How does radiation interact with matter?
Radiation interacts with stable atoms by knocking off electrons or creating charged particles, called “ions”. There are two basic ways of measuring radiation interactions. The first is to determine how much radioactivity is present (in units of curies or becquerels), which can be used to predict how many interactions will occur. The other is to actually measure how much of that radiation is actually absorbed by a body or item (in units or millisieverts or millirem).
What happens to ions?
Ions can recombine to form the original atom, they can create ions of their own, or they can recombine with other ions to form new compounds. When the second and third interactions occur, other atoms in their vicinity are disturbed. This forms the basis for radiation health effects in humans.
What happens if ionization occurs in living tissue?
In general, one of two things result. First, it can kill a cell. This is known as an acute effect. Second, it can damage a cell. If the damaged cell is repairable, there is no effect. If the damage is non-repairable but the cell function has not changed, there is still no effect. But if the damage causes the cell function to change, that cell is called a mutated cell. Some mutations can lead to cancer.
What happens if a human is exposed to a lot of radiation all at once?
Depending upon the level of exposure, that person will suffer from what is known as Acute Radiation Syndrome. The following is a description of effects versus dose:
For comparison purposes, the maximum an individual is allowed to receive from occupational exposure to ionizing radiation is 5,000 millirem in a year.
What happens if a human is exposed to radiation over a period of time?
While a dose of 300,000 millirem, if it is received all at once, can be fatal, that same dose given over a period of months or years may have no effect at all. This is because the human body has a way of repairing itself from potentially harmful effects of all kinds, not just radiation exposure. It is this important repair mechanism that makes radiation therapy for treatment of certain types of cancers possible.
What are the risks associated with radiation exposure?
Generally speaking, no observable risks or effects are seen from either acute or chronic doses of 25,000 millirem. However, we must use statistics to predict the likelihood of long-term effects, such as cancer. Unfortunately, there are complications, such as natural incidence of cancer and cancer caused by other agents such as smoking, that make these evaluations difficult.
The radiation protection industry, for a number of years, has conservatively assumed that there is some risk associated with any radiation dose, no matter how small. The risk is assumed to increase linearly with dose, meaning the higher the dose, the greater the risk. Based upon these very conservative assumptions, the risk of dying from cancer as a result of a 1,000 millirem radiation dose is 5 in 10,000 or 0.0005.
Is a risk of 0.0005 a large risk?
When compared to the types of risks people incur every day of their lives, that risk is actually quite small. For example, the U. S. Department of Labor gives the following lifetime probabilities of death:
However, one of the fundamental principles of radiation protection is that no radiation dose is acceptable unless there is a corresponding benefit associated with that dose that is at least as large as the risk.
Another guiding principle is that all radiation doses should be kept to the minimum practical level. The process of evaluating possible doses to people to ensure that they are necessary and kept to a minimum is known in the nuclear industry under the title of As Low As Reasonably Achievable (ALARA). Companies that hold licenses to possess and use radioactive sources are required by regulation to conduct ALARA evaluations.
Are there any benefits to radiation exposure?
Yes. The use of radiation has brought tremendous benefits to our everyday lives during the past 50 years. Radioactivity and controlled radiation exposure are used, for example, to sterilize medical supplies, to improve the keeping qualities of foodstuffs, in industrial processes, in medicine, in the study of the environment and pollution, in agriculture, and in hydrology. We even use radiation and radioactivity in our homes, and we depend on many devices that use radiation of one form or another almost on a daily basis. These benefits are largely taken for granted, if they are realized at all.
How is radiation used in medicine?
Medical diagnosis and treatment is the main source of public exposure to man-made radiation, but the benefit in terms of human lives and health is enormous.
Radiation is a major tool in the treatment of certain kinds of cancer. Irradiating tissues affected by a tumor have proven effective in inhibiting the tumor’s growth or in destroying it.
Radioactivity plays an essential part in some diagnostic procedures. Together with imaging devices and computers, radioactivity is used to assess the condition and functioning of various body organs such as the heart, lung, brain, liver and kidney. Without radioactivity, these assessments would be difficult or impossible.
The use of radiation to sterilize medical products, such as surgical dressings, sutures, catheters, spare body parts, syringes, and other important items is a standard procedure. Radiation does not introduce undesirable residues whereas sterilization by chemicals or gases may. Many of these products are difficult to sterilize by heat or steam.