What is ionizing radiation? Can it harm us? What does it have to do with nuclear weapons? (Part Three)
This story is a little complicated, a little technical. It will take three entries to tell it. This is the third one. Since ionizing radiation is part of our lives, inescapably, it’s worth getting a handle on it.
Nuclear chain reactions in atomic bombs produce large blasts of “prompt” ionizing radiation in amounts large enough to kill us right away, or very soon and certainly, if we get a good dose of it. The dose we will get depends on our distance from the detonation and whether we are or aren’t shielded somehow.
The good news here, if it is that, is that if you are close enough to the detonation of a nuclear bomb to be killed right away by the “prompt” radiation it produces, you will probably already have been killed by the heat and blast. That’s the idea of “overkill” that emerged during the nuclear arms race as we learned more about the effects of nuclear weapons.
Later we can get hit by ionizing radiation being emitted by the fallout produced by the nuclear detonation. That depends on where the fallout falls, or rains out, and in what concentrations. A lot of uncertainty here. You’d need a dosimeter to know what does you were getting.
If we don’t get one of those very large “prompt” doses of ionizing radiation when a bomb goes off, but do get a smaller dose, we may have been killed by it and we may not have been. The wrinkle here is that the harm that is caused by non-fatal doses of ionizing radiation is “stochastic”-- a matter of odds. It can’t be predicted with certainty. It will kill some of us, certainly, but it might kill you or me down the road and might not, and we have no way of knowing which or when.
We know it increases our risk of dying and we know it will kill some of us before our time. Scientists can now confidently predict that some numbers of people will die from these lower doses of radiation who wouldn’t have died otherwise until later. But we can’t say who will die or when, or even, much of the time, if the ionizing radiation is what killed them. Maybe it was those darned cigarettes. Which, by the way, whatever else cigarettes do, deliver ionizing radiation to our lungs.
Is there a dose of ionizing radiation low enough to be simply safe? The health physicists—professionals who first began to appear during the Manhattan Project and whose first job was to keep the scientists and engineers in the Manhattan Project safe--thought at first that doses low enough not to redden skin might be safe. Most health physicists now believe that while lower doses are safer, they are never simply safe.
Most health physicists now believe that the damage from ionizing radiation is directly cumulative. That is, every dose we get adds something to the risk created for us by previous doses. Maybe not a lot, but some. And it adds up.
Let’s look on the bright side. Even if nuclear bombs aren’t exploding in our neighborhoods, all of us are always getting hit with some ionizing radiation. It doesn’t kill all of us, obviously. Or even most of us. We can realistically hope, it seems, that our body will find a way to cope with the ionizing radiation we inescapably experience until something else does us in.
Carefully managed ionizing radiation has proved to have a great many medical uses. The x-rays and mammograms and CAT-scans we get in the hospital, all of which add to our totals, can help the doctors keep other things from killing us early. A trade-off there. Lots of those in life.
When we finally realized that our tests of nuclear weapons in the atmosphere were producing fallout that was a source of ionizing radiation that would kill some of us before our time, we drafted and signed the Partial Test Ban Treaty (1963). By “we” I mean us, the United Kingdom, and the Soviet Union. In the treaty we agreed not to test nuclear weapons in the atmosphere any more. Since 1963, none of us has. We’ve done plenty of tests since then, but all undergrounds. None in the atmosphere.
Should we, even so, explode a “strategic” nuclear bomb in the atmosphere every generation or so, as publicly as possible, just to help us have a healthy understanding of what these weapons can do? Might we forget? Forget what we might never have grasped in the first place?
Next: What’s the difference between a “clean” and a “dirty” nuclear bomb?