Marie Curie doubt, the Curies sought to isolate polonium and radium in pure form. Pitchblende is a complex mineral; the chemical separation of its constituents was an arduous task. The discovery of polonium had been relatively easy; chemically it resembles the element bismuth, and polonium was the only bismuth-like substance in the ore. Radium, however, was more elusive; it is closely related chemically to barium, and pitchblende contains both elements. By 1898 the Curies had obtained traces of radium, but appreciable quantities, uncontaminated with barium, were still beyond reach. The Curies undertook the arduous task of separating out radium salt by differential
Polonium general population is exposed to small amounts of polonium as a radon daughter in indoor air; the isotopes Po and Po are thought to cause the majority of the estimated 15,000–22,000 lung cancer deaths in the US every year that have been attributed to indoor radon. Tobacco smoking causes additional exposure to polonium. The maximum allowable body burden for ingested Po is only , which is equivalent to a particle massing only 6.8 picograms. The maximum permissible workplace concentration of airborne Po is about 10 Bq/m ( µCi/cm). The target organs for polonium in humans are the spleen and liver.