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effects of low-level radiation. He has won several awards for several (probably 5 to 10) separate gene mutations. Some of these original research into the causes of atherosclerosis, which is the mutations might be inherited, but most occur from exposure to growth of fatty "plaque" inside the blood vessels, often causing gene-damaging substances in the environment. fatal heart attacks. In 1974, the American College of Cardiology Here is a way to understand multiple causation. Gofman gives selected him as one of the 25 leading researchers in cardiology of __ the following hypothetical example of 100 cases of cancer: the past quarter-century. ¢ 40 cancers caused by co-action of X-rays + smoking + poor In the early 1960s, the US Atomic Energy Commission (AEC) diet; asked Gofman to develop a Biomedical Research Division at the ¢ 25 cancers caused by co-action of X-rays + poor diet + AEC's Livermore National Laboratory (LNL), to evaluate the inherited genetic mutations; health effects of all types of nuclear activities. In 1970, he * 25 cancers caused by co-action of X-rays + smoking + became convinced that radiation was more dangerous than previ- inherited genetic mutations; ously believed, and he spoke out against Project Plowshare (the * 10 cancers caused by co-action of smoking + poor diet + AEC's plan to explode hundreds of nuclear weapons to release gas inherited genetic mutations. trapped in rock beneath the Rocky Mountains and to excavate In the first case, the 40 cancers are caused by genetic mutations new harbours and canals by exploding nuclear bombs above that are, in turn, caused by X-rays, smoking and poor diet. Each ground). He also called for a five-year moratorium on the AEC's of these three factors is necessary for the cancer to occur; if any plan to develop 1,000 commercial nuclear power plants. one of the three factors is missing, the cancer will not occur. By 1974, Gofman's government funding was cut. He then We can see in this example that X-rays contribute to 40 + 25 + began a series of books on the dangers of radiation: Radiation 25 = 90 cases out of 100. In this example, if X-rays were not pre- and Human Health (1981); X-Rays: Health Effects of Common sent, 90% of the cancers would not occur. Now, in the same Exams (1985); Radiation-induced Cancer From Low-Dose example, look at poor diet. Poor diet contributes to 40 + 25 + 10 Exposure: An Independent Analysis (1990), Preventing Breast = 75 of the 100 cases. If poor diet were not present, 75% of the Cancer: The Story of a Major, Proven, Preventable Cause of cancers in this example would not occur. This Disease (1995, 2nd ed. 1996); We can see in this example that we and Radiation from Medical have X-rays "causing" 90% of the Procedures in the Pathogenesis of Gofman calculates that in 1993, cancers—"causing" in the sense that Cancer and Ischemic Heart Disease the cancers wouldn't occur in the (1999) 35363738. 50% of all cancers in women and absence of X-rays. But we also have Gofman is a superb teacher. In his 74% of all cancers in men were poor diet "causing" 75% of the same books, he explains the raw data, cancers, meaning that 75% of the where it came from, its shortcomings, attributable to X-rays. cancers wouldn't occur in the how it might be improved (or why absence of poor diet. we're stuck with what we've got). In other words, about 60% of all Thus we can see that when Then he moves the reader step by . . Gofman says X-rays are responsible step towards his conclusions, explain- cancers in the US In 1993 were for a large proportion of all cancers ing each step for the novice as well as attributable to X-rays. in the US, he is not saying that X- the expert. When he is forced to rays are the only cause of those can- make assumptions, he explains why cers. However, he is saying that he thinks he is making the right ones. most of those cancers would not He often describes alternative assumptions and the effect they occur in the absence of X-rays. would have on his conclusions. Nothing of importance is omitted. It is important to point out that Gofman is not opposed to med- As a result, Gofman's books are lengthy—typically 500 to 900 ical X-rays. Rather, he is opposed to unnecessary exposures from pages filled with tables of data accompanied by detailed explana- X-rays. He has shown over the years—and he is definitely not tions. The reader gets a thorough education in the topic, satisfac- alone in this—that medical X-ray exposures in the US could be tory for both novice and professional. I consider Gofman one of _ cut by at least 50% with no loss of medical information. The the greatest teachers of the 20th century. His work has already careful use of modern X-ray equipment and techniques can reduce changed the way the world views the dangers of radiation, and his X-ray exposures by half (or more) without sacrificing any medical latest book will—eventually, after a long fight—revolutionise the benefits. Thus, at least half the cancers caused by medical X-rays way the world looks at medical radiation. His work will save, are completely unnecessary. cumulatively, tens of millions of lives. How many unnecessary cancers are we talking about? Gofman In his latest (1999) book, Gofman presents strong evidence that calculates that in 1993, 50% of all cancers in women and 74% of medical radiation is a major cause of cancer and of atherosclerosis all cancers in men were attributable to X-rays. In other words, (coronary heart disease). By "medical radiation", Dr Gofman is about 60% of all cancers in the US in 1993 were attributable to X- referring mainly to X-rays, including fluoroscopy and CT rays. About 500,000 people die of cancer each year in the US. If ("CAT") scans. The mechanism is simple to state: radiation 60% of these deaths are attributable to X-rays and half are unnec- causes genetic mutations which eventually give rise to disease. essary, we are talking about 150,000 unnecessary cancer deaths What is Gofman saying? Does he mean that medical radiation —_each year in the US. is necessarily the only cause of cancer and coronary heart disease? Gofman calculates that the proportion of coronary heart disease Certainly not. Does he mean that cancer is not caused by (CHD) attributable to X-rays is slightly higher than the proportion smoking, poor diet, genetic inheritance, pesticides, diesel exhaust, of cancers. Among men in 1993, 63% of CHD deaths were dioxin and toxic chemicals encountered on the job? Certainly not. attributable to X-rays, and 78% among women. So, in rough Cancer and heart disease both have multiple causes. For a cancer numbers, 70% of CHD deaths are attributable to X-rays, Gofman (or an atherosclerotic plaque) to develop, a cell must undergo believes. Since CHD caused roughly 460,000 deaths in the US in several (probably 5 to 10) separate gene mutations. Some of these mutations might be inherited, but most occur from exposure to gene-damaging substances in the environment. Here is a way to understand multiple causation. Gofman gives the following hypothetical example of 100 cases of cancer: * 40 cancers caused by co-action of X-rays + smoking + poor NEXUS ¢ 37 74% of all cancers in men were attributable to X-rays. attributable to X-rays. AUGUST - SEPTEMBER 2000