Amidst protests and rallies over airport security procedures, what's often overlooked is that flying itself dwarfs the radiation doses delivered by the new body scanners.
"Most people are unaware about the fact that there is significant radiation exposure associated with air travel because they are well above the Earth's atmosphere," said Robert J. Barish, a radiological and health physicist in New York City. "You'd get as much radiation in a whole-body scanner as you'd get in two minutes at 30,000 feet."
For casual flyers, there probably isn't much to worry about, Barish said. But flying raises real risks for pilots, flight attendants, and the half a million business travelers who spend much of their time in the air.
Most of the time, companies fail to tell employees about the radiation risks their jobs entail, and Barish can easily imagine a day when a high-profile traveler gets cancer and decides to sue his employer for putting him at risk without warning.
In a new paper, soon to be published in the Employee Responsibilities and Rights Journal, Barish argues that airplane personnel should be classified as "radiation workers." And with that designation, they should be educated and monitored appropriately, much like doctors who routinely deliver X-rays and cancer treatments.
"If you are a business frequent flyer who travels more than 85,000 miles a year on typical cross-country, international-type routes, your exposure goes above the limits that you would be allowed if those exposures came from any kind of medical, industrial, nuclear or other sources here on the planet," Barish said. "It takes only seven trips from New York to Tokyo to exceed the general public limits."
Cosmic radiation comes from our sun and other stars in the form of particles, such as protons, and electromagnetic waves, such as X-rays. These energetic rays stream through our bodies all the time, though Earth's atmosphere deflects most of them before they reach us.
The higher you go in altitude, from say New York to Denver, the less atmosphere there is to protect you, and the more radiation hits you. In an airplane, according to Barish's new paper, exposure levels are several hundred times higher than they are on the ground.
Health concerns arise because cosmic radiation is a form of ionizing radiation, which means it can knock electrons off of atoms in our bodies. Enough exposure leads to the tissue harm and genetic damage that cause cancers and other problems.
Whether frequent flyers actually suffer more radiation-driven bodily harm than homebodies do is still unknown. There is evidence that female flight attendants have higher rates of breast cancer than the rest of the population, but there are other good explanations for the phenomenon. Constantly crossing time zones, for example, throws off melatonin, serotonin and other hormonal systems, which are known to play roles in causing some cancers.
In fact, pilots actually have lower rates of cancer than other groups, Barish said, probably because they have mandatory and regular check-ups, increasing the chances that health problems will be caught early. This so-called healthy worker effect could mask some of the radiation dangers they face.
As our sun enters a new phase of activity in its 11-year-or-so cycle, the risks of flying may be rising. Solar storms throw out as much as 20 percent more cosmic radiation than a less active sun does, Barish said, meaning that travelers on a poorly timed flight could get exposed to far more radiation than they banked on.
"During a solar flare event, one flight can give you as much exposure as several flights," Barish said, adding that solar storms have previously caused flights to be diverted from the poles, where the Earth's magnetic field diverts most of the sun's radiation. "There are not that many every year, but if you're just unlucky, you can end up in them."
When it comes to backscatter scanners, the technology is so new that it's fair to keep asking questions about their safety, especially for groups like pilots who are already getting exposed to a lot of radiation in their jobs, said medical physicist James Hevezi, chair of the American College of Radiation Medical Physics Commission.
So far, he said, the scanners seem to be on par with other low-energy medical devices that have been shown to have negligible health effects. Unlike X-ray machines in doctor's offices that penetrate the entire body, the scanners use just enough radiation to get through a person's clothes and bounce off the skin.
"It's worthwhile to discuss this and maybe worry about it in the small sense of trying to figure out where the scanners stand compared to other sources of radiation," Hevezi said. "But the data shows them to be pretty safe, at least right now."