Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 2/6)
Character Range: 2421739–2424581

PCP 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.

    3.3.2         Dermal absorption
PCP is rapidly absorbed across the skin, and therefore dermal exposure potentially represents a significant route of exposure. The US EPA (2004) has identified a dermal absorption fraction of 0.25 (25%), based on a study by Wester et al. (1993) for PCP in soil. The study found that in vivo absorption in monkeys of PCP in soil was similar to PCP in acetone, with 24% of PCP absorbed over a 24-hour period.

Few other studies are available with quantitative values and hence the dermal absorption value of 0.24 (24%) from Wester et al. (1993) has been used in the derivation of HILs for PCP.

    3.3.3         Inhalation of Dust
PCP 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.

    3.3.4         Plant Uptake
In a review paper, McAllister et al. (1996) reported that available data on the plant uptake and transformation of PCP is inconsistent among studies and is inconclusive with regard to the abilities of specific plants to take up the compound. It was observed that the biodegradation of PCP by microorganisms and its adsorption to soil limit the availability of the compound for plant uptake (ATSDR 2001).

Further review by MfE (2011) considered that plant uptake of PCP is not a significant pathway of exposure given that PCP is known to be metabolised by plants (resulting in an over-prediction of plant uptake by the models available), bioconcentration factors relevant to plant uptake are low, and recent papers relating to PCP and plants where uptake is noted are associated with phytoremediation through enhanced microbial activity at plant roots.

On the basis of the above, plant uptake of PCP is not considered significant. In addition, the application of general plant uptake equations is not considered appropriate.

    3.3.5         Intakes from Other Sources – Background
Limited information is available on background exposures to PCP by the general population (PCP intakes have not been addressed in the Australian Total Diet Surveys). PCP is no longer used in Australia and while it is persistent, background levels are expected to be low. Dietary intakes are expected to be the most significant background source (ATSDR 2001). Total intakes of PCP (dominated by food intakes) have been estimated to