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X-rays, CT scans, and Bananas - How Much Radiation Is Too Much?

By — One of many Cancer blogs on

I have a lot of tools in my office that I use to help me diagnose and fix medical problems. Some of these tools are simple. I use my reflex hammer to evaluate the nervous system and my stethoscope amplifies sounds that come from within the body. Some tools are more complex, like the EKG for instance, which measures electrical impulses from the heart. It's my job to know how to use these tools properly, when their use is warranted and how to interpret the information gained from their use.

A tool in my office that yields a lot of questions is the X-ray machine. For many, x-rays conjure up visions of spying, violating, dangerous rays that penetrate the body. Too much radiation can be dangerous, and this type of testing must be weighed out in regards to risks and benefits. But we also are exposed to radiation on a daily basis in our day to day lives - medical care, airports, travel, and even through the sun's rays and the food we eat.  

A Quick Primer 

Radiation is a form or energy that is emitted from a body and through space with the ability to be absorbed by another body. Different forms of radiation exist - the most common being electromagnetic and nuclear. 

Nuclear Reactor

Electromagnetic radiation exists as waves of electrical and magnetic energy with radio waves and all forms of light being the most common examples. This type of radiation is ever-present in our daily environment and generally considered harmless in typical doses. 

Nuclear radiation occurs when atoms break down and emit particles. Ionizing radiation is the most common process and can damage bodies that absorb the radiation energy, such as our body's DNA. The energy produced in this breakdown is also harnessed for energy (nuclear reactors) and destruction (nuclear bombs). Radiation exposure is measured in millirems (mrems) and is considered additive. In other words, radiation from different exposures compound in their effects on our bodies over our lifetimes.

Ionizing Radiation

Ionizing radiation can help or hurt depending on various factors. It passes through the body altered by different structures and is used to develop images in the medical and security fields. Higher doses are used to kill cancer, but exposure to healthy tissue can cause destruction or mutations, which actually lead to cancer. Young organisms (children, infants, and fetuses), along with other rapidly reproducing tissues, are more susceptible to potentially damaging radiation. The question raised when it comes to our bodies is, "How much is too much?" 

Airport Security

In this post-9/11 era, few would argue the need for airport security. Still, people who travel frequently should probably consider the risk that comes with radiation exposure.

Airport Security

Two types of scanners exist in airports: backscatter scanners and millimeter wave scanners. While backscatter scanners use ionizing radiation, the newer millimeter wave scanners use harmless electromagnetic radiation. Most all backscatter radiation exposure occurs to the skin, and the amount is miniscule, (0.002 mrems). To put things in perspective, the exposure from flying at higher altitudes is about 0.5 mrems per hour. (Roughly the same radiation exposure as eating a banana.) Still, with millimeter scanners available, backscatter scanners are phasing out. In fact, the Transportation and Safety Administration (TSA) set the goal that it would have backscatter scanners out of America's airports by June of this year. The bottom line: Don't worry about airport security as a source of harmful radiation.


X-ray testing uses ionizing radiation, passed through tissue of the body to examine internal structures. This test is vital in achieving accurate diagnoses with broken bones and pneumonia, and annual mammograms in women over the age of 50 have been shown to save lives by detecting tumors early.

Still, the ionizing radiation does pose some degree of risk. A chest x-ray exposes the body to 10 mrem of radiation, while a mammogram gives 42 mrem. Putting things in perspective, a mammogram is about the same amount of radiation that we typically get from our diet in a year. It's not a lot, but it is something, so the need for testing should be weighed out. More caution should be taken in x-raying children, and pregnant women should not be x-rayed. Rapidly turning over cells like those in the testes and thyroid gland should be shielded from the x-ray when possible.

Other Radiology Testing

CT scans (or computer-aided tomography) utilize a lot of ionizing radiation relatively speaking. A CT of the abdomen, for instance, exposes the body to 1000 mrem - about three times the body's average radiation exposure in a year from various sources. MRI and ultrasound, on the other hand, don't utilize ionizing radiation to produce images and therefore don't pose any radiation risk. Because of the higher degree of radiation exposure, risks and benefits should be weighed in considering a CT scan. And like with x-ray, special consideration should be given to certain tissue exposure and the very young.

Radiation Therapy

Radiation Therapy

Radiation therapy is primarily used to treat certain types of cancer. Cancer cells are often duplicating and growing rapidly. As such, they are more susceptible to destruction by radiation. Simply put, ionizing radiation kills cancer cells faster than it kills the healthy cells around the tumor. Given the severity of cancer, the risk to benefit considerations of radiation therapy are a bit more weighty than those regarding an x-ray or CT scan. The specific focus and amount of radiation is precisely calculated. After radiation treatment, patients are watched more closely for the development of other complications in the area of exposure, such as a different cancer or damage to the healthy tissue. 

Other Sources

As started before, radiation hits our body from a number of different sources.  The American Nuclear Society reports the following as common sources:

In Conclusion

Radiation is all around us. It helps us, but it can also harm our bodies and environment. Because any ionizing radiation has the potential for harm in the body, it's impossible to set a universally safe level. When it comes to radiation, it's important to weigh risks and benefits, especially with higher degrees of potential exposure. You can calculate your yearly estimated radiation exposure by visiting the American Nuclear Society.

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