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Guidance for risk assessment

Last updated on April 18, 2023

This webpage provides information on conducting risk assessments within the provincial contaminated sites framework. This webpage supplements existing provisions in risk assessment protocols established under the Environmental Management Act (EMA) and is subject to change as risk assessment methodology, policy, and guidance is updated.

Screening level risk assessment (SLRA)

Protocol 13: Screening Level Risk Assessment (PDF, 847KB) sets requirements for evaluation of whether contamination at a specific site meets risk-based standards for human health and the environment. The SLRA process involves an assessment of exposure pathways and receptors.

Contaminated sites that have acceptable risk under SLRA are considered to satisfy Contaminated Sites Regulation (CSR) risk-based standards. No further risk assessment or remediation is required at such sites if site conditions do not change.

Ongoing environmental monitoring, to ensure the maintenance of site conditions, may be necessary at sites where assessment is done via SLRA. 

Risk assessors are cautioned that the use of SLRA is subject to precluding conditions. These are listed in Protocol 13. 

SLRA cannot be used at high-risk sites or at sites where contaminated vapours, surface water, or sediments require a risk assessment.

Detailed risk assessment

Detailed risk assessment (DRA) involves a systematic process of evaluating the risk that examines in detail the potential adverse effects on human health and/or ecological health resulting from exposure to contaminants in environmental media.

DRA requires the use of a formal framework described within:

And where applicable:

Two types of environmental quality standards apply at contaminated sites:

  • Generic numerical standards prescribed in CSR Schedules 3.1 - 3.4 
  • Risk-based standards.

The use of risk-based standards is generally intended to address residual contamination at a site.

Risk-based standards should not be used preferentially over other strategies that may remediate a site more permanently, without sufficient justification.  

Applicants must follow the legislation and protocols to successfully remediate a contaminated site. The ministry additionally offers resources, guidance and policies.

The ministry requires complete rationale and supporting documentation to be submitted for all components of a DRA in applications to the ministry to support remediation.  

Humans health risk assessment (HHRA)

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General HHRA guidance documents

Qualified professionals must follow the requirements in Protocol 1.

In addition, specific guidance in the Health Canada, Federal Contaminated Site Risk Assessment In Canada Part I: Guidance on Human Health Preliminary Quantitative Risk Assessment (PQRA), Version 2.0 (2012) which may be particularly useful include: 

  • Table 2. Problem Formulation Checklist
  • Table 3. Recommended Human Receptors and their Characteristics for Preliminary Quantitative Risk Assessments
  • Table 4. Exposure Duration and Frequency Assumptions for Preliminary Quantitative Risk Assessments
  • Table 5. Recommended General Equations Dose Estimation
  • Table 7. Potency Equivalence Factors for Carcinogenic Polycyclic Aromatic Hydrocarbons
  • Table 8. Toxic Equivalency Factors for Dioxins, Furans, and Certain Polychlorinated Biphenyls

In addition, the ministry recommends the use of the absorption factors provided in Table 3, Dermal Relative Absorption Factors (RAFdermal) of Selected Substances of Health Canada, Federal Contaminated Site Risk Assessment In Canada, Part II: Health Canada Toxicological Reference Values (TRVs), Version 2.0 (2010) guidance.

Other Health Canada documents and versions in addition to those listed above may be used if the acceptable rationale for their use is provided to the ministry.

 

Soil vapour assessment

For assessments concerned with evaluating risk associated with exposure to soil vapours, Protocol 22: Application of Vapour Attenuation Factors to Characterize Vapour Contamination (PDF, 421KB) must be followed.

