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

• determining estimated daily intake (EDI) of that chemical
unrelated to any specific contaminated site (i.e. normal
"background" exposure); and
• defining generic exposure scenarios appropriate to each land
use.
Soil guidelines must ensure that total exposure to a contaminant
(EDI + on-site exposure at the guideline concentration) will
present negligible risk.
Some of the steps employed to derive human health soil
remediation guidelines are similar to those used in a site-specific
risk assessment. However, to establish these generic guidelines,
several basic assumptions were made about the sensitive receptor
and the nature of chemical exposure for each land use. Guidelines
derived for non-carcinogens are based on an assumed threshold
for toxic effects. For carcinogens presenting some risk at any level
of exposure, guidelines are derived based on estimated lifetime
incremental cancer risk from exposure to soil.
Chemical constituents in soil can migrate and contaminate other
media. For example, soil contaminants can:
• leach into a groundwater drinking source;
• migrate in a vapour phase into basements and contaminate
indoor air;
• be taken up by plants and garden produce.
These important indirect and direct soil exposure pathways are
considered in check mechanisms in this protocol. There are five
checks but only two types of check mechanisms. The first check
mechanism uses probabilistic analysis to determine generic input
values for the model parameters. Both the groundwater and
volatilization into indoor air checks use this method, and the
results of the check may adjust the final soil quality guideline. The
second check mechanism uses conservative models which may or
may not adjust a guideline value (Management Adjustment
Factors). The Subcommittee uses the term, Management
Adjustment Factors, to acknowledge the necessarily imprecise
nature of these models, which use conservative point estimates,
based on data and professional judgement, for generic input
values. Management Adjustment Factors are used in the check
vi