The sky is falling, the sky is falling! or perhaps we should say, The X-rays are falling, the X-rays are falling!
Once again, the press (with the help of some in the medical community) is raising misleading and alarmist fears.
Late last month, The New England Journal of Medicine (NEJM) published a review article "Computed Tomography — An Increasing Source of Radiation Exposure" written by two scientists, David J. Brenner and Eric J. Hall, of the Columbia University Medical Center, New York.
Based on superficial readings of the article and superficial interviews with experts, newspaper articles headlined "CT Scans Raise Cancer Risk" and "Unnecessary CT scans exposing patients to excessive radiation" metastasized all over the country.
Although the NEJM article concedes, "most diagnostic CT scans are associated with very favorable ratios of benefit to risk," it ignores very important benefits and inflates hypothetical risks. Disproven premises, compounded by inappropriate projections, underlie the authors' approach.
Let's start with the false, underlying assumption "that any dose of radiation, no matter how small, and how it is delivered, is harmful" as pointed out by professor Jadwiga (Jodi) Strzelczyk, Ph.D., associate professor of Radiological Sciences at the University of Colorado Health Sciences Center.
This assumption, also known as the linear no-threshold hypothesis (LNT), is false, according to hundreds of recent scientific studies. For example, in a 2001 report, the National Council on Radiation Protection (NCRP) notes "that the rates of cancer in most populations exposed to low-level radiation have not been found to be detectably increased, and that in most cases the rates have appeared to be decreased."
In other words, the hypothetical assumption of cancer risk underlying the NEJM report does not happen. In fact, in most cases the cancer risk rates appear "to be decreased." In other words, low levels of radiation are associated with less cancer, not more.
The French Academy of Medicine "denounces utilization of the linear no-threshold (LNT) relation to estimate the effect of low doses . . ." Many other professional scientific groups, such as the American Nuclear Society and the Health Physics Society, agree.
Too much of anything can kill, such as water, oxygen, radiation, and aspirin.
But a moderate amount of these same things improves — or is essential to — health. For example, taken all at the same time, 100 aspirin tablets kill.
But two tablets cure headaches. And 1/4 of a tablet can help prevent heart attacks and stroke.
The American Nuclear Society, the Health Physics Society and many other professional radiation experts agree that radiation doses below 0.1 or 0.2 Gray (Gy) produce risks that are either too small to be observed or are non-existent. (To minimize confusion, I'm converting other radiation dose units to Gray units.)
In contrast, the NEJM authors claim that doses as low as 0.01 Gray in adults provide a "most likely [though small] risk" of causing cancer. They speculate that 2 percent of future cancer in America might be caused by CT radiation.
More recently, Doug Boreham published an article "Scientists find low-dose radiation a benefit" in "The Hamilton Spectator"
(http://www.thespec.com/article/290638). He writes, "Based on actual biological scientific evidence, and not calculated extrapolation, an opposite conclusion about CT cancer risk is equally plausible. That is, cancer risk in North America may be reduced by 2 percent over the coming decades because of low-dose medical CT exposures."
Boreham is an associate professor in the department of medical physics and applied radiation sciences at the McMaster University, Canada; his research "has shown that low doses can have beneficial effects to living organisms."
The NEJM authors give greatest weight to studies of Japanese people exposed to a different radiation mix (including neutrons) more than half a century ago and in a very different socioeconomic situation than North American patients having CT examinations.
At the same time, the authors ignore the fact that Japanese a-bomb survivors are living longer lives than Japanese people not exposed to radiation.
Many people unconsciously accept the unstated hypothesis of the LNT hypothesis, namely that doses of many different things build up in the human body over time, eventually resulting in bad effects.
Living things don't work this way.
Plants as well as animals flush the effects of many substances (such as aspirin, radiation, and just about everything else) out of their systems over time. Cells in living beings repair themselves continuously, removing the effects of individual molecular biochemical or radiation events.
The LNT hypothesis is the basis for another discredited idea, the "collective risk" concept. If doses did build up over time, a collective risk hypothesis might be worthy of further investigation. This idea would predict that 50 people each taking two aspirin is the equivalent of one person taking 100 at the same time. If that were the case, there would be a lot more aspirin deaths than anyone claims. Show me the bodies.
The NEJM authors also ignore wider indications of human health and functioning, such as overall health and longevity.
For example, the Nuclear Shipyard Workers Study (NSWS) reported by Johns Hopkins researchers in 1991 http://cedr.lbl.gov/pub/1732/1732.pdf produced radiation dose measurements inherently more accurately than the estimates made for the 1945 Japanese atomic bomb survivors.
Profesor John Cameron of the University of Wisconsin analyzed some of the data in this study. According to Cameron, it is "the world's best epidemiological study of nuclear workers." People working on nuclear-powered ships received an occupational dose "comparable to background doses received by people living in mountain states" (http://units.aps.org/units/fps/newsletters/2001/october/a5oct01.cfm).
Cameron found the nuclear workers receiving a total dose greater than 0.005 Gray "had a death rate from all causes 24% lower than the control group."
This is a very significant statistical difference (16 standard deviations lower than the controls, for you numerically minded readers.)
The cancer death rate for this group was over four standard deviations lower than the control group, also a significant statistical difference. This supports the hypothesis that a moderate dose rate of radiation is beneficial to the health.
Based on these demonstrated results, Cameron suggests people living in the U.S. Gulf States, with low background radiation, are suffering from radiation deficiency; they have a higher cancer death rate compared with people living in the mountain states where natural cosmic rays and natural radiation from rocks provide higher radiation doses.
As Theodore Rockwell, Sc.D., vice president of Radiation, Science and Health, Inc. (www.radscihealth.org/rsh/ )and retired nuclear engineer notes, these NEJM authors hold a "discredited position" about the effects of low-level radiation.
This unfortunate episode of false alarmism also demonstrates the difficulty, as well as the short-sightedness, of looking at just one hypothetical facet of medical care while ignoring other, more important factors and recent scientific advances (such as beneficial effects of radiation on overall health and longevity).
It's even more difficult to keep medical care itself in human perspective; as one shocked doctor reported in a letter to the NEJM some years ago, "You know, doctor, there are some things in life more important than health."
CT examinations should be done to meet the patient's needs. Outdated and disproven ideas about radiation should not limit medical judgment.
At this point, you may well know more about low-level radiation than most doctors. If your doctor seems overly concerned about ionizing radiation from X-ray, CT, or nuclear medical examinations, you might be doing him a favor by showing him this information.
Robert J. Cihak, M.D., is a senior fellow and board member of the Discovery Institute and a past president of the Association of American Physicians and Surgeons.
Michael Arnold Glueck, M.D., comments on medical-legal issues and is a visiting fellow in Economics and Citizenship at the International Trade Education Foundation of the Washington International Trade Council. Both authors retired from the medical practice of diagnostic radiology more than a decade ago.
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