How are people exposed to radiation?

Everyone on the planet is exposed, to slightly different extents, to a background of natural radiation. It arises from naturally occurring radioactive materials in rocks, soils, food and air. Because types of rock vary so too does the level of radiation coming from the ground; exposure thus depends on where you live. There is also an effect from cosmic radiation. Cosmic rays are more intense at higher altitudes so frequent flyers are exposed more. Everyone is also exposed to man-made radiation. The most significant of these artificial sources is medical X- rays. There is also some exposure from industrial practices, such as weld radiography, and discharges from nuclear plants. There are still traces of radioactivity remaining in the environment from nuclear weapons testing.