''Considering the results of a separate test, radioactive materials in the air and drinking water are confined to levels that would not affect health,'' an official of the Education, Culture, Sports, Science and Technology said. ''The impact on agricultural crops needs to be examined mainly by the Health, Labor and Welfare Ministry.''
In a notice to the nation's 47 prefectures, the health ministry called on local governments on Monday to advise residents to stop giving babies water in forms such as baby formula if radioactive iodine is found in drinking water at levels greater than 100 becquerels per kiloliter.
''Babies can easily absorb radioactive iodine in their thyroid glands,'' a ministry official said, explaining the reason for issuing the notice. The intake limit set by the central government is 300 becquerels per kiloliter of water.
The science ministry said separately traces of the substances were detected in drinking water sampled Sunday in nine prefectures but they were all below the intake limits set by the government.
The nationwide survey showed both radioactive iodine and cesium were found in Ibaraki, Tochigi and Gunma prefectures, while iodine alone was found in Saitama, Chiba, Tokyo, Kanagawa, Niigata and Yamanashi.
In Fukushima Prefecture, where the stricken Fukushima Daiichi nuclear power plant is located, the prefectural government said 23 becquerels of iodine was found per kiloliter of water.
Yamanashi appeared in the latest iodine list, after not being listed in the previous survey based on samples taken Saturday.
Cesium was detected in a sample in Tokyo on Saturday but was not detected Sunday. It was detected in Gunma on Sunday, though the prefecture was not cited in the previous survey.
Among other prefectures, 12 becquerels of iodine was detected in Ibaraki, 10 becquerels in Tochigi, 5.9 becquerels in Gunma, 2.9 becquerels in Tokyo, and 3.6 becquerels in Niigata, among other locations, the ministry's tally showed.
As for cesium, 2.8 becquerels was found in Tochigi and 1.2 becquerels in Gunma.
The central government's Nuclear Safety Commission of Japan sets the intake limit for iodine at 300 becquerels per kiloliter of water and 200 becquerels for cesium.
Due to damage caused by the massive earthquake on March 11, research is currently impossible in some areas. Fukushima Prefecture is publishing data based on its own research.
Meanwhile, the government's task force to tackle nuclear accidents instructed municipal governments near the crisis-hit Fukushima plant on Monday to ease conditions under which they require people to undergo mandatory decontamination.
A radiation level of 100,000 counts per minute will be introduced as a new standard for decontamination, up from 6,000 counts per minute, the government said, adding that raising the bar will not endanger health.
The government's Nuclear and Industrial Safety Agency said the decision was made based on advice from domestic nuclear experts and the International Atomic Energy Agency.
As the number of people who want to undergo radiation checks has surged, a lack of staff and equipment for the tests and decontamination was feared.
The task force also urged the municipalities to tell residents not to take iodine preparations that prevent the absorption of radioactive iodine without expert guidance.
The intake of such preparations can help to prevent thyroid cancer but can involve side effects including allergic reactions."
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