Does the National Classification System for Contaminated Sites accurately characterise risks?

摘要

The National Classification System for Contaminated Sites (NCSCS) is a tool established by the Canadian Council of Ministers of the Environment (CCME) and is used by federal agencies and departments to prioritise contaminated site management and its funding. Given adequate information, the NCSCS can be used to categorise a contaminated site into one of four classes. However, does the output of an NCSCS evaluation accurately reflect contaminated site risks? Do high NCSCS scores truly represent high risk? Can the NCSCS be used to rank a portfolio of sites? These questions are addressed by comparing NCSCS scores to the results of preliminary quantitative risk assessments (PQRAs) focused on human and ecological receptors. Environmental data on 20 contaminated sites from across Canada and listed in the Federal Contaminated Site Inventory were used in this comparison. Although the output from both the NCSCS and PQRAs have significant uncertainties, the authors conclude that the NCSCS categorisations do not always accurately reflect the relative level of risk at a site. Second, NCSCS score ranks are positively correlated with PQRA result ranks; however, the amount of data scatter prevents forming a mathematical relationship between the two measures. Third, NCSCS scores can be used to rank sites and a relation to estimate the probability that one site has greater risk than another is provided.