People and objects can be shielded from radiation. Alpha radiation can be stopped by a sheet of paper and will not penetrate skin, but it is harmful if ingested or inhaled. Beta radiation can pass through an inch of water or skin, but not through a thin sheet of aluminum, plywood or steel. Gamma rays and neutrons are the most penetrating radiation and can pass through many materials, including the human body. Dense materials like lead or thick concrete must be used to stop gamma rays and neutrons.
Radiation is a natural part of our environment.
The majority of other radiation exposure is from medical sources, such as X-rays.