On this day...

21st December, 1898

 Huband-and-wife team The Curies discover radium. This was at a time of huge excitement over radiation - certain elements were discovered to be emitting more energy than existing scientific ideas could account for - but nobody knew that radiation was actually bad for you. It wasn't just radium (named after how radioactive it was) they discovered, Polonium (named after Poland, Maries home) was one they discovered just before.
 These were exciting times; Becquerel had shown that uranium could give x-rays, not getting the energy from somewhere else, but actually getting the energy from the uranium itself. Marie showed that the energy was coming from the atoms of the uranium. As this went against everything known about energy transfer at the time, Marie was understnadably cautious that no-one would take her seriously, but at the same time was determined to get it out there as quickly as possible so that no other scientist would get the credit (and the race was on - interest in this field was, excuse the pun, hot).
 Marie was instrumental in inventing a technique that made it easier to seperate the radium from radioactive residues, to pursue possible healing properties. Both the curies worked completely exposed to radium innocent to radiation poisoning, so they had no idea they were damaging their health. This probably had no significant effect on Pierre, who was killed on the 19th April 1906 in a street accident - he was run over by a horse, and fractured his skull. They had been co-rewarded the 1903 nobel prize, and Pierre had been given a proffesorship at the Sorbonne, but unfortunately he hadn't had long to enjoy it.
Marie was devastated, but she continued her work, suffering depression and kidney failure, because she felt that her work was important. In 1910, she finally succeeded in isolating pure radium. However, the radium choloride she and pierre first made together was used as a primitive cancer therapy, which is why she spent her life advocating radium and roadioactivity.
 Back at the turn of the 20th century, radiation was almost magical, but scientifically proven, so people trusted it to have magical properties. It could cure cancer, depression, all kinds of problems; radium 'health' spas popped up. Water impregnated with radium sold by the expensive bottle. An American playboy, Ebers Myers, was advised by his doctor to drink radium water. There were plenty of frauds out there who sold normal water and just kidded on it was radium water, but Ebers was so rich that he could get hold of the real stuff. He died from jaw cancer. Radiation is deeply dangerous stuff. Because it glows in the dark (it produces its own light), radium in the form of paint was used on watches; women in the factories would lick the paintbrush to get a fine line, exposing themselves to radiation. Most of them died from various cancers, but - caught up in litigation - the manufacturers insisted they had syphilis. However, in the investigation it was found that management had taken the precautionary principle and protected themselves from exposure to radon.
However, at no point did Marie ever find out that her lifes work was damaging her. All that stuff was still in the future. She died from aplastic anaemia in 1934, almost certainly brought on by the decades of radiation exposure.She had carried test tubes containing radioactive isotopes in her pocket and stored them in her desk drawer, remarking on the pretty light that the substances gave off in the dark. In fact, her notebooks are still so highly radioactive they are too dangerous for naked hands to handle, and portective clothing must be worn if you want to take them out of the lead-lined boxes.
 Radon is a highly dangerous radioactive material. It has caused suffering. But Maries work was important. Radon was used to treat cancer, and who knows how long otherwise it might have taken for cancer therapies to go down that road, where they would almost certainly have used radon as well. To understand why atoms emit their own radiation spontaneously was an important step in understanding how our universe works. Her discoveries helped build a framework for other discoveries to be made in this field, and others, a faltering and clumsy perpetual drift of science towards the truth.