MARK TWAIN EFFECT

Mark Twain told a story about a seriously ill man who consulted his doctor. The doctor advised him to stop drinking, stop smoking, and stop philandering. The man followed this advice and recovered his health. Later a woman acquaintance fell ill, so he told her about this wonderful doctor. She consulted the doctor and received the same advice. The woman, however, neither drank, smoked, or philandered, and was unable, therefore, to follow the doctor's advice. So, she died.

A reasonable working hypothesis, even a simple one, is helpful in many ways. In this framework, it may be that Mark Twain's humor can help us to understand "Vitamin R'' (radon in the January 1994 AtE) and an increasing family including "vitamins'' Cs (cesium 137), Co (cobalt 60), T (tritium or hydrogen 3), and X (x-rays).

S. Okada and N. Momoshima, Health Physics, vol. 65 (1993) p.605 give references to several research papers dealing with the "adaptive response'' to ³H, ¹⁴C, ⁶⁰Co, ³²P, and x-rays. It has been found that pretreatment of human cells with these sources of ionizing radiation makes the cells more resistant to chromosome damage by ionizing radiation. T. Lazo, Health Physics Society Newsletter, vol. 22 (1994) p 6 gives additional references related to the tendency for tritium "to be 'immunizing' against radiation damage.'' A particle of ionizing radiation and the reactive substances it produces are often very damaging to the structure of any biological macromolecule that is unfortunate enough to encounter them. This fact has made the so-called linear, non-threshold model of radiation damage popular. For the same reason, an identical model has also become popular for toxic chemical damage to chromosomes. With this model, chemical and radiation damage to living systems at high doses (where such damage is easily measured) is extrapolated linearly to zero doses. This extrapolation is then used to calculate damage estimates at low doses (incorrectly).

Proponents of the linear model overlook the fact that living cells have very active defense and repair machinery. This machinery responds to both external effects like ionizing radiation and also internal processes that are an inseparable part of the chemical activity of life itself. Moreover, this molecular machinery is turned on and off by living cells in accordance with the need for its services.

Nuclear Issues, vol. 15, no. 12 (1993) pp 2-3 reports that a 1985 study of UK Atomic Energy Authority workers showed a 22% lower death rate from cancer than the national average, and a similar study of 10,000 Atomic Energy of Canada Limited workers and of several thousand Ontario Hydro nuclear power station workers showed a similar 33% lower mortality. The similar results from nationwide radon surveys in the United States (AtE January 1994) show that this effect is not restricted to selected populations. Radon at high enough doses probably does increase cancer incidence, but at low levels it actually decreases cancer incidence. So, the linear model is wrong.