Re: Rocketdyne Worker study

["Dr. Marvin Goldman" <mgoldman@ucdavis.edu>]

Otto:
Is there anything in print documenting the refutation of Alice Stewart's
work; any recalibration or alternative quantitative report.  I know people
have questioned the selection process; but she did this some 3 decades or
more ago. It is unlikely it would ever be repeated.
Marvin
At 12:54 PM 11/5/97 -0600, you wrote:
>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
>		******************************************************
>
>