Airport scanners: Are they a danger to your health?

Even if you didn't have to go to the airport this past Thanksgiving weekend, you probably heard a lot of talk about the new full body scanners used at many security checkpoints. Travelers had questions about what exactly the scanners showed—would the scanners reveal too much of one's anatomy to security agents? Would they cause delays getting through security? And do they expose a person to dangerous amounts of radiation?

For the first two questions, you'll have to check with the Transportation and Security Administration (TSA). But, let's consider how airport scanners (and other sources of radiation) might affect your health. How justified are people's fears about radiation from microwave ovens, X-rays, cell phones, and airport scanners? Where are the real risks of radiation?

What is Radiation?

Radiation is a form of energy that travels as high-speed particles or waves.

Most health concerns have to do with ionizing radiation. This is a type of radiation with enough energy to alter molecules or atomic bonds, or disrupt atoms leading to the formation of charged particles (ions). This may:

• Damage cells and alter their ability to repair the damage normally

• Alter the normal ability of cells to control their growth, which is a key feature of cancer cells. Studies going back to the early 1900s demonstrate that radiation can increase the risk of cancer.

• Cause damage to DNA, leading to dangerous mutations that may be passed on to one's offspring

The most common sources of ionizing radiation are:

• Natural sources (such as cosmic rays from outer space)

• Medical tests or treatments

• Military applications

People in certain occupations, such as uranium miners, nuclear plant workers, or health care workers involved in X-ray tests or radiation treatments, may be exposed to more ionizing radiation than the average person.

Exposure to high levels of ionizing radiation is a clear hazard. It can cause radiation poisoning. Symptoms include nausea, hair loss, skin burns, and organ damage. It can cause death within days to weeks.

Even exposure to low levels of ionizing radiation (such as, over time, having multiple chest x-rays) is a concern, but just how much trouble low-level ionizing radiation causes is not entirely clear.

Radar, microwave ovens, and cell phones produce radiation, but they don't generally create ionizing radiation. Even so, the safety of prolonged exposure to low-level, non-ionizing radiation also remains somewhat controversial. For example, there have been reports that cell phones may cause brain tumors; however, this is far from proven and some of the best studies find no link.

As for airport scanners, there are currently two types in use: those that use non-ionizing radiation and those that use ionizing radiation. Most of the concern has been centered on ionizing radiation (as discussed above). However, the type of scanner used is less important than the total amount of radiation you're exposed to by airport scanners and other sources.

How Much Is Too Much?

It may surprise you to learn that most of us can't avoid radiation exposure. That's because the act of living on earth carries with it some ionizing radiation exposure.

Natural sources of radiation include cosmic rays from outer space, which increase slightly during air travel, and radioactive substances in the soil.

To get some perspective on this, the average person is exposed to 360 millirems (mrem) per year. Most of this comes from natural sources. But it's not uncommon for people to be exposed to much more than that, particularly if they have many medical tests. And, according to some international standards, the upper limit of safe occupational exposure is 5,000 mrems in a single year.

Consider these common radiation exposures:

Source	Amount
Round-trip air travel from New York City to Los Angeles	3 mrem
Chest X-ray	5-10 mrem
Mammogram	70 mrem
Medical tests and natural sources for the average American	200-300 mrem
CT scan	1,000 mrem
Full-body airport scanner	.005 to .025 mrem

Now, compare that to these dangerous amounts:

• 75,000 to 100,000 mrem – the dose that causes symptoms of radiation sickness, including vomiting, diarrhea, mouth soreness, bleeding, weakness and hair loss

• 400,000 mrem – a dose that will kill 50% of those exposed

• 600,000 mrem – a lethal dose after which 100% of those exposed die (as calculated after the atomic bombs were dropped on Japan during World War II)

Given these numbers, the amount provided by airport scanners is considered a drop in the bucket. But, while it's possible that some minimal exposure to radiation may be harmless, there is still no official safe amount of exposure that covers all circumstances. Since it's impossible to avoid all radiation and very difficult to study the health effects of low-level radiation, the best we can do is limit our exposure to well below levels considered dangerous.

I know people who avoid standing near their microwave ovens. That's almost certainly a waste of effort. Unless the oven is malfunctioning or has been modified in some way, modern microwave ovens are remarkably safe and do not emit potentially harmful ionizing radiation. In fact, the biggest danger of a microwave oven is similar to that of other ovens: getting burned if you touch hot or steaming food. Similarly, it's unlikely you are accomplishing much by avoiding airport scanners.

The Cumulative Effects of Low-Level Radiation

The lethal dose of radiation and doses that cause symptoms are well established and well accepted. But that's not true for the repeated effects of low-level radiation over time. For example, it's not clear how much radiation related to medical testing might be harmful. A study in 2007 suggested that the rising popularity of computed tomography (CT) scans could account for up to 2% of cancers. This estimate was based largely on the assumption that small amounts of radiation over time (as with multiple CT scans) may cause a small number of deaths.

But that may be wrong. It's largely unproven whether or not cumulative, low-level radiation is dangerous. As a result, the widely held belief that even the smallest amount of radiation may cause cancer or other ailments may be wrong. This is a controversial subject among people most interested in the health effects of radiation, including doctors, patients, scientists, the Environmental Protection Agency (EPA), industrial producers of radiation, and people who live or work near nuclear power plants.

So what should you do? Anyone exposed to radiation from a medical treatment or a job should weigh the risks of such exposure against the benefits. For example, if a medical test might provide information that will guide lifesaving treatment, the small risk of an X-ray test may be outweighed by the potential benefit. On the other hand, unnecessary exposure should be avoided. We take particular care, for example, to avoid unnecessary or excessive radiation exposure of the testicles or ovaries as it could damage the DNA of a future fetus.

Low-level radiation over a prolonged period of time may — or may not — be as harmful as a one-time higher dose. As for the airport scanners, it would take hundreds or thousands of trips through airport security to equal the amount of natural radiation most of us endure every year. That's why the TSA and other security experts have little concern about the safety of airport scanners.

Radiation as Therapy

Scientific evidence supports the use of radiation to treat certain cancers when used with chemotherapy, surgery, or both. For example, radiation is commonly a part of the treatment plan for prostate and breast cancers. In one long-term study published in 2005, among women with high-risk breast cancers (those whose cancers were most likely to recur), adding radiation therapy to surgery and chemotherapy improved survival by more than 30%.

Can Radiation Be Good for You?

Although it's a controversial, there is at least indirect evidence that low levels of radiation may actually have health benefits. For example, studies suggest that shipyard workers and people who live in western U.S. states — groups with higher than average radiation exposure — have lower cancer rates than people in other states with less exposure. While no one would recommend unnecessary and preventable radiation exposure, these studies call into the question the assumption that radiation is uniformly harmful.

The Bottom Line

The effects of radiation are complicated and there is much that we do not know about them. Too much can certainly cause harm. But excessive fear of radiation is not warranted either. Some cancer patients turn down radiation therapy because of this fear. In these cases, concerns about the harm associated with radiation may be more harmful than radiation itself.

It makes sense to be careful with radiation. But it may not be as bad as you think—and in my view, it's not worth avoiding air travel or even having the new pat-down over concerns about radiation from airport scanners.