Radium and radon are important contributors to environmental radioactivity. Radon occurs naturally as a result of decay of radioactive elements in soil and it can accumulate in houses built on areas where such decay occurs. Radon is a major cause of cancer; it is estimated to contribute to ~2% of all cancer related deaths in Europe. Radium, like radon, is radioactive and is found in small quantities in nature and is hazardous to life if radiation exceeds 20-50 mSv/year. Radium is a decay product of uranium and thorium. Radium may also be released into the environment by human activity, for example, in improperly discarded products painted with radioluminescent paint. Radium In the oil and gas industries Residues from the oil and gas industry often contain radium and its daughters. The sulfate scale from an oil well can be very radium rich. The water inside an oil field is often very rich in strontium, barium and radium while seawater is very rich in sulfate so if water from an oil well is discharged into the sea or mixed with seawater the radium is likely to be brought out of solution by the barium/strontium sulfate which acts as a carrier precipitate. Radioluminescent (glow in the dark) products Local contamination from radium-based radioluminescent paints having been improperly disposed of is not unknown. In radioactive quackery Eben Byers was a wealthy American socialite whose death in 1932 from using a radioactive quackery product called Radithor is a prominent example of a death caused by radium. Radithor contained ~1 μCi (40 kBq) of 226Ra and 1 μCi of 228Ra per bottle. Radithor was taken by mouth and radium, being a calcium mimic, has a very long biological halflife in bone. Radon Most of the dose is due to the decay of the polonium (218Po) and lead (214Pb) daughters of 222Rn. By controlling exposure to the daughters the radioactive dose to the skin and lungs can be reduced by at least 90%. This can be done by wearing a dust mask, and wearing a suit to cover the entire body. Note that exposure to smoke at the same time as radon and radon daughters will increase the harmful effect of the radon. In uranium miners radon has been found to be more carcinogenic in smokers than in non-smokers. Occurrence Radon concentration in open air varies between 1 and 100 Bq m−3. Radon can be found in