Answer:
The notebooks are still hazardous because the Curies didn't use protective equipment (nor did they have it) and the close proximity of the radioactive isotopes allowed for spreading of radioactivity. Since Radium-226 was kept in bottles and drawers in the Curies' home, it was in close proximity to their items. This allowed for Radium-226 to radiate to other items. In turn, those items absorbed the radiation and become radioactive. Today, Marie Curie is buried under a lead-lined coffin and her belongings can be visited ONLY with protective gear and signing a liability form.
Explanation: