Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 4/5)
Character Range: 2176916–2179852

and other soluble cobalt (II) salts as Group 2B—possible human carcinogen. IARC provided further review in 2006 classifying cobalt sulphate and other soluble cobalt (II) salts as Group 2B, cobalt metal without tungsten carbide as Group 2B and cobalt metal with tungsten carbide as Group 2A (probable human carcinogen).

It is noted that US EPA has not evaluated cobalt with respect to classification of carcinogenicity.

    6.4.2         Review of Available Values/Information
While data is limited, based on the weight of evidence cobalt is not (or is weakly) genotoxic (RIVM 2001: ATSDR 2004). However it is noted that some information suggests that some metallic cobalt species may be genotoxic, and this may need to be considered in occupational environments. On this basis, it is recommended that a threshold approach be adopted for the derivation of an HIL for cobalt in soil.

Few quantitative evaluations are available for cobalt, however the following are available from Level 1 Australian and International sources:
Source              Value                          Basis/Comments
Australian
ADWG (NHMRC 2011)   No evaluation available
International
WHO  (2011)         No evaluation available
WHO (2006)          TC = 0.0001 mg/m3              WHO (2006) derived a TC in air of 0.0001 mg/m3 based on a NOAEC from an occupational inhalation study with conversions to address exposures by the general population. WHO did not derive an oral threshold value, due to the lack of suitable data.
RIVM (2001)         TDI = 0.0014 mg/kg/day         RIVM (2001) derived a TDI of 0.0014 mg/kg/day based on a LOAEL of 0.04 mg/kg/day associated with cardiomyopathy from oral exposures in workers and an uncertainty factor of 30.
                    TC = 0.0005 mg/m3              The TC is based on a LOAEC of 0.005 mg/m3 for interstitial lung disease in workers and an uncertainty factor of 100.
ATSDR (2004)        Inhalation MRL = 0.0001 mg/m3  Chronic inhalation MRL of 0.0001 mg/m3 based on a NOAEL of 0.0013 mg/m3 (adjusted) for decreased respiratory function in workers and an uncertainty factor of 10. No chronic oral MRL is available from ATSDR (2004).
US EPA (IRIS 2012)  No evaluation available

Note that the current HIL for cobalt was established on the basis of a derived PTDI that ranged from 15 µg/kg/day.
Only one oral value is available from RIVM (2001), which is recommended to be adopted for the derivation of a soil HIL. The available inhalation values are fairly consistent with the most recent detailed evaluations provided by WHO and ATSDR, which are recommended.

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

6.5              Calculated HILs
On the basis of the above, the following HILs have been derived for cobalt (refer to Appendix B for equations used to calculate the HILs