As we enter this busy holiday travel season it appears that deep vein thrombosis or blood clots are not the only worry on air travelers minds when it comes to health risks. The new concern, that has the media buzzing, is exposure to radiation from the new airport scanners.
By the end of 2011 it's estimated that in airports around the country there will be over 1000 new scanners, which employ very low energy backscatter X-rays. They are used to look under our clothing to check for concealed weapons. In fact these the X-rays are so weak they are intended to bounce off our bodies as opposed to penetrating inside like a diagnostic medical X-ray. In fact they would be useless if they penetrated deep into our bodies.
The stated radiation dose from these scanners is 0.02 microsieverts. A microsievert (μSv)is one millionth of a sievert (Sv), which is a standard international unit of radiation dose. It reflects the biological effect of the radiation. Microsieverts, denoted μSv are the units used to measure the effective dose of radiation in a medical procedure. To give you an idea of the scale of different exposures in medical procedures, a chest X-ray's effective radiation dose is 100 μSv, a mammogram's is 400 μSv and CT scan of the abdomen and pelvis is about 15,000 μSv. This is according to a consumer website (www.radiologyInfo.org) sponsored jointly by the American College of Radiology (ACR) and the Radiological Society of North America (RSNA).
We all experience natural environmental background radiation from both the earth's radioactive materials and the cosmic radiation from the atmosphere. According to ACR and RSNA, it's estimated that on average a person is exposed to about 3000μSv per year. This dose varies depending on where we live. Living at higher altitudes such as Denver exposes you to 1500μSv more per year than if you live at sea level. Radon gas is one of the more common exposures people get from their homes. This also varies depending on where you live, but on average it is about 2000μSv per year. Even a transcontinental flight exposes you to about 30μSv.
The National Council on Radiation Protection and Measurements (NCRP) along with the ACR states that a traveler would require more that 1,000 backscatter scans a year to reach the low dose of a standard chest X-ray. However, just as statistics for prognosis and survival of cancer are really only applicable to populations or groups of patients and are not a good predictor for an individual patient, critics are afraid the converse would apply for these statistics? Meaning it's a numbers game, so while each individual traveler's risk may be minuscule, if you scanned over 700 million travelers a year, would cancers develop in some people?
I posed this question to a colleague and expert, Dr. Barry Daly M.D., professor of Radiology and vice chair for research in the department of Radiology at the University of Maryland School of Medicine. He told me even if you scanned all these travelers and then looked at the population, it is still only a very minimal theoretical risk. And because of the very low dose of penetration of the backscatter scan, any cancer risk would be limited to skin cancers. Other experts have also echoed this, adding that if any skin cancers did develop they would probably be basal cell carcinomas. Incidentally these are the most curable form of skin cancer.
There are other types of scanners on the market that use non-ionizing radiation, radio waves called Millimeter-wave scanners. And while the TSA plans on using both of these types of technologies in scanners, as passengers we probably won't be able to choose which scanner we want to go through at airports.
However, as a physician, it seems somewhat ironic to me that people are voicing these concerns about what is essentially a very tiny dose of radiation. Especially when I see so many patients who don't take action to reduce their known and proven cancer risks. Smoking causes 30 percent of all cancer deaths and about 80-90 precent of lung cancer deaths in the United States. Yet according the Centers for Disease Control and Prevention (CDC) still over one fifth of American adults smoke.
The National Cancer Institute (NCI) estimates that obesity and physical inactivity account for about 30 percent of several major cancers, such as colon, breast, uterine, kidney and esophageal cancer. Despite these statistics, still almost one third of the population qualifies as obese. Looking at just skin cancers, which account for the most common form of cancer in the United States, according to the American Cancer Society (ACS) the fasting rising type of skin cancer is malignant melanoma. So whether it comes from the sun or artificial light, ultraviolet (UV) radiation is a proven carcinogen and this is yet another example of how we don't take precautions to reduce our cancer risks.
With that said, if you are still worried and want to reduce this minuscule added exposure, you do have the choice. Just submit to a pat down, where only your pride, not your skin's DNA would be theoretically jeopardized. But in today's world, we cannot have it all. It is unrealistic to say to TSA, " Don't profile me, don't radiate me, don't touch me but I expect to be completely safe and secure when I fly!" Unfortunately, we are all going to have to compromise a bit or stay home.
Follow Leigh Vinocur, M.D. on Twitter: www.twitter.com/doctor_leigh