Radiation from Space (Cosmic Radiation)
On Earth, we are constantly exposed to low levels of radiation. One natural source of radiation is from space. This type of radiation is called cosmic radiation.
What is cosmic radiation?
Cosmic radiation consists of high-energy charged particles, x-rays and gamma rays produced in space. Charged particles react with the earth’s atmosphere to produce secondary radiation which reaches the earth.
Cosmic radiation is produced by the stars, including our own sun.
Another form of radiation that comes from our sun is ultraviolet (UV) radiation. UV radiation is not considered cosmic radiation. Unlike cosmic radiation, UV radiation is lower in energy and is considered non-ionizing radiation.
Radiation dose due to cosmic radiation will vary with altitude. Higher altitudes mean greater exposure to cosmic radiation. Cosmic radiation is more intense in the upper atmosphere and most intense in deep space.
The average annual dose or exposure from cosmic radiation is 0.33 mSv (33 mrem) or 11% of a person’s yearly exposure due to all natural sources of radiation. This yearly amount of radiation is similar to the amount of radiation from three chest x-rays.
|Source of Natural Radiation||Average Annual Dose||Percent of Average Annual Dose|
|Internal (by Inhalation)||2.28 mSv (228 mrem)||73%|
|External (from Cosmic Exposure)||0.33 mSv (33 mrem)||11%|
|Internal (by Ingestion)||0.29 mSv (29 mrem)||9%|
|External (from Terrestrial Exposure)||0.21 mSv (21 mrem)||7%|
Reference: National Council on Radiation Protection and Measurements. NCRP Report No. 160, Ionizing Radiation Exposure of the Population of the United States. https://ncrponline.org/publications/reports/ncrp-report-160/external icon
Cosmic radiation exposes the body to radiation in a manner similar to exposure from a medical X-ray. The average annual dose due to cosmic radiation in the US is 0.34 mSv (34 mrem) per year. This low radiation dose is unlikely to affect human health.