Here's why:

* Naturally Occurring: Radon is a naturally occurring radioactive gas that is formed by the radioactive decay of uranium and thorium, which are found in rocks and soil.

* Underground Formation: Radon is typically found underground, where it can accumulate in higher concentrations.

* Gas: Radon is a gas, meaning it can easily move through the air and enter homes and buildings.

It's important to note that radon is a health hazard as it can cause lung cancer. Regular testing and mitigation strategies are important in areas where radon levels are elevated.