Re: PHYSICS NEWS UPDATE -- Number 694 July 29, 2004 by Phillip F. Schewe, Ben Stein

From: Gregory L. Hansen (glhansen_at_steel.ucs.indiana.edu)
Date: 07/31/04 

Date: Sat, 31 Jul 2004 01:35:57 +0000 (UTC)

In article <0qplg051lkrfjpcrtc95vpl5j1cors09uo@4ax.com>,
Eric Gisse <fseggNOSPAM@uaf.edu> wrote:
>On Fri, 30 Jul 2004 22:04:28 +0000 (UTC),
>glhansen@steel.ucs.indiana.edu (Gregory L. Hansen) wrote:
>
>>In article <Pine.LNX.4.44.0407291149150.21683-100000@erodium.hep.wisc.edu>,
>>Creighton Hogg <wchogg@hep.wisc.edu> wrote:
>>>
>>>
>>>On Thu, 29 Jul 2004, Uncle Al wrote:
>>>
>>>> Sam Wormley wrote:
>>>>
>>>> > the researchers' preliminary calculations indicate that an accurate
>>>> > test for breast cancer could be performed at a dose similar to that
>>>> > of a current mammography examination.
>>>>
>>>> Dose or risk? DOSE! "similar" = "factor of 10" There is that
>>>> bit about the nuclear reactor, too, or a spallation gizmo.
>>>> Mammograms are explicitly carcinogenic for their radiation dose,
>>>> but "real hazard is outweighed by theoretical therapeutic
>>>> benefits."
>>>
>>>Okay, I'm honestly curious. What's your source for the claim that
>>>"mammograms are explicitly carcinogenic for their radiation dose".
>>>I've never heard that before.
>>
>>If you go with the LNT model, a banana is carcinogenic.
>
>LNT?
>
>For whatever reason it makes me think 'no safe dosage'.

Linear, No Threshold. The risk is proportional to the dose, and there is
no safe dose; risk=0 only when dose=0. That makes any source of naturally
occuring potassium, like in food, or in you, a hazard. An interesting
radiation unit was proposed, I forget the name, but one unit is equal to
the normal internal dose that a human gets from his own tissues.

LNT is a controversial model. DNA is damaged all the time by radiation,
chemicals, microbes, and thermodynamics, and there are a number of
mechanisms that repair it. Another possibility is that radiation is only
hazardous when the dose overwhelms the body's ability to repair. There's
some evidence that small amounts of radiation are even good for you,
although that's also controversial. The main reason for the controversy
is that the effects are so small at small doses, the error bars so large,
that you just can't say where the line intercepts the y-axis.

But public policy is made with the conservative LNT model. And so you
could, if you like, use that model to calculate the number of people that
die per year from banana-induced cancers. (I haven't done the calculation
myself.) 

-- 
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Groundskeeper Willy