Radon is a "naturally occurring gas" which is found in most soils and rocks and also can cause "lung cancer".
<u>EXPLANATION:</u>
Radon is a "chemical element" which is found to be tasteless, odorless, colorless, and highly radioactive. Due to the radioactive nature of radon, it is very dangerous and causes lung cancer.
Apart from the soils and rocks, the residues of radon could be found on petroleum, spring water and hot springs.