Prussian Blue to reduce radiocaesium accumulation in fish in lakes affected by the Chornobyl accident

Fish in lakes situated within the Chornobyl exclusion zone have been highly contaminated since the accident and have not been utilized as food for humans. In the present study, field experiments with less-contaminated silver Prussian carp (Carassius gibelio (Bloch, 1782)) caged in contaminated lake within the Chornobyl exclusion zone was performed from June to October 2021 to investigate the effectiveness of clean feed containing potassium ferric hexacyanoferrate (KFCF) KFe[Fe(CN)₆], a kind of Prussian Blue as a countermeasure to reduce ¹³⁷Cs accumulation in fish. The addition of clean feed containing 0.1% or 1% KFCF resulted respectively in 2.4 ± 0.4 or 4.2 ± 0.7 times lower activity concentration of ¹³⁷Cs in muscle tissue of the carp compared to control fish with clean feed without KFCF and in 7-16 or 12-27 times lower activities compared to fish without additional clean feeding. After 18 weeks exposure, ¹³⁷Cs levels in all the caged fish except for the control group were below the European permissible level (600 Bq kg^-1) for consumption. In contrast, KFCF did not affect the intake of ⁹⁰Sr in fish, although additional feed increased the growth rate and thereby accumulation in bone tissues. Hence, the use of clean feed containing KFCF is judged to be an effective and inexpensive countermeasure to reduce the ¹³⁷Cs contamination of edible fish muscles.