Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p6
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 6/9)
Character Range: 2857998–2860768

18
where:
         TRVo  = toxicity reference value relevant for the quantification of oral intakes, (as (mg/kg/day)-1 for non-threshold contaminants)
         TR = target risk for non-threshold contaminants (unitless)
         ∑ = signifies the sum over all receptor groups x considered (in the HILs derived, these groups include a child (C) and adult (A))
         UFyx = plant uptake factors calculated using Equation 16 for both adults and children (kg/day)
    EFx = exposure frequency for all receptor groups x (days/year)
    EDx = exposure duration for all receptor groups x (years)
    BWx = body weight for all receptor groups x (kg)
    ATNT = averaging time for non-threshold contaminants (days, = 70 years x 365 days)

Note that the calculation of intakes derived from home-grown produce has been included in the derivation of HIL A where relevant. However, it is noted that, for some compounds such as metals, the assessment of intakes derived from the consumption of home-grown produce as well as intakes derived from the diet (as estimated from total diet surveys) results in double counting of intakes that may be derived from produce.
To address the potential for double counting of these intakes it is assumed that 50% of the intake derived from home-grown produce (10% of total intake) is already accounted for in the data available on intakes derived from all dietary sources. Hence, the derivation of the HIL for plant uptake for metals has been adjusted to address this issue (refer to Appendix A for compound-specific data).

1.4         Calculation of particulate emission factor
Soil-derived dust concentrations in outdoor air have been estimated using a particulate emission factor (PEF) using the approach outlined by US EPA (1996; 2002) and EA (2009). The PEF represents an estimate of the relationship between the concentration of a contaminant in soil and its concentration in air as a consequence of dust resuspension. Dust particles considered in the PEF are assumed to be less than 10 µm is diameter. This has been calculated using the following equation:
      Equation 19
where:

    PEFO  = particulate emission factor outdoors (mg/kg soil per mg/m3 air)
         Q/C  = air dispersion factor which describes the dispersion of soil particles in the atmosphere of a theoretical outdoor box. A value of 90.8 (g/m2/s per kg/m3) has been used in the derivation of HILs. The value is a default value recommended by US EPA (2002) for small sites (0.5 acres).
         V  = the fraction of outdoor surface cover (0= bare soil), dimensionless (0.75 for HIL A, 0.9 for HIL B and 0.8 for HIL D)
         Um  = mean annual wind speed at a height of 10m (m/s), assumed to be 8.75 km/hr (or 2.4 m/s) based on the average 9 am and 3 pm winds from