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 2/6)
Character Range: 2475225–2478197

JMPR (1985) was considered. An additional factor of 3 was used because of the uncertainties associated with the bioavailability estimates adopted and exposure levels in the future.
    * Dermal absorption of aldrin and dieldrin was considered to be 5%.
    * Oral bioavailability of organochlorine pesticides was considered to be 10%.
    * Based on intakes derived from soil (ingestion, dermal absorption and dust inhalation), an HIL of 10 mg/kg was calculated.

2.3              Significance of Exposure Pathways

2.3.1         Oral Bioavailability
Insufficient data is available to adequately define the bioavailability of aldrin and dieldrin in the range of contaminated sites that may need to be considered in Australia. On this basis, 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.

2.3.2         Dermal absorption
A proposed range for dermal absorption of pesticides from soil was 1%10% (Ryan et al. 1987). The reported absorption of topically applied pesticides and herbicides in acetone to in vitro human skin was reported to be within this range for lindane, aldrin, dieldrin, malathion, parathion, and 2,4-D in Feldmann & Maibach, (1974). WHO (1989) noted that aldrin and dieldrin are readily absorbed by oral, inhalation and dermal routes. Absorption through the intact skin was about 78% of the applied dose in a human volunteer study. On this basis, adopting the default of 0.1 (10%) recommended by US EPA (1995) for pesticides is considered reasonable.

2.3.3         Inhalation of Dust
Aldrin and dieldrin are 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 derivation of soil HILs.

2.3.4         Plant Uptake
Aldrin and dieldrin have the potential to bioconcentrate in terrestrial ecosystems. However, the available studies show mixed results with respect to plant uptake. Some studies show potential uptake (more significantly into roots) while others have shown no plant uptake (from these compounds bound to soil) (ATSDR 2002). Both aldrin and dieldrin have high Koc values (log Koc = 6.677.67, ATSDR 2002), suggesting that these compounds are largely bound to soil particulates and immobile in soil. For plant uptake to be significant, the chemicals must be able to partition to soil water. With respect to aldrin and dieldrin bound to the soil, this is considered to be insignificant. Hence, the potential for plant uptake of aldrin and dieldrin from soil contamination is considered negligible.

It is noted, however that should these compounds be present in other media such as groundwater (used for irrigation) or solution, then