Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:8:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 8 (pt 3/4)
Character Range: 2554406–2557907

an uncertainty factor of 1000 (including a 10 fold factor to address concern for threshold carcinogenicity and the limited database). Methoxychlor is noted to be included in the rolling revision of the WHO DWG. No revised evaluations are currently available.
ATSDR (2002)        No chronic oral MRL derived  No chronic MRL derived, however an intermediate duration MRL of 0.005 mg/kg/day was derived.
OEHHA (1999)        RfD = 0.005 mg/kg/day        A public health goal (drinking water guideline) of 0.03 mg/L was derived on the basis of an RfD of 0.005 mg/kg/day derived from a LOAEL of 5 mg/kg/day associated with developmental effects in female rats, and an uncertainty factor of 1000.

US EPA (IRIS 2012)  RfD = 0.005 mg/kg/day        Oral RfD (last reviewed in 1990) based on a NOEL of 5 mg/kg/day associated with reproductive effects in rabbits, and an uncertainty factor 1000.

Based on the available data above, essentially two threshold values are available, though they are significantly different. The ADI available from JMPR has not been reviewed since 1977 and has not considered the studies used in subsequent evaluations in WHO (2011) and presented by the OEHHA, ATSDR and US EPA. While the older JMPR has been adopted by OCS (2012) and NHMRC (2011), the lower value presented in the current WHO DWG is more technically sound and has been adopted for the purpose of deriving soil HILs. 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.

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

8.5              Calculated HILs
On the basis of the above the following HILs have been derived for methoxychlor (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           300                              43                                              --                 57  <1
Residential B           500                              16                                              --                 84  <1
Recreational C          400                              27                                              --                 73  <1
Commercial D            2500                             12                                              --                 88  <1

-- Pathway not included in derivation of HIL

8.6              References
ATSDR 2002, Toxicological Profile for Methoxychlor, Agency for Toxic Substances and Disease Registry, available from http://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=778&tid=151.
ATSDR 2009, Addendum to the Toxicological Profile for Methoxychlor, Agency for Toxic Substances and Disease Registry, available from http://www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=778&tid=151.
FSANZ 2011, The 23rd Australian Total Diet Study, Food Standards Australia and New Zealand.
IARC 1987, Summaries & Evaluations, Methoxychlor, Suppl 7, p.66, International Agency for Research on Cancer.
JMPR 1977, Methoxychlor, Evaluation of the Joint Meeting on Pesticide Residue, available at http://www.inchem.org/documents/jmpr/jmpmono/v077pr37.htm.