Check·Up Gum (1980s)
The reason that Check·Up Gum is featured here is that the zirconium silicate contained elevated levels of uranium and thorium (e.g., 100 pCi/g). The amount of zirconium silicate in the gum was such that the uranium concentration is approximately 7 pCi per gram of gum. Since the uranium series is in secular equilibrium, the gum also contains 7 pCi of Ra-226 per gram. As a matter of interest, there have been many situations where this level of radium in soil has required remedial action.
Although Check·Up Gum is no longer produced, zirconium silicate continues to be used in dental pastes and some toothpastes. Nevertheless, consumers can rest assured that the radiation dose is negligible—the radioactive material is bound up in the zirconium silicate and would not be assimilated even if swallowed.