Risk assessment for environmental contamination: an overview of the fundamentals and application of risk assessment at contaminated sites

Abstract

Many jurisdictions throughout Canada and the United States allow the decision to proceed with an active site cleanup, an evaluation or monitoring program, or site closure to be determined from the results of a risk assessment. Risk assessment can protect both human health and the environment while providing significant savings to industry and government by reducing unnecessary environmental expenditures and allowing for the more efficient allocation of resources. Risk assessment is a dynamic process which is evolving as new methods for contaminant fate and transport modelling, more complete toxicological data, and more standardized statistical methods become available. Principal methodologies for conducting risk assessments are provided by the United States Environmental Protection Agency (USEPA), the American Society for Testing and Materials (ASTM), and the Canadian Council of Ministers of the Environment (CCME). Risk assessment methodologies include both "forward" risk calculations and "reverse" risk calculations. Uncertainties inherent in risk assessment methodologies can be difficult to quantify and are dealt with by incorporating conservative assumptions throughout the risk assessment process. Institutional controls may be required to ensure the continued validity of assumptions. There is a trend toward the increased application and acceptance of risk assessment, although Canada remains well behind the United States. To ensure the expanded use of risk assessment in Canada, more training for both regulators and environmental professionals, increased public awareness, and the adaptation of the risk assessment methodologies being applied in the United States to reflect the environmental policies and technical concerns of interest across Canada will be required.Key words: risk assessment, petroleum, risk-based corrective action, site remediation, remediation objectives, Canada, institutional controls, ethics.