Radiation: Medical, Nuclear, and Net-Power

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Today , I feel inundated. Outside, the rain, life blood of California, continues. Inside, on the Tube, the mindless flood of misinformation about potential nuclear disaster continues. While hundreds of thousands  of Japanese are displaced from their ruined homes, and thousands are dead and dying  from the tidal wave and the toxic wasteland it created, our  free press  professionals inject yet another dose of  hyped news into the jugular vein of  a fright addicted public:

MSNBC feed  3/27/2011 :14:48 AM ET, this appears;  the precise date and time  offer  a patina of  pseudo science:


Then, with no coherent attempt to provide perspective  or describe ‘ normal’ the radiation is asserted to be 1000 mSv per hour, the equivalent to (sic) “29 CT scans according to NBC News Experts.”   Nowhere does it suggest that the 1000 mSv dose requires sitting in the contaminated pool for an hour.  The Expert comparison to 29 CT scans is simply absurd.  It seems clear that scandalous, out of context, ridiculous statements, like  vague, mindless comparisons to past nuclear accidents, sell newspapers, magazines, and TV time, but do not  inform.

On the other hand, we are rarely told  much about radiation from medical imaging. Perhaps our national dosing of medical ionizing radiation is something we are willing to accept for value received. Perhaps it is excessive. But whichever the case, we generally remain as ignorant of one sort of radiation risk as the other.  How infuriating! And how unfortunate that our public comprehension of ionizing irradiation is so little better than it was three generations ago at the dawn of the nuclear age. Was it reasonable to expect our media to inform rather than to merely profit through clever exaggeration? If so, they have failed. “Nucular” or “nuclear,” who cares! Ignorance and fear are the same no matter what its name!  No wonder we may rush to buy gas masks, iodine or KI on our way home from a whole body scan.

We cannot rely on ‘experts’.  And fortunately we no longer have to. The net is there, all the information is there.  As we might infer from significant books like ‘The Wisdom of Crowds’ , people can collectively be less stupid than individuals; now, thanks to the net, we can be well informed about ionizing radiation even if we are not nuclear physicists. We can have, or quickly find, the best available pertinent facts.  Moreover, an order for a CT scan is a prescription for irradiating ionization. It well may be worth the exposure. But both physicians and patients can and should thoughtfully consider the risks versus benefits of prescribed  radiation, and avoid unnecessary exposures.

My introduction to nuclear warfare, thanks to the US Navy, dates back decades. Although the more practical facts of the physics haven’t changed that  much, my knowledge of it, I fear, has gone through quite a few half-lives of attrition. So I had to look to the net for help. The information is all there.  I won’t claim that the material to be found is coherent; it is sometimes conflicting and often confusing.  But that is true of all  pronouncements including those of experts,  because no one puts information out anywhere without a particular view, or even at times a particular self interest. We live in a time when it is within reach of every person, every tweeter, every  web surfer to uncover as many  facts as exist!  I found the information below to be  readily accessible and pertinent:

Tissue doses of radiation are often measured or stated in ”milli sieverts” (mSv), a quantity of ionizing radiation dose absorbed and affecting body cells. While ionizing radiation resulting from nuclear explosions is quite variable due to the number of isotopes and other factors, X-ray irradiation is comparatively uniform, so that mSv are a reliable and useful estimate of risk of most common radiation to people. The numbers are  very useful even when open to argument because of the many variables. Here are some mSv comparisons with an older  tissue dose radiation measure, REMs, or Roentgen Equivalents, Man. (Sorry, women; you have Madam Curie):

• 1 rem = 0.01 Sv = 10 mSv

• 1 mrem = 0.00001 Sv = 0.01 mSv = 10 μSv

• 1 Sv = 100 rem = 100,000 mrem (or millirem)

• 1 mSv = 100 mrem = 0.1 rem

• 1 μSv = 0.1 mrem

(In this essay I use only mSv to make comparisons cleaner.)

Comparative risk of radiation exposure is important and useful both to physicians whose decisions determine the dosages prescribed to patients and to those of us who are exposed to otherwise confusing information and misinformation. It helps to have perspective, which is valuable even when  ‘experts’ argue about precise numbers.  In the much maligned airport screenings, for example, it may help to know that one would undergo:

400 airport screenings to absorb the same mSv as one chest X-ray;

12,000 screenings compares to one mammogram;

20,000 screenings compares to one abdominal CT scan;

40,000 screenings is comparable to one whole body scan;

60,000 to one barium enema; and,

80,000 screenings to one neonatal abdominal CT scan.

Estimates of relative radiation risk from medical imaging, and procedures,  are extremely variable. Yet it is clear that cumulative doses are increasing, and that medical radiation exposure can be significant; whether people disagree by 10 or even 30 percent matters little. The following is a conflation of my remote memory and the harvest from the net today. Here are a few net.ferences:

http://xkcd.com/radiation/ emedicine.medscape.

But the sources are so many, and so easy to access, that for more I will ask  readers to jump into the net and flail about on your own.  I found the accompanying dose estimates of interest. These doses are all in mSv.

Estimated irradiation for medical procedures; Dose in mSv

chest X-ray______________0.1–0.2

each dental X-ray ________ 0.2

head CT________________ 1.5

mammogram ____________ 3

CT abdomen ____________  5.3

chest CT ________________5.8

heart CT and angio________ 6–13

barium enema ___________12–15

angio/vascular study_______19

infant Abdomen CT________ 20

angio/cardiac study ________70

Estimates of average yearly radiation exposure Dose in mSv

background radiation (earth sun, etc) __________________2–3

living within 50 miles of a nuclear power generating plant__ 0.009

living within 50 miles of a coal powered generating plant___ 0.03

daily use of a computer screen or other CRT____________  0.1

commercial full time occupational high altitude air travel____ 2

maximum  allowed annual dose  for nuclear plant workers   _  50

lowest one year dose clearly related to cancer___________ 100

Estimates of acute (or per day) radiation dose Dose in mSv

living within 10 miles of the 3 Mile Island accident____ 0.01

Sacramento to Paris commercial air flight__________  0.085

dose limit for workers in a life saving emergency ___250

one hour next to the Chernobyl meltdown ________300

dose causing transient symptoms______________ 400

dose causing severe radiation sickness or death_ _ 2000

lethal dose_________________________2000–4000

After combing the web, and collating  information from diverse sources, surely I have made errors. So please call them to my attention, dear reader. Let us hope that airport screening will become more rational, and less driven by political nonsense; that unwise dosing of people with medical X-rays will cease; and that the media will act and report responsibly. But hopes are not always fulfilled; we are wise to maintain an informed perspective in case hope fails us.


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