Re: [Know_Nukes] Sr-90--->The cancer time bomb facing Scots born duringColdWar

[andrew_mcewan@nrl.moh.govt.nz]

The newspaper report seems to be dredging up very old information and attempting to make a cheap story out of it.  The 'covert' research has not been

anything of the kind - many countries at the time (60s and 70s) analysed - and reported - post mortem bone samples for Sr-90 content, and it was

expected and demonstrated that the highest concentrations would occur in young children, both because of their milk intake and rate of growth of new

bone.  (Concerns, however, have been expressed recently in a number of countries - including the UK and Australia - that relatives were not informed

that post mortem samples were being used for this purpose.)



Details of Sr-90 deposition from atmospheric test fallout have been detailed in successive UNSCEAR reports, and also the radiation doses resulting.

The peak deposition period was around 1963 in the northern hemisphere and around 1964 in the southern hemisphere, as a consequence of the intense

period of atmospheric tests over 1961 and 1962 before the introduction of the test ban treaty.  Peak deposition densities occurred in the northern and

southern temperate zones. The effective dose commitments from Sr-90 from all years of atmospheric testing calculated in the UNSCEAR 1993 report are

0.18 mSv for the north temperate zone (40-50 degrees north) and 0.05 mSv for the south temperate zone.  In the 1960s there was considerable concern

about Sr-90 and it was thought it was the radionuclide that would be the greatest contributor to human exposure.  It was later realised that the doses

from Cs-137 were more important and UNSCEAR 1993 shows the effective dose commitments from Cs-137 from all atmospheric tests as 0.79 mSv in the north

temperate zone and 0.21 mSv in the south temperate zone.  I have calculated a maximum (adult) dose in the year of peak fallout deposition for New

Zealand of 0.031 mSv (years 1965 and 1966), which implies peak annual committed doses in the northern temperate zone of around 0.18 mSv.  Doses to

bone marrow and bone surfaces in young children would have been considerably greater than for adults, but the overall effective doses would still be

within the range of doses received annually from natural sources.



Andrew McEwan

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Andrew C McEwan PhD

National Radiation Laboratory

PO Box 25-099

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Andrew_McEwan@nrl.moh.govt.nz