I meant to include some stuff on radiation exposure and limits. BTW, I have
a quote on acceptable limits for a fetus
First sources:
From
http://www.umich.edu/~radinfo/introduction/radrus.html
SOURCE DOSE (mSv/yr)
NATURAL
Radon 2
Cosmic 0.27
Terrestrial 0.28
Internal 0.39
ARTIFICIAL
Medical X ray 0.39
Nuclear medicine 0.14
Consumer products 0.1
Occupational <0.01
Nuclear Fuel Cycle <0.01
Fallout <0.01
Miscellaneous <0.01
Total 3.6
You see that nuclear fuel cycle is a minute fraction of the total. Further,
I've gotten a more precise upper limit on the nuclear power:
at http://www.umich.edu/~radinfo/introduction/risk.html
I've obtained:
<.001 mSv/yr.
You will also note the catagory "internal." That's the body's natural
radioactivity. The radioactivity human bodies have had since humans first
existed. Its from potassium, BTW. That's why you would die if you didn't
intake radioactive material. Sleeping with someone eight hours a night
would probably increase this risk by about 5%-10%: or about .02 to .04
mSv/yr. That's measurably worse than the risk from nuclear power.
We also see the allowable exposure for various people at the site listed
just above:
Occupational Dose limit (US - NRC) 50 mSv/year
Occupational Exposure Limits for Minors 5 mSv/year
Occupational Exposure Limits for Fetus 5 mSv
Public dose limits due to licensed activities (NRC) 1 mSv/year
So, there is an allowable dose rate for fetuses.
The site has a wealth of other sources, mostly US. Let me quote a few:
First the natural environmental background varies a lot:
Ave
Background Radiation (East, West, Central US) 460 microSv/year
Background Radiation (Colorado Plateau) 900 microSv/year
Background Radiation (Atlantic and Gulf in US) 230 microSv/year
Even with this variation, we cannot measure a corresponding variation in the
cancer rates. That should eventually help us put an upper limit on cancer
rates due to low level radiation. It would be an interesting study.
Now, some other sources:
Building materials (concrete) 30 microSv/year
Drinking Water 50 microSv/year
Pocket watch (radium dial) 60 microSv/year
Eyeglasses (containing thorium) 60 - 110 microSv/year
Coast to coast Airplane roundtrip 50 microSv
With all of these sources, and the natural variation in radiation, why is a
< 1 microSv source so critical? (1000 microSv = 1mSv)
Dan M.
