[cdn-nucl-l] FW: Comments on your reply to cdn and Mr. Whiteside

["Adam McLean" <adam.mclean@utoronto.ca>]

More on Radiation hormesis from the biological perspective from Jerry...
Be sure to check out:
http://www.cns-snc.ca/branches/Toronto/radiation/radiation.html
for more info.

Our body is hit on average by ~15,000 photons/particles per second from
natural background radiation.

When a cell is hit, it is damaged.  This leads to several options:
1.  The cell may be beyond any repair, and it dies.
2.  The cell may be repaired, but the repair is very bad, and the cells
sends out perverted chemical signals which trigger internal hormones or
other local defences, e.g., p53, to kill the cell (the cell commits
suicide).
3.  The cell may be repaired, but the repair is not so bad and the cell does
not commit suicide.  In this case, the immune system (e.g., killer T-cells)
receives a cell's signals, senses that the cell is abnormal and kills it.
4.  The cell is repaired reasonably well so it can function, more or less as
designed.  It survives, but it is altered (mutated).
5.  The cell is repaired perfectly.

It takes many thousands of mutations to a cell, before it would develop into
a cancerous cell.  And then there are defences that control the growth of
the cell/tumour, so that it may not be fatal to the person.

The normal human metabolism (oxidation) produces cell mutations at a rate
that is 10 million times greater than the rate due to normal background
radiation.  So the rate of mutations due to low level radiation is
negligible!!!!

Low acute doses of radiation (i.e., ~1 to ~40 rad or cGy) stimulate the
activities of our defences: e.g., antioxidant production, cell repair and
cell suicide (e.g. p53 hormone) and the immune system.  They work at a
faster than normal rate to prevent, repair and remove all cell alterations
(metabolism-induced as well as radiation-induced).  The net effect of low
doses is therefore beneficial.

High acute doses of radiation (i.e. >50 rad or cGy) impair/degrade our
defences (the local and the global ones).  The net effect of high doses is
harmful.

Increased levels (dose rates) of long-term radiation (chronic exposures),
higher than normal background radiation, also stimulate our defences,
although gross overdoses of radium, thorium (e.g., thoratrast), etc. weaken
our defences.

Use of the terms: carcinogen, toxin, poison, etc. is bad science.  It's the
dose that makes the poison.  Small doses of zinc, copper, selenium,
radiation, etc. are stimulating.  Therefore, you can talk about a toxic
dose, but not a toxic substance.