Households that consumed relatively large quantities of fruits and mushrooms produced in Fukushima Prefecture tended to ingest more radioactive cesium in their food than those who did not, according to a joint study by The Asahi Shimbun and Kyoto University.
Households that consumed relatively large quantities of fruits and mushrooms produced in Fukushima Prefecture tended to ingest more radioactive cesium in their food than those who did not, according to a joint study by The Asahi Shimbun and Kyoto University.
An analysis of diet samples provided by 26 households across Fukushima Prefecture, part of a wider study of intake in several areas of Japan, found that some Fukushima households ate 50-300 grams of local fruits and 30-40 grams of local mushrooms per head per day.
There appeared to be a correlation between the level of consumption of those foods and the ingestion of radioactive cesium, but the study did not clarify exactly which ingredients were to blame because it did not break down cesium content by ingredient.
However, the study team did conduct separate research into persimmons and apples shipped from farmers in Fukushima Prefecture. They found that the persimmons contained roughly 40-200 becquerels of radioactive cesium per kilogram, while the apples carried 20-50 becquerels per kilogram.
Those levels are below the current, provisional safety standard of 500 becquerels per kilogram.
Eating 100 grams of such fruits a day would mean an intake of between 2 and 20 becquerels of cesium. A sustained daily intake of 20 becquerels would amount to annual internal radiation exposure of only 0.12 millisievert, far below the maximum limit of 5 millisieverts according to the current, provisional safety standards.
The level is also about one-eighth of the new, stricter safety standard of 1 millisievert that will take effect in April.
Central and local governments have banned the shipment and distribution of food items exceeding the provisional safety standard of 500 becquerels per kilogram.
As of Jan. 18, shipment bans have been imposed under the Law on Special Measures Concerning Nuclear Emergency Preparedness in eight prefectures: Fukushima, Ibaraki, Tochigi, Chiba, Kanagawa, Gunma, Miyagi and Iwate. A variety of foods have been targeted, including consignments of tea leaves and shiitake mushrooms grown on tree logs.
Fukushima Prefecture has been particularly badly affected. Bans have been imposed on shipments of bamboo sprouts from eight municipalities in the prefecture, "yuzu" citrus fruits from five municipalities, chestnuts from two cities, kiwi fruits from two cities and rice from three cities. All fishermen in Fukushima Prefecture have voluntarily confined themselves to port because monitoring tests by the prefectural government continue to register cesium content exceeding the provisional safety limit in certain fish species, including greenling.