Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 2/5)
Character Range: 2603708–2606519

has been adopted in the derivation of an HIL. It is noted that a site-specific assessment of bioavailability can be undertaken where required.

2.3.2         Dermal absorption
A dermal absorption value of 0.05 (5%) is available from US EPA (2004) based on a study by Wester et al. (1996). This study evaluated potential dermal absorption of 2,4-D from soil, where absorption over time changed over time (noted to be not-linear). Data from the study showed low absorption over 8 hours (0.03-0.05%) with slightly higher absorption over 16 hours (2.2%). Limited other data is available on the dermal absorption of 2,4-D from soil, hence the value of 0.05 (5%) has been adopted.

2.3.3         Inhalation of Dust
2,4-D 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.

2.3.4         Plant Uptake
Most chlorophenoxy herbicides are toxic to plants and, as such, will be phytotoxic to almost all broadleaf crops including tomatoes, grapes and fruit trees well before plant uptake into edible portions of fruit and vegetable crops is of significance. Hence the uptake of these compounds into home-grown produce has not been considered in the derivation of an HIL A.

Note that the phytotoxic effects of these compounds may need to be addressed on a site-specific basis if detected in soil.

2.3.5         Intakes from Other Sources – Background
Exposure concentrations provided by WHO (1984, 1987) (as well as noted in APVMA (2006)) are derived from areas where 2,4-D is used and is not expected from the presence of 2,4-D contamination in soil. The intakes, however, may be of concern if the HILs were being applied to an area where products containing 2,4-D are used (or have been used in the recent past).

With respect to background intakes of 2,4-D, the following is noted from WHO (1987):
    * It is expected background intakes for the general population will be associated with the presence of residues in food and water.
    * Intakes from air is considered negligible.
    * Where 2,4-D is not used, intakes by the general population are considered negligible.
    * In areas where 2,4-D is used, background intakes from air, food and water are estimated to be 0.3–2 µg/kg/day.
FSANZ (2011) has estimated that the 90th percentile intake of 2,4-D by young children aged 25 years (most sensitive) is 0.014 µg/kg/day or 0.000014 mg/kg/day. This intake is negligible in comparison with the adopted TRV of 0.01 mg/kg/day.

On the basis of the above, background intakes of 2,4-D have been assumed to be essentially negligible (where 2,4-D