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Understanding Radiation Hazards
Is Dan Rather more dangerous than Three Mile Island?
The reports of tens of thousands of deaths in Russia from Chernobyl together with the extreme public concern, almost panic in some cases, about the nuclear radiation which came here from Chernobyl and the similar concerns after Three Mile Island demonstrate that we nuclear scientists have failed to provide a common-sense view of health effects from radiation. As with any potential hazard, the general rule is to avoid unnecessary exposure. However, few of us worry about an occasional sunburn, even though extended sun exposure, like high radiation exposure, can cause cancer. Yet we seem to agonize over any exposure to nuclear radiation.
The way in which radiation affects health can be simply put. The radiation unit "rem" is used to measure the amount of nuclear radiation an individual has absorbed. Someone who receives a radiation dose much above 100 rem in a short period of time may feel nauseous and is likely to experience symptoms similar to the flu. At 500 rem there is about a 50 percent chance of death within a few weeks. On the other hand, a person receiving less than 100 rem is apt to notice no short term ill effects at all.
There is an increased risk of future cancer for doses of 100 rem and above. If 100 persons each receive 100 rem, then in time one of them would be expected to get radiation- induced cancer. (Sixteen of the 100 will get cancer unconnected with radiation.) Such cancer-dose relationships are deduced from Hiroshima and Nagasaki and populations of medical patients who received radiation doses in the 100-rem range.
At much lower, more common radiation exposures, no clear effects on health have been found despite more than forty years of trying to find them. If there are any effects, they are so small they are masked by normal variations in health unconnected with radiation. Nevertheless, to provide a conservative estimate it is ASSUMED that any level of radiation has an effect even if it is undetectible. It is ASSUMED that one cancer will result whether (as indicated above) 100 people each receive 100 rem, 1000 people receive 10 rem, or 10 000 people receive 1 rem. In other words, a collective dose of 10 000 rem spread among many people is assumed to produce one cancer among them regardless of how small the individual doses are. When applied to aspirin, this assumption says that if a hundred aspirin will kill a person, then one person will die if 100 people each take one aspirin.
There is no evidence that this assumption is truer for low doses of radiation than for low doses of aspirin; but depending on one's intent, it can be used to set prudent radiation policy, to scare people, to make headlines, or to have fun.
Let's consider Dan Rather, this decade's most watched T.V. news person. A television set emits a negligibly small amount of radiation. Nevertheless, the total viewing audience of 17 million who each day watch the 30-minute CBS Evening News collectively receive an estimated yearly does of about 1000 rem.
To simplify our discussion (and with apologies to Peter Jennings and Tom Brokaw), let us define a 1000-rem radiation dose distributed among many people as a "Rather." Viewers of the half-hour long CBS Evening News collectively receive one Rather per year. The Three Mile Island nuclear accident in 1979 caused a total population dose of
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