January 7th, 2010
12:19 PM ET

Could airport scanners give too much radiation?

As a feature of CNNhealth.com, our team of expert doctors will answer readers' questions. Here's a question for Dr. Gupta.

From Annette in Washington D.C.:

“I would like to know if the full body screening proposed for all our airports presents any health hazards – more specifically harmful radiation that could lead to long term problems, especially for frequent fliers.”


Annette, you are not alone in your concern about these new scanners. We’ve received many e-mails like yours. So we talked with a radiologist and a physicist whose job it is to make sure people are safe when they’re getting treated with radiation. Those experts say these scans are completely safe.

I should point out that the TSA is using two types of screening machines. One, the millimeter wave imaging machine, uses radio frequency energy to image the body. According to the TSA these deliver 10,000 times less energy than your cell phone. The other type of machine, backscatter X-ray, is what has people talking because these units rely on X-ray technology.

These X-rays are very low level, they bounce radiation off the skin and back to the machine. This is how authorities can scan for dangerous items under someone’s clothes. But this also means the radiation is at very low levels. It's bouncing off the skin, not penetrating it or your organs. This is unlike a medical X-ray which is a higher level radiation penetrating the skin to see bones and other tissue.

Medical professionals working around these levels of radiation are required to wear a badge that measures radiation. Dr. Wayne Olan, director of neuroradiology and MRI at Suburban Hospital Johns Hopkins Medicine sent us a picture of such a badge explaining that he and his co-workers are required to submit their badges every month to ensure they have not been overexposed. He tells us the max whole-body dose of radiation is 5,000 millirem per year. To put these scans in perspective, it would take you 125 thousand trips through these scanners to max out.

In fact, passing through this backscatter X-ray scanner actually exposes you to a hundred times less radiation than a flight from say Boston to Los Angeles. When you fly you are exposed to cosmic rays so the backround radiation is higher at higher altitudes. This is is the same reason people in Denver are exposed to more radiation per year than, say, folks living in Miami, because Denver is at higher altitude.

The American Cancer Society told us that because the radiation levels being reported are low, its experts don’t see this being a serious issue for infrequent travelers.

The bottom line: Every expert we talked to said these were safe even if you're a frequent flier. The radiation just won't add up but the TSA says you do have the option of a pat-down if you're concerned.

About this blog

Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.