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

[Rainer.Facius at dlr.de]

"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:

I have no means to assess the bearing of this suggestion in the nuclear
shipyard context. 

In my (German) experience an employer offering a specific open position
sends applicants which first of all he sees fit for a specific task to a
physician together with an elementary workplace/job description. The
result of the physician's employment medical is conveyed to the employer
in terms of:

"Yes or No" the applicant is fit for the specified job - period.

In this setting it is beyond the discretion of the physician to direct
someone to another position and hence here this selection bias could be
ruled out.

Best Regards, Rainer


Dr. Rainer Facius
German Aerospace Center
Institute of Aerospace Medicine
Linder Hoehe
51147 Koeln
GERMANY
Voice: +49 2203 601 3147 or 3150
FAX:   +49 2203 61970
 

________________________________

Von: howard long [mailto:hflong at pacbell.net] 
Gesendet: Mittwoch, 28. Juni 2006 20:05
An: Facius, Rainer; crispy_bird at yahoo.com; jjcohen at prodigy.net;
mike.bohan at yale.edu; radsafe at radlab.nl
Betreff: Cameron's refutation of "Alara Does Work" 


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
	
	
	________________________________
	
	Von: radsafe-bounces at radlab.nl im Auftrag von John Jacobus
	Gesendet: Fr 21.04.2006 22:38
	An: Facius, Rainer; hflong at pacbell.net; jjcohen at prodigy.net;
mike.bohan at yale.edu; radsafe at radlab.nl
	Betreff: Re: AW: AW: [ RadSafe ] Cameron's refutation of "Alara
Does Work" 
	
	Rainer,
	Here you go.
	
	Have a good weekend.
	-- John
	
	--- Rainer.Facius at dlr.de wrote:
	
	> Thank you John for your speedy reaction.
	> 
	> Do you have a copy of this paper or do I have to
	> order it through our library?
	> 
	> Kind regards, Rainer
	>
	> ________________________________
	>
	> Von: John Jacobus [mailto:crispy_bird at yahoo.com]
	> Gesendet: Fr 21.04.2006 22:18
	> An: Facius, Rainer; hflong at pacbell.net;
	> jjcohen at prodigy.net; mike.bohan at yale.edu;
	> radsafe at radlab.nl
	> Betreff: Re: AW: [ RadSafe ] Cameron's refutation of
	> "Alara Does Work"
	>
	>
	>
	> Rainer,
	> I would say that the Boice paper, J Radiol Prot.
	> 2001
	> Dec; 21(4);400-3, detailing the limitations of the
	> shipyard worker study should shed doubt on Dr.
	> Cameron's assertions.
	>