While officials played down the immediate risks to consumers, the findings further unsettled a nation worried about the long-term effects of the hobbled reactors.
The Tokyo Electric Power Company, with help from the Japan Self-Defense Force, police officers and firefighters, continued efforts to cool the damaged reactors on Saturday to try to stave off a full-scale fuel meltdown and contain the fallout. The latest plan involved running a mile-long electrical transmission line to Reactor No. 2 at the Fukushima Daiichi Nuclear Power Station to try to restore power to its cooling system.
About 500 workers from the utility connected the power line on Saturday. They were checking the cooling system, which has been disabled since the earthquake and tsunami hit more than a week ago, and hope to restart it on Sunday.
Restoring power at the plant could provide a glimmer of hope after days of increasingly dire news that now includes contaminated food.
Yukio Edano, the chief cabinet secretary, said that spinach and milk were the only products found to have abnormally high radiation levels. The level of radioactivity found in the spinach would, if consumed for a year, equal the radiation received in a single CAT scan, he said, while that detected in milk would amount to just a fraction of a CAT scan.
“These levels do not pose an immediate threat to your health,” Mr. Edano said, adding that the Health, Labor and Welfare Ministry would provide additional details. “Please stay calm.”
Still, the Fukushima Prefecture asked all dairy farms within 18 miles of the nuclear plant on Saturday to halt all milk shipments. Officials also halted shipments of spinach from the entire prefecture.
The milk with the elevated radiation levels was found at farms in Fukushima Prefecture on farms about 19 miles from the nuclear plants. The contaminated spinach was found one prefecture to the south, in Ibaraki Prefecture, on farms 60 to 90 miles south of the plants.
Food safety inspectors said the iodine-131 in the tested milk was up to five times the level the government deems safe, and the spinach had levels more than seven times the safe level. The spinach also contained slightly higher than allowable amounts of cesium-137.
Minuscule amounts of radioactive iodine were also detected in the water supply in Tokyo and its five surrounding prefectures. In Tokyo, about 160 miles from the Fukushima Daiichi plant, the level was less than 1 percent of that considered dangerous by the government. In Fukushima city, about 50 miles from the power plant, the levels were still below half of the legal limit.
Iodine-131 and cesium-137 are two of the more dangerous elements that are feared to have been released from the plants in Fukushima. Iodine-131 can be dangerous to human health, especially if absorbed through milk and milk products, because it can accumulate in the thyroid and cause cancer. Cesium-137 can damage cells and lead to an increased risk of cancer.
The iodine levels are well beyond what the Food and Drug Administration in the United States considers a cause for concern. But experts say Japan’s reassurances about food safety were probably accurate.
Dr. Harold M. Swartz, a professor of medicine at Dartmouth who studies radiation exposure in people, said that the contamination levels were low and that the government’s advice was “probably reasonable.” But, he added, because people are so afraid of radiation, they are likely to avoid these foods altogether.
“Seems unnecessary to eat these” foods, said another expert, Dr. David J. Brenner, director of the Center for Radiological Research at Columbia University. “I wouldn’t.”
That judgment was shared by Katsuko Sato, 76, who was shopping at a supermarket in central Tokyo on Saturday evening. She said she would stop buying spinach and, after watching Mr. Edano’s news conference, she called her family and friends to urge them not to, either.
“I’m not going to believe the government because I don’t think only spinach from Ibaraki will be affected,” she said.
A handful of vegetable shop owners in Tokyo said they were concerned about the report, but continued to sell vegetables from Fukushima and Ibaraki because they had not been told to stop.
Mark McDonald and Ayasa Aizawa contributed reporting from Tokyo, and Denise Grady from New York.
