Canada: Vapour Intrusion: What You Can’t See, Smell, Hear, Taste Or Feel Can Hurt You!

Last Updated: June 27 2013
Article by Marc McAree

By Marc McAree, Luciella Longo and Mark Youden1
Willms & Shier Environmental Lawyers LLP


When it comes to contaminated property and its impacts to the environment, there is more than meets the eye. What may first come to mind are rusted barrels, oil stains, impacted soil and groundwater, industrial operations, service stations, dry cleaners, excavation and remediation and other more high-tech remedial options. And, in many instances there is a "hidden", but ever present issue that can wreak havoc for those assessing, remediating or risk assessing contaminated sites, and for those selling, purchasing, mortgaging and redeveloping these properties. It is vapour intrusion.

Across Canada, there is limited consistency in how vapour intrusion is regulated. Some provinces address the issue directly through their site assessment and remediation regime for contaminated sites, while others do not. The federal government has published some helpful guidance on the issue. This paper provides an overview of the vapour intrusion regulatory framework and guidance across Canada and into the United States.

Also, vapour intrusion litigation has percolated to the surface in Ontario and south of the border in the United States. A select number of cases are briefly described below.


Vapour intrusion, though invisible to the eye and inaudible to the ear, gives many in-the-know cause to pause. Vapour movement via preferential pathways into overlying buildings and other enclosed spaces is the concern. The toxicity of vapour and its potential impact on human health is the overriding peril. Vapour intrusion results when volatile chemicals from sub-surface contaminated groundwater or soil enter an overlying building or enclosed space.2Vapours are emitted from volatile chemicals and may migrate through subsurface soil and into indoor air spaces.3 Examples of volatile chemicals include volatile organic compounds, select semi-volatile organic compounds, and some inorganic analytes, such as elemental mercury, radon, and hydrogen sulfide.4

Safety hazards, acute health effects, and/or odours are examples of some of the impacts that may result from vapour intrusion.5In many cases, the chemical concentrations are low, or depending on site-specific conditions, vapours may not be present at detectable concentrations.6However, low concentrations of volatile chemicals are not necessarily without their impacts.7 The main concern in situations where low concentrations of volatile chemicals are present is that long-term exposure to such chemicals may pose an unacceptable risk of chronic health effects.8

What can complicate the picture of impacts from vapour intrusion is the potential presence of some of the same chemicals from emission sources within the building or enclosed space (e.g., household solvents, gasoline, cleaners) that may pose, separately or in combination with soil vapour, a significant human health risk.9 Distinguishing contributions from different emission sources can pose intricate investigation and remedial challenges, and legal complexity.10

Consultants can collect samples from different media (e.g., indoor air, outdoor air, sub-slab soil gas) in carrying out vapour intrusion assessments.11Soil samples are the least likely of the different media to be significantly affected by background interferences that can confound the interpretation of indoor air sample results.12 Thus, a critical component of vapour intrusion assessment is soil gas sampling.13 The challenge with soil gas sampling and analysis is the use of widely differing protocols.14Environmental consultants may employ modified methods which may lead to further differences in testing outcomes.15

Vapours arising from the presence of volatile chemicals in contaminated soil and groundwater plumes follow the path of least resistance, such as via cracks in the foundation of buildings and openings for utility lines. This area above the water table to surface is the "vadose zone" or unsaturated zone. In the vadose zone, migration pathways of least resistance and building ventilation systems influence vapour entry points and the rate of intrusion in the building.16

Vapour intrusion impacts often give rise to many questions. What standards and tools exist for both employers and employees to address vapour intrusion in the workplace? For buyers and sellers of contaminated property, the old adage, buyer beware, can take on a new meaning. Are vendors expected to disclose? How clean is clean in addressing vapour intrusion? What are prudent buyers expected to discover in the face of a patchwork of vapour intrusion standards and guidance? How does vapour intrusion risk management impact who will foot the bill to address those impacts? Will banks be wary about financing transactions where vapour intrusion is an issue? And, how far will insurers go in placing coverage and excluding vapour intrusion related risks? These questions underscore the importance of owners of contaminated sites turning their minds to these questions.



Federal and provincial governments address vapour intrusion on two fronts, namely through the protection of the environment and through the protection of human health. In all cases, consideration of the applicable contaminated sites regime is necessary.

At the federal level, a "contaminated site" is one at which substances occur at concentrations above background levels and pose, or are likely to pose, an immediate or long-term hazard to human health or the environment.17A contaminated site exceeds the levels specified in policies and regulations.18 There are no contaminated sites federal statutes or regulations. However, the federal government has published contaminated sites and vapour intrusion guidance.

