Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 2/9)
Character Range: 2147378–2150243

the previous HIL (HIL A = 100 mg/kg) for Cr VI is presented by Soong & Emmett (1993). In summary, the HIL was derived on the basis of the following:
    * Intakes of Cr VI from other sources were estimated with dietary intakes considered most significant for the general population. Intakes from air, water and food were estimated to be approximately 600 µg/day for a young child.
    * A provisional tolerable daily intake (PTDI) of 5 µg/kg/week referenced from the US EPA was adopted as the toxicity reference value.
    * Ingestion of both soil and dust has been considered assuming 100% is bioavailable and is absorbed.
    * Dermal absorption and inhalation of dust were not specifically included in the derivation; however, consideration of a cancer potency factor for inhalation exposures was reviewed and noted to result in higher HIL.
    * Skin hypersensitivity was also assessed, noting that the derived criteria ranging from 100200 mg/kg was considered not to pose a risk to health.

5.3              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.

    5.3.1         Oral Bioavailability
Bioavailability has not been considered in the previous HIL, as insufficient data is available. 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.

    5.3.2         Dermal absorption
Review of dermal exposure to chromium by MfE (2011) has indicated the following:
    * Dermal exposure to chromium has been demonstrated to produce irritant and allergic contact dermatitis (Guy et al. 1999; ATSDR 2008; Baars et al. 2001). Primary irritant dermatitis is related to the direct cytotoxic properties of chromium, while allergic contact dermatitis is an inflammatory response mediated by the immune system (ATSDR 2008).
    * A number of studies have investigated the exposure level necessary to elicit a 10% response in sensitised individuals. These authors also suggest that a soil concentration of 500 mg Cr VI/kg would be protective of 90% of those individuals that are sensitised to chromium, and 99.84% of the general population, assuming that 10% of the Cr VI is bioavailable. Another study estimated that 0.1% or less of the Cr VI in chromite ore processing residue would leach out in the presence of human sweat (Horowitz & Finley 1993, cited in ATSDR 2008), suggesting that soil concentrations up to 50  000 mg/kg may not elicit an allergic response.
    * As allergic contact dermatitis is an inflammatory response mediated by the