Re: NSWS etc.

[Kai Kaletsch <eic@shaw.ca>]

Chris,



I pretty much agree with everything you say here. There is one implied

misconception that has surfaced a few times on this list and nobody has

commented on yet. It goes something like:



"If there was a benefit to radiation exposure, then the high dose group

should be healthier than the medium dose group."



The obvious problem is that no one claims that the beneficial effects are

LNT.



The more difficult problem is that I know of no beneficial agent where the

amount of benefit is related to the cumulative dose. The benefit is usually

very dependent on how the dose is delivered. In some instances (vitamins) it

seems that the body should have them available all the time. In other

instances you get the benefit from a high dose followed by a period of no

dose. For example: reasonably intense exercise for an hour 3 times a week is

better for most people than moving slowly all the time.



In the studies where only the total dose is measured, the best we can hope

for is to find a "radiation deficiency syndrome" in the group that is

exposed to the least amount of radiation.(Just as you will find deficiency

syndromes in people who don't get enough vitamins or exercise, no matter how

these are administered.)



Once we realize that the beneficial effects of radiation are more likely to

be related to dose rate, rather than cumulative dose, there are no more

contradictions between the ecological and case control data sets.



Kai





----- 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 9:34 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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