We're constantly exposed to very low levels of radiation - and all without us noticing
Background radiation comes from many sources:
1. Radioactivity of naturally occurring unstable isotopes which are all around us - in the air, in food, in building materials and in the rocks under our feet
2. Radiation from space which is known as cosmic rays. These mostly come from the Sun. Luckily the earth's atmosphere protects us from much of this radiation The earth's magnetic field also deflects cosmic rays away from Earth.
4. Radiation due to human activity e.g. fallout from nuclear explosions or dumped nuclear waste. But this represents a tiny proportion of the total background radiation.
Level of Background Radiation depends where you ar
1. At high altitudes (e.g. in jet planes) it increases because of more exposure to cosmic rays. That means commercial pilots have an increased risk of getting some types of cancer.
2. Underground in mines it increases because of all the rocks around.
3. Certain underground rocks (e.g. granite) can cause higher levels at the surface especially if they release radioactive radon gas which tends to get trapped inside people's houses.