Hello, Chuck! With all this discussion of radiation leaks from Japan’s nuclear power plant, it made my family and me wonder: Where else is radiation seeping into our homes and lives? – “Calm but Concerned,” Tacoma, Wash.

Last week, I began to answer this question by explaining the different types of radiation. In this article, I’ll give some examples of the daily ways we are exposed to radiation, their doses and how we calculate their doses.

Humans always have lived in a radioactive world. The Earth itself emits radiation. Radiation also comes to us from outer space, naturally occurring radon in the air and inside our own bodies (from water and food we consume).

An oversimplified explanation is that the type, use, dose and degree (or length) of radiation exposure determine how productive or destructive it will be.

For example, when appropriately harnessed and routed, radiation can be helpful, as in providing us with electricity or X-rays. Moreover, radiation therapy on cancer uses a special kind of high-energy beam to damage cancer cells’ DNA, leaving them incapable of dividing and replicating.

On the other hand, overexposure is almost always detrimental in some way. The most obvious example at the moment is the radiation leaks coming from the damaged Fukushima Dai-ichi nuclear facility.

Biological radiation damage is measured in units called sieverts (metric) or rem (used in the U.S.). One sievert equals 100 rem. The average radiation dose per person in the U.S. is 620 millirem, or 6.2 millisieverts, per year.

The radiation level a couple of weeks ago at the leaking Japanese nuclear facility was about 0.4 sievert per hour.

Compare those levels of radiation with those surveyed by Dr. Sanjay Gupta, whose facts were verified by nuclear radiation expert Daniel Polanski. Gupta reported that if you live in the U.S., “you are being exposed to around 3 mSv a year from background radiation. Get a chest X-ray, and on average, you will receive around .02 mSv, according to the Food and Drug Administration. A CT-scan of the chest, and you are getting a few hundred times that: a one-time dose of about 7 mSv, the FDA says.”

Gupta went on to explain: “To get an idea if someone will develop radiation sickness, you need to know the sieverts and also the length of exposure. For example, exposure to a full sievert at one time would be considered a mild exposure. Within six hours, one would start to feel nauseated. In the case of a larger exposure, between 2 and 6 sieverts, nausea would come on in about two hours, as well as significant bleeding from the intestines. Above 6 sieverts, and mortality starts to approach 90 percent.”

Here’s a glance at a few more everyday sources of radiation exposure and how they rate, according to data from the American Nuclear Society and the Environmental Protection Agency. Keep in mind that the average radiation dose per person per year is about 620 millirem and that the doses below are per-year exposures unless otherwise stated.

  • Living in a state that borders the Gulf of Mexico or the Atlantic Ocean: 16 millirem
  • Living on the Colorado Plateau: 63 millirem
  • Living anywhere else in the continental U.S.: 30 millirem
  • Living within 50 miles of a nuclear power plant: 0.01 millirem
  • From air (radon): 228 millirem
  • Viewing a TV or a computer monitor that uses CRT technology: 1 millirem
  • Smoke detector: 0.008 millirem
  • Smoking a pack of cigarettes every day of the year: 36 millirem
  • Flying on a jet plane: 0.5 millirem per hour in the air
  • Dental X-ray: 0.5 millirem
  • Chest X-ray: 10 millirem
  • Mammogram: 42 millirem
  • Abdominal X-ray: 700 millirem
  • CT scan of the chest: 700 millirem
  • CT scan of the whole body: 1 rem

I encourage you to calculate your own radiation exposure. The American Nuclear Society actually offers an online survey you can take to total your annual radiation exposure.

Incidentally, the radiation produced by a microwave oven is nonionizing. Therefore, it, unlike the ionizing radiation from the items on the above list, does not carry cancer risks. And though cell phones emit radio waves – which are a form of radiation – according to the National Cancer Institute, “there is currently no conclusive evidence that nonionizing radiation emitted by cell phones is associated with cancer risk.”

Though minuscule doses of radiation coming from items such as cell phones, microwaves, computers and televisions may not deter usage, remember that it all adds up in the end. So keep track of your total exposure. And question authorities, for even airline security machines are known to emit 10 times the radiation of what was first suspected.

The bottom line is this: All radiation, ionized and nonionized, can be harmful when we are overexposed to it. And the only safe route against overexposure is to minimize our use or consumption of, or exposure to, those things that emit unnatural, excessive radiation. This is definitely a case in which less is more.

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