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You can estimate EMCL values using Tier 3 of the ERICA Tool. You need CR values with associated probability distribution functions (pdfs) for the radionuclide you are interested in (and kd values together with associated pdfs if considering an aquatic ecosystem). You need to make predictions for all reference organism assuming 1 Bq per unit media concentration; note for aquatic ecosystems you need to determine both a water and sediment EMCL separately. The EMCL is calculated by dividing your screening level dose rate (10 μGy/h default in the ERICA Tool) by the 5th 95th percentile dose rate to the most exposed organism (i.e. the highest 5th 95th percentile dose rate for any reference organism) assuming 1 Bq per unit media concentration.

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• Enter 1 radionuclide at a time as need to include all the reference organisms (otherwise there may too much data to 'run' the assessment with sufficient simulations).
• Enter your mean concentration ratio (CR) and associated standard deviation (SD) values for each reference organism using the 'Edit distribution' tab choosing the appropriate distribution function (generally select 'lognormal' if n>1 and 'exponential' if n=1, leaving the 'lower' and 'upper cut off' as their default if you have no information).
• Check Occupancy Factors are those which would result in maximal exposure for a particular reference organism.
• Enter a value of 1 into the media concentration cells. Note for aquatic ecosystems you will need to run water and sediment as separate assessments (when you estimate the water EMCL enter a value of 1 into the water activity concentration and leave the sediment blank; when estimating the sediment EMCL enter a value of 1 into the sediment activity concentration and leave the water blank).
• Select all the simulation parameters displayed and enter at least 1000 as the number of simulations.
• The statistics associated with the total dose rate are now available for each reference organism separately.
• Find the organism predicted to be most exposed where this is defined as that with the highest predicted 5th 95th percentile total dose rate.
• The EMCL is then be calculated by dividing your screening dose rate by the predicted 5th 95th percentile dose rate for the most exposed organism (assuming unit activity concentration in the media).

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