Cancer can be triggered by many different influences, including the penetrating radiation such as x-ray, neutron and alpha-beta-gamma rays emitted by radioactive substances. The biological effects of radiation have been investigated for nearly one hundred years. The first such effect, but steps from cancer, has been observed on Pierre Curie, Marie Curie’s husband. After a strong radioactive source in his pocket watch, he noticed a red spot on her skin, below the source.
The probability of cancer depends on the dose of radiation received. The purpose of this paper is to describe the effects of different doses. The unit of dose is the Sievert (Sv). It is defined in terms of energy deposited in a body penetrating radiation. As a nuclear physicist, I was often exposed to penetrating radiation. Whenever I was wearing a small dosimeter of one type or another. Lower doses are expressed in millisieverts (mSv). The former unit of dose, rem, is still widely used by physicians (1Sv = 100 rem).
People often ask me “How is harmful nuclear radiation? My answer is always the same, “It depends on the dose received.” I develop then, summarized below.
A dose of 10 Sv will likely result in death, a day or two.
SV 5 kill approximately 50% of exposed individuals.
SV 2 can also be fatal, particularly without prompt treatment.
0.25 Sv = 250 mSv is the limit for emergency workers in rescue operations.
0.10 Sv = 100 mSv dose is clearly linked to the risk of cancer later.
0.05 Sv = 50 mSv is the annual limit for radiation workers, like me.
0.004 Sv = 4 mSv is the typical annual dose due to natural radiation (cosmic rays, etc.).
0.003 Sv = 3 mSV is the typical dose for mammography.
Cancer is often treated by x-ray. This sounds like a paradox; The x-rays are the cause of the cancer, how can they be used to heal? Yes, x rays kill living cells and this can lead to cancer. But cancer cells are killed faster than healthy cells. With a properly chosen deal, e.g. 0.5 Sv, a radiologist may kill cells healthy only 20 for each 100 cancer cells. Many of these treatments, for example, a monthly, may give an additional two or three years of life, rather than a single patient or less, with no treatment. A dose of 0.5 Sv would never be prescribed to a person in good health. The doses caused by x-ray diagnostic uses are generally much smaller than those received in therapeutic treatments.
