Natural radiation in the environment comes from two sources: cosmic rays and radiation present in the earth crust. Cosmic rays have already been discussed in 'Air Travel and Cosmic Radiation' of the column 'Radiation Tidbits' in e-Bulletin on Educational Resources. This article focuses on radiation present in the earth crust.

Naturally-occurring radiation has been part of the earth since the latter came into existence. Such primordial radiation existing in the earth crust diffuses slowly into air, water and the body of living organisms (animals and plants). As it cannot be felt or sensed by human beings, it was not until about a hundred years ago when scientists began to invent measuring instruments and discovered the existence of radiation.

Written by: Yeung Siu-wai

Naturally-occurring radiation exists everywhere in nature

(2)     What are the factors affecting the radiation level in soil ?

(3)     How does natural radiation enter our body through the biosphere ?

(4)     Where does the radiation in human body come from ?

(5)     Where does the radiation in air come from ?

(6)     Where does the indoor radon come from ?

(7)     How does radon affect the human body ?

(8)     How can the damage of radon to human beings be reduced ?

(9)     What is the natural radiation level in Hong Kong ? Is it safe ?
          How does it compare with other places in the world ?

(10)   Where can I get more information on radiation ?

References

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