[ RadSafe ] A-bomb survivors face greater risk of thyroid cancers

[Dawson, Fred Mr]

The Guardian reports :-

A-bomb survivors face greater risk of thyroid cancers 

http://www.guardian.co.uk/japan/story/0,,1720460,00.html

http://www.rerf.or.jp/

Survivors of the two atomic bombs dropped on Japan at the end of the
second world war are now at greater risk of developing certain thyroid
diseases, including tumours and cysts, according to a study. The risk
increases the younger the survivor was at the time of exposure to the
bombs' radiation.

The thyroid gland sits under the voice box and produces hormones to
regulate growth and metabolism. Diseases there are a useful way for
scientists to study the effects of radiation on the body. Thyroid
cancers were the first solid tumours to increase in frequency among
atomic bomb survivors, for example

Misa Imaizumi, of the Radiation Effects Research Foundation, studied
more than 4,000 survivors of the 1945 atomic bombs on Hiroshima and
Nagasaki between 2000 and 2003 to look for thyroid problems. The
Japanese researchers found thyroid diseases in almost 45% of the
participants, with the risk of developing problems related directly to
the level of exposure. 

"The present study revealed that 55 to 58 years after radiation
exposure, a significant linear dose-response relationship existed in the
prevalence of not only malignant thyroid tumours but also benign thyroid
nodules, and that the relationship was significantly higher in those
exposed at younger ages," the researchers write in the Journal of the
American Medical Association. 

"On the other hand, autoimmune thyroid diseases were not found to be
significantly associated with radiation exposure in this study. Careful
examination of the thyroid is still important long after radiation
exposure, especially for people exposed at younger ages." 
John Boice, of Vanderbilt University school of medicine, writes in an
accompanying article: "The study of atomic bomb survivors remains the
single most important study of radiation effects in humans, but the
exposure was brief, lasting less than a second." 
He added it was "remarkable that a biological effect from a single brief
environmental exposure nearly 60 years in the past is still present and
can be detected". 

Survivors aged under 10 at the time of the bombs were most at risk of
developing thyroid problems, but there was no significant increase in
risk (beyond the radiation exposure itself) for those exposed after the
age of 20. 

For those who were children in 1945, the increased risk seemingly lasts
for life. "The radiosensitivity of the young thyroid gland is high and
most likely relates to subsequent proliferative activity of the gland
during puberty and growth, but the reasons for the absence of risk
following adult exposures are not entirely clear," said Dr Boice





Fred Dawson

Fwp_dawson at hotmail.com