[ RadSafe ] Re: Cameron's refutation of "Alara Does Work"

[John Jacobus]

Dr. Long,
As one one worked with medical records at one of the
Naval shipyards, all workers who were involved with
radiation exposure would have a screen physical. 
Frequently, those who had relatives with cancers would
be excluded from work involving radiaion.  

Yes, I would think that this would bias the data,
leading to a sicker cohort of not non-radaition
workers.  That is why the study does not exhibit a
healthy worker effect, despite the conclusion of
Rainer, who is neither an epidemiologist nor has
access to the original data.

Of course, I doubt that this selection bias was taken
into account by Matanoski as she only had the records
but not the directives on worker selection.  

--- howard long <hflong at pacbell.net> wrote:

> Ranier, your careful review of the Boice commentary
> on Matanoski's presentation of the vast Nuclear
> Shipyard Study, confirms my belief that healthy
> worker effect cannot explain the 3 years of life
> apparently added by exposure of Gulf Coast workers
> to 0.5 rem extra.
>    
>   The only credible (although minor) healthy worker
> selection I have seen proposed, was here on Radsafe.
> It was that a doctor giving employment exams might
> unconsciously have directed persons of less vigorous
> health away from imagined hazards of radiation
> exposure, to otherwise identical work. 
>    
>   Howard Long
>   
> Rainer.Facius at dlr.de wrote:
>   Dear John:
> 
> Thank you for providing the Boice Jr. (2001) paper
> commenting on Matanoski's Nuclear Shipyard Study. I
> took some time to compare his remarks with the
> original report and therefore my reply is somewhat
> late.
> 
> First of all my comparison leads me to conclude,
> that Boice delivered a very compressed but overall
> fair summary of Matanoski's report.
> 
> Secondly, his assessment of the high general quality
> of Matanoski's work and report is in line with
> Sponsler and Camerons's (2005) evaluation.
> 
> Boice does nowhere claim that the observed
> significantly lower total mortality of the >= 5 mSv
> nuclear as compared to the non-nuclear worker group
> is the result of bias. 
> 
> He addresses some points of concern without calling
> into question the principal quality of the results.
> 
> Boice's concentration on leukaemia data - though
> understandable - is somewhat moot, given the small
> number of cases and indeed he does not draw any
> conclusions from discrepancies with his
> expectations. 
> 
> Regarding race, Boice states "It appears that race
> was not considered in the analysis which could be an
> important confounder for certain cancers". It is
> true that Matanoski could not stratify their data
> with respect to race since the personnel files did
> not contain this information. It is not true that
> this confounder was not considered. Mantoniski et
> al. discuss in quite some length this problem and
> present their reasons to conclude that their
> findings would not be seriously affected. 
> 
> An objection sometimes raised against the validity
> of Matanoski's study is the (apparent) absence of
> the healthy worker effect frequently seen in
> occupational studies. Boice also does state this
> absence without drawing the usual conclusion - most
> appropriately so. 
> 
> Although the literature does differentiate a dozen
> or so 'healthy worker effects' the bulk of this
> selection bias can be attributed to two mechanisms,
> (i) the "healthy worker hire effect" and the
> "healthy worker survivor effect". The first bias
> excludes potential workers whose illness prevents
> them from seeking or finding employment. The
> corresponding biased SMRs ususally scatter around
> 0.90 (90%) and hardly ever fall below 0.80.
> Furthermore this selection bias dilutes within the
> first years of employment. The "healthy worker
> survivor effect" results from "differential job
> migration" either into another less demanding
> occupation or out of the workforce altogether due to
> illness occurring during employment. 
> 
> Although the healthy worker hire effect is regularly
> invoked when radioepidemiological studies find
> massively lower cancer mortalities (and they usually
> do) to explain this discrepancy with expectations,
> this argument rarely exceeds the standing of an ad
> hoc explanation. So far I never have seen this
> 'explanation to be offered and then accompanied by
> an obviously mandatory discussion of which checks of
> employment medicals do have prognostic power to
> select against employers more likely to develop
> cancer than others. 
> 
> Regarding the healthy worker survivor effect I have
> so far not found quantitative data as to its typical
> size regarding non cancer diseases, but here too
> such arguments - where needed to explain too low
> radiogenic cancer mortalities - do never accompany
> its invocation with a proper discussion of what
> amount of mortality reduction might reasonably be
> ascribed to it. Apparently, "anything goes".
> Furthermore, since cancer is predominantly a disease
> of advanced age, the age dependence of the healthy
> worker survivor effect should be addressed too.
> Finally, the design of some radioepidemiological
> studies - such as the studies on European aircrew -
> excluded its influence altogether - which did not
> prevent some of the investigators to invoke it
> nevertheless. 
> 
> After all, the Matanoski study does exhibit the
> healthy worker effect for diseases were you would
> expect to see it, i.e., for mortality from diseases
> of circulatory system - the dominant single cause of
> mortality in the age of workforces. The diagram in
> the attached PDF-file (again available upon request
> if the moderator intercepts it) clearly demonstrates
> that the healthy worker effect is there as it
> properly should be. Regarding its absence from total
> cancer mortality, the diagram reveals enhanced
> mortality from cancers of the respiratory system as
> the cause. Matanoski's report as well as Boice's
> discussion appropriately invoke known workplace
> related agents which cause this enhanced cancer
> mortality which in turn masks the otherwise reduced
> mortality from other cancers. 
> 
> Therefore, the objection - by others than Boice - of
> a missing healthy worker effect is misplaced and
> futile. 
> 
> In summary, none of the limitations as he enumerates
> them make Boice to conclude that the observed
> reduced cancer mortality can be explained as arising
> from bias.
> 
> Boice's final 'overcautious' assessment "While the
> study is 'consistent' with no effect follow low-dose
> radiation exposures, the relatively small doses and
> narrow dose distribution limits interpretation."
> spells out the reason why personally I do hesitate
> to publicize the Matanoski data as a 'proof' for
> radiation hormesis.
> 
> Nevertheless, your discarding these data altogether
> as irrelevant is neither backed by statements from
> Boice's paper that you kindly provided to me nor by
> their limitations - as they were properly spelled
> out by Matanoski et al. in the first hand.
> 
> Kind regards, Rainer
> 
> 

+++++++++++++++++++
"You get a lot more authority when the workforce doesn't think it's amateur hour on the top floor."
GEN. MICHAEL V. HAYDEN, President Bush's nominee for C.I.A. director.

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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