenic, dermal absorption of arsenic is generally considered to be negligible. US EPA (2004) guidance uses a dermal absorption factor of 3% based on Wester et al. (1993), who examined the dermal uptake of arsenic in solution. However, recent studies