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SAM Calculation
Version 2017.07
The Stress Addition Model (SAM) predicts the effects of independent stressor combinations. For more information see Matthias Liess et al., 2016.
Data
Concentration: Toxicant concentrations.
SurvivalTOX: Measured survival effects for the toxicant stress alone.
SurvivalTOX+ENV: Measured survival effects for the toxicant stress in presence of an additional environmental stress. The value marked in red indicates the survival by the environmental stressor alone. This value is used for modeling the survival of both stressors by the SAM.
SAMTOX+ENV: Survival curve of both stessors modeled by the SAM.
EATOX+ENV: Survival curve of both stessors modeled by effect addition (EA).
CATOX+ENV: Survival curve of both stessors modeled by concentration addition (CA).
To calculate EA and CA, the traditional approaches of pharmacology had to be adapted, see Matthias Liess et al., 2016.
Plot
Smmoth Curve: Improves curve fitting by applying (i) the Williams transformation in case of hormesis and (ii) linear interpolation to generate 10 smoothing data points on a logarithmic scale which replace the original input data. For more details see Matthias Liess et al., 2016.
Asymmetric Curve: Data is fitted applying the classic log-logistic model for concentration-response relationships. By default, the following three parameters are used: the upper limit of survival effects, a shape parameter and a scale parameter (the lower limit of survival is fixed to 0). By the option of 'asymmetric curve', an additional parameter for asymmetry of the concentration-response relationship can be applied. The full function and further explanations are given in Matthias Liess et al., 2016.
Lethal effect concentrations (LC10 and LC50) are displayed as triangles. Numeric values are available by hovering the mouse cursor over the triangle.