Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p8
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 8/18)
Character Range: 2991633–2994541

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 the limited data available and the relative insignificance of the dermal absorption pathway for volatile organics, a default of 3% has been assumed in the derivation of HILs, where no other chemical-specific data is available.

The potential significance of dermal absorption and the DAF values adopted in the derivation of HILs are presented for each compound in Appendix A.

    5.3.3         Indoor and outdoor inhalation of dust
Inhalation of dust derived from contaminated soil in both the indoor and outdoor settings has been considered in the derivation of HILs. An assessment of exposure via this pathway depends on three key factors:
    * the concentration of dust particles in indoor and outdoor air
    * the fraction of indoor and outdoor dust particles derived from the contaminated site
    * the rate of contaminant absorption by the lungs.

5.3.3.1         Outdoor dust concentrations
For the purpose of developing the HILs for scenarios A, B and D, soil-derived dust concentrations in outdoor air have been calculated using the approach proposed by Cowherd et al. (1985) and adopted by US EPA (2002) and EA (2009e). This approach uses a particulate emission factor (PEF), which relates the concentration of respirable dust particles (diameter <10 µm) in the air with wind speed, vegetative cover and the area of the site occupied by exposed soil. The outdoor dust concentration calculated by this means is assumed to consist of 100% site-derived soil. The value of the PEF depends upon a number of variables that are detailed in Appendix B; of most significance for the relevance of the HIL to a site is the proportion of a site area that is occupied by surface cover (for example, vegetation or hardstand), which is represented by V in Table 6.

Table 6. Proportion of surface cover (V) assumed in HIL scenarios
                                       HIL A        HIL B        HIL D
                                       residential  residential  Commercial /industrial
Fraction of outdoor surface cover (V)  0.75         0.9          0.8

For HIL C, dust concentrations have been estimated for more open areas assuming poor ground cover and activities (such as sporting games) that involve the generation of dust. In this case, a dust in air concentration of 39 µg/m3 (95th percentile from Australian data as presented by enHealth 2012a) has been used, where 100% is assumed to be derived from the contaminated site.

5.3.3.2         Indoor dust concentrations
For the purpose of deriving the HILs, soil-derived dust concentrations in indoor air have been generally calculated using the approach proposed by EA (2009e). Indoor dust concentrations