Three years after the meltdowns at the Fukushima No. 1 nuclear power plant, fears and rumors still circulate among people both inside and outside of Fukushima Prefecture over radiation contamination of food.
Surveys and experts, however, concur that available data indicate there are no alarm signals concerning human health, at least for now.
A Fukushima-based consumers’ cooperative has been monitoring levels of radioactive materials contained in meals actually cooked and eaten at hundreds of households in Fukushima Prefecture over the past three years.
The results have shown the amount of radioactive materials in samples of meals have been extremely small and are insignificant when compared with the fluctuating ranges of the amount of radioactive potassium 40, which naturally occurs in numerous noncontaminated foods such as dried “kombu” seaweed, tea, bananas, spinach, beef, fish, rice and bread.
“People may have various opinions, so we can’t say this data alone guarantee safety or provide a sense of safety for people,” said Yoshihiro Shishido, a worker in charge of the survey at Co-op Fukushima, based in the city of Fukushima.
“But you can say only extremely small amounts (of radioactive materials) have been detected in our survey,” he said.
In surveys conducted between July last year and last month, Co-op Fukushima asked each of the 200 Fukushima households that have participated in the survey to prepare an extra portion of the meal when they cook for their families for two days, and thus offer a total of six meals per household as samples, together with any other snacks and drinks they ate or drank.
More than 90 percent of those households ate foods produced in Fukushima Prefecture. The samples were submitted for testing at a research lab operated by the Japanese Consumers’ Co-operative Union.
Of all the samples, only meals from six households were found to contain radioactive cesium in their meals, and the highest reading of cesium-137 was 2.6 becquerels per 1 kg, and that of cesium-134 was 1.1 becquerel per kilogram.
Meanwhile, the average adult, weighing 60 kg and unaffected by the Fukushima crisis, usually maintains a natural level of 4,000 becquerels of radioactive potassium in their body, meaning that person is exposed to internal radiation 24 hours a day.
If a person keeps eating the same meals of the six households for one year, additional internal radiation exposure from cesium will total up to 0.04 millisieverts.
According to the International Commission on Radiological Protection, an exposure of 100 millisieverts increases the risk of dying of a cancer by 0.5 percent.
“You can say this amount is very low when compared with the state-set safety level of 1 millisievert per year,” Shishido said.
Surveys by Co-op Fukushima and many other research institutes mainly focus on the amount of radioactive cesium, not on other radioactive materials such as strontium-90, plutonium and ruthenium because surveys on such substances consume much time and costs.
But the Health, Welfare and Labor Ministry has claimed its safety standard of 1 millisievert per year from food and drink products is based on sufficient safety margins for noncesium radioactive materials as well, based on the amount of such materials that are estimated to have been released from the Fukushima plant and could have accumulated in a variety of food products.
Meanwhile, the number of contaminated fish caught in the ocean around Japan has steadily kept decreasing until recently, despite continuing leaks of polluted water from the crippled power plant. This is probably due to dilution.
According to data published by the Fisheries Agency, of 1,225 samples of fish and other seafood caught in Fukushima Prefecture and the sea near the prefecture this January and February, 21 samples, or 1.7 percent, exceeded the state-set safety level of radioactive cesium of 100 becquerels per kilogram. The ratio of contamination has steadily fallen, from a high of 26.4 percent two years ago.
For now, commercial fishing off Fukushima Prefecture has been suspended except for trial operations of 26 types of marine life, including various shellfish species, squid and octopus, which have been found to contain little or no radioactive cesium in recent samples.
If any fish are confirmed to be contaminated with cesium exceeding the safety threshold, shipments of that species from the area will be stopped, according to the government.
People who are still worried are advised to avoid eating the meat of wild animals, and also wild mushrooms and wild vegetables as well as bottom-dwelling fish and freshwater fish, whose data have shown higher accumulations of radioactive materials.
For example, shipments of meat from wild boars, deer and bears, wild mushrooms and mountain vegetables are still banned in certain parts of Fukushima, Iwate, Miyagi, Ibaraki, Tochigi and Gunma prefectures.
Of 19,180 fish and other seafood samples that underwent radiation surveys between April 1 last year through March 5 this year, 280 items, or 1.5 percent, were found to have exceeded the state-set regulatory level of radioactive cesium of 100 becquerels per kilogram.
Of those 280 items, 172 were fish and other kinds of seafood caught off Fukushima, and 56 were fresh fish caught in rivers and ponds within the prefecture.
Of the 172, 160 were fish living on or close to the seabed, such as “hirame” and “karei” flounder, “ainame” greenling and “mebaru” rockfish. The highest cesium level detected among Fukushima fish was 1,700 becquerels per 1 kg in a sample of greenling.
In other prefectures, Gunma Prefecture recorded 22 samples of contaminated freshwater fish exceeding safety levels, such as “iwana” mountain trout and “wakasagi” lake smelt, with the most contaminated sample being a lake smelt containing 200 becquerels of cesium per 1 kg.
In Chiba Prefecture, samples from 13 freshwater fish, such as “funa” and “koi” carp, exceeded safety levels. The most affected item was carp, which contained 220 becquerels of radioactive cesium per kilogram.
Miyagi Prefecture recorded seven samples of contaminated sea fish and a further seven samples of freshwater fish. Of them, the most contaminated item was “kurodai” sea bream, which was found to contain 310 becquerels of cesium per kilogram.