On 2011-09-29, Jim Wilkins wrote:

"Ignoramus8377" wrote in message
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Uranium emits alpha radiation. Alpha rays can be stopped by toilet
paper, clothes, etc. However, if a hot alpha emitting dust particle
ends up inside he body (say lungs), it can cause cancer.
i

That appears to be more theoretical than real. Studies of humans
accidentally exposed to low levels don't prove a large increase in cancers
or even a significantly shorter lifespan. Radiation mainly kills cells,
which is why it's used to cure cancer.
http://www.nlm.nih.gov/medlineplus/r...ontherapy.html

There's a debate whether the effects of high exposure extrapolate to low
levels, or the body can tolerate and repair a small dose.
http://www.cancer.gov/cancertopics/factsheet/Risk/radon
http://www.physics.isu.edu/radinf/natural.htm
http://en.wikipedia.org/wiki/Potassium-40
"An adult human body contains about 160 grams of potassium, hence about
0.000117 x 160 = 0.0187 grams of 40K; whose decay produces about 5,000
disintegrations per second continuously throughout the life of the body."

The fact that the debate occurs shows that the evidence is inconclusive. We
have a tolerance level for carbon monoxide, sharp objects, broken bones and
water though overexposure can be fatal.

jsw



I actually agree with it, except that it applies to external ionizing
radiation, and not to radiactive particles inside the body.

i