By Phil Stewart
WASHINGTON (Reuters) - The Pentagon on Wednesday posted a website mapping the amount of radiation to which the tens of thousands of Americans in Japan at the time of last year's earthquake and nuclear disaster were exposed and said none of the doses posed health risks.
The 9.0 magnitude March 11, 2011 earthquake and tsunami devastated the Fukushima Daiichi nuclear plant north of Tokyo, triggering meltdowns, spewing radiation and prompting the Pentagon to announce voluntary evacuation for families of service members stationed in Japan.
The temblor generated a tsunami wave of up to 10 meters (33 feet) that swamped the Fukushima plant and the surrounding Tohoku region of central Honshu.
The website, http://registry.csd.disa.mil/otr, showed radiation dosages between March 12 and May 11 at 13 locations in Japan where most of the nearly 70,000 U.S. military-affiliated population lived.
It showed the highest rate of adult exposure at Camp Sendai, just north of Fukushima, where the estimated adult dose of whole body radiation was 0.12 rem and 1.20 for the thyroid - the organ most affected by radiation.
By comparison, a full-body CAT scan yields a whole body exposure of 5.0 rem.
Those American personnel who were stationed at Camp Sendai who check the website will see a message saying: "Your whole-body and thyroid radiation dose estimates are well below levels associated with adverse medical conditions."
"Since the estimated radiation doses and health risks associated with this event are so low, no one is being placed in a medical surveillance program to monitor their long-term health outcomes," the website said.
There were no children at Sendai, but children between one- and two-years-old at the Hyakuri Airbase south of Fukushima had an estimated whole body exposure of 0.16 rem and 2.70 rem.
The Pentagon said that by the end of the year it will issue final radiation dose estimates, including estimates for some 8,000 people who had their external or internal radiation measured directly.
Scientists are still studying the effects from Fukushima, the world's worst nuclear accident since Chernobyl a quarter of a century earlier. Some nuclear experts have said Japan was slow to open up to foreign experts who could have helped it better contain the accident and manage the public health risks.
Last May, the operator of the crippled plant disclosed that radiation released in the first days of the Fukushima disaster was almost 2-1/2 times the amount first estimated by Japanese safety regulators.
Tokyo Electric Power said its own analysis put the amount of radiation released in the first three weeks of the accident at about one-sixth the radiation released during the 1986 Chernobyl disaster.
(Editing by Todd Eastham)