Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 2/7)
Character Range: 2458022–2460837

soil and water surfaces followed by deposition of DDT onto surfaces through dry and wet deposition processes. Due to the persistence of DDT and its metabolites in the environment, potential for bioaccumulation and potential for long-range transport, DDT is listed under the Stockholm Convention on Persistent Organic Pollutants.

The following information primarily relates to DDT which has been adopted as the most appropriate indicator for the assessment of all three compounds due to the similarity of toxic effects and toxicokinetics. A larger database of data is also available for DDT.

1.2              Previous HIL
The derivation of the previous HIL (HIL A = 200 mg/kg) for DDT+DDE+DDD is presented by Beard (1993) and NEPC (1999). In summary, the HIL was derived on the basis of the following:
    * Background intakes were considered in the derivation of the current HIL (Beard 1993) with the intake from food estimated to range from 0.001 mg/kg/day for adults to 0.546 mg/kg/day for infants. Intakes from water and air were essentially negligible compared with that derived from food.
    * An ADI of 0.002 mg/kg/day was adopted as the toxicity reference value (based on the ADI from WHO and an additional uncertainty factor of 10).
    * Based on intakes derived from soil (ingestion), an HIL of 200 mg/kg was calculated.
    * It is noted that the review undertaken also considered an oral RfD of 0.0005 mg/kg/day reference from the US EPA and a LOAEL and NOAEL.

1.3              Significance of Exposure Pathways

1.3.1         Oral Bioavailability
Insufficient data is available to adequately define the bioavailability of DDT 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.

1.3.2         Dermal absorption
Dermal absorption of DDT is considered to be very low and has been considered to be negligible in the derivation of the previous HIL. Review of dermal absorption of DDT by MfE (2011) indicated the following: 'US EPA (2004) recommends a dermal absorption factor of 0.03 (3%), which is based on data from Wester et al. (1990). These authors indicate that only 1.0% of DDT from soil penetrated into human skin over a 24-hour period, and none (<0.1%) of this partitioned into human plasma. Additionally, 3.3% of DDT from soil was absorbed percutaneously following in vivo exposure of rhesus monkeys. Taking the geometric mean of these values yields an average dermal absorption factor of 0.018 (1.8%).'

As few other reviews are available in relation to dermal absorption of DDT, the average value estimated by Wester et al. (1990) as referenced by