Protocol for the Derivation of Environmental and Human ... - CCME

Part B, Section 7
ingestion (SQG I ) should ensure that ingestion of the soil and ingestion of plants growing on that soil does
not result in the animal receiving more than 75% of the DTED:
(exposure from soil + exposure from food) = 0.75 * DTED [1]
For soil ingestion, the exposure is equal to the concentration in soil multiplied by the soil ingestion rate
(SIR) and a bioavailability factor and divided by the body weight of the animal exposed:
Exposure from soil ingestion = SQG I × SIR × BF [2]
BW
Where SQG I = soil quality guideline for soil and food ingestion (mg kg -1 )
SIR = soil ingestion rate (kg dw soil/day)
BF = bioavailability factor (unitless)
BW = body weight (kg)
Likewise, for food ingestion, the exposure is equal to the concentration in food multiplied by the food
ingestion rate (FIR) and a bioconcentration factor and divided by the body weight of the animal
exposed:
Exposure from food ingestion = SQG I * FIR * BCF [3]
BW
Where SQG I = soil quality guideline for soil and food ingestion (mg kg -1 )
FIR = food ingestion rate (kg dw food/day)
BCF = bioconcentration factor (unitless)
BW = body weight (kg)
Equations (2) and (3) can be incorporated into equation (1) to provide the following equation:
SQG I × SIR × BF + SQG I × FIR × BCF = 0.75 DTED [4]
BW
BW
Finally, equation (4) can be rearranged to give the final equation for deriving a soil quality guideline for
ingestion (SQG I ) that will prevent grazing animals from being exposed to more than 75% of the DTED
resulting from the ingestion of soil and plants:
SQG I = 0.75 × DTED × BW [5]
(SIR × BF) + (FIR × BCF)
where,
SQG I = soil quality guideline for soil and food ingestion (mg/kg dw soil)
DTED = daily threshold effects dose (mg/kg bw⋅day)
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