According to www.chlorellafactor.com, “chlorella has traditionally been used throughout world history as a method to help remove radioactive isotopes from the body. This is likely because in laboratory tests, chlorella binds very quickly and strongly to many different metals and elements, including those isotopes typically released in a radiation accident or nuclear attack.” The bigger worry should be contamination from metals and synthetic chemicals. The yaeyama chlorella in the Bioray product is very clean. You can read reports from the Japanese makers of yaeyama chlorella here: http://www.yaeyamachlorella.com/En/index.shtml