Late last year, the American Pilots Association persuaded the TSA to allow pilots exemption from screening by full-body scanners. Captain Dave Bates, president of the association, argued that pilots "experience significantly higher exposure than most other occupations, and there is mounting evidence of higher-than-average cancer rates as a consequence." (1)
But what about the rest of us?
I fly twice a week, northern to southern California, to and from work. I am also the author of a biography of pioneer radiation scientist Alice Stewart, who discovered, in the 1950s, that if you x-ray a pregnant woman, you double the risk of a childhood cancer ("The Woman Who Knew too Much: Alice Stewart and the Secrets of Radiation"). Media discussions of airport scanners have focused on privacy issues, but these pale beside the danger of increased radiation exposure.
When Dr. Stewart published her findings about the link between fetal x-rays and childhood cancer (2), she met with tremendous opposition. The dose emitted by x-rays was a fraction of the dose experts "knew" was safe -- how could it possibly kill a child? So contrary were her findings to what everyone was sure of that doctors went right on x-raying pregnant women. Stewart hung in there, proving her case, but it took until the 1980s before doctors stopped x-raying pregnant women, all the while "experts" were reassuring us that the technology was safe.
"People don't believe in radiation because it's out of sight, out of mind," as Stewart said; "then twenty or thirty years later, someone drops dead." Radiation can't be seen, smelled, or touched. Since it may take decades for its effects to be felt, it's difficult to trace a cancer to a specific exposure. But radiation is the deadliest of carcinogens, the only one that affects every single organ in the body. And there is little agreement about how low a dose is a safe dose, to this day.
Since the 1930s, when the International Commission on Radiation Protection began setting guidelines for permissible exposure, it has been lowering the permissible dose -- by a factor of 2 in 1950, then again by a factor of about 3 in 1956. (3) (Permissible dose is set lower as dangers are found to be higher.)
"There is something disturbing about the repeated assurances, 'this time folks, we have got it right,' comments Dr. Morris Greenberg, a senior public official in Britain, "when on each occasion, a previous understatement of hazard is revealed." (4) Meanwhile, each successive report of the Biological Effects of Ionizing Radiation committee, a committee of the prestigious National Academy of Sciences, has acknowledged a greater danger to low-dose radiation. Their most recent report states there is "no evidence of a threshold below which no cellular damage occurs." (5) That is, even the lowest of doses may be dangerous, as Stewart claimed.
X-ray equipment is dangerous. Even highly trained technicians may get it wrong -- as we saw in the overdosing of hundreds of patients from CT scans at hospitals last year. (6) Do we really want minimally trained airport security workers, in the confusion and rush of security lines, operating this machinery? And how about risk to the workers themselves -- where are the long-term studies assuring us about them?
Physicians and scientists at the University of California, San Francisco wrote a "Letter of Concern" cautioning that the x-ray beam of airport body scanners is "very intense." A glitch could result in "an intense radiation dose to a single spot on the skin." These scientists, experts in cancer, biophysics, biochemistry, and imaging, note "the proximity of the testicles to skin" and worry about the effects of radiation on the cornea. They warn that "real independent safety data do not exist," that there has not been "sufficient review of the intermediate and long-term effects of radiation exposure associated with airport scanners."
"There is good reason to believe that these scanners will increase the risk of cancer to children and other vulnerable populations," the scientists conclude. (7)
Vulnerable populations? That's a lot of us. A radiation dose is not an absolute (8), in terms of effect, but varies according to how old we are, whether we're female or male, how healthy we are, how well or badly nourished, how weakened by previous exposures to illness, chemicals, or radiation.
A fetus is very vulnerable, as Stewart discovered. Should pregnant women be walking through these scanners? How about women who do not know they're pregnant? How about children and people over 65? How about anyone who's had cancer or cancer treatments or other immune-compromising conditions that make them more vulnerable to radiation? With one in three in our population getting cancer, that's a lot of vulnerable people.
As an all-too-frequent flyer, female, over 65, with a two-decade history of commuting and a cumulative radiation exposure equivalent to some pilots, I'm taking the pat-down, as humiliating and harassing as it is.
References:
(2) Alice Stewart, "A Survey of Childhood Malignancies," British
Medical Journal, June 28, 1958; follow-up in 1961,
Stewart's quotes are from Greene, The Woman Who Knew Too Much: Alice
Stewart and the Secrets of Radiation, University of Michigan Press,
1999
(3) Lauriston S. Taylor, "History of the International Commission
on Radiological Protection," Health Physics, 1: 97-104. Also, Peter
Bunyard, "Radiation risks -- how low can one get?" Ecologist, Sept/Oct
1978, 8, 5
(4) Morris Greenberg, "The Evolution of Attitudes to the Human
Hazards of Ionizing Radiation and to its Investigators," American
Journal of Industrial Medicine, 1991, 20, 717-2
(5) BEIR VII www.slidefinder.net/A/Abrams_BEIR_VII_PPT/28907822/p2
(6) Walt Bogdanich, "California tightens oversight of CT scans", NYT,
Oct 1, 2010
(7) UCSF Scientists Speak Out Against Airport Full-Body Scans,"
(8) For the "variability of actual health effects of radiation in
various populations," see "Letter to the BEIR VII Committee of the
National Academy of Sciences," from 133 organizations and individuals
from 13 countries worldwide,