Re: NSWS etc.

["Jerry Cohen" <jjcohen@PRODIGY.NET>]

Thank you for your thoughtful comments. If , as a society, we needed "solid,

incontrovertible evidence" to make decisions, we would be paralyzed. The

best

we can do is to make judgments based on the preponderance of evidence. All

epidemiological evidence is subject to some degree of question. On

this basis, IMHO, hormesis seems to be far more likely than LNT.



----- Original Message -----

From: Dr Christoph Hofmeyr <chofmeyr@nnr.co.za>

To: Jerry Cohen <jjcohen@prodigy.net>

Cc: <radsafe@list.vanderbilt.edu>

Sent: Thursday, February 13, 2003 7:34 AM

Subject: NSWS etc.





Jerry Cohen,

I would like to see very solid, incontrovertible evidence on questions

like hormesis, and that is why I tend to ask very critical and sceptical

questions in this regard. It is a bit of a disappointment that the NSWS,

which had the potential to provide the evidence, has apparently some

flaws concerning the NNW control group, which turned out to be rather

sickly, apparently due to negative selection factors.  Dr Cameron

conceded these and even elaborated thereon.  Comparing the low dose and

higher dose cohorts shows almost identical mortality over a wide range

of causes of death.  The only really elevated cause was (rare)

mesothelioma (between 5 and 6 times the American average), due to

asbestos and practically the same between low & high dose cohorts.  Both

NW cohorts show about the same 'healthy worker effect' and there does

not seem to be any significant dose effect. A problem might be that

these cohorts were not well 'controlled'.

Dr John Cameron sees the British radiologists' data as more incisive.

The earlier ones might have had much more significant doses and they did

apparently show an increase in cancer but not in total mortality, while

the later ones had comparable cancer mortality with other medical

practitioners (the controls) and somewhat lower due to other causes, if

I remember correctly.  I do pose the question concerning the controls:

'other' medical practitioners might have  been more exposed to pathogens

due to close contact with patients than maybe the radiologists.  The

latter also often have assistants doing the exposures, which the

radiologist interprets.  In the days of fluoroscopy the radiologist was

more exposed.  However, I might be simplifying matters - one should read

the paper properly.  Compared with expectations from the atomic bomb

survivors (I guess LNT), all British radiologists over the years had a

much lower cancer mortality.

Add to the above the Chernobyl missing cancers, and the case for a

definite threshold seems rather solid, whereas IMHO indications of a

positive health effect are less certain.

Chris Hofmeyr

chofmeyr@nnr.co.za



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