News like this may be part of the reason of Professor Hayakawa's hostility toward farmers in Fukushima.
Where did this cesium come from? Water? Air? Soil?
Answer: None of the above. It came from a polyethylene sheet covering to keep the crop warm.
What is wrong with the sheet? It is the same polyethylene sheet that was in use when the reactors blew up in Fukushima I Nuclear Power Plant in March last year.
Why did the farmer continue to use the contaminated sheet? No one knows. Probably because no one told him not to use.
The spinach in question has already been sold, and probably consumed.
From Yomiuri Shinbun (4/11/2012):
Fukushima Prefecture announced on April 11 that radioactive cesium exceeding the national safety limit (100 becquerels/kg ) was detected from spinach grown in Fukushima City.
The spinach is sold at the direct sales depots in the city. The prefectural government is recalling it, and has asked Fukushima City to voluntarily halt shipment.
According to the prefectural government, 520 becquerels/kg of radioactive cesium was detected from spinach harvested on April 6 at a farm in Fukushima City. The total 21 kilograms of the spinach from this farm were shipped to the farm produce sales depots between March 26 to April 6.
Spinach growers use polyethylene sheet to keep the crop warm. The farm had been using the same sheet ever since the nuclear accident in March last year. 310,000 becquerels/kg of radioactive cesium was detected from the sheet. According to the prefectural government, it is highly likely that radioactive materials on the sheet were transferred to the spinach.
Last year, spinach from Fukushima in March and April regularly tested with thousands of becquerels/kg of radioactive cesium, in addition to radioactive iodine. A quick browse at Fukushima Prefecture's site on agricultural products found 34,000 becquerels/kg of radioactive cesium in spinach.
NHK, on the same news, says the prefectural government is doing an emergency check on about 500 farms that produce spinach using the polyethylene sheet.
By now, you know this lack of thinking is not confined to farmers in Fukushima. Remember the subsidiary of Chiba JA (ag producer co-op) "recycling" the dirt attached to the plastic sheet used for greenhouses? The dirt was found with 58,000 becquerels/kg of radioactive cesium, but the dirt had been already sold to a tree nursery. I wonder what happened to the dirt.