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

Part C, Section 5
5.3.3 Evaluation for Contamination of Produce, Milk, and Meat
Humans can be indirectly exposed to contaminants in soil through food-chain contamination of produce,
meat, and milk. For agricultural land use, it is likely that some meat, produce, and milk will be produced
and consumed on-site. Fruits and vegetables grown in residential gardens may also be a source of
human exposure to contaminants. To ensure that soil remediation guidelines do not result in an
unacceptable contribution to total daily intake of contaminants via homegrown produce, meat, and milk,
it is necessary to compare the expected intake of contaminants from these sources with the total daily
intake.
The procedure and assumptions for estimating the daily intake of contaminants in food grown on a
contaminated site are described in Appendix B. The procedure relies on the use of bioconcentration
factors. The identification of foods of concern with regard to bioconcentration will depend on the
contaminant's physio-chemical properties. For the remediated agricultural site, estimates of contaminant
concentrations in food are compared to the Maximum Residue Limits (MRLs) found in the Food and
Drug Act (1985). Where MRLs are exceeded, the soil quality guideline will be lowered to ensure that
unacceptable contamination of meat, milk, or produce will not occur at the remediated agricultural site.
Where MRLs are not available and food chain effects are considered likely to occur on agricultural
sites, the SEQCCS recommends further assessment of the potential extra exposure via foods grown or
produced on soil at the soil quality guidelines. For this purpose, the SEQCCS assumed that for
agricultural lands, 50% of meat and produce, and 100% of milk consumed by residents was produced
on site (Appendix B). This approach reflects the variations in growing seasons and dependence on
other food sources. For residential lands, it is assumed that 10% of produce (no meat or dairy
products) is grown in a backyard garden.
Where calculations indicate that this exposure from foods grown on a site remediated to the preliminary
agricultural guideline is greater than the background food exposure plus 20% of the difference between
the TDI and the EDI, the generic soil quality guideline will be lowered. Generic guidelines for an
agricultural setting will therefore be protective of exposure from local produce consumption.
Acknowledging potential variations in lifestyle, geographical considerations, and frequency of garden
produce consumption, the SEQCCS has some reservations about considering local food consumption
in generating generic guidelines for a residential setting. The SEQCCS therefore recommends that
generic guidelines for residential sites not take into account exposure from local produce consumption.
However, residential guidelines values calculated on a 10% consumption of homegrown produce will
be available in each contaminant assessment document. For residential sites with homegrown produce,
the SEQCCS recommends that the modification of generic residential guidelines to include this exposure
pathway be considered in determining a site-specific remediation objective.
5.3.4 Evaluation for Contamination of Indoor Air by Volatilization
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