THE HARD NUMBERS AND COMPARISONS

Although more than 90% of all genetic mutations are due to causes other than radiation, it is radiation-induced mutations that are best understood. The number of genetic effects per million liveborn children in the US is now about 100,000; in a population exposed to 1 rem per 30-year generation, the number of genetic effects lies between 5 and 90 cases. This number is so small that it can only be indirectly calculated, not directly observed; even so, because of natural selection, this small number disappears again over a few generations if only one generation was exposed to the additional radiation (case B in the figure).

But even if the exposure keeps increasing with each generation, an equilibrium state is reached within a few generations, as shown in A.

Thus, slight changes disappear after a few generations; and real monstrosities cannot appear at all.

The figure is adapted from the Norwegian report (see references below); the numerical values are taken from the 1980 BEIR Report. The latter also estimated the effects of radiation on cancer incidence, and the relatively minor disagreements among the committee members were greatly played up by the press at the time. However, the chapter on genetic mutations and the values given here were approved unanimously.

These figures are more illuminating when compared with other phenomena that are known to correlate with genetic mutations. They have been pointed out by Prof. Bernard Cohen.

One well known factor in genetic effects is the age of the parents at conception. The risk of genetic mutations increases with the parents' (especially the father's) age: for example, a woman's risk of bearing a mongoloid child increases from 0.002 at age 25 to 0.016 at age 40, that is, by a factor of 8 over 15 years. When all of these effects are taken into account, it turns out that the genetic effects from 100% nuclear electric power in the US would be equivalent to raising the average age of parents by 2.6 days. Between 1960 and 1973, the average age of parents did, in fact, increase by about 50 days, resulting in 20 times more genetic effects than 100% nuclear electric power would have produced.

The second comparison is even more amusing, though less exact. Wearing pants increases the temperature of the male sex cells, which in turn is known to increase the chances of genetic mutations. Under certain simplifying assumptions, Prof. Cohen finds that the male custom of wearing pants is 800 times more effective for genetic mutations than 100% nuclear US electric power would be; the genetic effects of the latter could be compensated if the average American male would reduce this habit by 80 pant-seconds per day.

[More: An eminently readable account by B.L. Cohen, "Genetic effects of natural radiation," appears in the excellent Canadian quarterly Ascent, vol. 3, no.3, 1982 ($2.50, AECL, 275 Slater St., Ottawa, Ont., Canada K1A OS4). A scientific paper by the same author, "Perspective on genetic effects in radiation," has been submitted to Health Physics, but not yet published (it includes the pant-wearing phenomenon). The numerical values are taken from The Effects on Populations of Exposure to Low Levels of Ionizing Radiation: 1980, Committee on the Biological Effects of Ionizing Radiation (BEIR), National Academy of Sciences, Washington, DC 1980. The figure is based on one in Nuclear Power and Safety, Norwegian Government Commission, 1978 (English translation: Columbia Univ. Press, 1980).]