Post by Joe Neubarth on Dec 31, 2011 13:47:25 GMT -5
Ionizing radiation has enough energy to knock electrons off of atoms or molecules, thus creating ions. This is called ionization. Ionized molecules are unstable and quickly undergo chemical changes, which, if you have had high school Chemistry involves in the grabbing or giving up of electrons. Take an electron away from a molecule of water and you end up with two ions H and OH. One is positive and the other negative and both can cause further damage to tissue by breaking other molecular bonds such as in a DNA strand.
I often tell people that when radiation hits a DNA strand, three things can happen:
1. The cell can repair the damage correctly and go on doing what it is supposed to do.
2. The cell can die. Other cells will grow in its place and everything will be fine.
3. The cell can repair the DNA incorrectly, thus resulting in a living cell that does not understand what it is supposed to do. Once that cell starts replicating, you have cancer.
Thus, if ionizing radiation passes through a cell in the body, it can lead to mutations (changes) in the cell's DNA, (The important part of the cell that contains its genes (blueprints for what the cell is supposed to do in the body). The amount of overall damage in the cell is related to the dose of radiation it receives; yet, serious damage to a DNA strand can be the result of just one X-ray or Cosmic ray or Gamma ray striking that strand. The damage takes place in only a fraction of a second, but other changes such as the growth of cancer may take ten to twenty years to develop.
Types of ionizing radiation include x-rays, gamma rays, some high-energy UV rays, and particles given off by radioactive materials such as alpha particles and protons. These forms of radiation have different energy levels and can penetrate cells to different extents, but all are capable of causing ionization.
Does ionizing radiation cause cancer?
Ionizing radiation is a “proven human carcinogen” (cancer causing agent). The evidence for this comes from many different sources, including studies of atomic bomb survivors in Japan, people exposed during the Chernobyl nuclear accident, people treated with high doses of radiation for cancer and other conditions, and people exposed to high levels of radiation at work, such as uranium miners. When X-ray machines were first sold to dentists to help them diagnose problems their patients had, there were no cautionary instructions issued with the machines. Within a dozen years thousands of dentists lost their fingers and hands to aggressive cancers that were caused because the dentists were holding the negatives for the X-rays. Just because they were smart enough to be doctors does not mean that they had the education to know what damage X-rays could do to living tissue.
There have been hundreds of studies of cause and effect between radiation and ensuing cancer growth. Most studies on radiation and cancer risk have looked at people exposed to very high doses of radiation in the situations mentioned above.
It is harder to measure the much smaller increase in cancer risk that might come from much lower levels of radiation exposure. Most studies have not been able to detect an increased risk of cancer among people exposed to low levels of radiation. For example, people living at high altitudes, who are exposed to more natural background radiation from cosmic rays than people living at sea level, do not have noticeably higher cancer rates. Higher cancer rates have been documented, but are dependent upon the nature of the study.
Still, most scientists and regulatory agencies agree that even small doses of ionizing radiation increase cancer risk, although by a very small amount. In general, the risk of cancer from radiation exposure increases as the dose of radiation increases. Likewise, the lower the exposure is, the smaller the increase in risk. But there is no threshold below which ionizing radiation is thought to be totally safe.
Although radiation exposure affects the occurrence of various types of cancer, it does not affect their aggressiveness (tendency to grow and spread).
Types of cancer linked to ionizing radiation
Ionizing radiation increases the risk of certain types of cancer more than others.
The thyroid gland and bone marrow are particularly sensitive to radiation. Leukemia, a type of cancer that arises in the bone marrow, is the most common radiation-induced cancer. Leukemias may appear as early as a few years after radiation exposure.
Other types of cancer can also result from radiation exposure, although they may take longer to develop (usually at least 10 to 15 years).
Some of the other cancers most strongly linked to radiation exposure in studies include:
• Lung cancer
• Skin cancer
• Thyroid cancer
• Multiple myeloma
• Breast cancer
• Stomach cancer
These are not necessarily the only cancer types that may be linked to radiation, however.
