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

The Subcommittee considers that exposure from consumption of local garden produce, meat and milk
has to be calculated as part of the generic guidelines for every contaminant for this land use. Generic
guidelines for an agricultural setting will be protective of exposure from local produce consumption.
Because of the potential variation in lifestyle (i.e., geographical considerations, frequency of
consumption), the Subcommittee decided that generic guidelines for a residential scenario would not
take into account exposure from local produce consumption. However, guideline values which calculate
the contribution of local produce to total intake will still be available in each assessment document.
Therefore, the Subcommittee does not recommend using generic guidelines for a residential setting with
a garden. When there is a garden, the calculated value presented in each assessment document would
have to be considered as remediation objectives.
1.1 Assumptions
Based on the results of a study (USDA, 1983 in Versar, 1989), the homegrown fraction of total
vegetables (leafy, head, and root/tuber) consumed in rural, suburban and urban areas have been
calculated. The values presented in Table B.1 were estimated from the available data distributions
based on climatic and lifestyle considerations (MEFQ, 1995).
As shown in Table B.1, 50% of all produce (i.e., vegetables) consumed on an agricultural site is grown
on site, and 50% of the meat and 100% of the milk consumed is from local origin. For residential land,
the contribution of homegrown produce (i.e., from local gardens) to daily contaminant intake is
considerably less (10%) and is not considered at all for milk or meat. Based on a health risk assessment
prepared by the Ontario Ministry of the Environment, the percentage of total fruits and vegetables
consumed originating from a backyard garden is 7%. The value recommended by the Subcommittee is
10% (Table B.1).
2.0 Bioconcentration of Soil Contaminants into Produce
The concentration of a chemical in produce resulting from soil contaminated at the preliminary human
health-based soil quality guidelines PSQG HH may be estimated as:
C p (mg/kg) = B v × PSQG HH (mg/kg) [1]
Where C p is the concentration in produce, and B v is the chemical-specific (and possibly plant-specific)
bioconcentration factor.
When a chemical-specific bioconcentration factor is not available, Travois and Arms (1988) have
developed the following model using the octanal/water partition coefficient (log K ow ):
log B v = 1.59 - 0.58 log K ow , [2]
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