by Leif Kullman
More about radiation physics matters
Mankind has been exposed to radiation from time out of mind, it is a part of our natural background. In spite of this fact it is important to keep the annual medical and dental diagnostic doses as low as reasonable achievable (ALARA-principle). The last words are one of the main principles in radiation protection work, stated by ICRP (the International Commission of Radiological Protection).
Let us look at the different sources of ionizing
radiation in the enviroment for an average individual (see figure) in Sweden.
The different sources according to the figure can be described in more detail:
Natural background radiation (~20%): These are among others
- Cosmic rays
- From the earth´s crust, external
- From certain foodstuffs, internal
Other radiological sources: About 1 percent: These are
- Fallout from nuclear explosions
- Prospective occupational exposure
Radon in our housing is an important background factor: It contributes in Sweden to about 64% of the total radiation.
Radon is a decay product of uranium, which is present in granite. The gas diffuses from the rocks and can be trapped in poorly ventilated houses, which are built on large granite deposits. The gas is breathed into the lungs and gets caught there.
Medical diagnostic radiation: Only a small amount of this source, a couple of percent of the total amount, comes from dental radiography.
We can therefore conclude that radon and its decay products are the great culprits in radiation safety matters. We, in the dental profession, only contribute with a very, very small part of the total sum of the radiation burden in mankind. In spite of this fact we must contribute with our share for the health of mankind and never forget the ALARA-principle.
