Civil Engineering Reference
In-Depth Information
4.4.6 Occupational Radiation Exposure
All employees who might receive enhanced radiation doses during their occupation
are subject to radiation protection monitoring. These persons are monitored through
personal dosimeters. The average individual dose of 324,000 monitored employees,
e.g. in Germany was 0.14 mSv/year in 2008. Only 57,000 monitored employees out
of these 324,000 employees received an average individual dose of 0.8 mSv/year in
2008 [
13
].
Aircrews received an average effective dose of at least 2.4 mSv/year from
cosmic radiation during the flight in 2009 [
13
].
4.5 Radiobiological Effects
When ionizing radiation (
α
-,
β
-,
γ
-radiation, neutrons, protons, ions) hits a biological
cell and penetrates it, this gives rise to ionization of the atoms in various molecules
of the cell. This may alter these molecules. Especially alterations (separations) of
the DNA containing the hereditary information produce radiation consequences.
The results may be
- mutation of the cell,
- death of the cell.
Each cell has a high repair potential [
9
,
11
,
15
,
16
]. As a result, most molecular
alterations will have no consequences. However, it may also happen that a mutant
cell is produced which passes its modified genetic function on. A cell changed in
this way may cause carcinoma or leukemia (somatic effect). When the mutation in a
gonad cell is passed on to a descendant, this is called a
genetic
effect.
It is commonly assumed, although not unchallenged [
9
], that there is no radiation
dose threshold for these mutant effects. Under this assumption, the radiation dose/
effect relation begins at the zero point, rises linearly [
5
,
7
], assumes a quadratic
curve shape at higher radiation doses, and then levels off again at very high
radiation doses when cell death occurs.
In the lower radiation dose range, the biological effect of radiation can be
measured only on a statistical basis, and is therefore referred to as a
stochastic
effect. When significant numbers of cells are damaged or die in the higher radiation
dose range, this is called a
deterministic
effect of radiation.
