No matter how the government tweak the safety limits for radioactive cesium in food items, the public are left fending for themselves after all.
First, if you don't measure it, you won't know it.
Chiba Prefecture says it has just found out that fresh shiitake mushrooms sold at an unmanned farm stand had 740 becquerels/kg of radioactive cesium. The mushrooms have already been consumed. The prefectural government assures us that the amount is small, and there will be "no immediate, direct" consequence on health.
As if all cesium people ingest is from this shiitake crop.
From Jiji Tsushin (4/9/2012):
740 becquerels from Shiitake sold at an unmanned farm stand in Chiba, already sold and consumed
Chiba Prefecture announced on April 9 that shiitake mushrooms cultivated outdoors in Shirai City were found with 740 becquerels/kg of radioactive cesium, exceeding the safety limit of 100 becquerels/kg [notice it is not provisional anymore; it's permanent]. The farmer had already sold 4 kilograms of these mushrooms, and all had been consumed. The prefectural government requested the city to voluntarily halt shipment.
The prefectural government says, "The amount of consumption and the amount of radioactivity are not so great, so it is inconceivable that there will be an immediate, direct damage."
The old, provisional safety limit was 500 becquerels/kg, and the radioactivity of these mushrooms even exceeded the old level. And the same old "requesting voluntary halt" to save money. (Voluntary action is not compensated by the government.)
Second, if you change testing methodology, voila, it is below the safety limit.
Ibaraki Prefecture is one of the prefectures in northern Kanto region whose teas tested above the provisional safety limit of 500 becquerels/kg last year. But now, the national government has changed the rule for teas. Teas are to be tested after they are brewed. So unless the tea has over 1,000 bequerels/kg of cesium, the brewed tea (liquid) will be well below 10 becquerels/kg (new safety limit for water).
From Jiji Tsushin (4/9/2012):
Restriction lifted from the spring "bancha" tea from Daigo, Ibaraki Prefecture, as the amount of radioactive cesium is below the safety limit, says the national government
The national government lifted the restriction on shipment of the spring "bancha" tea from Daigo-machi in Ibaraki Prefecture on Spril 9, as the amount of radioactive cesium was below the safety limit (10 becquerels/kg in brewed tea) in three locations tested.
The shipment of tea from Daigo was halted when radioactive cesium exceeding the provisional safety limit (500 becquerels/kg) was found from fresh tea leaves in June last year.
I went to the Ibaraki Prefecture's website to look for the original data. The data does include the measurement of radioactive cesium the "old way" - measuring the dried tea leaves. If the old way of applying the safety limit on the dried leaves, there are many teas that easily exceed the new safety limit.
From Ibaraki Prefecture's test result, the top red bracket shows the measurement of cesium in "aracha" tea (bulk tea before blending) from Daigo-machi, and the bottom red bracket shows the measurement of cesium in the liquid after the tea is brewed:
Well, there are slight problems with the new way of only measuring brewed tea. There are people who "eat" tea leaves (although I doubt they still do it after the accident, but who knows). I drink "konacha", or powdered tea which is a strong, sushi-shop style green tea that is cheaper and stronger. My cup is left with green "sludge" at the bottom, which I ingest (my tea is from 2010). Many use green tea powders as health supplements.