The radioactive decay of other naturally occurring elements produces the radioactive gases radon and thoron.
Space (cosmic radiation) (cosmic radiation).
Biologically produced radioactive minerals Internal (in your body) (in your body). Terrestrial (in the earth) (in the ground).
According to the NRC, the majority of people's main source of man-made radiation is medical imaging. However, as doses vary greatly, your circumstances will determine your yearly dose. Roughly 1.5 mrem is produced by dental X-rays and about 10 mrem by chest X-rays.
If you live in a rural location, it comes from wells, whereas if you live in an urban area, it comes from lakes and rivers where it may take up radiation from the rocks and soil.
Secondhand smoke is the combination of smoke from the burning end of a cigarette and the smoke breathed out by smokers. Secondhand smoke contains more than 7,000 chemicals. Hundreds are toxic and about 70 can cause cancer.
