Deborah Harrell <[EMAIL PROTECTED]> wrote:
But I did note in a later post (different thread, I
think 'reactor woes'?) that it *is* possible that
normal background radiation helps 'prime' immune cells
to hunt for mutant cells, just as exposure to normal
gut bacteria seems to help the immune system tackle
pathogenic bacteria later.
Yes; we know the latter is true. I wonder whether the former is.
Certainly, one can entertain the idea that normal background radiation
causes some cells to change in a way that the immune system recognizes
as `not us' and so goes after them.
It would seem to me that we have had lots of experience over the past
century with people receiving doses of radiation that can be
sufficiently well estimated, such as miners breathing radon gas in a
mine, so that epidemiological investigations could be made.
Perhaps they have been made, but the highly politicized character of
the field has made it very difficult to find them.
The current problem is that defining the line between
"probably safe dose" and "harmful" is controversial;
Yes, that is a problem -- I think the language is not helpful; rather
than make an ordered sequence of categories
safe dose
probably safe dose
probably harmful
harmful
I think it would be better to drop the word "probably " and use some
other term, such as "mostly but not entirely".
But in addition to that, as you say,
... considered to be a "safe" cumulative fetal exposure, yet
_there_is_documented_increase_in_leukemia_, albeit quite small,
with as little as 1-2 rads cumulative (as a fetus)!
As a practical matter, a widely accepted authority has to define what
is considered `more than small' for death rates. (Traditionally,
religions have done this.) The goal is to define what is a socially
acceptable death rate. After all `safe' is not a medical term, but a
description of the level of danger.
This is a separate issue from determining what the death rate actually
is.
According to some of my old notes, such "a widely accepted authority"
must do something that amounts to a ritual:
Rituals bring into being certain states of affairs. "When
authorized persons declare peace in a proper manner, peace is
declared whether or not the antagonists are persuaded" to comply.
(p. 189)
In addition, these states of affairs are judged according to
criteria that are provided by rituals. If "a man is properly
dubbed to a knighthood and then violates the code of chivalry, ...
we do not say that the dubbing was faulty," but that the knight is
faulty. The state of affairs created by a ritual is judged "by
the degree to which it conforms to the stipulations of the
ritual." (p. 189)
A descriptive statement, on the contary, is "assessed by the
degree to which it conforms to the state of affairs it purports to
describe." A yellow house is accurate described only if the hous
is indeed yellow. The two sources of criteria are "exactly
inverse." (p.198)
(Quotations from Roy Rappaport, an anthropologist, who published
"Ecology, Meaning & Religion" in 1979.)
However, currently no one agrees on what should socially be
considered an acceptable death rate.
But I would like to find out what the actual death rates are, at least
for processes that can be measured. For example, in the US, coal
fired electric power plants release radioactive uranium dust in their
smoke. I have been told that if coal fired electric power plants had
to meet the same standards for `off-site radiation release' as nuclear
electric power plants, all the coal fired electric power plants in the
US would be shut down. But I don't know for sure; and I don't know
the death rates.
The other issue is harder: predicting the future. As far as I know,
whether or not the society can agree an acceptable death rate, no one
can figure the probability or improbability that some group of
suicidal soldiers highjacks a large freight carrying jet and flies it
into a nuclear power plant's spent fuel storage building and
distributes radioactive materials over the surroundings.
As for another remark ....
5 rads (I think those were the units!)
Ah! To be so young again.... :-)
Rads are not the original units.
http://www.ieer.org/ensec/no-4/units.html
Roentgen: The old unit of radiation exposure. It is a unit of
gamma radiation measured by the amount of ionization in the air.
In non-bony biological tissue, a roentgen delivers a dose equal to
about 0.93 rad.
Rad (radiation absorbed dose): a unit of absorbed dose of
radiation defined as deposition of 100 ergs of energy per gram of
tissue.
And, in another change, people seem to be using Sieverts more often
nowadays than rems; and I have seen reference to Gy, too:
Gray (Gy): A unit of absorbed radiation dose equal to 100 rads.
Rem (radiation equivalent man): a unit of equivalent absorbed dose
of radiation, which takes into account the varying ways in which
ionizing radiations transfer their energy to human tissue (known
as relative biological effectiveness or RBE). While rads and
grays measure deposition of energy in tissue, rem and sieverts
measure biological damage. Rems are derived from rads by
mutiplying rads by a "quality factor" which approximates the RBE
For beta and gamma radiation the quality factor is taken as
one-that is rems equals rads. For alpha radiation, the quality
factor is taken as 20-that is rems equal 20 times rads.
Sievert (Sv): a unit of equivalent absorbed dose equal to 100
rems.
--
Robert J. Chassell Rattlesnake Enterprises
http://www.rattlesnake.com GnuPG Key ID: 004B4AC8
http://www.teak.cc [EMAIL PROTECTED]
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