At the provincial level, contaminated sites are not always legally defined. For example, in Ontario, the assessment of contaminated sites is grounded in definitions such as "contaminant" and "adverse effect", and the application of the Records of Site Condition Regulation. In British Columbia, for example, the term "contaminated site" is defined in regulation.

The power to regulate contaminated sites at both the federal and provincial level is grounded in the constitutional powers allocated to each level of government. Property and land management falls within the jurisdiction of provincial regulation, while the federal government has the power to regulate lands over which it owns or has an interest.19Where both federal and provincial legislation exists, Environment Canada states that the more stringent of the two regimes will apply to federal contaminated sites.20



One objective of the Canadian Environmental Protection Act, 199921 ("CEPA") is to protect the environment and human health from unregulated exposure to toxic substances. There are a number of regulations under CEPA that relate to contaminated sites including the PCB Treatment and Destruction Regulations, Storage of PCB Material Regulations and Contaminated Fuel Regulations. However, no federal law directly regulates the investigation and remediation of federally regulated contaminated sites.

A number of guidelines about the assessment and monitoring of vapour intrusion at contaminated sites have been developed by Environment Canada for federal properties. These guidelines are not legally enforceable unless expressly adopted by reference in regulatory instruments such as control orders.22 In addition to guidelines, there are federal programs and initiatives in place to address federal contaminated sites and vapour intrusion.

The federal government is responsible for land and natural resources in northern regions of the country along with pockets of land scattered across the country, such as military bases and training areas, airports, ports and harbours, laboratories, and other areas used for federal operations.23Contaminated sites on Aboriginal reserves also form part of the federal government's responsibility.24


The Federal Contaminated Sites Action Plan ("FCSAP"), a $3.5 billion 15 year program established in 2005, is a long-term program that funds 16 federal departments, agencies, and Crown corporations (called custodians). The program also funds experts to provide support to four federal departments.25 The purpose of the FCSAP is to reduce environmental and human health risks from known federal contaminated sites and associated federal financial liabilities. The FCSAP is rolling out in phases. Phase I (2004-2011) dealt with assessing 6,400 sites and remediating approximately 650 sites. Phase II (2011-2016) continues Phase I with focus on remediating the highest priority sites.

In the 2012 Spring Report of the Commissioner of the Environment and Sustainable Development, the Commissioner reported that in March 2011 the government had identifiedaround 22,000 sites with suspected or actual contamination in the Federal Contaminated Sites Inventory.26 The inventory contains sites under federal custodianship as well as non-federal sites for which the government accepts responsibility. 27

The federal government has systems and processes to assess risks at contaminated sites as well as current or potential adverse impacts on human health or the environment.28 There is a process to prioritize sites for action based on risk level.29

Most confirmed federal contaminated sites have soil contamination from fuelling activities, spills, leaks from above ground storage tanks, or dumping of contamination.30Often there are contaminant impacts to groundwater and surface water quality.31Further, mobile contaminants can volatilize and affect outdoor and indoor air quality.32

Vapour intrusion is considered part of the FCSAP through the recognition of impacts to human health due to the volatilization of contaminant vapour. The FCSAP is aimed at timely assessment and remediation of contaminated sites, and minimizing vapour intrusion impacts on human health. Contaminated sites are assessed using the FCSAP and based on their current or potential to create adverse impacts on human health and the environment.33 The Canadian Council of Ministers of the Environment's ("CCME") National Classification System for Contaminated Sites ("NCSCS") is an important management and screening tool for prioritizing, investigating and remediating contaminated sites under the federal program.34



The NCSCS is a guidance document originally published in 1992, revised in 2008, and further revised in 2010 to correct formula errors.35This guidance document provides a method to identify, evaluate and classify, and prioritize contaminated sites according to their current or potential adverse impact on human health and the environment.36Finally, NCSCS assists the government to allocate funding to investigate and remediate contaminated sites based on their priority level.37

Under the NCSCS, contaminated sites are assessed and ranked taking into account three key factors: contaminant characteristics, migration potential and exposure.38The CCME has developed a Soil Quality Index Calculator for use under the NCSCS. The calculator aids in evaluating the relative hazard by comparing contaminant concentrations with soil quality guidelines.39The identification and assessment of vapour issues under the NCSCS is caught within the net of contaminants of potential concern in vapour, migration potential and potential for human exposure.40The NCSCS is intended for use by those with contaminated site experience.41Site classification should be amended as steps are taken towards remediation and to reflect the appropriate site classification and prioritization.42


In 2008, the CCME commissioned a study titled, Final Scoping Assessment of Soil Vapour Monitoring Protocols for Evaluating Subsurface Vapour Intrusion into Indoor Air. The studyculminated in a summary of existing guidance documents that convey a clearer understandingabout requirements for vapour intrusion assessment under different site conditions.43 The studyrevealed that there is no one guidance document that includes all information and processesrequired to adequately assess vapour intrusion at contaminated sites.44

Recommendations in the study about vapour intrusion directed the CCME to one of the following options

  • endorse several documents allowing for flexibility in carrying out site assessments at properties with different site conditions
  • write a new and more comprehensive document
  • write a companion document that identifies factors leading to low quality data, or
  • compile recommendations from the commissioned study into a procedure that would allow the appropriate flexibility required for different sites.45

Upon review of the CCME website, there is no indication that CCME adopted any of the recommendations set out above.



