Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 7/9)
Character Range: 2160177–2162928

of an RfC.

The following are available for inhalation exposures for Cr VI particulates or dust from Level 1 Australian and International sources:
    * No Australian guideline values are available for Cr VI.
    * US EPA (available on IRIS) derived an inhalation RfC of 0.0001 mg/m3 for Cr VI particulates based on lower respiratory effects in a subchronic rat study. The US EPA review of particulate exposures indicated chromium inhalation induced pneumocyte toxicity and suggested that inflammation is essential for the induction of most chromium inhalation effects and may influence the carcinogenicity of Cr(VI) compounds. The US EPA has also derived a separate RfC (lower) for exposure to chromic acid mists and dissolved Cr VI aerosols, which would be relevant for the assessment of an occupational environment.
    * ITER (1998) derived an inhalation RfC of 0.0003 mg/m3 for Cr VI particulates based on the same study as US EPA considered but the value derived was on the basis of an arithmetic average of benchmark concentrations for the pulmonary inflammation  end point.
In addition the following are also available:
    * WHO (2000) has derived a range of air guideline values based on an inhalation unit risk of 0.04 (g/m3)-1 derived from the mean of a number of occupational studies. US EPA (IRIS 2012) also derived a unit risk of 0.012 (g/m3)-1 derived from one occupational study (also considered by WHO).
    * DEFRA & EA (2002) has derived an index dose of 0.001 µg/kg/day for Cr VI based on occupational inhalation studies based on a lung cancer  end point, consideration of the WHO non-threshold approach and a target risk level of 10-4.
    * RIVM (2001) has adopted a cancer risk value of 0.0025 µg/m3 based on occupational inhalation studies based on a lung cancer  end point, consideration of the WHO non-threshold approach and a target risk level of 10-4. It is noted that a 10-4 target risk level is used for inhalation guidelines by DEFRA & EA (2002) and RIVM (2001). The value results in guidelines that address background levels of Cr VI reported in ambient air, which range up to 30% of total chromium reported (up to 0.00150.0025 µg/m3).
    * ATSDR (2008) has derived a chronic inhalation MRL for Cr VI aerosols and mists, not considered relevant to the derivation of a soil HIL.

    5.4.3         Recommendation
On the basis of the discussion above, the following toxicity reference values (TRVs) have been adopted for Cr VI in the derivation of HILs:

5.5              Calculated HILs
On the basis of the above (and using the assumptions presented in this document) an HIL A has been derived at 80 mg/kg, essentially the same (with consideration of uncertainties and accuracy of HIL calculations) as the existing