Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 1/4)
Character Range: 2589118–2592096

1                   2,4,5-T

1.1              General
2,4,5-T is the common name for 2,4,5-trichlorophenoxyacetic acid (or 2,4,5-triphenoxyacetic acid), a chlorophenoxy herbicide.

Several comprehensive reviews of 2,4,5-T in the environment and its toxicity to humans are available and should be consulted for more detailed information not presented in this summary ( OCS 2004; HSDB 2010). The following provides a summary of the key aspects of 2,4,5-T that are relevant to the derivation of a soil HIL.

The herbicide was also commercially produced as an amine salt, alkali metal salt and ester derivative of 2,4,5-T. Pure 2,4,5-T is a white to light tan solid. It is slightly soluble in water whereas the amine and alkali metal salt derivatives are highly soluble. The ester, however, is insoluble in water. 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD), a known human carcinogen, was a common contaminant in the manufacture of 2,4,5-T and its derivatives and was typically present in the low mg/kg to high mg/kg level (OCS 2004). 2,4,5-T with TCDD contamination is now controlled in international trade through the 'Rotterdam Convention' (Joint FAO/UNEP 2005). It is noted that 2,4,5-T is not expected to persist in the environment for any significant period of time but TCDD will remain and should be considered in a site-specific assessment where a 2,4,5-T source may have been present.

2,4,5-T and its derivatives were introduced in the 1960s and were used as herbicides for broad-leaved wood plants such as blackberries. 2,4,5-T was also combined with the compound 2,4-D to form the 'agent orange' herbicide which was widely used by the US military in the Vietnam war (OCS 2004). 2,4,5-T and its derivatives were withdrawn from use in the late 1980s and are no longer approved for use or marketed in Australia.

1.2              Previous HIL
No previous HIL is available for 2,4,5-T (NEPC 1999).

1.3              Significance of Exposure Pathways

1.3.1         Oral Bioavailability
Insufficient data is available to adequately define the bioavailability of 2,4,5-T, hence a default approach of assuming 100% oral bioavailability has been adopted in the derivation of an HIL. It is noted that a site-specific assessment of bioavailability can be undertaken where required.

1.3.2         Dermal absorption
Insufficient data is available on the dermal absorption of 2,4,5-T from soil. Hence the default value of 0.1 (10%) suggested by US EPA (1995) for pesticides has been adopted in the derivation of HILs.

1.3.3         Inhalation of Dust
2,4,5-T is not considered sufficiently volatile to be of significance and inhalation exposures associated with particulates outdoors and indoors are expected to be of less significance than ingestion of soil. While likely to be negligible, potential inhalation exposures associated with dust have been considered in the HIL derived.

1.3.4         Plant Uptake
Most chlorophenoxy herbicides are toxic to plants and, as such, will be