Wall Street Journal has the levels (hat tip to Japan Probe for finding).
I'm stunned, but we are told by the government's chief spokesman not to worry, and frankly what he says makes perfect sense at this point:
Mr. Edano said that the level of radioactive materials detected in the milk means that if a person drank that milk every day for a year, based on average Japanese milk consumption, total exposure to radioactivity would be about the same as one CT scan. If a person ate the spinach in question for one year, the radioactivity would be about one-fifth of one CT scan, he said.
Mr. Edano said that the health ministry will collect more data to find out whether contaminated foods are limited to certain areas, and whether it is necessary to restrict the consumption or shipment of certain food products. The ministry will also investigate other products besides milk and spinach, he added.
(Note: CT scan = computerised tomography, a kind of X-ray machine)
Late on Saturday night, NHK World reported this and interviewed an expert from Gakushuin University, Professor Yasuyuki Muramatsu:
Muramatsu says consumers should not eat the spinach as the detected levels of radiation are well above the legal limit. But he adds that the standard takes safety into account, and the amount of radiation is unlikely to pose a negative impact on human health, unless the product is eaten consistently.
I will update this post if I find more relevant information.
Update 1: As spinach on farms are contaminated, it could mean that other crops and the natural environment may have gotten doses of radioactivity, at least in some places, but we don't know enough at this point to say if that is posing any risks at all.
Update 2: Videos and more information over at News on Japan.
Update 3: CNN talked to Dr. James Cox, professor of radiation oncology at the M.D. Anderson Cancer Center in Houston, who said "the reported levels posed little or no health concerns."
"The immediate risk in terms of health effects are probably nonexistent, and the long-term risk is very low," said Cox, a CNN consultant.
Update 4: On Wednesday, Kyodo reports that radioactive materials have been found in 11 types of vegetable grown in Fukushima Prefecture, including broccoli and cabbage, and the Health, Labor and Welfare Ministry called on consumers not to eat the 11 vegetables, also including spinach and the komatsuna leaf vegetable, produced in the prefecture.
The ministry detected radioactive cesium that is 164 times the limit -- 82,000 becquerels -- in kukitachina leaves from Motomiya, along with 15,000 becquerels of radioactive iodine which is more than seven times the limit, it said. The ministry also detected a level of cesium drastically exceeding the limit in some of the other vegetables, it said.
Shipments of spinach from Fukushima have already been halted based on a special law for dealing with the nuclear disaster. In the latest test, the ministry detected radioactive materials from spinach produced in seven municipalities in the prefecture, including the city of Tamura.
The ministry decided to call on consumers to refrain from consuming those 11 vegetables after consulting with experts at the Nuclear Safety Commission of Japan, ministry officials said.
(Note: NHK writes "becquerel" only but the usual unit is "becquerel/kg" to describe levels detected for example in food.)
Update 5: Bloomberg has the details about safe limits set by Japan's government for different foods (the list is also on the MHLW website as a pdf document).