Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 7/18)
Character Range: 2989065–2991872

area not covered during warm weather (that is, the child is wearing shorts or skirt, a short-sleeved shirt and no socks or shoes).

The total skin surface area recommended by enHealth (2012a) for adult exposure is
20 000 cm2. In the residential and open space scenarios, it is assumed that 31.5% of this area is exposed, based on typical clothing worn during gardening and yard work and outdoor recreational activities. In the commercial/industrial exposure scenario, 19% of the adult skin surface area is assumed to be exposed, which is equivalent to only the head, hands and forearms (US EPA 2011).

5.3.2.2         Soil/dust skin adherence
Dermal exposure to soil contamination is highly dependent on the amount of soil that adheres to the skin following contact. Studies on soil adherence to the skin have shown that it varies according to soil type, the part of the body examined and the type of activities being undertaken when the soil is in contact with the skin; hence, the soil-to-skin adherence factor is a relatively uncertain parameter in any quantitative risk assessment process (US EPA 2004b). The soil-to-skin adherence factor applied in the generation of the HILs was 0.5 mg/cm2, which is the default value recommended by enHealth (2012a).

5.3.2.3         Dermal absorption
The process of absorption of chemicals through the skin is described by the dermal absorption factor (DAF), which estimates the percentage of the adhered layer of soil contamination that is able to pass through the skin. The DAF considered in the derivation of the HILs is based on a review of the available data for each compound. It is noted that limited data is available for dermal absorption and hence where data is not available and dermal absorption is of potential significance, default values have been adopted, as described below.

For semi-volatile organic compounds where no compound-specific data is available, a default dermal absorption factor of 0.1 (10%) has been adopted consistent with US EPA Region III (US EPA 1995) and EA (2009e).

Dermal absorption of volatile organics is especially difficult to assess, because most studies have involved occluding (covering) the skin. This may give artificially high skin absorption values, since these compounds would also be expected to volatilise from the skin (MfE 2011a). US EPA Region III recommends using a dermal absorption value of 0.05% for substances with a vapour pressure similar to that of benzene (vapour pressure approximately 95.2 mm Hg). For volatiles which have vapour pressures lower than that of benzene (and where less volatilisation from the skin may occur)—a default skin absorption value of 3% is recommended (US EPA 1995). Review of dermal absorption for benzene by EA (2009f) suggests a value of 1% may be more appropriate. Given