JAPAN | Ocean radiation tests may ignore threat to seafood

Posted on July 28, 2011


JAPAN | JAPAN TIMES | 28 July 2011

Environmental group calls for more detailed data


The government has to release more data from ocean radiation tests to accurately assess the contamination threat to seafood, according to a statement by the Oceanographic Society of Japan.

The government should release radiation readings in seawater that are below its minimum measurement level, because even at those low quantities the radioactive elements may pose a danger when concentrated in seafood, the group, which counts 1,860 marine scientists as its members, said earlier this week.

“Depending on the species, fish have been known to accumulate as much as 100 times the amount of pollutants in the environment,” said Jota Kanda, a professor at Tokyo University of Marine Science and Technology specializing in marine environment.

Radiation threats to Japan’s food chain are multiplying as cesium emissions from the crippled Fukushima No. 1 nuclear power plant spread. Aeon Co., Japan’s biggest supermarket chain, said Monday 4,108 kg of beef suspected of being contaminated by radiation was inadvertently put on sale at 174 stores across the country.

The government on July 19 banned cattle shipments from Fukushima Prefecture, though not before some had been slaughtered and shipped. A ban on shiitake was extended to another area of Fukushima on July 23 because of high cesium levels, the health ministry said.

Testing of seafood off the coast of Fukushima uncovered 68 cases of fish and marine life with radiation readings exceeding the government’s safety limit, according to a report by the Ministry of Health, Labor and Welfare.

The prefecture tested 505 seafood items to discover excessive radiation levels in 15 cases of “ayu” sweetfish, which is generally a freshwater fish, seven cases of salmon, seven cases of greenling and six cases of sand lance, according the report. Ibaraki reported five cases of excessive radiation levels after testing 265 samples.

Seafood tests by 15 other prefectures found no other cases of contamination, according to the report. Miyagi tested 44 samples, while Iwate tested two samples.

“The scope of testing needs to increase, especially in the neighboring prefectures of Miyagi and Iwate,” Kanda said. “In Chernobyl’s case, it took about six months to a year for cesium concentrations in fish to peak.”

That said, the concentrated release of radioactive material into Fukushima’s coastal waters is “unprecedented,” Kanda said.

Radiation in food is measured in becquerel, a gauge of the strength of radioactivity in materials such as iodine-131 and cesium-137. A becquerel represents one radioactive decay per second, which involves the release of atomic energy that can damage human cells and DNA, with prolonged exposure causing leukemia and other forms of cancer, according to the World Nuclear Association.

Levels of cesium-134 in seawater near the Fukushima plant’s reactor 3 rose to levels 30 times the allowed safety standards last week, according to tests performed by Tokyo Electric Power Co., NHK reported.

“The concern is that the contaminants will travel up the food chain reaching greater concentration in higher animals,” Eiji Tanaka, a professor at Tokyo University of Marine Science and Technology specializing in marine bioresources, said in an email Tuesday. “The pollutants may spread to bluefin tuna and minke whales.”

Tests of seawater farther off Fukushima, Miyagi and Ibaraki prefectures showed no traces of radioactive elements, according to a July 22 report by the Ministry of Education, Culture, Sports, Science and Technology.

The minimum detection limit is defined as 4 becquerels per liter for iodine-131, 6 bq/l for cesium-134 and 9 bq/l for cesium-137, the report said.

“Which means that at 5 becquerels per liter, the ministry will proclaim the water safe, but concentration in fish may exceed the 500 becquerel limit” per kilogram set by the government, Kanda said.

Posted in: JAPAN