Keywords: prioritisation system, comparative risk approach, risk rankings, environmental risks
A process to reconcile priorities among agencies responsible for environmental health risks
Government agencies responsible for environmental protection need a process that establishes priorities among competing issues. Examples are described, drawing particularly on the experience of the US Environmental Protection Agency. Prioritisation systems should have certain characteristics responsiveness to the various agencies' mandates, flexibility, discriminatory power, transparency and accountability, mechanisms for dealing with uncertainty, and robustness. This council, which consisted of both federal and provincial agencies, requested assistance in developing an explicit system for prioritising issues with different characteristics and constituencies. Simple scoring systems tend to "clump" priorities in a middle range and had not been satisfactory. We independently devised a system, for a Canadian government council with responsibility for prioritising environmental risks to health, in five steps: Step 1 is a screening step to confirm that issues fell within the mandate of the agencies participating and were properly aggregated or disaggregated into single, meaningful questions. Step 2 assigns categories on each of three scales representing the magnitude of the worst likely effect, the distribution of the hazard or impact across Canada and whether the issue represented a single hazard, a set of exposure-related problems or a generic problem. These are represented by a 3 x 3 x 3 matrix, in three dimensions. Step 3 involves applying a weighting system to each scale and each axis, consistent for all issues being considered. A numerical score is derived. Step 4 involves ranking the issues on an interim list and Step 5 is a review of the list with a consensus exercise to break any ties. The system may appear complicated but has the advantages of good resolution of issues and easy adaptation by simple changes in the weighting scale. It also tends to reduce political distortions on setting priorities because the technical parameters are agreed upon in advance. Examples are given of applications of the system to real issues that were facing the council at the time.