[ RadSafe ] Boost for N-test veterans' case

a c mcewan acmcewan at clear.net.nz
Wed May 16 18:27:01 CDT 2007

Fred Dawson posted a news article which stated

"New research shows an apparent link between British nuclear tests in the
South Pacific in the 1950s and genetic defects seen in veterans.
Massey University in New Zealand said changes to veterans' chromosomes could
be attributed to their participation in the tests at Christmas Island.
Lawyers for British veterans who served there said the study strengthened
their claim against the Ministry of Defence. The MoD, which has denied the
claim, said it would review the new findings."

I read a report on this study a year ago in which it was claimed that there
were significant differences in the frequencies of sister chromatid
exchanges in chromosomes of study group participants compared with a control
group. Colleagues in the UK advised that "This assay requires culturing
cells to their second division and exchanges are observed through a
harlequin staining technique. The chemical BrdU used to observe the effect
produces many of the observed exchanges. Ionising radiation is not efficient
at producing these exchange aberrations and when seen in human lymphocytes
they are usually taken to be markers of chemical exposure."

Comments I provided at the time on the report follow.
The observed frequencies of SCEs in individuals vary widely in both the
study (1 to 34) and control (2 to 28) groups, with similar wide standard
deviations about the means for both groups. Further, the mean SCEs observed
are not greatly different but generally lower than those observed in normal
populations elsewhere (p.20 of the report). While the small difference in
the mean SCE scores is of statistical significance the potential for
confounding factors in comparing the two groups needs to be recognised.
While the authors collected information on a number of potential confounders
these are not explored in any detail. The very different smoking habits of
the test veterans compared with controls is noted but discounted on the
basis that the impact of smoking on SCE frequencies is not long lived.
However, no information is given on the current smoking habits of the groups
and how these may differ. Furthermore no correlations were attempted between
current individual smoking habits and SCE scores, which might have provided
some indication of smoking as a factor giving rise to SCEs.

The authors also provided no information on whether there is any difference
in medications being taken by the two groups, nor did they explore the
possibility of drug-induced effects on SCE scores. If the study group, for
whatever reason, has a different socio-economic level with different welfare
or sickness benefit dependency, there could be an associated difference in
medication use.

The authors also seem to imply that SCEs caused by smoking are of
short-lived duration, while those caused by putative radiation exposure are
longer lasting (e.g. on p.7). No explanation is offered as to why this might
be the case. However, on p. 26 of the report they state that if the
difference in the mean SCE scores of the study group versus the controls
were to be attributed to radiation exposure "this would imply, a priori,
that radionuclides were still present in their system". They concluded (on
p.28) that the small difference they observed in mean SCE scores between the
study group and controls was attributable to "residues of radiation
particles that may still be present in the bodies of the veterans", and that
small body burdens of alpha emitters (e.g. uranium, plutonium) "could be the
source responsible" (first paragraph on p.27).

This postulate is without foundation.

Andrew McEwan

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