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Re: Shipyard workers etc[Scanned]
Chris,
I think you raise a very important point. If we can identify a mechanism by
which sick people are actively moved out of one group and into another, the
results of a comparison will be difficult to interpret. You raise the
possibility that people predisposed to cancer would have been taken out of
the nuclear cohort and moved to the non-nuclear one by the medical screening
process. I was hoping that someone more familiar with the study would
comment on this.
Is it really possible that someone could "fail" the medical screening
because of family history? I am familiar with two types of occupational
screening: You could fail the physical if you were not fit enough for the
work (nothing to do with radiation). The other type of screening was
intended for early detection of cancers and had nothing to do with job
placement.
Of course, it could also be that people with a family history of cancer
might be more worried about it and refused to work in the nuclear yards. It
is probably not possible to control for everything and no one study can
provide all the answers. I think the shipyard worker study is one more
reasonably strong data point.
It should also be pointed out that moving sick people from one group into
another can be an issue in all types of epidemiological studies, whether
they are ecological, cohort or case control. For example, if lung cancer
changes lifestyle, so that one keeps doors and windows shut just a few
percent more (too small a change to be measurable on a questionnaire) and
this raises radon levels in the living areas, then you move sick people from
the low radon group to the high radon group. I have yet to see anyone
quantitatively address that problem.
Overall, I think we have a tendency to throw data into the data analysis
technology too quickly, without examining possible cause and effect
mechanisms first. The solution to the seemingly contradictory data sets will
not be found by calculating yet another correlation coefficient or p value
or by talking about non-identifiable cross confounders.
OK, I'll get off the soap box now.
Kai
----- Original Message -----
From: "Dr Christoph Hofmeyr" <chofmeyr@nnr.co.za>
To: <strom@pnl.gov>
Cc: <radsafe@list.vanderbilt.edu>
Sent: Thursday, February 06, 2003 4:33 AM
Subject: RE: Shipyard workers etc[Scanned]
> Daniel Strom,
> I would like to expand on an observation I made in an earlier comment. I
> believe the 'healthy worker effect' can only be expected if there is
> some form of medical screening. In the case of the Nuclear Shipyard
> Worker Study that is true for the Nuclear Worker groups (plus 3-yearly
> medicals for the higher exposed cohort), but apparently the Non-NW group
> was not medically screened and also contained those that had failed the
> medical screening for radworkers (which included things like family
> health history, etc.). In that case I see nothing unexpected or
> sinister in the control cohort more or less reflecting the American
> average. IMHO the lack of medical screening does put a question mark on
> the validity of the control cohort. It might be more correct to compare
> the low dose (<0.5 rem) and higher dose cohorts, which both had the same
> screening (although there was still a difference in routine medical
> supervision). There seems to be hardly any significant mortality
> differences between these two cohorts (although these cohorts might not
> be well controlled in terms of relevant parameters like age, duration,
> etc.).
> Own thoughts.
> Chris Hofmeyr
> chofmeyr@nnr.co.za
>
>
> -----Original Message-----
> From: Thurman Wenzl [mailto:tbwenzl@YAHOO.COM]
> Sent: 05 February 2003 01:10
> To: radsafe@list.vanderbilt.edu
> Subject: Shipyard workers etc[Scanned]
>
>
> I know it's a little late to be following up on this
> dialog of nearly a month ago, but I didn't notice if
> anyone pointed out that the Matanoski study, never
> having appeared in the peer-reviewed literature, is
> available from CEDR - at (I think) cedr.lbl.gov (all
> 452 pages)
>
> On dose distributions, she reported that about 9% of
> her monitored cohort had cum doses above 5 rem, while
> Rinsky (1981 Lancet on Portsmouth shipyard only)
> reported about 11.3% above that point (with a median
> of 540 mrem).
>
> NIOSH is following up on the Rinsky study.
>
> Thurman Wenzl
> ..usual disclaimers..; these are my own thoughts.
>
> From: "Strom, Daniel J" <strom@PNL.GOV>
> Date: Thu, 09 Jan 2003 15:17:38 -0800
> Reply-To: "Strom, Daniel J" <strom@PNL.GOV>
> Sender: owner-radsafe@list.vanderbilt.edu
>
> ------------------------------------------------------------------------
> --------
>
> Ted,
>
> The NWs were quite comparable to other working groups
> in non-shipyard
> studies, regardless of dose. The result that sticks
> out like a sore thumb in
> the NSWS is the NNWs, not the NWs. The NNWs
> systematically differ from NWs
> and NNWs in other cohorts. This result is inconsistent
> with other rad and
> non-rad occupational epidemiology studies.
>
> - Dan Strom
>
>
>
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