The universe is filled with radiation. It’s everywhere. It comes up from the ground and down from the sky. Low, routine doses are often expressed in millirems (1,000 millirems equal one rem) or millisieverts (one millisievert is 100 millirems). Most epidemiologists – like our own Peter Caracappo, just retired from Rensselaer Polytechnic Institute – think that very low levels have no effect on health. For example, two smoke detectors in your home give you an annual radiation exposure of 0.02 millirems. No one thinks that this is harmful. Tibetans and Peruvians who live high up and thus receive significant radiation (60 millirems annually) do not experience higher rates of leukemia or other cancers.
At the other extreme, an emergency worker who picks up 8,000 quick millirems, or eight rems – a bit more than the annual five rems allowed by law – has detectable changes in blood chemistry. Nausea starts after 50 rems. Cell and tissue destruction shows itself as hemorrhaging at 100 rems. At 500 rems, half of people exposed will die within 30 days. At 2,000 rems, death is inevitable, within hours or a few days. (For comparison, the most-exposed employee at the Japan nuclear plant had a reported exposure of eight rems – if this can be trusted.)
There are two types of radiation. Electromagnetic radiation is an alternating pulse of magnetism and electricity. It’s not harmful unless the waves are closer together than those of visible light. It’s these shorter waves that can break apart (ionize) atoms, cause gene mutations and ultimately produce cancer. Some of these arrive in sunlight, as ultraviolet (UV). Each one-percent increase in a person’s lifetime UV exposure boosts her odds of contracting skin cancer by that same one percent. Waves even shorter – gamma rays and X-rays – are more penetrating and produce ionizations much more easily. So this is the first meaning of radiation: light with waves spaced closely together.
The second type is actual solid particles. The damage they do depends on their mass, speed and whether the body absorbs them so that they stick around. Radioactive cesium, for example, mimics calcium and thus lodges in bones, while radioactive iodine-131 is absorbed by the thyroid gland.
Radiation is absolutely everywhere. The average person gets 360 millirems a year, or 3.6 millisieverts. Fully 82 percent of this comes from natural sources. But many experts believe that we now actually get 600 millirems annually, thanks to increased widespread use of computed tomography (CT) scans.
Let’s make it simple: You want your yearly dose to be less than one rem, or ten millisieverts, or 1,000 millirems. Since radiation comes from the Sun and stars and our atmosphere blocks some, the higher up you live, the more you get. You get 26 millirems just for living on the surface of Earth. Add five millirems for each 1,000-foot elevation of your home. If you live in Tannersville, you annually get 12 millirems more than folks in Kingston.
If your home is stone, brick or concrete, add seven millirems, since these materials are slightly radioactive. A basement often delivers radon. This is a biggie. The average homeowner gets 200 millirems yearly – one-fifth of a rem – from his or her home’s radon-polluted air, coming up from below. A venting fan can greatly reduce this.
Add 40 millirems that you unavoidably get from food and water. Add 50 millirems from natural radiation emanating from within your own body, like from its potassium. Yikes! Add one millirem from radiation in the air left over from those atomic tests in the ‘50s.
Jet travel hits you with radiation, which can add up. A single round-trip flight to California at 39,000 feet exposes a person to six millirems. Airline crews typically get 1,600 millirems annually: about one-and-a-half full rems. This is apparently why their cancer rate is one percent higher than the rest of us.
Add 40 millirems for each medical X-ray that you take. But listen up: A single CT scan gives you at least 1,000 millirems – an entire rem! A whole-body CT scan can give you three rems. That’s the same radiation that Hiroshima survivors got if they were two miles from Ground Zero. Yes, a single full-body CAT scan equals being at Hiroshima on that infamous August 6.
So you always want to know: how much? That was the bottom line repeatedly hammered during the course that I took on radiological defense. If you’re getting significantly less than a rem annually, you can confine your paranoia to cholesterol.
As for Japan in March 2011: Peak radiation near the reactors is reportedly 40 rems per hour. That would prevent any prudent worker from remaining more than ten minutes. By comparison, many workers at Chernobyl received 100 to 600 rems, which is why several of them soon died.
In contrast, that so-called “plume” from Japan barely registered above background when it arrived at California. You could live in that “plume” for 200 years and it still wouldn’t equal the radiation from your home’s smoke detector. That was pure sensationalism, which created unnecessary widespread fear. So no, definitely don’t take any iodine pills.
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