Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p12
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 12/16)
Character Range: 2081957–2084823

per year.

The relevance of inhalation values derived from studies near smelters to the assessment of contaminated arsenic in soil in areas away from smelters is not well founded. Hence it is recommended that a threshold approach is considered for the assessment of inhalation exposures associated with arsenic in soil. The threshold TC derived by RIVM (2001) of 1 μg/m3 is lower than the cumulative exposure value identified by WHO (2001) of 750 μg/m3.years as statistically associated with an increase in lung cancer. The values are considered reasonably comparable if the exposure occurs over a period of 40 years and appropriate uncertainty factors are applied to convert from a lowest observable adverse effect level (LOAEL) to a NOAEL. In addition the TC is consistent with the TC05 value derived by Health Canada (1993) associated with lung cancer in humans and an incremental lifetime risk of 1 in 100,000. The value adopted is lower than the recommended PTDI adopted for the assessment of oral intakes (when the TC is converted to a daily intake). Hence use of the RIVM TC has been considered appropriate and adequately protective of all health effects associated with inhalation exposures that may be derived from soil, including carcinogenicity.

    1.4.5         Recommendation
On the basis of the discussion above the following toxicity reference values (TRVs) have been adopted for arsenic in the derivation of HILs:

1.5              Calculated HILs
The following comments relate to the derivation of an HIL A (the most sensitive exposure scenario) for arsenic:
    * Using the proposed oral TRV, and the exposure pathways/assumptions presented in this document, with 100% bioavailability, HIL A = 130 mg/kg. Given the uncertainties discussed above in relation to the identification of a relevant TRV, and uncertainties associated with the calculation of the HIL, the calculated value is considered to be essentially no different from the previous HIL of 100 mg/kg.
    * Using the proposed oral TRV, and the exposure pathways/assumptions presented in this document, with 70% bioavailability, HIL A = 180 mg/kg. Given the uncertainties discussed above in relation to the identification of a relevant TRV, and uncertainties associated with the calculation of the HIL, the calculated value is considered to be essentially no different from the previous HIL of 100 mg/kg.
    * Using the proposed oral TRV, and the exposure pathways/assumptions presented in this document, with 25% bioavailability, HIL A = 380 mg/kg.
    * With consideration of the uncertainties noted, it is not considered appropriate to modify the existing HIL A of 100 mg/kg (where arsenic bioaccessibility is within the range of 70100%).

On the basis of the above the following HILs have been derived for arsenic (refer to Appendix B for equations used to calculate the HILs and