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

Part B, Section 7
parameter uncertainty at a minimum and also reduce the need for large inter-species extrapolations.
Therefore, until more data are available for other receptors, it is the opinion of the SEQCCS that
guidelines for soil and food ingestion should only be derived for grazing herbivores on agricultural lands.
Figure 14 gives an overview of the derivation procedure.
7.6.1 Determining the Daily Threshold Effects Dose
The first step requires the determination of the species considered to be most at threat from
contaminated soil and food ingestion.
7.6.1.1 Determining the Species Most at Threat from Soil and Food Ingestion. Oral
toxicological data from grazing and foraging species are used to determine which species are potentially
at threat from the ingestion of contaminants. The species "most" threatened has the lowest reported
LOAEL. A minimum of three studies must be considered. At least two of these must be oral
mammalian studies and one must be an oral avian study. A maximum of one laboratory rodent study
may be used to fulfil the data requirements for mammalian species if needed. A grazing herbivore (e.g.
ungulates) with high ingestion rate to body weight ratios should be considered in the minimum data set,
Where possible, field data should be used in conjunction with laboratory data.
If minimum data requirements cannot be met when determining the Daily Treshold Effect Dose (DTED),
then no soil quality guidelines for soil and food ingestion shall be set. Data gaps will be identified for
further research.
7.6.1.2 Calculation of the Daily Threshold Effect Dose. The DTED is estimated using the lowest
observed (adverse) effect level (LO{A}EL) from the species determined to be most threatened in
section 7.6.1.1, divided by an uncertainty factor. The DTED is calculated according to the following
equation.
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DTED = lowest LOAEL/UF
where DTED = daily threshold effects dose (mg/kg bw⋅day)
LO(A)EL = lowest observed effect dose (mg/kg bw⋅day)
UF = uncertainty factor (if needed)
An uncertainty factor between one and five can be applied using expert judgement. The following
criteria are a guide for UF application:
1. The LO(A)EL is considered to be "biologically significant" and not just statistically different from
controls and therefore extrapolation below the LOEC is required.
2. The LO(A)EL is taken from an acute lethal or sublethal study.
3. Only the absolute minimum data requirements have been met.