Marie Curie's personal notebooks are still so radioactive that they must be stored in lead-lined boxes.

Marie Curie, a two-time Nobel Prize winner, conducted her pioneering research on radioactivity between 1898 and 1934 without modern safety protocols. During this era, the biological dangers of ionizing radiation were not yet understood, leading her to carry test tubes of radium in her pockets. This direct contact resulted in the heavy contamination of her laboratory equipment, furniture, and personal items, including her cookbooks and clothing.The primary contaminant is Radium-226, an isotope that Marie and Pierre Curie first isolated in 1898. Radium-226 is particularly hazardous because it has a half-life of approximately 1,600 years. This means it will take sixteen centuries for just half of the radioactive atoms currently present in her notebooks to decay into a more stable form. Consequently, these artifacts will remain a significant health risk for thousands of years.Currently, the collection is housed at the Bibliothèque Nationale de France in Paris. To prevent radiation exposure, the manuscripts are kept in lead-shielded boxes in a basement vault. Scholars who wish to consult the documents must wear specialized protective clothing and gloves. They are also required to sign a waiver acknowledging the risks, as the items still emit alpha and beta particles that can be harmful if inhaled or touched.