Cosmic radiation is made up of radiation that comes from the sun and from outer space. The Earth’s atmosphere and magnetic field are natural shields and cosmic radiation levels are therefore lower at lower altitudes. The Earth’s population is continually exposed to natural background radiation from soil, rock and building materials as well as from cosmic radiation that reaches the Earth’s surface.
Cosmic radiation is more intense over polar regions than over the equator because of the shape of the Earth’s magnetic field and the “flattening” of the atmosphere over the poles. Although cosmic radiation levels are higher at aircraft cruising altitudes than at sea level, research has not shown any significant health effects for aircraft passengers or crew.