More topics

Guidance for risk assessment

Last updated on February 24, 2025

This webpage provides information on conducting risk assessments within the provincial contaminated sites framework. It 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.

Risk-based standards are generally intended to address residual contamination at a site. They should not be used preferentially over other strategies that may remediate a site more permanently, without sufficient justification.  

On this page

Screening level risk assessment (SLRA)

Protocol 13: Screening Level Risk Assessment (PDF, 847KB) sets requirements for evaluation of whether contamination at a site meets risk-based standards for human health and the environment. The SLRA process involves an assessment of exposure pathways and receptors at non-high risk sites. The use of SLRA is subject to several precluding conditions listed in this protocol. 

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. 

Detailed risk assessment

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

This process is described in:

And where applicable:

Expand All | Collapse All
 

Human health risk assessment (HHRA)

Health Canada’s guidance for Federal Contaminated Site Risk Assessment in Canada may be useful when conducting an HHRA and is available at: Guidance Documents – Contaminated sites – Environmental and workplace health - Canada.ca.

Human health conceptual site model (CSM)

Human health Conceptual Site Models (CSMs) should 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)

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
  • Dust inhalation

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

In all cases, environmental consultants must use best available science and select exposure parameters appropriate for their site. 

Human health Toxicity Reference Values (TRVs)

Protocol 1: Detailed Risk Assessment (Revised) (PDF, 559KB) describes the procedure required for selection of human health TRVs. TRVs from Canadian agencies generally incorporate Canadian, as opposed to foreign, policy assumptions and values. TRVs obtained from the US EPA or elsewhere should be checked and adjusted against risk assumptions used in British Columbia.

Probabilistic HHRA

Probabilistic HHRA methods can often provide better information on the variability and uncertainty of risks. Follow US EPA risk assessment guidance to conduct a probabilistic risk assessment. Rationale related to the selection of input parameter distributions and their applicability should be adequately documented.

 

Ecological risk assessment (ERA)

Expand All | Collapse All
 

General ERA guidance documents

The following ministry protocols and technical guidance apply when conducting an ERA for contaminated sites:

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

It should be noted that where technical guidance differs from Protocol 1, the protocol requirements must be followed. 

 

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 understand 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)

Conceptual Site Models (CSMs) should 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)
 

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-approval 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 toxicity test methods provided in the following guidance should be considered:

 

Probabilistic ERA approach

The following guidance should be consulted when conducting an ERA using a probabilistic approach:

 

For specific risk assessment questions, 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.