ABSTRACT
Species sensitivity distributions (SSDs) are exposure–-response models for biotic communities. You may wonder why, of all types of exposure–-response models, SSDs are worthy of their own chapter. First, they are particularly important because, since 1985, they have been the standard tool in derivation of water quality benchmark values in the U.S. and many other nations. Second, they are often misunderstood. Third, their derivation requires many decisions relative to other exposure–-response models. Fourth, I have a personal attachment to SSDs. I identified them as a distinct type of model and gave them their name at an OECD (1992) workshop. Then, SSDs gave me the opportunity to work with excellent scientists at the Rijksinstituut voor Volksgezondheid en Milieu (RIVM) in reviewing the uses of SSDs and elucidating issues in their implementation (Posthuma, Suter, and Traas 2002).