The ministry also recommends the following guidelines: 

 

Human health conceptual site model (CSM)

The ministry recommends that human health Conceptual Site Models (CSMs) include the following:

  • A visual representation of contaminant sources, routes of transport, exposure media, exposure pathways, and receptor groups
  • Clearly illustrated exposure pathways types such as complete, incomplete, and insignificant, and rationale to support these labels in the text of the risk assessment
  • A box diagram CSM where a pictorial CSM may be overly complex and cumbersome to follow
  • An indication of how specific exposure pathways and receptor groups may be separated by spatial boundaries where migration of contaminants occurs (for example, site vs. off-site)

An example CSM is shown in Figure A1-13 in:

 

Human health exposure parameters

Protocol 1 requires the consideration of exposure parameters prescribed in:

In some cases, environmental consultants are required to evaluate scenarios that were not included in Protocol 28, and additional exposure parameters are needed.

For example:

  • Consumption of country foods
  • Bathing

For these exposure scenarios, the ministry recommends consulting the Health Canada and U.S. Environmental Protection Agency (US EPA) guidance below for appropriate exposure parameters and equations.

Health Canada

US EPA

 

Human health Toxicity Reference Values (TRVs)

TRVs from Canadian agencies generally incorporate Canadian, as opposed to foreign, policy assumptions and values. Canadian agency TRVs are widely used within Canada for public health and environmental decision-making outside of the contaminated sites field. Their use generally ensures greater consistency between contaminated sites risk assessments and risk assessments conducted for other purposes.

However, TRVs from American environmental agencies are typically subject to more frequent peer review, revision and updating. US EPA TRVs have been used by the ministry in setting most of the numerical standards of the CSR. Protocol 1: Detailed Risk Assessment (Revised) (PDF, 559KB) describes the procedure required for selection of human health TRVs.

 

Probabilistic HHRA

Probabilistic HHRA methods can often provide better information on the variability and uncertainty of risks. For probabilistic HHRA, the ministry recommends the use of the following US EPA risk assessment guidance:

When probabilistic methods are used, the ministry expects that rationale related to the selection of input parameter distributions and their applicability will be adequately documented.

 

Ecological risk assessment (ERA)

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General ERA guidance documents

The following ministry protocols and technical guidance apply to the performance of ERA for contaminated sites:

The ministry also recommends consideration of the following guidance for ERA:

It should be noted that where the Science Advisory Board for Contaminated Sites in British Columbia: Detailed Ecological Risk Assessment (DERA) in British Columbia Technical Guidance (September 2008) document differs from the updated Protocol 1, this protocol supersedes this guidance document.

 

Ecological receptor selection

Selecting key ecological receptors for the ERA is necessary because it is impractical to assess risks to every organism potentially using the site. The social, economic, political, cultural and ecological importance of receptors is considered when determining which ones are used for evaluation in the risk assessment. The information provided in Protocol 1: Detailed Risk Assessment (Revised) (PDF, 559KB), Protocol 20: Detailed Ecological Risk Assessment Requirements (Revised) (PDF, 479KB) and on this webpage focuses on the ecological factors considered when creating regional and site-specific species lists.

Consultation with the appropriate regulatory agencies, stakeholder groups, and Indigenous People may be required to discern values driven by non-ecological factors. One such factor is the inclusion of species whose population status is already at risk regionally (for example, extirpated/endangered/threatened [red-listed] or sensitive/vulnerable/ special concern [blue-listed] species).

In ERA, the primary focus is on assessing effects and impacts at the community or population level; however, when species at risk are potentially present at the site, assessment at the individual organism level is required (for example, Canadian Federal Species at Risk Act and B.C. Wildlife Act). The ministry expects a thorough assessment of habitat considered critical to supporting endangered and threatened species or individuals.

The selection of ecological receptors to be assessed in an ERA typically starts by evaluating the potential habitats present at a site, its adjacent areas, and its receiving environments. This is often followed by a desktop study to identify what species may be present due to the identified habitat types, and potentially a field study to more thoroughly evaluate the potential presence of certain species. In some cases, further surveys may be conducted for particular species at risk, or other species identified as valuable at the site.

 

Field studies

Field studies can reduce uncertainty by obtaining data specific to the site and adjacent areas, such as the abundance and diversity of organisms, toxicity of the media present at the site, and biologically relevant concentrations (for example, tissue concentrations).

