Natural radiation in Germany

From the beginning, humankind lives in a radiating environment owing to the natural sources of radiation.

Thus natural radiation exposure leads to an annual effective dose for a member of the public in Germany of 2.1 millisieverts on average. Depending on the place of residence, dietary and life habits, it sometimes adds up from 1 millisievert to 10 millisieverts.

Incorporation of natural radioactive substances by inhalation or ingestion

Natural radiation exposure is composed of a dominant internal and an external component.

Via air and nutrition, human beings have always absorbed natural radioactive substances:

• The inhalation of the radioactive gas radon and its decay products results in an average annual dose of 1.1 millisieverts.
• Natural radionuclides of the radioactive decay chains of thorium and uranium as well as potassium-40 and carbon-14 are taken up via food, which adds on average 0.3 millisievert annually.

External exposure by cosmic radiation and terrestrial radiation

External radiation exposure represents about one third of the total natural radiation exposure - resulting in an annual dose of approximately 0.7 millisievert.

Cosmic radiation

About half of it is due to cosmic radiation, which reaches the earth from the deep space and mainly consists of high-energy particles. On its way through the atmosphere to the ground cosmic radiation is partially absorbed owing to nuclear reactions with the atomic nuclei of the air molecules.

Therefore, its intensity depends on the altitude. It is lowest at sea level and increases with the altitude of a site. On the Zugspitze, Germany's highest mountain, it is four times higher than on the coast.

Terrestrial radiation

Terrestrial radiation is also part of external radiation exposure. It originates from natural radioactive substances existing in the soils and rock layers of the earth's crust in regional different concentrations.

Rocks and soils again are important raw materials for mineral building materials. The radionuclides contained therein pass over to the building materials such as bricks and concrete and thus also contribute to the external radiation exposure for people living in dwellings. On average, the terrestrial radiation adds up to an annual dose of 0.4 millisievert for members of the public, around 0.1 millisievert outdoor and 0.3 millisievert indoor.

Medical and technical applications

In addition to natural radioactivity, humans are also affected by radiation from medical and technical applications, especially from X-ray diagnostics. The resulting average radiation exposure in Germany is about 1.5 millisieverts per year.