Answers to Frequently Asked Questions
The word “radiation” may conjure up images of the recent Fukushima meltdown, but actually, radiation is all around us. A small amount of what scientists call “background radiation” exists everywhere on the earth, and according to the Nuclear Regulatory Commission (NRC), “Radiation is naturally present in our environment as it has been since the birth of the planet.” However, it was only in the 1890s that scientists discovered radiation, and since then they have developed a wide range of uses for it.
What is radiation? Where does it come from?
According to the International Atomic Energy Agency (IAEA), the term radioactivity describes the disintegration of atoms, which happens when the nuclei of some unstable elements disintegrate and energy is released in the form of radiation. Scientists say that radiation is energy that occurs in the form of waves or beams, which are generally invisible, weightless, odorless, and without positive or negative charges. Some radiation waves, such as light and heat, can be both seen and felt, but others, such as X-rays, can only be detected with instruments designed for that purpose.
Over 100 years ago, scientists discovered that many elements commonly found on earth also occur as atoms in formations called isotopes, some of which are radioactive, that is, they give off energy in several different forms. This emitted energy is what the scientists call radiation.
“In the 1890s, a gentleman name Röntgen developed a tube using an electrical discharge and took a picture of his wife’s hand,” says Dr. James Busch, a radiologist with Diagnostic Radiology Consultants. “He realized he could actually see the bones in her skeleton. From that time forward, radiation was increasingly used for diagnostic purposes in medicine.” Today Röntgen is considered the father of diagnostic radiology.
Are there different kinds of radiation?
There are different things that we call “radiation,” but the type most people are referring to in regards to tissue damage is ionizing radiation, composed of electromagnetic waves or atomic nuclei. This does damage by knocking electrons in atoms off their orbits (ionization).
Non-ionizing radiation is the type that we use and are exposed to every day. Microwave ovens use microwaves to heat food; toasters use infrared waves. Also in this non-ionizing category are visible light, radar, laser, and ultraviolet light.
Some forms of non-ionizing radiation can change tissue if we are exposed to them too much. For example, overexposure to ultraviolet (UV) light from lying out in the sun can cause skin cancer, and even a modest amount can result in skin burns. The strong energy emitted from lasers is useful in medicine for the removal of warts and some skin cancers, and can even break up kidney stones.
How is radiation measured? How much poses a risk?
When measuring a person’s biological risk of suffering health effects from radiation, scientists usually use the SI millisievert (mSv). The millisievert deal with the product of energy absorbed in the human tissues and the quality of radiation that is absorbed, that is, its ability to cause damage.
“Around 6 mSv is what the average person gets per year,” says Dr. Busch. “It’s mainly from radon in the ground. You also get radiation from the sun, so if you live in higher altitudes, you get higher doses. Being at sea level is less of a risk.”
In regards to how much can cause damage, the following categories of exposure have been cited by medical researchers in the New England Journal of Medicine.
- Low: under 3 mSv per year
Moderate: up to 20 mSv per year - High: up 50 mSv per year (this is the annual limit for people working with radiation equipment)
- Very High: more than 50 mSv per year
The various types of radiation can be beneficial or harmful, depending on their use and how they are controlled. Generally, radioactive sources are regulated so that people and the environment can be protected from unwise and unnecessary exposure.
How is radiation used in imaging? What about cancer treatment?
In radiology, the branch of medicine that uses imaging to diagnose and treat diseases, many different techniques utilizing the different types of radiation are used.
X-rays direct radiation through parts of the body where the radiation is absorbed. Different strengths of radiation are used, depending on the part of the body being studied.
Fluoroscopy includes X-rays that employ a contrast, such as iodine, to show images of movement inside the body. The cardiovascular system and the gastrointestinal tract can be viewed through this method.
Computed Axial Tomography, which we know as CAT or CT scan, uses Xrays and computers to create images that show slices of soft and hard body tissue.
Ultrasound uses high frequency sound waves to look at soft tissue in the body. Because this type of radiation uses sound waves, no ionizing or potentially damaging radiation is absorbed into the body.
Magnetic Resonance Imaging (MRI) uses radiofrequency signals in conjunction with strong magnetic fields to produce an image. MRIs do not use any damaging ionizing radiation.
Dual Energy X-ray Absorbtiometry (DEXA) is the kind of imaging usually employed in scanning for osteoporosis.
