Radiation exposure, natural

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In Germany the natural radiation exposure for most of the inhabitants amounts to 1 to 6 mSv/year with an average value of 2.1 mSv/year. External radiation exposure contributes to one third, and internal radiation exposure to two thirds of the effective dose from all natural radiation sources. The dose due to external irradiation comes in nearly equal proportions from cosmic radiation, potassium-40 and nuclides of the uranium and thorium chain. Approximately three quarters of the effective dose due to incorporated radionuclides is made up of radon-222 and radon-220 and in particular their short-lived decay products, followed by potassium-40 and polonium-210.

Exposure by	Annual effective dose in mSv
	External irradiation	Internal irradiation	Total
Cosmic radiation:
at sea level:
ionizing component	0.24		} 0.27
neutrons	0.03
at 1,000 m altitude:
ionizing component	0.32		} 0.4
neutrons	0.08
Cosmogenic radionuclides		0.02	0.02
Primordial radionuclides:
K-40	0.18	0.17	0.35
U-238-chain
U-238 -> Ra-226	} 0.12	0.02	} 1.3
Rn-222 - > Po-214		1.1
Pb-210 -> Po-210		0.05
Th-232-chain:
Th-232 -> Ra-224	}0.14	0.01	0.2
Rn-220 -> Tl-208		0.07
Total	0.7	1.4	2.1

Contributions of various sources of natural radiation exposure in Germany

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