Re: Rocketdyne Worker study

[Warren_Church@uml.edu (Warren Church)]

Sounds like creative epidemeology to me.

Warren Church  warren_church@uml.edu

----------
> From: Otto G. Raabe <ograabe@ucdavis.edu>
> To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject: Re: Rocketdyne Worker study
> Date: Wednesday, November 05, 1997 1:54 PM
> 
> November 5, 1997
> Davis, CA
> 
> Dear RadSafers:
> 
> The Rocketdyne Worker Study is subject to flawed or perhaps biased
> interpretation. "The study population consisted of 4,563 employees
> monitored for external radiation and 2,297 employees monitored for
internal
> radiation, with the second group being mostly a subset of the first." The
> report of the study shows clearly that: "Compared with the general U.S.
> population, Rocketdyne/AI workers monitored for external or
> internal-radiation exposure experienced lower mortality rates from all
> causes, and heart disease. Comparison of monitored Rocketdyne/AI workers
> with NIOSH-cohort members of comparable pay type showed lower mortality
> rates for all causes and heart disease, but similar mortality rates for
> total cancers. Compared with either reference population, monitored
> Rocketdyne/AI workers also experienced a higher mortality rate from
> leukemias." However, those higher leukemia rates were not statistically
> significant.
> 
> To get any significant results at all suggesting a deleterious effect
from
> radiation exposure, the investigators had to ignore the low cancer rates
in
> these workers, and limit comparisons to within the study groups. The
> employees of Rocketdyne are said to show the "healthy worker effect"
> justifying the ignoring of the comparisons to outside control population
data.
> 
> The next step was to do many statistical tests (many more than 100 are
> listed in the report) with various arbitrary lag times and look for any
> significant results. By this process some were found. By grouping all
> hemato- and lymphopoetic cancers into one group (including lymphosarcoma
> and excluding chronic lymphatic leukemias), one group at >200 mSv
external
> exposure had 2 cases that were mathematically significant. These two
cases
> drove the trend test to be significant when lower doses were considered
> that did not in themselves show any significant effect. Also, 2 persons
> dies of lung cancer in the >200 mSv group. The authors seemed to be
unsure
> about whether prior radiation exposure could be important, so that in
many
> of these comparisons even significantly higher prior radiation exposures
> received at some earlier job were ignored. 
> 
> To get a any significant results from the internal exposure phase of the
> study, the authors has to create a special grouping of cancers called
> "Upper Aerodigestive Tract Cancers". Although this is not a known target
of
> any of the internal emitters to which workers were exposed, they
concluded
> that among the 5 cases for exposures above 5 mSv that there was a
> significant increase in these types of cancer compared to the 3 cases
> observed in the unexposed group. It is not clear to me that the logistic
> model used for these analyses is appropriate for such small numbers of
> observed cases. Also, the internal dosimetry metric is not an actual
> internal dose, but rather an unusual interpretation of bioassay data.
> 
> The authors did not report having looked at these few cases that drove
> their findingd to see if there were other explanations for these slightly
> high occurrence rates in these two particular groups. What about personal
> habits? What about chemical exposures? What about adjusting the
> significance levels for the fishing expedition style of epistemology?
> 
> The report of the mostly anti-nuclear advisory committee seems to a
> reworking of one of Alice Stewarts old anti-nuclear essays.
Unfortunately,
> that highly biased advisory committee report is being widely quoted. 
> 
> I learned at the NCRP meeting last April, that Alice Stewarts pioneering
> work on exposure of pregnant women to x rays with respect to childhood
> leukemia has been discredited because of selection bias. Most studies by
> Alice Stewart have looked for any effects that may appear to be elevated
> after radiation exposure while ignoring those that may be reduced. 
> 		*****************************************************
> 		Prof. Otto G. Raabe, Ph.D., CHP
>                 [President, Health Physics Society, 1997-1998]
> 		Institute of Toxicology & Environmental Health (ITEH)
> 		     (Street address: Old Davis Road)
> 		University of California, Davis, CA 95616
> 		Phone: 530-752-7754     FAX: 530-758-6140
> 		E-Mail: ograabe@ucdavis.edu
> 		******************************************************