It's a colorless gas produced by the decay of uranium andof the most common forms of background radiation comes from radon. Radon occurs in places where there's a lot of uranium in the underlying rock. Radon collects in buildings, and the Environmental Protection Agency calls it the second-largest cause of lung cancer in the United States. X-rays are used in medical imaging and mammography. Many isotopes are used to track the movement of molecules in scientific research.
Nuclear decay produces heat to drive turbines in nuclear power stations and ships.
The decay of radioactive carbon is used to date archeological sites. Gamma radiation can sterilize food and medical equipment. And that's just a sampling. Ionizing radiation breaks apart atoms and molecules, causing many types of damage to living organisms, depending on the type of radiation, the target organ, and the intensity and duration of the exposure. Depends on who you ask.