Natural decrease of radioelements in food
In 1987, one year after Chernobyl, the contamination of agricultural production came from the root uptake of radioactive cesium atoms present in the ground rather than by deposits on the leaves and grass as it was in the weeks after the accident . The Caesium transfer to plants and food was much lower and declined steadily over the years. Twenty years later, the contamination of agricultural products was 10-30 times smaller than in 1987 and 1000 to 10 000 times lower than that it was at the time of deposit in early May 1986.
Source IRSN