Thresholds and Status evaluation

The good status is achieved when the activity concentration of radionuclide cesium-137 (137Cs) is below 2.5 Bq kg-1 for herring, 2.9 Bq kg-1 for flounder and plaice and 15 Bq m-3 for seawater. The quantitative boundaries used for defining the threshold values corresponds to pre-Chernobyl activity concentration levels, in other words the levels before 1984.


Thresholds figure 1.png

Thresholds figure 1. Good status is achieved when the activity concentration levels of the radionuclide cesium-137 (137Cs) are below the threshold value, i.e. at pre-Chernobyl level. The threshold values are 2.5 Bq kg-1 for herring, 2.9 Bq kg-1 for flounder and plaice and 15 Bq m-3 for seawater.

 

The activity concentration of the radionuclide cesium-137 (137Cs) is evaluated in herring, flatfish and seawater and compared against the threshold values. Currently, no internationally accepted criteria for the assessment of good status in fish exist. There are only upper levels available in the literature, where fish will suffer from doses of radioactive substances (e. g. ICRP 2008). Therefore, threshold values for 137Cs concentrations in seawater and biota have been set at pre-Chernobyl levels. The good status boundaries are averages based on monitoring measurements from 1984-1985 calculated from data in the HELCOM MORS database.

Threshold values are uniform across all assessment units due to uniform distribution of pre-Chernobyl radiation levels caused by atmospheric fallout from nuclear weapons testing.

The confidence of the threshold values is considered to be high, as there are numerous observations from the pre-Chernobyl time, even if the length of the time series is short (1984-1985).