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Heart Risk due to Low Radiation Doses:
Major Additional Evidence
Very strong evidence exists supporting the hypothesis that medical imaging by fluoroscopy and planar x-rays is an important causal co-actor in ischemic heart disease (IHD) as well as in human cancer --- an hypothesis described in Medical News Today, 29 Aug 2008 (“Heart Risk Due to Low Radiation Doses Worth Investigating Say Scientists,” by Catharine Paddock, PhD, referring to Batti, Sigurdson, & Mabuchi in Lancet Aug 30, 2008. Details at the end of this file.*)
Powerful support for the hypothesis was uncovered and published in 1999 in a monograph (ISBN 0932682979) entitled Radiation from Medical Procedures in the Pathogenesis of Cancer and Ischemic Heart Disease: Dose-Response Studies with Physicians per 100,000 Population, by the late John W. Gofman, M.D., Ph.D. His previous pioneering accomplishments in scientific research are described in an obituary (now online at www.berkeley.edu/news/media/releases/2007/09/04_GofmanObit.shtml ) .
Unfortunately, his wife's failing health and then his own failing health prevented him from presenting his new findings widely. But fortunately, the complete monograph is available from www.amazon.com and its Executive Summary, table of contents, extensive reference list, and its first five chapters are available, free, online at www.ratical.org/radiation/CNR/RMP/execsumm.html. On the same site are the six main critiques by peer-reviewers at www.ratical.org/radiation/CNR/RMP/6critiques.html.
His findings about x-ray induced IHD fell out of the age-adjusted mortality rates by United States census divisions from all major causes of death at mid-century --- data that Professor Gofman studied in order to make a reality check on the grim possibility that accumulated lifetime exposures to medical x-rays (including fluoroscopy) became a major contributing cause of cancer during the 20th century.
As a result of his dose-response studies, Professor Gofman proposed that lifetime accumulated exposures to medical x-rays may well be a necessary causal co-actor in over half of the age-adjusted mortality rates in the United States both from cancer and from ischemic heart disease. In other words, over half the current baseline cancer and IHD mortality rates might well be absent in the absence of past accumulated exposure to medical x-rays.
The “over 50%” estimates are necessarily ballpark estimates --- meaning a lack of appropriate data requires the use of several important approximations and assumptions, forthrightly identified in the book. The familiar estimate, that medical x-rays account for only 1% of the U.S. cancer burden, is also a ballpark estimate.
If you are deeply doubtful that x-rays could do so much harm without anyone recognizing it --- despite 100 years of their use in medicine --- the reasons for failure to recognize become clear in Chapter 2 of the monograph, www.ratical.org/radiation/CNR/RMP/chp2F.html . The abbreviated explanation is that past x-ray doses have seldom been measured, although they have been a proven mutagen since 1929. There are no data on anyone's lifetime accumulated doses to each organ. In addition, the cumulative unmeasured x-ray doses badly undermine risk-values extracted from study of persons exposed to ionizing radiation from non-x-ray sources (Japanese atomic bomb survivors, nuclear workers, airline flight personnel).
If these problems obscured very large risks from x-rays so well --- Dr. Gofman missed them for nearly 20 years --- why did he decide it was imperative to make a reality-check on the ballpark 1% estimate mentioned above? The story unfolds in Chapter 2. And how did he do it? He designed a novel method, set forth in detail in Chapters 3 and 4, which delivers its own ballpark estimate. No one can do better than ballpark, for the reasons stated above.
Despite natural doubts about his findings, your intellectual curiosity and responsibilities should persuade you to look at six unforgettable graphs from his monograph: www.ratical.org/radiation/CNR/RMP/chp1F.html#fig1a . These graphs plot age-adjusted mortality per 100,000 persons (males and females separately) versus physician-density per 100,000 persons, by Census Divisions. The necessary approximation (supported elsewhere in the mainstream literature) is that the average number of x-rays given per 100,000 population is approximately proportional to the number of physicians per 100,000 population, in each of the nine U.S. Census Divisions.
The analysis uncovered a startling similarity between the positive dose-responses from cancer and from ischemic heart disease. Quite intriguing. Each dose-response is statistically extremely significant too. By contrast, the flat or negative dose-responses for noncancer nonIHD causes of death look unmistakably different. Just by accident? He studied not only all cancers combined, but the major individual cancers. He studied not only all noncancer deaths combined, but all the major noncancer causes individually. That is how IHD revealed itself to be unlike other noncancer causes. All individual analyses are in the monograph.
Because correlation alone cannot prove causation, Dr. Gofman considered other explanations, besides x-rays, for these powerful relationships (Chapter 68), and could find none better (Chapter 69). Therefore, he proposed that mutations acquired in the coronary arteries can be atherogenic, just as mutations in other organs can be carcinogenic. Indeed, acquired (non-inherited) mutations would explain why atheromas grow in distinct places and not everywhere in the coronary arteries. Similarly, solid tumors are also localized prior to metastasis. Dr. Gofman, the highly honored “father of clinical lipidology,” proposes in Chapters 45 and 46 how atherogenic mutations and atherogenic plasma lipoproteins may interact.
Prior to the very strong findings in his 1999 monograph, Dr. Gofman had regarded earlier evidence as too “thin” to believe that acquired mutations in the coronary arteries might initiate or accelerate atheromas. Astonished by his own new findings, he reviewed the earlier evidence and proposals by others, including some supportive experimental animal studies of apparent radiation-induced or accelerated atherosclerosis (described in Chapter 44, Part 8), and also the typical types of cardiac injuries reported following very high-dose medical irradiation delivered during cancer therapies (described in Appendix J).
As Medical News Today indicates in its title, a causal relationship between low-dose ionizing radiation and IHD is “worth investigating” further, especially since acquired mutations in the heart can accumulate with each additional radiation exposure. The growing use of fluoroscopy and CT in medicine makes it imperative to become familiar with verbatim excerpts from three major reports on the “safe-dose fallacy,” provided in Appendix B of the 1999 monograph.**
Ms. Egan O'Connor, September 1, 2008, San Francisco.
(Dr. Gofman's co-worker on radiation issues for 35 years,
and editor of his last five radiation monographs.)
* The journal that inspired Medical News Today (www.medicalnewstoday.com) to publish its article on August 29th was the Lancet: Vol. 372, No.9640; pp 697-699, Aug. 30, 2008, in which Bhatti, Sigurdson & Mabuchi at the U.S. National Cancer Institute issued a low-key “comment” entitled, “Can Low-Dose Radiation Increase Risk of Cardiovascular Disease?”
** Also online at www.ratical.org/radiation/CNR/PBC/chp45.html.