According to Mainichi Shinbun, the Japanese authorities are finding out that the different parts of the same cow have different concentration of radioactive cesium. Not only that, the same part of the meat from the same cow can yield two different test results. That means even the meat that was tested and deemed "safe" (tested below 500 becquerels/kg of radioactive cesium) may not have been safe after all.
Before they actually started to measure, the prevailing opinion from the radiation experts was that radioactive cesium would get evenly distributed in the muscles throughout the body. Amateur hour at the radiation experts, too. (Now they are changing tunes.)
So, no one knew, and no one knows what they're doing. I seem to fondly recall some of the words of Japan's consumer advocates - "the experts say it's safe...", or "why should we waste taxpayers' money testing all cows?", or "if only media did the good job of providing accurate information..." Amateur hours there, too.
My message to consumers: caveat emptor.
From Mainichi Shinbun Japanese, Tokyo Morning Edition (7/31/2011):
福島第１原発事故の影響で放射性セシウムに汚染された肉牛が見つかった問題で、同じ１頭の牛でも部位などにより検出値の違いが出るケースが指摘されている。専門家も「セシウム濃度は部位により異なる」と説明している。各自治体が今後踏み切る全頭検査の信頼性を高めるため、国は検査の統一指針づくりを迫られそうだ。
Regarding the beef contaminated with radioactive cesium due to the Fukushima I Nuclear Power Plant accident, there are cases where the different levels of cesium are detected from the different parts of the same cow. Experts explain that "the level of cesium differs depending on the parts." The national government will have to come up with the guideline so that the reliability of the radiation tests to be done on all cows by the local governments.
宮城県は２８日、１頭の牛の肉で、部位によって国の暫定規制値（１キロ当たり５００ベクレル）を超えたり、下回る検査結果が出たことを明らかにした。
On July 28, Miyagi Prefecture disclosed that the radioactive cesium was detected that exceeded the national provisional safety limit (500 becquerels/kg) in one part of the cow, while another part was found with cesium less than the safety limit.
この牛は仙台市内で６月２１日に解体され、肩肉（二十数キロ）が流通した横浜市が検査した結果、規制値未満の３８０ベクレルだった。ところが、もも肉（３７・７キロ）の流通先の北海道が肉を調べたところ、５３０ベクレルを示した。
This cow was processed in Sendai City [in Miyagi Prefecture] on June 21. When Yokohama City [in Kanagawa Prefecture] tested the shoulder meat, 380 becquerels/kg of cesium was detected. However, when Hokkaido tested the round of the same cow, 530 becquerels/kg of cesium was detected.
宮城県から６月１日、東京都内に出荷された、別の牛の肉では同じ部位で検査値の食い違いがあった。都内の食肉卸業者が、この牛の肩肉（１２・９キロ）を自主検査し、１１５０ベクレルを検出。しかし川崎市が、この肩肉の残りを調べたところ、６１８ベクレルだった。
In the case of another cow shipped from Miyagi to Tokyo on June 1, the same meat yielded two different test results. When a meat dealer in Tokyo tested part of the shoulder meat voluntarily, 1,150 becquerels/kg of cesium was detected. However, when Kawasaki City tested the same shoulder meat from the same cow, it was only 618 becquerels/kg.
県によると、この４件の検査ともゲルマニウム半導体検出器を使っていた。県は「精密に調べられるもので、機器に問題はない」と話す。ただ、課題は検査手法の統一基準がない点で、県は「検査した肉の部分がどのくらいの脂肪分を含んでいるかや、肉の詰め方で結果に差が出る」と説明する。
According to Miyagi Prefecture, they used the germanium semiconductor detectors in all 4 cases. The prefecture says "The detectors allow a thorough analysis, and there's no problem with the detectors." The problem is the lack of standard procedure for testing, and the prefecture explains "you get different results depending on the fat content, or how the meat is packed."
自治体が今後、全頭検査に相次いで踏み切るのに先立ち、厚生労働省は２９日、検査の基本方針を発表した。ゲルマニウム半導体検出器より短時間で調べられる簡易測定機器の使用を認めるなどの内容だが、調べる部位には言及していない。
In preparation for the testing of all cows by the local governments, the Ministry of Health, Labor and Welfare announced the basic plan for the testing on July 29. The plan allows the use of simpler testing devices that can test the meat in less time than the germanium semiconductor detectors, but there was no mention in the plan as to which part of the meat should be tested.
厚労省は検出値のばらつきは把握しているが、「これまでの例ではセシウムは筋肉に均質に蓄積するとされている。全頭検査を重ねて適切な対処方法を見つけていくしかない」（監視安全課）と説明。各自治体には、同じ牛で１カ所でも規制値を超える部位が見つかれば、全量を出荷停止するよう求めている。
The Ministry of Health and Labor is aware of the differing numbers, but says "From the cases so far, cesium is supposed to accumulate evenly in the muscles. We will just have to find out the appropriate way to deal with the problem by carrying out more tests" (Ministry's Monitoring and Safety Section). The Ministry is asking the local government to stop the entire shipment of the meat from the cow even if only one part of the meat is found with cesium exceeding the provisional limit.