Cesium levels still exceed standards in wild mushrooms, seafood, game

March 06, 2013


Nearly a year after the government set tougher safety standards for radioactive materials in food and drink, roughly 2,000 samples--mostly from wild mushrooms, seafood and game--were found to exceed the new limit.

Most of the food products showing cesium levels higher than the safety standards were not for commercial distribution and were collected only for the test.

Marine products such as flatfish, boar and other wild meat and mushrooms accounted for 80 percent of the contaminated items seen in tests from April 2012 to January 2013. The vegetables that exceeded the standards were mostly gathered from the wild.

All drinking water, infant formula and baby milk tested showed lower cesium levels than the standards.

Under the standards that took effect on April 1, 2012, the limit for general food items is 100 becquerels of radioactive cesium per kilogram. The limit for milk and infant formula is 50 becquerels per kilogram. The new standards are much tougher than the tentative ones decided on immediately after the accident at the Fukushima No. 1 nuclear power plant following the March 11, 2011, Great East Japan Earthquake.

"After a round of the seasons with the new standards, we have gone through almost all of the food items that could contain radioactivity," a health ministry official said.

Experts say radiation levels will be affected for a long time. Cesium 137, for instance, has a half-life of 30 years, and radioactive contamination in mountainous areas can reach seawater through river flow.

Yasuyuki Muramatsu, a chemistry professor at Gakushuin University who has been studying the radioactive content in mushrooms, said some types of fungi may absorb higher radioactivity levels.

"It depends upon the variety," he said. "But wild mushrooms need to be tested for at least 10 years."

Muramatsu has tested wild mushrooms growing in Fukushima Prefecture.

He said there was no sign of cesium levels having decreased in the second year after the accident.

While cesium has no longer been detected in rivers and seawater, it can cling to organic substances such as clay and fallen leaves.

"Bottom fish, which consume marine organisms that eat accumulated leaves in the sea bottom, are likely to remain contaminated," said Tatsuo Aono, an expert in marine radioecology at the National Institute of Radiological Sciences.

According to the Ministry of Health, Labor and Welfare, the central and local governments carried out about 230,000 tests for cesium between April 2012 and January 2013.

Of those tests, about 2,000, or 0.9 percent, had cesium levels that exceeded government standards. Cesium levels are diminishing, the ministry said.

Fifty-five percent of the samples with higher cesium levels were detected in Fukushima Prefecture, while Iwate, Tochigi, Miyagi, Ibaraki and Gunma prefectures each had more than 100 samples that exceeded the government limit.

The central government asked 17 prefectural governments mainly in eastern Japan to test food and drink for cesium. When high levels are detected in a food item, its distribution is stopped either voluntarily by the producer or by a government ban.

While the government focused its testing on foods and areas that showed high levels of radioactivity in the past, the results painted a different picture.

More than 60 percent of the food samples tested were beef, as radioactive cesium had been detected in cows that were fed rice straw immediately following the Fukushima No. 1 accident. But none of the roughly 17,000 tests conducted on beef in January exceeded the government limit.

On the other hand, only 1,493 commercially distributed food items, including vegetables and fruits, were tested. Of those, only one item, dried mushrooms, were found to have had radioactive levels exceeding the government standards.

While the risk of radiation-contaminated food escaping the tests and appearing on store shelves has been sharply reduced, it is still not zero.

Since April 2012, the government has introduced new shipping bans on more than 130 food items in 14 prefectures.

On the other hand, shipping bans on many other items have been lifted after their radiation levels dropped below the government standards.

The government plans to review food items to be tested from fiscal 2013, which starts in April.

(This article was written by Senior Staff Writer Fumikazu Asai and Akiyoshi Abe.)

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A vendor displays a card saying wild mushrooms are produced in Akita Prefecture, outside the regulation zone. (Asahi Shimbun file photo)

A vendor displays a card saying wild mushrooms are produced in Akita Prefecture, outside the regulation zone. (Asahi Shimbun file photo)

  • A vendor displays a card saying wild mushrooms are produced in Akita Prefecture, outside the regulation zone. (Asahi Shimbun file photo)

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