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5F - Probabilistic approaches (MOP/194) The use of SSD in defining a PEC:PNEC to risk function. Smit, Mathijs1, Karman, Chris1, Holthaus, Karlijn1, Tamis, Jaqueline1, 1 TNO-MEP, Den Helder, The Netherlands ABSTRACT- The PEC:PNEC ratio (i.e. risk quotient) is often used as an expression of the ecological risk. It has to be taken into consideration that a PEC:PNEC ratio is no real measure of risk, but merely an indication of the likelihood that the ecosystem is affected. However, this PEC:PNEC ratio can be translated into a real risk measure (i.e. the probability that an organism will be affected). The general relationship between a PEC:PNEC ratio and the corresponding risk to biota is in fact a function of the sensitivity of all species. The mean sensitivity is determining the position of the distribution on the X-axis and the variation in sensitivity is determining the slope of the curve. In order to translate PEC:PNEC ratios into risk estimates, the position of the distribution has to be calibrated, so that the risk at a PEC:PNEC ratio of 1 equals a risk that is considered acceptable (e.g. 5%). In this project SSDs for produced water components (discharged from offshore oil and gas production platforms) have been defined and sources of variation have been indicated. These functions have been implemented in a Risk Analysis tool for produced water releases. This method has proven to be useful for the assessment of environmental risk of mixtures of chemicals discharged as an effluent. Currently, the methodology is mainly in use for produced water risk assessment and implemented in risk assessment tools such as the EIF (Environmental Impact Factor). Key words: Risk assessment, SSD, probablistic, produced water |
