Tokyo (CNN) -- New tests Thursday showed that radioactive iodine in Tokyo's tap water has dropped to levels considered safe for babies -- just hours after authorities announced plans to distribute bottled water to tens of thousands of parents around the Japanese metropolis.
Tests at the Kanamichi Water Purification Plant, which provides water to 23 wards in Tokyo as well as five other cities, showed 79 becquerels of radioactive iodine per kilogram of water, the city government said in a news release.
A becquerel is a measurement of radioactive intensity by weight.
This is below the 100 becquerel level, the maximum considered safe for infants ages 1 and younger. And it is well below the 210 becquerel reading measured Tuesday night.
As a result, Tokyo Gov. Shintaro Ishihara told reporters Thursday that he was lifting the recommendation that babies not drink tap water -- though bottled water will continue to be distributed to households with youngsters.
Shintaro said that 240,000 bottles will be given out Thursday, with a similar number set to be distributed on Friday.
Despite the development, concerns remain over how radiation from the Fukushima Daiichi nuclear power plant may affect food, water and air in the Asian nation.
The power facility and its six reactors were seriously damaged by a March 11 earthquake and subsequent tsunami.
Most of the 9,737 confirmed dead perished soon after the quake and walls of water struck northeast Japan. At least 16,501 remain missing and 2,766 were injured, the National Police Agency said in a statement Thursday afternoon.
Test results released Thursday afternoon showed two water treatment plants in the Chiba prefecture still have radioactive iodine levels above the legal limit for infants.
The Chiba Nogiko water treatment plant had a measure of 220 becquerels of radioactive iodine per kilogram of water, while the Kuriyama facility had a reading of 180 becquerels, according to a statement from Chiba's waterworks bureau.
These two plants provide water for the city of Matsudo, about 20 miles northeast of Tokyo.
Companies that package bottled water are being encouraged to increase their production, Chief Cabinet Secretary Yukio Edano said.
The level set for infants is "very conservative," said Dr. James Cox, radiation oncologist at MD Anderson Cancer Center in Houston, Texas, and a CNN consultant. But elevated radiation levels are considered a problem for small children, because their thyroid glands are more susceptible to radiation.
"Erring on the side of caution for the extreme degree for children makes good sense," Cox said. For adults, "as far as the immediate health risk, something that would make people sick, I don't think that would come close to it."
And on Thursday, Japan's leading obstetrics and gynecological organization said that pregnant and nursing women should continue to drink tap water -- even if the levels of radioactive iodine rise up to 500 becquerels. Over 280 days, the length of a typical pregnancy, that intake of radioactive iodine would still not be considered overly harmful, according to the group.
The society contends, in a news release, that the harm from not drinking water and dehydrating is far greater for mothers than consuming tap water at their current levels.
The assessments appeared to have little effect on Tokyo residents, who snapped up bottled water in droves.
Grocery store owner Seiji Sasaki said he had 40 cases of water in his store, but they were gone quickly.
Japanese officials also expanded food shipment restrictions Wednesday after the Health Ministry said tests detected radioactive materials at levels exceeding legal limits in 12 types of vegetables grown near the Fukushima plant.
Authorities found high levels of iodine-131 and cesium-134,137 in Mizuna -- a Japanese mustard plant -- shipped from Ibaraki Prefecture on Wednesday.
Ministry officials said the discovery is not at levels that would harm human health, but have instructed distributors and buyers to remove the vegetable from stores.
Prime Minister Naoto Kan also asked Ibaraki Prefecture to suspend shipments of raw milk and parsley, Edano said.
The government of Fukushima Prefecture also told residents not to eat leafy vegetables, he said.
Radiation levels in the food would not cause health problems right away, Edano said, but if they rise, they may reach levels risky to human health.
The decision to prohibit produce sales is another potentially devastating blow to a part of northeast Japan hit by the earthquake and tsunami.
Fukushima ranks among Japan's top producers of fruits, vegetables and rice. Ibaraki, south of Fukushima, supplies Tokyo with a significant amount of fruits and vegetables and is the third-largest pork producer in the nation.
"This is our livelihood," a Fukushima farmer told Japanese television network TV Asahi. "It's a huge problem that we are unable to ship all our produce. We raised (this produce) with our own hands. It's unbearable that we would have to throw it all away."
On Thursday, Edano indicated that the government was prepared to compensate farmers and others whose income was threatened by the effects of the radiation spikes. He said that it wasn't yet clear how that might happen, whether it was buying up the existing crops or some other form.
Russian authorities have banned imports of all food products from six regions of Japan, according to a news release posted on the website on the consumer protection watchdog Rospotrebnadzor.
On Wednesday, Hong Kong said that it was restricting food and milk imports from certain prefectures over the radiation concerns. The United States had previously announced import alerts covering milk, milk products, fresh vegetables and fruit from prefectures near the reactors.
Low radiation levels have also reached as far as Sweden.
"We have now recorded readings of radioactive iodine in Sweden, just as we expected," said Leif Moberg, head of research at the Swedish Radiation Safety Authority. "The amount is however very low and it does not pose any health risk at all for humans or the environment,"
At three of the six measuring stations in Sweden -- in Stockholm, Umea and Kiruna -- small amounts of iodine -131 were recorded. The agency described the levels as "lower than the normal background radiation from the ground."
Another growing concern is the impact on Japan's sizable fishing fleet. The nation's Kyodo News agency reported that levels of radioactive iodine were rising Thursday off the eastern coast, leaving fishermen worried about future income.
"I don't know when this will end," said Seiji Nakzato, 75, a fisherman from Tokyo. "Business is down. People don't want to buy fish because they're afraid of radiation."