The Health, Labor and Welfare Ministry said consumers should avoid eating potentially contaminated vegetables grown near the faltering power plant, including broccoli, spinach, cabbage and cauliflower.
The advisory from the ministry came following consultations with the Nuclear Safety Commission of Japan.
The ministry said the vegetables should not be consumed for the time being and noted that the National Federation of Agricultural Cooperative Associations has halted shipments of potentially contaminated produce as of Monday.
According to the health ministry, consuming 100 grams of the most contaminated vegetable for 10 days is the equivalent of ingesting half the amount of radiation a person would typically be exposed to in the natural environment in one year.
More than 160 times the safety standard of radioactive cesium were detected in a leafy vegetable known as "kukitatena," according to tests, along with levels of radioactive iodine that were seven times over the legal limit in Fukushima Prefecture.
The prefecture has been instructed to refrain from consuming and shipping turnips and similar green leaf vegetables grown in the prefecture including, "shinobufuyuna," "santona," "chijirena," "kosaitai" and "aburana" rape vegetables.
Fukushima Prefecture previously received an official order from the government to halt all shipments of parsley and raw milk and on Wednesday neighboring Ibaraki prefecture received the same order to halt its shipments of raw milk and parsley.
Minute traces of radioactive substances have been detected in tap water in nine prefectures following radioactive leaks from the troubled Fukushima Daiichi nuclear power plant, local media reported Monday, citing government data.
But the amount of the health-threatening substances were below the safety intake limits set by the Nuclear Safety Commission.
According to a nationwide survey by the science and technology ministry, radioactive iodine was detected in tap water of the six prefectures of Saitama, Chiba, Tokyo, Kanagawa, Niigata and Yamanashi while iodine and cesium were detected in Tochigi and Gunma prefectures.
In Fukushima Prefecture, where the nuclear plant is located, iodine was detected in a sample collected at 8 a.m. Monday.
In Tokyo cesium was detected on Saturday but was not found Sunday.
The safety intake limit set by the Nuclear Safety Commission is 300 becquerels per kiloliter of water for iodine and 200 becquerels for cesium.
Radioactive leaks were detected after a series of explosions and fires at four of the plant’s six reactors following the failure of their cooling functions due to the damaged power supplies in the 9.0 magnitude earthquake that hit Japan on March 11.
The authorities advised residents living within 20-30 km radius of the plant to stay indoors and set the area 20 km around the plant as an exclusion zone where residents have been evacuated.
Japan’s Tokyo Electric Power Co. ( TEPCO) on Tuesday connected the No. 4 or the fifth reactor at the quake-hit Fukushima No. 1 nuclear power plant to an external power supply, as smoke is seen rising from the No. 2 and No. 3 reactor buildings.
As was the case with Monday’s sighting of smoke billowing from the same building, the smoke seen at the No. 2 reactor is likely to be steam and the smoke at the No. 3 reactor caused by burning rubble, Japan’s defense minister said.
But while no explosions in the vicinity were heard, the International Atomic Energy Agency officials said Monday that levels of radiation up to 1,600 times higher than normal were detected in an area 20 kilometers away from the troubled nuclear plant.
According to the IAEA, radiation levels of 161 microsievert per hour were detected in the town of Namie in Fukushima Prefecture. The government maintained its official exclusion zone of a 20 kilometer radius from the plant and advised people within a 20-30 kilometer radius to stay indoors and switch off air conditioning.
The utility has been battling to get the six reactors at the plant back online following the March 11 magnitude 9.0 megaquake and tsunami that knocked out the plant’s critical cooling systems and led to partial meltdowns of some of the reactors’ cores.
TEPCO said however that it had managed to connect its No. 1 reactor on Monday night to an external power source.
The utility said the No. 1, No. 2, No. 5 and No. 6 reactors are now all set to receive power from independent sources which is a critical first step to revive reactors’ cooling systems.
But due to the radioactive substances being passed through the plant’s discharging outlets, TEPCO announced Monday that highly concentrated radioactive substances have been detected in seawater close to the plant.
According to TEPCO, radioactive iodine-131 was detected in seawater samples at levels 126.7 times higher than the legal concentration limit.
Levels of cesium-134 registered 24.8 times higher and those of cesium-137 16.5 times higher.
Meanwhile, trace amounts of cobalt 58 were also detected in seawater samples.
Prior to the March 11 quake and ensuing tsunami, no radioactive substances were detected in the seawater near the plant, the utility said. Industry minister Banri Kaieda said Monday that the situation remains "extremely tough."