<P> About 100,000 Bq / m (2.7 nCi / L) was measured in Stanley Watras's basement . </P> <Tr> <Td> 1,000,000 </Td> <Td> 27000 </Td> <Td> Concentrations reaching 1,000,000 Bq / m can be found in unventilated uranium mines . </Td> </Tr> <Tr> <Td> 5.54 × 10 </Td> <Td> ~ 1.5 × 10 </Td> <Td> Theoretical upper limit: Radon gas (Rn) at 100% concentration (1 atmosphere, 0 ° C); 1.538 × 10 curies / gram; 5.54 × 10 Bq / m . </Td> </Tr> <P> An early - 20th - century form of quackery was the treatment of maladies in a radiotorium . It was a small, sealed room for patients to be exposed to radon for its "medicinal effects". The carcinogenic nature of radon due to its ionizing radiation became apparent later on . Radon's molecule - damaging radioactivity has been used to kill cancerous cells, but it does not increase the health of healthy cells . The ionizing radiation causes the formation of free radicals, which results in genetic and other cell damage, resulting in increased rates of illness, including cancer . </P>

Radon is used as a tracer in medical research because it