Flying and Excess Radiation
The doses of radiation experienced in everyday life, especially flying long distances in jet aircraft, pose risks we should carefully heed.
In the aftermath of the foiled "underwear bomber" attack on Christmas Day, there's a major push to install whole-body X-ray scanning machines at airport screening areas.
The effort is being led by former Homeland Security Chief Michael Chertoff, now a paid consultant for a manufacturer of these X-ray machines. He's calling for their "large-scale deployment." Estimated to cost $3 billion over the next eight years, the Homeland Security department plans to have 1,800 scanners in place at U.S. airports by 2014.
In a Washington Post op-ed on New Year's Day, Chertoff dismissed objections raised about these devices. "The 'safety' concern'" he claimed "is particularly specious, because the technologies expose people to no more radiation than is experienced in daily life."
Not quite. Whole body X-ray scanning machines were developed and first used to detect theft at gold and diamond mines on and inside the bodies of workers in Africa. They are fluoroscopic X-ray machines that provide a real time image of a person's body using "back-scatter" or "soft" X-rays. They emit much less penetrating energy than machines found in a medical setting, such as CAT scanners. However, like all machines, if their design, manufacture, calibration, maintenance are defective, then doses to passengers and security staff could be larger than claimed. The recent reporting of dozens of cases of harm to patients from the misuse of CAT scans should serve as a cautionary warning.
Unfortunately, the doses of radiation experienced in everyday life, especially flying long distances in jet aircraft, pose risks we should also carefully heed.
The earth's atmosphere is a massive shield protecting life on earth from cosmic radiation. At sea level, this atmospheric radiation shield is roughly equivalent to a wall of water about 33' thick. With the rise in altitude, atmospheric shielding decreases and radiation doses increase. At 30,000 feet above sea level, radiation doses increase by 90 times. Solar flares can increase doses by a factor of 100 above that. For this reason, flight crews, are considered by the United Nation's Scientific Committee on the Effects of Atomic Radiation as radiation workers who, because of exposure to cosmic radiation, are the most highly exposed group in the world.
According to UN data, in 2000, air crews made up about 3 percent of the radiation workers in the world, but received about 24 percent of the total collective dose for all exposed workers, which include people employed at uranium mines, nuclear weapons sites, and nuclear power plants. The average estimated annual dose to flight personnel, and frequent international flyers such as professional couriers, is about 2.5 times higher than the combined average for all radiation workers.
Aircrew and frequent long-distance passengers are chronically exposed to more biologically damaging forms of radiation, such as neutrons, than the majority of nuclear workers.
Women who are pregnant have a heightened risk of cancer to their embryos. During the early part of the first trimester, when radiation sensitivity is the highest, some women may not know they are pregnant. This is why European airlines ground pregnant aircrew to prevent overexposure.
Over the past decade, at least 11 studies of military and commercial air crews show significant increased risks of dying from cancers considered to be radiogenic. The aircraft environment includes other potential and multiple risk factors which are not as well understood as radiation, such as electromagnetic fields, changes in body hormones, time-zone changes, pesticides, pressure changes, chronic fatigue, and lifestyles.
Given the economic problems airlines face, this problem is the last thing that they want to surface. But, if crew members and passengers already face largely unreported radiation risks from long-distance flying, we should have the right to know just how whole-body radiation scanning machines are part of this risk.