Positron Emission Tomography (PET scan) injects a radioactive contrast agent into the body. When the injected tracer begins to decay, it sends out positron particles that are picked up by the PET scanner, and reconstructs a 3D image.
Radiotherapy, also called radiation therapy is the medical use of ionizing radiation as part of cancer treatment. Radiotherapy aims to damage the DNA of cancer cells, destroying them or slowing their growth. The treatment is painless, but has its side effects as the body absorbs the ionizing radiation. Common side effects include skin damage, swelling, hair loss, and fatigue.
According to the America Cancer Society, radiotherapy may be more helpful in some cases than others. Some types of cancer are more sensitive to radiation than others and some cancers are in areas that are easier to treat with radiation without causing major side effects. If your doctor recommends radiation treatment, it is because he or she feels that the benefits outweigh possible side effects.
How safe are X-rays? What about CT scans?
Scientists say that the odds of developing cancer from X-rays are quite small, but the more you are exposed, and the younger you are when you are radiated have an impact on the level of risk. “There are certain tissues in the body that are at more at risk of developing cancer from ionizing radiation,” says Dr. Busch. “The thyroid, breast, and lung are the most common. Despite the proven benefit of screening mammograms, this is why they are not routinely recommended until after age 40 to maximize the benefit to risk.”
An estimated 72 million CT scans were performed in the U.S. in 2011. According to the Mayo Clinic, CT scans have a “very small” potential for increasing risk of cancer.
“Medical exposure is usually less than 10 percent of a person’s total exposure to radiation,” says Dr. Busch. “In traditional radiography—like a chest x-ray—the benefit far outweighs the dose because the dose is so small compared to your lifetime dose or annual dose. People that are constantly being scanned can have a long-term increased risk of cancer. But for the vast majority of people, medical imaging poses no threat.”
The Society of Nuclear Medicine asserts that the benefits of medical imaging by far outweigh the risk of radiation.
Can I really get radiation from the microwave? What about my cell phone? The airport scanner?
All electronic devices do generate slight electromagnet fields. However, microwave radiation doesn’t have enough power to damage your DNA. Despite the public’s concerns, the National Research Council reports finding no link between microwave radiation and cancer. Neither does microwave cooking make food radioactive, change its protein structure, or contaminate it in any way.
As of 2010, there were 303 million cell phone users in the U.S. Cell phones emit a form of non-ionizing electromagnetic radiation. According to the National Cancer Institute, the amount of radiofrequency energy a cell phone user is exposed to depends on the technology of the phone, the distance between the phone’s antenna and the user, the extent and type of use, and the user’s distance from cell phone towers. A limited number of studies have shown evidence of statistical association of cell phone use and the risk of resulting brain tumors, but most studies have shown no association. The American Cancer Society (ACS) states that based on evidence from the International Agency for Research, a branch of the World Health Organization, there could be some risk of cell phones being associated with cancer.
However, the ACS says the evidence is not strong enough to show a causal relationship. Those who are concerned, says the ACS, can limit their exposure by wearing an ear piece and limiting their cell phone use, particularly among children.
Do scanners at the airport cause cancer? A New York Times “In Transit” column recently reported that some Transportation Security Administration (TSA) employees believed there was a link. E-mails exchanged between TSA employees’ representatives and the Department of Homeland Security officials raised concerns about airports in Boston and Atlanta, where a growing number of their coworkers had experienced various forms of cancer. The TSA responded that a 2010 test had shown the scanners were safe and that independent third party tests showed emissions well below the applicable limits— in fact, to exceed yearly limits of radiation exposure set by the American National Standards Institute, a passenger would have to be screened about 17,000 times in a 12-month period.
“You do receive radiation from the airport scanners. Nothing even close to a CT scan, but it’s there,” says Busch. “The mythbuster of this is that you receive much more radiation from the subsequent flight in the high altitude than you do from the metal detector on the ground. If you take a flight from Atlanta to L.A. and back, you will get almost half the exposure as a single chest X-ray.”
The use of radiation and nuclear techniques in medicine and other areas has been a boon to society. The medical benefits, in terms of lives saved, have been enormous. Knowledge may not altogether remove our fears, but it should give us a healthy appreciation for the benefits of radiation.
Judith P. Nembhard
Judith P. Nembhard is a Chattanooga resident. She is a graduate of the University of Maryland where she received her Ph.D. in English education. Judith is a member of the Chattanooga Writers Guild and has two sons. Judith is a lifelong educator and a published writer.
