[ RadSafe ] RE: Increase in cancer in Sweden can be traced toChernobyl

[Bjorn Cedervall]

I was present during the thesis defence today. My interpretation of the 
discussion held by the opponent is that it was shown that there is _no_ 
basis to believe in a causal relation between the Chernobyl fallout and the 
increased cancer incidence in northern Sweden. Much of the discussion 
leading to this related to the choice of age groups, lack of individual dose 
estimates, reference areas and years and also lack of solid support by 
Hill's criteria.

The Swedish doctoral thesis procedure includes a critical review by a 
refereeing/scrutinizing scientific committee. This committee concluded 
unanimously that they did not agree with the conclusions (including of 
course the most controversial about causality) reached by the key author of 
the study.

The Chernobyl fallout in Sweden resulted in an accumulated dose of about 
6000 personsievert (Sv).
In order to statistically detect an extra 1 mSv to a population about one 
billion exposed people are needed (based on data like the followup of atomic 
bomb survivors from Japan). Most people in the fallout areas in Sweden will 
not be exposed to more than the order of 1 mSv (accumulated dose, in extreme 
cases perhaps as much as 10 mSv - these are estimates but as already 
mentioned individual dose estimates are lacking). The Swedish population is 
9 million people but most of these live in the Stockholm area (1.5 million) 
or further south in Sweden. Even though the exposure situations were very 
different (Chernobyl fallout vs. Hiroshima/Nagasaki exposure) the difference 
in dose levels seem so large that the claimed causality association seems 
improbable.

Notice also that there are two versions of the end of the abstract:
http://www.diva-portal.org/liu/abstract.xsql?dbid=8886
If you click on the pdf file and read the end of the abstract (page 6) you 
will find three more lines (about causality) at the end - these lines also 
appeared in the paper copy of the thesis - lines which the refereeing 
committee must have unanimously disagreed about.

Then reflect over this report being actively press released, and as far as I 
understand, before the outcome thesis procedure had come to an end (or 
without taking the message of the refereeing committee into account).

With these lines I represent myself - if any of the above is wrong or need 
to be modified it will be done ASAP.

Bjorn Cedervall                bcradsafers at hotmail.com
PhD, Associate professor (Medical Radiation Biology)

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