Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:9:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 9 (pt 3/4)
Character Range: 2564604–2567687

and neoplastic lesions in the liver is poorly understood. Mirex has not been genotoxic in numerous short-term in vitro and a few in vivo tests (also noted by WHO 1984), leading to the hypothesis that tumorigenic responses to mirex in the liver do not directly involve a genotoxic mechanism and may involve proliferation of cells initiated spontaneously, or by some other agent, to become tumours. Review by ATSDR (1995) suggested that, based on weight of evidence, mirex is a probable tumour promoter.

On this basis, it is appropriate that a threshold approach be adopted. The following are available from Level 1 Australian and International sources:

Source              Value                    Basis/Comments
Australian
ADWG (NHMRC 2011)   No evaluation available
OCS (2012)          No evaluation available
International
JMPR/WHO (1984)     No ADI established       No ADI was established by WHO (1984) or by JMPR.
WHO (2011)          No evaluation available  No guideline established as mirex is listed as excluded from the DWG as it is unlikely to occur in drinking-water.
ATSDR (1995)        MRL = 0.0008 mg/kg/day   Chronic oral MRL based on a NOAEL of 0.05 mg/kg/day for dose-dependent liver changes in a chronic duration rat study, and an uncertainty factor of 100.
US EPA (IRIS 2012)  RfD = 0.0002 mg/kg/day   Oral RfD currently within IRIS (last reviewed in 1992) based on a NOAEL of 0.07 mg/kg/day associated with liver effects in a chronic duration rat study, and an uncertainty factor of 300.
                                             Mirex is currently being reassessed by the US EPA with a draft (2003) review deriving an oral RfD of 0.0005 mg/kg/day derived using a benchmark approach based on a LED10 of 0.15 mg/kg/day associated with liver effects in male and female rats, and an uncertainty factor of 300. A non-threshold (linear) assessment was also presented. This draft review has not been finalised as at March 2012.

Limited quantitative data is available for mirex, with the few values available within the same order or magnitude. As there are so few evaluations available, the lower value currently available on IRIS is considered reasonable. No inhalation or dermal data are available, hence it is recommended that all intakes associated with contaminated soil be assessed on the basis of the oral TRV.

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

9.5              Calculated HILs
On the basis of the above, the following HILs have been derived for mirex (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           10                               43                                              --                 57  <1
Residential B