Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 2/8)
Character Range: 2126630–2129537

calculated to be 0.32 µg/day, approximately 28% of the adopted toxicity reference value. This intake was considered to provide a significant buffer below the tolerable daily absorption.

4.3              Significance of Exposure Pathways
Ingestion of soil and dust is considered the most significant pathway of exposure for inorganics in soil. The consideration of bioavailability and inclusion of other exposure pathways in the derivation of a soil HIL has been further reviewed, as noted below.

    4.3.1         Oral Bioavailability
While bioavailability (inhalation only) has been considered in the previous HIL, insufficient data is available to adequately define the bioavailability of cadmium. On this basis, a default approach of assuming 100% oral (and inhalation) bioavailability has been adopted in the derivation of an HIL. It is noted that a site-specific assessment of bioavailability can be undertaken where required.

    4.3.2         Dermal absorption
Review of dermal absorption by MfE (2011) has noted the following: 'The US EPA (2004) recommends a dermal absorption factor of 0.001 (0.1%) for cadmium, based on Wester et al. (1992). These authors determined the in vitro percutaneous absorption of cadmium as the chloride salt from soil and water, using human skin. Cadmium from soil penetrated the skin at 0.06% and 0.13% of the applied dose, with 0.01% and 0.07% respectively absorbed into the receptor fluid after 16 hours of exposure. Taking the geometric mean of the summed amounts bound to skin and that in the receptor fluid yields an average absorption factor of 0.0012 or 0.12%, similar to that recommended by the US EPA (2004). This low rate of absorption indicates that dermal exposure is a negligible route of exposure, and could be ignored in the derivation of soil guideline values for contaminated land in New Zealand, as has been done by other jurisdictions.'

On the basis of the above, dermal absorption has not been considered in the derivation of soil HILs.

    4.3.3         Inhalation of Dust
Cadmium is not volatile and inhalation exposures associated with particulates outdoors and indoors are expected to be of less significance than ingestion of soil. While likely to be negligible, potential inhalation exposures associated with dust have been considered in the HIL derived.

    4.3.4         Plant Uptake
In the review of cadmium presented by Langley (1991), a study by Tiller et al. (1976) was cited that involved evaluation of the uptake of cadmium into home-grown fruit and vegetables from soil in Port Pirie. The study showed concentrations of cadmium that were higher than those reported in produce samples from Adelaide shops. Hence cadmium uptake by edible fruit and vegetable crops is expected to be sufficiently significant to warrant inclusion in the derivation of soil HILs.

Further review of plant uptake of cadmium is presented by the EA (EA