Normal Species Sensitivity Distributions and Probabilistic Ecological Risk Assessment

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A species sensitivity distribution (SSD) is a probabilistic model for the variation of the sensitivity of biological species for one particular toxicant or a set of toxicants. The toxicity endpoint considered may be acute or chronic in nature. The model is probabilistic in that — in its basic form — the species sensitivity data are only analyzed with regard to their statistical variability. One way of applying SSDs is to protect laboratory or field species assemblages by estimating reasonable toxicant concentrations that are safe, and to assess the risk in situations where these concentrations do not conform to these objectives.