Scientific Basis for Central Nervous System Damage by Incorporated Radiation CS-137 (Cesium)

 stock here-- it has been known for a long time, and without a doubt, that even low levels of radiation in our food or water can have disastrous effects, even at levels of say 30 or 40 Bq/kG of consumed food.  
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http://chernobyl-today.org/index.php?option=com_content&view=article&id=97%3A2016-04-04-10-09-33&catid=18&Itemid=38&lang=en

And here is the study itself.
http://chernobyl-today.org/images/stories/bandazhevsky_lelevich_1995.pdf