Health Canada plays a part in assessing risks posed by sites and in evaluating toxicity of chemicals and wastes, and in monitoring human exposure to contaminants. 46

Health Canada is also part of the FCSAP which forms part of the framework designed to ensure improved and continuing federal environmental stewardship relating to contamination at federally owned or operated sites.47

The Federal Contaminated Site Risk Assessment in Canada, Part VII: Guidance for Soil Vapour Intrusion Assessment at Contaminated Sites guideline provides guidance to federal departmentsabout how to determine if there is potential for subsurface vapours to migrate into a building.48If there is vapour intrusion, the guidance document assists in determining if it poses anunacceptable risk to human health.49The document sets out questions and steps to follow toevaluate potential risks.50 In addition, the guidance is intended for application where there iscurrent occupation at residential or commercial contaminated sites, or where there is potential forthe presence of occupied buildings in a future land use scenario.51

The guidance document was meant to supplement the Health Canada Guidance on Human Health Preliminary Quantitative Risk Assessment ("PQRA"), which does not providequantitative guidance for the soil vapour intrusion pathway.52 Under the PQRA, there areminimum data requirements for vapour intrusion including

  • ensuring that chemicals of potential concern ("COPC") are analyzed based on historical land use
  • soil and/or groundwater are sampled a minimum of two times at a minimum of two sampling locations on either side of a building
  • samples should be collected at depth if not under the building, and
  • there should be a detailed conceptual site model.53


1 Marc McAree is a partner at Willms & Shier Environmental Lawyers LLP in Toronto and is certified as a Specialist in Environmental Law by the Law Society of Upper Canada. Luciella Longo was a 2011 summer law student at Willms & Shier Environmental Lawyers LLP and is currently articling at the firm. Mark Youden is currently a summer law student at Willms & Shier Environmental Lawyers LLP.

2 United States Environmental Protection Agency ("US EPA"). Online: .

3 Ibid.

4 Ibid.

5 Ibid.

6 Ibid.

7 Ibid.

8 Ibid.

9 Ibid.

10 Ibid.

11 Geosyntec, Final Scoping Assessment of Soil Vapour Monitoring Protocols for Evaluating Subsurface Vapour Intrusion into Indoor Air. Prepared for the Canadian Council of Ministers of the Environment ("CCME") (July, 2008). Online: .

12 Ibid.

13 Ibid.

14 Ibid.

15 Ibid.

16 US EPA, OSWER Final Guidance Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Sources to Indoor Air (External Review Draft) (2013). Online: final-guidance-20130411-reviewdraft.pdf.

17 Office of the Auditor General of Canada, 2012 Spring Report of the Commissioner of the Environment and Sustainable Development (2012). Online: .

18 Ibid.

19 CCME, Guidance Document on Management of Contaminated Sites in Canada (April, 1997) at page 4. Online: .

20 Ibid at page 5.

21 Canadian Environmental Protection Act, 1999 SC 1999, c 33.

22 CCME, Guidance Document on Management of Contaminated Sites in Canada (April, 1997) at page 7. Online: .

23 Supra note 17.

24 Ibid.

25 Ibid.

26 Ibid.

27 Ibid.

28 Ibid.

29 Ibid.

30 Ibid.

31 Ibid.

32 Ibid.

33 CCME, National Classification System for Contaminated Sites Guidance Document (2008). Online: .

34 Ibid at page 1.

35 Ibid.

36 Ibid.

37 Ibid at page 3.

38 Ibid at page 6.

39 Ibid at page 4.

40 Ibid.

41 Ibid.

42 Ibid.

43 Supra note 11 at page 22.

44 Ibid.

45 Ibid.

46 Supra note 19 at page 6.

47 Health Canada, Environmental and Workplace Health, Federal Contaminated Site Risk Assessment in Canada, Part VII Guidance for Soil Vapour Intrusion Assessment at Contaminated Sites (2010). Online: .

48 Ibid.

49 Ibid.

50 Ibid.

51 Ibid at page 4.

52 Ibid at page 1.

53 Health Canada, Contaminated Sites Division, Vapour Intrusion Guidance: Status Report at slide 8. Online: .

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