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. Much of what we know about cancer risks from radiation is based on studies of the survivors of the atomic bombs in Nagasaki and Hiroshima.
For most of these cancers, the risk was highest for those exposed as children, and was lower as the age at exposure increased. Children and adolescents living near the Chernobyl plant at the time of the accident had an increased risk of thyroid cancer linked to exposure to radioactive iodine.
Workers employed in cleanup operations from 1986-1990 had an increased risk of leukemia (all types). These individuals had higher and more prolonged radiation exposures that the population residing around the plant.
Studies suggest that some people who were children during the period of above ground nuclear testing in the US may develop thyroid cancer as a result of exposure to radioactive iodine in milk. Studies of these patients have helped us learn about how radiation affects cancer risk.
Peptic ulcer disease: A large study of people who were treated with high doses of radiation (an average of 15 GY or 15,000 MTV) for the treatment of peptic ulcers found a higher risk of cancer of the stomach and pancreas. Ringworm of the scalp: Studies of people who were treated with radiation to treat a fungal infection of the scalp (called scalp ringworm or Tina wapitis) have found an increased risk of basal cell skin cancers.
The risks of some other cancers, such as breast, liver, kidney, bladder, and other sarcomas, may also have been increased. Children treated with radiation to this area also have an increased risk of thyroid cancer.
The risk of cancer depends on a number of factors, include the dose of radiation, the part of the body being treated, the age of the person getting it (younger people are generally at greater risk), and the use of other treatments such as chemotherapy. Other factors might also play a role in how likely a person exposed to radiation is to develop cancer.
For example, some genetic conditions can mean that a person’s cells are more vulnerable to radiation damage, which might in turn raise their risk more than in someone without these gene changes. Some studies have estimated the risk of radiation exposure from imaging tests based on the risks from similar amounts of radiation exposure in the studies of the atomic bomb survivors.
Based on these studies, the US Food and Drug Administration (FDA) estimates that exposure to 10 MTV from an imaging test would be expected to increase the risk of death from cancer by about 1 chance in 2000. Studies of women who had been imaged many times with fluoroscopy as a teenager or young woman during treatment for tuberculosis have found an increased risk of breast cancer years later.
A study in England of exposure to radiation from CT scans found that children who received a dose of at least 30 may (the same as 30 MTV) to the bone marrow had 3 times the risk of leukemia compared to those who received a dose of 5 may or less. Several agencies (national and international) study different substances in the environment to determine if they can cause cancer.
The American Cancer Society looks to these organizations to evaluate the risks based on evidence from laboratory, animal, and human research studies. Based on animal and human evidence, several expert agencies have evaluated the cancer -causing nature of x -rays and gamma rays.
The National Toxicology Program (NTP) is formed from parts of several US government agencies, including the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA). The US Environmental Protection Agency (EPA) sets limits for exposure to x -rays and gamma rays in part because it recognizes that this form of radiation can cause cancer.
Most of the evidence linking high levels of radiation exposure to cancer comes from studies of specific groups of people, such as those who survived atom bomb blasts in Japan during World War II, survivors of the Chernobyl nuclear accident in the Soviet Union in 1986, and individuals such as uranium miners and nuclear power plant workers whose jobs entail exposure to high amounts of radiation. X -rays are also used in a variety of technologies such as cancer treatment and, at much lower levels, in medical and dental imaging, food irradiation, and airport screenings.
Fluoroscopy, which uses X -rays to make moving images of internal body structures, exposes patients to different amounts of radiation depending on the duration of the test. As a treatment for cancer and other diseases, X -rays and other forms of radiation have a long history, stretching back to the early 20th century, when German and French researchers discovered that X -rays could in some cases shrink or obliterate tumors.
Not long afterward, however, it was found that exposure to X -rays, particularly at high doses for an extended period of time, could also cause cancer. Over the past 100 years the safety of radiation therapy has improved markedly as technologists have devised ways of aiming radiation beams with extreme precision, delivering high doses directly to a tumor while minimizing the amount reaching surrounding tissue.
However, many common imaging tests use very low doses of radiation and pose only a minimal risk when performed properly. X -rays have saved millions of lives by helping doctors diagnose, monitor, and treat many medical conditions.
CT scans create 3-D pictures that allow doctors to view your organs and other tissues. They use higher doses of radiation than most other types of imaging tests, leading to an increased risk of cancer.
Experts agree that while the benefits are worth the risk, CT scans should be ordered only when medically necessary and no other lower-radiation alternatives exist. The effective doses from diagnostic CT scans are estimated to range from 1 to 10 MTV, which is comparable to a few months to several years of background radiation.
Dental professionals also take extra measures to limit the exposure to other parts of your head and neck by using special collars and shields. A dye is consumed or injected before the test to create a more detailed outline of your organs, arteries, and joints.
Protecting children during x -rays As a parent or caregiver, toucan limit the amount of radiation your child is exposed to by: Exposure to X -rays and gamma rays can lead to cancer, but medical imaging procedures have a relatively low risk.
The risk of death from cancer caused by 10 MTV from an imaging test is estimated at 1 chance in 2000. Studies show that radiation exposure from imaging tests, like x -rays or CT scans, is never safe.
Yet, these tests provide valuable information about your health, and allow your physician to make accurate diagnoses. CT's scans were developed in the 1970s and consist of multiple x -rays and thus significantly higher radiation exposure.
When this occurs within the human body, the cell either dies, repairs itself, or mutates incorrectly and can become cancerous. Numerous studies have validated the positive correlation between radiation exposure and cancer risk.
There is no scientifically validated number of x -rays or CT scans that you are granted in your lifetime without risk of harm. But, here’s a very helpful chart that provides details about common imaging tests and their corresponding effective radiation doses.
To optimize your longevity and vitality, we recommend avoiding known carcinogens, including radiation, whenever possible. However, remember it takes almost 40 x -rays or two CT scans to increase your risk of cancer by .05%.
If pregnant and in need of an imaging test, clearly understand the risks and ask if there are ways to protect the developing fetus.