Japanese authorities grappling with a nuclear disaster must hand out iodine tablets now and as widely as possible to avoid a potential leap in thyroid cancers, the head of a group of independent radiation experts said.
France's CRIIRAD group says Japan has underestimated the sensitivity of the thyroid gland to radioactivity and must lower its 100 millisieverts (mSv) threshold for administering iodine.
Failure to do so quickly could lead to an even higher jump in thyroid cancer cases in coming years than is anticipated, Corinne Castanier said.
"They should still do it (distribute iodine) now because the contamination continues but it will be less efficient. They have to limit the damage. It's not too late to act but they have to distribute them as widely and as fast as possible," she said.
In 2009 France lowered the threshold at which it administers iodine pills in case of nuclear disaster to 50 mSv, a measure of the amount of radiation received by people, from 100 mSv, following guidelines established by the World Health Organisation (WHO) in the wake of the Chernobyl accident.
The WHO also set its threshold for children, pregnant women and women breastfeeding at 10 mSv.
Greatest health risk
In a nuclear accident, it is the discharge of iodine 131 into the atmosphere that constitutes the greatest health risk. The nuclide's radioactivity halves after eight days.
If radioactive iodine is breathed in or swallowed, it will concentrate in the thyroid gland and increase the risk of thyroid cancer, the WHO said.
This risk can be lowered by taking potassium iodide pills to saturate the gland and help prevent the uptake of radioactive material when given before or shortly after exposure.
On 16 March Japanese authorities advised people living in a 20-km radius of the crippled plant to take iodine tablets five days after the catastrophic 9.0 earthquake and tsunami.
"Japanese authorities should have given out iodine tablets in a radius of 100-150 kilometers around the Fukushima-Daiichi plant and done so right after the accident," Castanier said.
No major negative impact
"There is no major negative impact in (taking) iodine tablets so they should distribute them as widely as possible," she said.
The level of radioactive iodine found in seawater near the stricken nuclear power plant was 4,385 times the legal limit on Thursday, the Japanese nuclear safety agency said. That was the highest level registered since the crisis began.
Radioactive discharge levels from the Fukushima plant were very high in the first days after the accident, Castanier said.(Reuters Health/March 2011)
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