REMEDIATION ronment and Climate Change Canada. Risk assessments for humans and the environment completed according to these guidance documents share several common elements, including a formulation of the problem, assessments of exposure and of toxicity, and a characterization of risk. A public communication strategy, forming part of risk management planning, is also developed in tandem with these other steps. PFAS risk assessment projects in Australia by GHD, which was founded in 1928, provide valuable insight into common risk assessment elements to consider when planning such projects in Canada.
Per- and polyfluoroalkyl substances (PFAS) are a component of many firefighting foams used by the military, airport authorities, and local fire and rescue agencies. Photo credit: wellphoto, AdobeStock
Lessons fROM PFAS Risk Assessment Projects By the GHD PFAS Working Group
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er- and polyfluoroalkyl substances (PFAS) encompass a family of thousands of man-made chemicals that contain a fluorinated carbon backbone. PFAS came into common use in the 1950s and '60s and have been used in hundreds of industrial processes and consumer products. They are considered useful because they are resistant to heat, water and oil. PFAS have been used in non-stick cookware, grease-resistant paper, fast food wrappers, microwave popcorn bags, stain-resistant carpets and fabrics, water-resistant clothing, cleaning products and personal care products. PFAS are also used in industrial processes and are a component of many of the firefighting foams used by the military, airport authorities, and local fire and rescue agencies. To date, use of these foams has most often been implicated when PFAS is found in groundwater, or the environment. At the 2018 Real Property Institute of Canada (RPIC) Federal Contaminated 20 | December 2018
Sites National Workshop (FCSNW) conference in Toronto, Ontario, GHD risk assessor Ian Collins presented a paper on the topic, Risk Assessment and Management of PFAS: Australian Lessons for Canadian Projects. WHAT IS RISK ASSESSMENT? Human health and ecological risk assessment evaluates whether a chemical in the environment may pose potential health risks to people and the environment, respectively. In this context, a potential health risk is identified when exposure to a chemical is high enough relative to the negative effects of the chemical that health consequences may occur. In Canada, human health and ecological risk assessment for federal contaminated lands is conducted under the Federal Contaminated Sites Action Plan (FCSAP). Under this, guidance on human health risk assessment is provided by Health Canada, and guidance on ecological risk assessment is provided by Envi-
SCIENCE WILL ADVANCE WHEN FORMULATING THE PROBLEM At the problem formulation stage of a risk assessment, risk assessors will identify the chemicals to be investigated (sources), who might be exposed to them (receptors), and how those exposures might occur (pathways). During this process, risk assessors compare the amounts of the chemicals on a contaminated site to levels that government agencies indicate are acceptable (Tier 1 values). Those chemicals under investigation that are of greatest concern, i.e., those that exceed the Tier 1 criteria, are subjected to a quantitative site-specific risk assessment. Australian entities have been proactive in their approach to investigate sites potentially impacted by PFAS, and these investigations have been undertaken around the country since at least 2013. Globally, and in Australia specifically, the acceptable levels for PFAS have changed very quickly over the past two years as new scientific research about the toxicity of PFAS has become available. Results of Tier 1 screening in 2017 may have indicated that a contaminated site in Australia was not a location of potential concern. However, when compared against the most recent criteria released in 2018, a site-specific risk assessment may be warranted, given the increased conservatism of the new screening levels. Risk assessments that use these levels for decision making may, therefore, need to be re-evaluated as the ever-advancing pace of research provides new toxicity information on PFAS. In a similar way, as the measure-
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