Calow, P. E.. The University of Sheffield, p.calow@sheffield.ac.uk

RISK ASSESSMENT AND UNCERTAINTY ANALYSIS FOR PROTECTION OF AQUATIC ECOSYSTEMS: CURRENT PRACTICE AND THOUGHTS ABOUT FUTURE DIRECTIONS.

Risk quotient analysis is used widely as a basis for ecological risk assessment in chemical control legislation. The risk quotient compares predicted exposure concentrations with predicted no-effect concentrations. These are often treated as single number indicators of risk but clearly involve uncertainties in both numerator and denominator. Uncertainty arises from lack of understanding, stochasticity, and measurement errors. Very often we know little about the relative contributions of these sources and can only make qualitative judgements about their impact on the risk quotient. Sometimes it is possible to more precisely quantify the aspects of uncertainty and to take them into account in risk quotient analysis using more quantitative techniques. This paper will describe a stepwise procedure that can provide a practical basis for uncertainty analysis by regulators involved with risk quotient analysis. Examples will be taken from recent work of the authors examining land and sea-based sources of contaminants in a marine system. Special consideration will be given to how the risk quotient approach can be made more ecologically relevant while remaining of practical value.

Day: Friday, Feb. 5

Time: 08:45 - 09:00am

Location: Hilton of Santa Fe

Code: SS11FR0845H