The types of cancer linked to radiation are also affected by the part of the body that is exposed. For example, people who get pelvic radiation therapy would not be expected to have higher rates of cancers in the head and neck because these areas weren't exposed to radiation.
Other factors may also play a role in how likely a person exposed to radiation is to develop cancer. Age is one such factor - children's growing bodies are more sensitive to radiation than adults. A person may also have gene changes that make their cells more vulnerable to radiation damage, which might in turn raise their risk more than in someone without these gene changes.
Sources of ionizing radiation
People may be exposed to ionizing radiation from 3 main sources:
• Natural background radiation comes from cosmic rays from our solar system and radioactive elements normally present in the soil. This is the major contributor to worldwide radiation exposure.
• Medical radiation comes in the form of diagnostic x-rays and other tests, as well as from radiation therapy. Radiation therapy is currently used to treat some types of cancer and involves dosages many thousand times higher than those used in diagnostic x-rays.
• Non-medical, man-made radiation can come from workplace and other sources, and is also a result of above ground nuclear weapons testing that took place before 1962.
Natural background radiation
We are all exposed to some amount of radiation just from being on this planet. This is known as background radiation. For most people, background radiation accounts for most of their exposure to ionizing radiation during the year. It comes from several different sources.
Cosmic rays: Cosmic rays are radioactive particles that hit the earth from outer space. They come from the sun and from other stars. The earth's atmosphere blocks a portion of these rays, but some of them reach the ground. Because the atmosphere blocks some cosmic rays, exposure is greater at higher altitudes. For example, people who live in Denver, Colorado, which is at a high elevation, are exposed to slightly more cosmic rays than people living at sea level.
People are also exposed to higher levels of cosmic rays during airplane flights. Airline pilots and flight attendants, who spend many hours at high elevations, are exposed to more of these rays, but it is not clear if they have an increased risk of cancer because of it.
Radiation in the earth: People are also exposed to small amounts of radiation from radioactive elements that occur naturally in rocks and soil. Some of these may end up in building materials used in houses and other structures. Tiny amounts of radiation may even be found in drinking water and in some plant-based foods as a result of being in contact with the soil. For people who smoke, tobacco can account for a significant portion of the yearly radiation they receive.
Radon: The largest source of natural background radiation for most people is radon. This is an odorless, colorless gas that is formed from the breakdown of radioactive elements in the ground. Radon levels are usually higher inside buildings and homes, especially in levels closer to the ground such as basements. Radon levels can vary a great deal, depending on where you live.
Medical radiation
Ionizing radiation is used in the diagnosis and treatment of some medical conditions. This can be in the form of radiation that penetrates from outside the body, or radioactive particles that are swallowed, injcted or inserted into the body.
Imaging tests: Modern imaging tests, such as x-rays, CT scans, and nuclear medicine tests (such as PET scans and bone scans) expose people to moderate levels of radiation in order to create internal pictures of the body.
The verifiable risk of cancer from exposure to any single radiological medical test is likely to be fairly small. Still, just concerns have been raised in recent years as the average amount of radiation a person is exposed to from medical tests has risen. The rapidly growing bodies of children are especially sensitive to radiation and they are very prone to certain childhood cancers. It is best to keep your children away from radiation exposure above background. It is also best to ensure that their background radiation is kept to a minimum as well.
Because of the very small but real risk, and the fact that radiation exposure from all sources can add up over one's lifetime, imaging tests that use radiation should only be done if there is a good medical reason to do so. The usefulness of the test must always be balanced against the possible risks from exposure to the radiation. In some cases, other imaging tests such as ultrasound or MRI may be an option. But if there is a reason to believe that an x-ray or CT scan is the best way to look for cancer or other diseases, the patient will most likely be helped more than the small dose of radiation can hurt.
Radiation therapy: Ionizing radiation is an effective way to treat certain kinds of cancer. During radiation therapy, high doses of ionizing radiation (much higher than those used for imaging tests) are directed at the cancer, resulting in the death of the cancer cells. I caution everybody that this can lead to DNA mutations in other cells that survive the radiation, which may eventually lead to the development of additional cancer or cancers.
