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 2/9)
Character Range: 2846975–2849937

HILdermal  = derived soil guideline associated with dermal absorption of contaminant in soil/dust by young child and/or adult, refer to Equations 6, 7 and 8
              HILplant uptake  = derived soil guideline associated with ingestion of contaminant in home-grown fruit and vegetable produce by young child and/or adult (where relevant), refer to Equations 15 to 18
              HILdust  = derived soil guideline associated with inhalation of contaminants in dust by young child and/or adult, refer to Equations 9, 10 and 11
This approach assumes that the pathways of exposure are all complete and are additive, and that the toxicological end point considered for all pathways of exposure are the same or additive.
The contribution of each individual pathway (HILpathway) to the total HIL has been calculated (and presented in Appendix A) as follows:

%pathway contribution = (1/HILpathway)/(1/HIL) x 100 (%)

For volatile compounds, only interim soil vapour HILs have been derived. This has been conducted on the basis of calculations relevant to inhalation of volatile contaminants in air by a young child and/or adult, refer to Equations 12, 13 and 14.

1.3         Pathway-specific equations

    1.3.1          Ingestion of soil/dust

Threshold contaminants (23-year-old child for HILs A, B and C and adult for HIL D)

            Equation 3
where:

         TRVo  = toxicity reference value relevant for the quantification of oral intakes, (as mg/kg/day for threshold contaminants)
         BIo  = background intakes relevant to oral/dermal exposures (from sources other than soil, which include food, water, air and consumer products where relevant) (as % of the TRVo)
    IRSC  = ingestion rate of soil/dust by young child (for HILs A, B and C) and adult (HIL D) (mg/day)
    BAo = oral bioavailability (unitless, expressed as a fraction of 1)
    CF = conversion factor of 1x10-6 to convert mg to kg
    EF = exposure frequency (days/year)
    EDC = exposure duration for young child (for HILs A, B and C) and adult (HIL D) (years)
    BWC = body weight of young child (for HILs A, B and C) and adult (HIL D) (kg)
    ATT = averaging time for threshold contaminants (days, = ED x 365 days)

Non-threshold contaminants (lifetime exposures)

            Equation 4

          Equation 5

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))
    IRsX  = ingestion rate of soil/dust by each receptor group x (mg/day)
    BAo = oral bioavailability (unitless)
    CF = conversion factor of 1x10-6 to convert mg to kg
    EFx = exposure frequency relevant to exposures by each receptor group x (days/year)
    EDx = exposure duration relevant to