Function for the calculation of the EC50 for bioluminescence from Microtox experiments with sediments. This function uses a model correcting for the fact that with increasing sediment concentration more bacteria will bind to the sediment so that their bioluminescence can no longer be measured. The model was developed by ECOSTAT. The software was developed in cooperation with Kees van Heerden from Caseware. This reseach was sponsored by the Netherlands National Institute for Coastal and Marine Management (RIKZ) of the Netherlands Ministry of Transport, Public Works and Water Management. The user version of the model to estimate this EC50 can be downloaded from the RIKZ website. On this site you can find it using the search strings "korrelgrootte" or "microtox". (This site is in Dutch.)