Overall, radiation therapy alone does not appear to be a very strong cause of second cancers. This is probably due to the fact that doctors try to focus the radiation on the cancer cells as much as possible, which means few normal cells are exposed to radiation. Still, some studies have linked radiation therapy with an increased risk of leukemia, thyroid cancer, early-onset breast cancer, and some other cancers. The amount of increased risk depends on a number of factors, include the dose of radiation, the location in the body, and the age of the person getting it. Since they have longer to live, younger patients are generally at greatly increased risk later on in their medically troubled lives.
If spot cancer growth does develop after radiation therapy, it seldom happens right away. For leukemia, most cases develop within 5 to 9 years after exposure. In contrast, other cancers usually take much longer to develop. Most of these cancers are not seen for over 10 years after radiation therapy, and some are diagnosed even more than 15 years later. This awareness strikes home one major issue, and sadly, that is the ensuing cancer that develops from therapy can never be traced back to the therapy.
The medical profession loudly ballyhoos using radiation to kill cancer cells. They definitely understand that radiation causes cell death and damage. When considering radiation exposure from radiation therapy treatment, the physicians will tell you that the positive benefits generally outweigh the risks. However, some combinations of radiation therapy and chemotherapy are more risky than others.
The treating physicians pretend to do their best to ensure the treatment that is given destroys the cancer. They will tell you that they are minimizing the risk that a secondary cancer will develop later on. Bolshoi! Secondary cancers do develop with regularity, but generally the initial medical problem is what kills you.
Other forms of man-made radiation
People may also be exposed to ionizing radiation from other man-made sources.
Nuclear tests and facilities: The United States government conducted above-ground nuclear tests in the South Pacific and in the state of Nevada between 1945 and 1962. Many people in the military at the time were part of training exercises in the area and were exposed to ionizing radiation from these tests. Others were exposed to radiation while working at facilities making the bombs or at other nuclear sites.
Non-military people by the millions who were living near or downwind of nuclear test sites have also been exposed to radioactive fission byproducts. Levels of radiation are likely to be far higher closer to the sites, but some radioactive particles from the tests entered the higher atmosphere and traveled great distances (even circumnavigating the globe), landing thousands of miles away from the original site.
While exposure levels were likely to be higher at the time of testing, some radiation in the soil today is the result of these tests. Over time, the radiation has been mixed with the surface soil and there is no noticeable radiation detection above what could be considered normal background radiation. (Normal? That can be up to ten times higher in some areas than others. In other words normal isn’t.) Yet, the particulate is still there ready to be absorbed as food where it damages the body with internal radiation. You do not want to eat farm produce from fallout contaminated areas, yet, our government tells us it is OK as long as it does not exceed limits. There is no limit below which ionizing radiation is safe. Eat radioactive food at your own peril, but feed it to your children only if you know it is safe.
The EPA consistently lies to you and will tell you that, “Workers in nuclear power plants may be exposed to higher levels of radiation than the general public, although their exposure levels are monitored carefully. Emissions of radiation from nuclear power plants are carefully monitored and controlled.” The (EPA) goes on to claim that, “Nuclear power plant operations account for less than one-hundredth (1/100) of a percent of the average American's total radiation exposure.” That is totally untrue. That is such a bold faced lie as to make the American EPA the laughing stock of the world.
Consumer products: Some consumer products contain small amounts of ionizing radiation. For example, tobacco products contain low levels of radiation, which may come from the soil it's grown in or the fertilizer used to help it grow. Tobacco accounts for a significant portion of the yearly radiation that smokers are exposed to and is the major cause of lung cancer.
According to the EPA, some building materials used in the home or other structures may contain low levels of naturally occurring radiation. This will vary depending on what they're made of. The EPA will tell you that the levels are unlikely to contribute much to a person's overall exposure to radiation. That is one of their deliberately misleading statements (Obfuscation) used to confuse the public into thinking that it does not increase their risk to cancer. It does, and can kill you, and people need to be made aware of that fact.