[ RadSafe ] Chemical hormesis - Re: U.S. Nuclear Power Industry Workers Study -HealthyWorker Effect

[Cadanau, Rod]

	An interesting speaker at a recent toxicology symposium spoke
about hormesis and chemical toxicology.  Hormesis can involve several
different mechanisms.  The same effect could be responsible for both
benefit and harm.  For instance, blood thinners can help reduce the
possibility of clots forming and causing strokes, but if too much is
given, excessive bleeding can become a problem.  The benefit can be from
a different effect than the harm.  Aspirin has a pain-reducing effect,
but it's also an acid.  Up to a certain amount, the stomach can easily
deal with the acid effects and allow the pain reducing benefits, but an
overdose causes the harmful effects to overcome the benefits.
Acetominophen (Tylenol) is metabolized by a particular enzyzme (which
also is part of metabolizing alcohol).  An overdose uses up all the
enzyme before more can be made and then liver damage starts.  
	Balancing these effects is an important part of determining
dosage.  Someone made the interesting point that pharmaceutical research
is essentially the search for hormetic effects of chemicals.


-----Original Message-----
From: John Jacobus [mailto:crispy_bird at yahoo.com] 
Sent: Wednesday, March 16, 2005 3:00 PM
To: Syd H. Levine; John_Sukosky at dom.com
Cc: radsafe
Subject: Re: [ RadSafe ] Re: U.S. Nuclear Power Industry Workers Study
-HealthyWorker Effect


Part of the problem is that biology is not like
physics.  Predictions made at high values do not
necessarily occur at low values.  Then there is the
problem of cellular studies vs. epidemiological
studies.  How cells respond to radiation may be
mediated by the response of other cells and enzymes,
etc. in the body. I guess that I doubt that there is a
risk or benefit at low doses and dose rates, but I may
be in the minority. 

I really don't know how common hormesis is in nature. 
I guess if you look for it, you will find it.  I have
never consider the analogy with vitamins to be that
strong of an argument.  We need vitamins for
biochemical functions.  Do we really need radiation? 
If so, how much?  Are people who live in "high"
radiation areas really that much healthier?
. . .