Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 3/4)
Character Range: 2594874–2597984

been reviewed in the WHO DWG (originally reviewed and established in 1996,) with a TDI of 0.003 mg/kg/day derived based on a NOAEL for reduced body weight gain, increased liver and kidney weights and renal toxicity in a 2 -year rat study. The same NOAEL was derived for reproductive effects from a three-generation rat study. It is noted that the derivation of the TDI included an additional 10 fold factor to address a suggested association between 2,4,5-T and soft-tissue sarcoma and non-Hodgkin lymphoma (not noted in other reviews available).

                                                                                                             2,4,5-T is included in the WHO plan for rolling revisions to the drinking water guidelines. No reviews with respect to this chemical are currently available.
ATSDR               No evaluation available
US EPA (IRIS 2012)  RfD = 0.01 mg/kg/day                                                                     The US EPA evaluation was established in 1982 and last reviewed in 1988 and provides an oral RfD of 0.01 mg/kg/day, based on a NOAEL of 3 mg/kg/day based on kidney effects in rats, and a 300-fold uncertainty factor.

                                                                                                             The value derived is considered protective of reproductive end points.

The available information from all the above sources is dated. There are some issues with the temporary ADI derived by the Joint FAO/WHO (1981) in that the study considered for the derivation of the ADI included the dioxin (TCDD) contaminant and addressed an end point not associated with 2,4,5-T alone. This value has subsequently been adopted in the derivation of the current ADWG without further review.

The value has been deleted from the current ADI list (OCS 2012). The TDI available in the current WHO DWG (2011) is based on the same studies as considered in 1981, though an additional uncertainty factor has been incorporated to address uncertainties in the database, including potential carcinogenic effects. The basis for this additional factor is not clear, as the carcinogenic effects noted have not been identified in other studies. On this basis, the most appropriate threshold reference value for 2,4,5-T is from US EPA, which is similar to the previous ADI from WHO (and is considered in the current ADWG (NHMRC 2011)).

No dermal or inhalation specific studies or data are available. For the presence of 2,4,5-T in soil, it is considered appropriate to consider use of the available US EPA RfD as a TRV for all pathways of exposures.

1.4.3         Recommendation
On the basis of the discussion above, the following toxicity reference values (TRVs) have been adopted for 2,4,5-T in the derivation of HILs:

1.5              Calculated HILs
On the basis of the above, the following HILs have been derived for 2,4,5-T (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