Why Marie Curie’s belongings are still kept in lead-lined boxes

Marie Curie and her husband spent nearly four years boiling down seven tonnes of pitchblende in a leaky Paris shed with no ventilation to isolate one-tenth of a gram of radium chloride. Today, the notebooks they kept during those years, between 1899 and 1902, are kept in lead-lined boxes at the Bibliothèque nationale de France. Anyone who wants to see them has to sign a waiver and wear protective gear beforehand. The same is the case with her cookbooks, furniture, doorknobs of her old apartment and even her coffin.The radioactivity she and Pierre coaxed out of eight tonnes of Bohemian pitchblende in a leaky Paris shed has a half-life of 1,600 years and will still be measurable when the person reading this is mere dust. Half-life is the amount of time it takes for a radioactive nucleus in a sample to decay into a more stable element. The couple spent nearly four years of grinding, boiling, dissolving and recrystallising what became about one-tenth of a gram of radium chloride, less than the grain of a rice.The shed on the rue LhomondTheir workspace was not the modern laboratories that scientists are used to these days. It was an abandoned dissecting room behind the Municipal School of Industrial Physics and Chemistry, with a glass roof that leaked when it rained and no fume hoods of any kind. In summer it baked. In winter the Curies wrote about their fingers going numb around the iron stirring rods.Pitchblende is a dense, tar-black uranium ore. The Curies had reasoned, from careful electrometer measurements Pierre had refined using his own piezoelectric instruments, that pitchblende was more radioactive than the uranium it contained could account for. Something else had to be in there. Something rarer, and stronger.Austria's imperial government agreed to ship the Curies the waste ore left over after uranium had been extracted for glassmaking. Eight thousand kilograms of it arrived on carts, dumped in the courtyard mixed with pine needles from the Bohemian forests. Marie processed it in twenty-kilogram batches. “I had to spend a whole day mixing a boiling mass with a heavy iron rod nearly as large as myself,” she wrote later. “I would be broken with fatigue at the day’s end.”The work of the CuriesThe chemistry was just brutal repetition. Dissolve pitchblende in hydrochloric acid. Precipitate the sulfides. Separate what remains active from what doesn’t. Then do it again with the active fraction. Again and again. Radium behaves chemically almost exactly like barium, which is why the ore contained radium at all and why isolating it was so agonising. Marie had to perform thousands of fractional recrystallisations, exploiting the tiny difference in solubility between radium chloride and barium chloride in hydrochloric acid. Each cycle concentrated the radium a little more and took hours.By 1902, she had her decigram. She measured radium’s atomic weight at 225, close to the modern value of 226. The substance glowed in the dark, warm to the touch, kicking off heat with no apparent fuel. Pierre carried a small vial of it in his waistcoat pocket to show visitors. By then, their fingertips were raw and inflamed and so were hers.Some doses of radiumBack in 1990, people didn't understand ionising radiation the way they do today. The Curies knew radium caused burns, Pierre deliberately strapped a sample to his arm to observe the lesion and they knew it could destroy tumour cells which is why radium therapy became one of the first cancer treatments.What they did not get was the cumulative exposure, alpha particles inhaled as radon gas, beta particles from decay products deposited in bone and gamma rays passing through everything. Marie stored radium samples in her desk drawer at home. She and Pierre described the shed years as “the best and happiest of our lives,” and would return in the evenings to watch the tubes glow on the shelves like “faint fairy lights.”It had become so embedded in their lives that at the age of 66, she died in 1934 of aplastic anaemia. Even her daughter Irene, who worked along with her at the Radium Institute, would die at 58 of leukaemia. Both illnesses were consistent with prolonged radiation exposure.The radioactive objectsRadium-226 has a half-life of about 1,600 years. Which means the radium contamination Marie tracked on her fingertips into her lab notebooks in 1902 has, in the intervening years, decayed by less than five per cent. It is essentially as radioactive as it was the day she wrote in it.Today, the Bibliothèque nationale de France holds her papers in lead-lined cases. Researchers who want to consult them must sign a liability release and handle the pages with protective equipment. Not just the books, Marie's personal effects at the Musee Curie in Paris, like the furniture, chair, and cookbooks are also protected like this.A 2025 BBC feature followed radiation surveyors retracing the Curies’ movements around Paris, still finding contamination in the plaster and floorboards of buildings the couple had worked in more than a century ago.Her body itself is buried in a lead-lined coffin. When her remains were transferred to the Pantheon in 1995, the first woman interred there on her own merit, the coffin was shielded with lead lining because her bones remain measurably radioactive.Two Nobles and a radioactive notebookThe Curies were so in love with science that when they were advised to patent the extraction process, they refused. Radium, Marie said, belonged to science. In 1903, the Nobel Committee awarded the physics prize jointly to Henri Becquerel and to Pierre and Marie Curie for their work on radioactivity, a word Marie had coined. She was the first woman ever to receive a Nobel. Neither Curie attended the ceremony; Pierre was ill and Marie was recovering from a miscarriage.Three years later, on 19 April 1906, Pierre stepped off a kerb on the rue Dauphine in the rain and was struck by a horse-drawn dray. The wheel crushed his skull. The Sorbonne handed Marie his teaching post, making her the first woman ever to hold a professorship at the ancient university. In 1911 she won a second Nobel, this time in chemistry, for the isolation of radium and the discovery of polonium, named after her occupied homeland. She remains the only person to have won Nobels in two different sciences.The shed on the rue Lhomond is gone. The Radium Institute, which she founded still stands, now part of the Institut Curie, one of the world’s leading cancer research centres. The gram of radium she brought back from the United States in 1921, after a fundraising tour arranged by the American journalist Marie Meloney, is still in the institute’s collection, stored under heavy shielding.Radium itself has largely fallen out of use, but notebooks endure. If you visit the Bibliothèque nationale and ask to see Marie Curie’s manuscript pages, a librarian will bring you a Geiger counter reading along with the request form. In 3,626 CE, when the radium she smeared on the pages has decayed by half, the pages will still carry what they discovered.