The
contamination of air and foodstuff s resulted in some
internal exposure to ionising radiation among almost all
people born since 1945, while gamma rays emitted from
radioactive fallout deposited on the ground resulted in
low-level external exposure. Although such radiation
exposure continues today, it is at very low levels.4
The main health concern from exposure to ionising
radiation emitted from radioactive fallout is the
develop ment of thyroid cancer among people exposed
in childhood.4,6 The thyroid gland cannot distinguish
stable iodine, a necessary dietary mineral, from
radioactive varieties of iodine, such as iodine-131,
produced in a nuclear explosion. The thyroid, most
sensitive to radiation at a young age, can receive an
internal dose after consumption of contaminated foods,
for example fresh milk and other dairy products that
accumulate radioactive iodine when dairy animals graze
contaminated pastures.6
In the USA, atomic weapons testing at the US
Government’s Nevada test site exposed the public
across the entire country, although most people were
exposed to only fairly low doses of ionising radiation.
Those youngest at the time of exposure would have
received the largest radiation dose because the ingested
radioactive iodine would be concentrated in a smaller
gland. The per person internal radiation dose to the
thyroid for the 160 million people alive in the USA