A technician in protective gear screens people in Nihonmatsu, northern… (Yuriko Nakao/ Reuters )
As meltdown risks rise at a damaged Japanese nuclear plant, and as nuclear fission byproducts are detected outside that plant, the world watches and worries about the radiation risks to nearby residents -- and to others.
If past crises are any indication, those worries will lead to lingering questions, second-guessing and outright fear regardless of how the current situation develops. So now's the time to learn a few basics.
MedlinePlus offers a quick primer on radiation exposure that begins with a definition of radiation (a form of energy) and quickly expands into its biological effects. In short, both long-term exposure to low amounts and short-term exposure to high amounts can cause health problems. It likely goes without saying that long-term exposure to high amounts of radiation is undesirable.
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The Environmental Protection Agency offers a more in-depth look at radiation in Radiation Risks and Realities. For today's news purposes, just skip to the part about ionizing radiation; the weaker form of radiation, non-ionizing, isn't the issue.
Worth noting is the fact that everyone is exposed to radiation. Every day. From many sources.
Then head straight to the agency's overview of the health effects of radiation.
There you'll find the symptoms of excess exposure; the connection between radiation and cancer; and why children are more sensitive to radiation. And that's for starters.
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About exposure, the EPA says this:
"There is no firm basis for setting a 'safe' level of exposure above background for stochastic effects. Many sources emit radiation that is well below natural background levels. This makes it extremely difficult to isolate its stochastic effects. In setting limits, EPA makes the conservative (cautious) assumption that any increase in radiation exposure is accompanied by an increased risk of stochastic effects. "
Stochastic, by the way, is associated with chronic exposure.
But then the agency says this:
"Health physicists generally agree on limiting a person's exposure beyond background radiation to about 100 mrem per year from all sources. Exceptions are occupational, medical or accidental exposures. (Medical X-rays generally deliver less than 10 mrem). EPA and other regulatory agencies generally limit exposures from specific source to the public to levels well under 100 mrem. This is far below the exposure levels that cause acute health effects."
Note the phrase "beyond background radiation."
You can estimate your own annual radiation dose via the agency's radiation calculator.
There, the agency notes: "In the United States, the average person is exposed to an effective dose equivalent of approximately 620 mrem (whole-body exposure) per year from all sources."
Questions include: Do you wear a plutonium powered pacemaker? Do you use gas lantern mantles when camping? Do you have a smoke detector in your home? Do you watch TV?
Such questions may seem beside the point. They're not. If we're going to begin analyzing the radiation exposure created by nuclear power accidents (and it seems safe to say that we are), we need something for comparison.
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