Field studies are critical in obtaining appropriate data that can later be fed into exposure and food chain modeling.

 

Ecological conceptual site model (CSM)

The ministry recommends that Conceptual Site Models (CSMs) include the following:

  • A visual representation of contaminant sources, routes of transport, exposure media, exposure pathways, and receptor groups
  • Clearly illustrated exposure pathway types such as complete, incomplete, and insignificant, and rationale to support these labels in the text of the risk assessment
  • A box diagram CSM where a pictorial CSM may be overly complex and cumbersome to follow
  • An indication of how specific exposure pathways and receptor groups may be separated by spatial boundaries where migration of contaminants occurs (for example, site vs. off-site)

Examples of CSMs are shown in Figures 2-2, 2-3, and 2-4 of:

 

Ecological exposure parameters

When selecting exposure parameters for estimating exposure to ecological receptors, the ministry recommends the following sources be consulted:

In addition, relevant information from other jurisdictions and pertinent peer-reviewed scientific literature may be used to supplement the above sources of ecological exposure parameters. In such cases, rationale for the use of a supplemental ecological exposure parameter should be included in the ERA report.

 

Ecological TRVs (EcoTRVs)

Carcinogenicity

Carcinogenicity is not usually selected as a chronic ecological effect endpoint unless the rate of cancer incidence is sufficient to threaten survival at the population level.

However, if a particular organism warrants protection at the level of the individual (for example, an individual of a rare and endangered species) cancer can be an appropriate chronic effect endpoint for that individual if data is available and adequate for assessment.

Selection of EcoTRVs effects concentrations

When selecting EcoTRVs from a verified source or deriving a de novo EcoTRV, requirements in Protocol 1 must be followed including the protection levels listed in Table 1. 

These protection levels are based on specific effects concentrations (ECx) of a substance, which are typically correlated to a specified effect on a percentage of the organisms exposed.

However, some effects concentrations are more dependent on study design and are therefore not recommended as the basis for EcoTRV selection unless an alternative is unavailable.

These include No Observed (Adverse) Effect Levels (NO(A)ELs); No Observed (Adverse) Effect Concentrations (NO(A)ECs); Lowest Observed (Adverse) Effect Levels (LO(A)ELs); or Lowest Observed (Adverse) Effect Concentrations (LO(A)ECs) and similarly derived benchmarks.

De novo derived EcoTRVs

When deriving a de novo EcoTRV for a site, the best available science needs to be considered. Toxicity studies are frequently added to databases, and data compilations are used to derive TRVs for specific jurisdictions.

When compiling toxicity data for the derivation of a de novo TRV, the ministry recommends that the following sources of toxicity data be considered:

Specific requirements for de novo TRV derivation methods are provided in Protocol 1. Note that a Pre-approvals under Protocol 6 may be required for use of a de novo TRV within a risk assessment.

 

Toxicity testing and interpretation

In addition to the ecological toxicity test methods referenced in Protocol 1, the ministry also recommends consideration of the toxicity test methods provided in the following guidance:

 

Probabilistic ERA approach

The ministry recommends consulting the following guidance when conducting an ERA using a probabilistic approach:

 

Protocol 6 pre-approvals

Protocol 6: Applications with Approved Professional Recommendations and Pre-approvals (PDF, 406KB), requires the Director’s pre-approval of certain risk assessment methodologies before an Approved Professional can apply to recommend approval for a risk-based Certificate of Compliance or Approval in Principle.

Refer to the Pre-approvals web page and the Protocol 6 Pre-approvals Application (Online) form which includes instructions for the form’s completion.

Sampling guidance to support risk assessment

The ministry’s policies on analytical laboratory methods and sampling methods to be used to support conducting risk assessment under the CSR in BC are provided below:

For specific risk assessment questions, visit the Land Remediation's Contact us.

The information on this web page does not replace the legislative requirements in the Environmental Management Act or its regulations and it does not list all provisions for contaminated site services.

If there are differences between this information and the Act, Regulation, or Protocols, the Act, Regulation, and Protocols apply.