Pinchin Indoor Air Quality Investigation Report Letter

Statement of Qualifications – Environmental Due Diligence & Remediation
Human Health and Ecological Risk Assessment in support of a Record of Site Condition under Ontario
Regulation 153/04
Comprehensive RAs are typically undertaken when there is a change in land use and contaminant
concentrations exceed generic site condition standards. They must examine potential risks to human and
ecological receptors and propose risk management measures if necessary. This RA process involves
liaison and approval by the Ontario Ministry of the Environment (MOE).
Due Diligence Risk Assessments
These RAs do not follow the format or scope of work required by the MOE for approval. They may be
conducted solely for the client’s purposes and may involve all or a portion of the site.
Risk Assessment Process
1. Problem Formulation and Conceptual Site Models – The first component of the RA process,
the problem formulation, determines the following:
i. the contaminants of concern (COCs);
ii. potential human or ecological receptors; and,
iii. the exposure pathways by which receptors may come into contact with COCs at the
Site.
The main purpose of the problem formulation stage is to distinguish between issues for which further
quantitative analysis is warranted from those that can be eliminated from further consideration. The
information from the problem formulation stage is summarized in a conceptual site model, which
illustrates the pathways of the COCs from their sources, through the relevant environmental media, to the
receptors of interest.
1. Exposure Assessment Modeling – The second component of the risk assessment, the exposure
assessment, involves estimating the dose of the contaminant received by the receptors for each
relevant exposure pathway identified in the problem formulation. Site-specific data are used to
characterize COC source concentrations (e.g. soil or groundwater concentrations), and reasonable
assumptions are employed to describe potential receptor contact with the COCs.
2. Toxicological/ Chemical Hazard Assessment – The toxicity (or hazard) assessment component
of an RA identifies toxicological reference values (TRVs) for each COC. A TRV is an
acceptable dose or the concentration of a COC that can be suitably tolerated by a receptor without
causing adverse health effects, and is used as a benchmark for comparison with site exposure
during risk characterization. Both the type of health effect (e.g. cancer) and the pathway by
which a chemical comes into contact with the receptor (e.g. inhalation) are considered when
selecting appropriate TRVs.
3. Risk Characterization - The final stage in the RA is risk characterization. The information from
the exposure and toxicity assessments is combined to produce numerical estimates of human and
ecological risk. This step is conducted for all COCs, receptors, and exposure scenarios of
concern. In order to file an RSC, the maximum concentrations of COCs at the Site are compared
to risk-based Property Specific Standards (PSS) to ensure that no residual risks exist at the Site.
Risk management may be required to meet the PSS, and would be described in the form of a Risk
Management Plan (RMP).
4. Risk Communication - It is often necessary to communicate the technical results of a risk
assessment to members of the public with questions about the health of people, animals and
plants at a site. This is often done by preparing a non-technical factsheet of the results and
meeting with residents to answer their questions directly.
Page 6 © Pinchin Environmental Ltd.