Radiation in Japan’s seas may not be long-term threat

RADIATION from fish and lobsters near Sellafield suggest radioactive material dumped into the sea from Japan’s Fukushima Dai-Ichi plant isn’t a long-term health threat, scientists said.

The Sellafield nuclear waste plant in Cumbria has discharged about 44 times more Cesium-137, one of the most harmful radioactive materials to humans, into the Irish Sea since 1952 than what has leaked from the Japanese plant this month, based on data from both sites. Still, average radiation doses by seafood consumers near Sellafield over 15 years have been half the recommended limit, studies show.

The research suggests bans on Japanese seafood are unnecessary, said Richard Wakeford, professor of epidemiology at the University of Manchester’s Dalton Nuclear Institute.

The US and EU have curbed imports from Japan, and some hotels have stopped serving seafood from the country because of radiation fears.

“It is not a long-term problem, and that’s what you learn from Sellafield,” Mr Wakeford said. “I don’t think there’s any need for this knee-jerk reaction, which is hitting someone when they’re down.”

Some 4,700 terabecquerel of radiation leaked from the plant into the sea between April 1-6, Junichi Matsumoto, general manager at plant operator Tokyo Electric Power Co, said.

That is 31,333 times more than what the utility said it dumped into the sea from April 5. The leak included 940 terabecquerel of Cesium-137, which takes 30 years to decay by half and can cause cancer if ingested.

Between 1952 and 2009, Sellafield legally discharged about 41,353 terabecquerel of Cesium-137, based on data from Britain’s Environment Agency and the Journal of Radiological Protection.

The biggest discharge in a single year was 5,200 terabecquerel in 1975.

The highest radiation doses were found in the 1970s among consumers of fish and shellfish in Cumbria.

The average dose in that group was as much as three millisieverts a year, according to a study published in 2000, triple the annual limit of one millisievert for man-made exposures set by the International Commission on Radiological Protection. The group’s average dose between 1995-2009 was 0.5 millisievert, data showed.

“Although it was fairly high levels being discharged, that initial discharge has stopped,” said Tony Irwin, a nuclear technology lecturer at the Australian National University, who helped review practices at Russian reactors after the world’s worst nuclear disaster at Chernobyl in 1986.

“You get a vast dilution with the sea. It was more of a short-term effect.”

People are exposed to an average of 2.4 millisieverts a year from the earth’s crust and cosmic rays, the World Nuclear Association in London states. Exposure of 100 millisieverts a year is the lowest level at which any increase in cancer is evident.

A becquerel is a measure of radioactivity and a terabecquerel is one trillion becquerel. A millisievert is a measure of the dose of radiation received by a person.

Japan plans to measure the radiation exposure of 150,000 residents near the Fukushima plant, the Yomiuri newspaper reported, citing Welfare Minister Ritsuo Hosokawa.

Contamination of the land within 100 kilometres of the plant is likely to have a greater long-term effect on human health than radiation in seawaters, said Peter Burns, former chairman of the United Nations Scientific Committee on the Effects of Atomic Radiation.

“The only significant pathway at this stage is the contamination that’s on the ground, and people getting external radiation from living in the contaminated area,” Mr Burns said.