Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:10:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 10 (pt 3/4)
Character Range: 2575382–2578791

due to limitations in the available database it cannot be concluded if toxaphene has genotoxic potential in vivo or not. Review by ATSDR (1996) suggests that toxaphene may be genotoxic. Review by ATSDR (1996) suggests that while organochlorines in general induce carcinogenic effects via an epigenetic mechanism rather than a genotoxic mechanism, the available data for toxaphene does not suggest that it meets all the criteria for an epigenetic carcinogen. Hence, ATSDR concludes that toxaphene may induce carcinogenicity via an epigenetic and genotoxic mechanism. The available data shows that toxaphene may be weakly genotoxic though there is insufficient data available to suggest that a non-threshold approach is relevant.

Few quantitative toxicity values are available for toxaphene with the following available from Level 1 Australian and International sources:

Source              Value                          Basis/Comments
Australian
ADWG                No evaluation available
OCS (2012)          No evaluation available
International
JMPR/WHO            No ADI established             NO ADI was established by WHO or by JMPR for toxaphene or campheclor.
WHO (2011)          No evaluation available
ATSDR (1996)        No chronic MRLs derived        No chronic duration MRLs derived, however ATSDR has derived an intermediate duration oral MRL of 0.001 mg/kg/day based on hepatic effects.
OEHHA (2003)        RfD = 0.00035 mg/kg/day        RfD derived to assess non-carcinogenic effects. Value based on a NOAEL of 0.35 mg/kg/day associated with slight hepatic changes in rats, and an uncertainty factor of 1000.
                                                   An oral slope factor has also been derived, however it is not considered to be relevant for this evaluation.
US EPA (IRIS 2012)  No threshold value calculated  The US EPA review has not derived any threshold TRVs. The only values derived are non-threshold oral and inhalation values not considered to be relevant for this evaluation. Oral slope factor (last reviewed in 1991) derived on the basis of hepatocellular carcinomas and neoplastic nodules in a dietary study in mice and a linearised multistage model.
                                                   Inhalation unit risk based on route extrapolation from the derived oral slope factor.
                                                   No threshold values available.

Limited quantitative data is available for toxaphene with the only threshold value available from OEHHA. No inhalation or dermal-specific data is available and hence the oral value has been used to assess intakes derived from all pathways of exposure.

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

10.5          Calculated HILs
On the basis of the above, the following HILs have been derived for toxaphene (refer to Appendix B for equations used to calculate the HILs and Appendix C for calculations):
HIL Scenario            HIL (mg/kg)                      Percentage Contribution from Exposure Pathways
Ingestion of Soil/Dust  Ingestion of Home-grown Produce  Dermal Absorption of Soil/Dust                  Inhalation (dust)
Residential A           20                               43                                              --                 57  <1
Residential