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Species Sensitivity Distribution (SSD) Toolbox

What is the SSD Toolbox?

Species sensitivity distributions (SSDs) are a common tool used for setting safe limits on chemical concentrations in surface waters. The SSD toolbox simplifies this process by gathering a variety of algorithms to support users in fitting, summarizing, visualizing and interpreting SSDs. The current version of the toolbox supports five distributions (normal, logistic, triangular, Gumbel, and Burr Type III).

The SSD Toolbox follows a three-step procedure.  First, results from separate toxicity tests on a given chemical using various aquatic animal species are compiled.  Second, a statistical distribution to which the test results are thought to conform is chosen and fit to the data.  Third, the fitted distribution is used to infer a concentration that will be protective of a desired proportion of species in a hypothetical aquatic community. 

With the SSD Toolbox risk assessors can quickly fit and visualize simple SSD's that are designed to be useful with both large and small datasets.