( CNN ) -- The disclosure Saturday by Japanese authorities that milk and spinach have shown higher-than-normal levels of radiation contamination has raised concerns about food safety and supplies in one of Japan 's most heavily populated regions . Tainted milk was found 30 kilometers ( 18 1/2 miles ) from the Fukushima Daiichi nuclear plant and spinach was collected as far as 100 kilometers ( 65 miles ) to the south , almost halfway to Tokyo . The plant was badly damaged after a 9.0 earthquake and subsequent tsunami hit the coast on March 11 . But Chief Cabinet Secretary Yukio Edano stressed to reporters Saturday afternoon that the levels were not extremely high : A person who consumed these products continuously for a year , he said , would take in the same amount of radiation as that of a single CT scan . The U.S. Food and Drug Administration said that equates to 7 millisieverts , more than double the 3 millisieverts that a person in an industrialized country is typically exposed to in a year . Health effects would become more evident , he said , if such products were taken in daily for a lifetime . Edano said high radiation levels were not systemic for all spinach and milk tested , and that more data would be collected and analyzed under the Japanese health ministry 's watch to help determine what steps to take next . The Fukushima prefecture , or province , is just to the northeast of Tokyo . According to the prefecture 's website , Fukushima plays an important role in supplying food , not only to Tokyo , but also to the nation . The prefecture is Japan 's fourth-largest farmland area and ranks among the top producer of fruits , vegetables , rice , tobacco and raw silk . The favorable climate lends itself to an active agricultural industry that includes livestock farming . The website also states that the prefecture 's 159 kilometer-long coastline is home to a thriving fishing and seafood processing industry , and the area 's haul of fish is among Japan 's largest . Neighboring Ibaraki prefecture supplies Tokyo with a significant amount of fruits and vegetables . Ibaraki is the largest producer of Andes melons in Japan , according to the prefecture 's website , as well as the country 's third-largest producer of pork . The impact on rice production in the area is also a source of concern . Rice is Japan 's largest crop . Rice paddies account for 55 % of Japan 's farmland , and about 85 % of the 2.3 million farms in Japan plant rice annually . While the value of the rice industry relative to the national economy has declined in recent years , rice production is culturally significant and an important part of Japanese heritage . Fukushima prefecture contributed 4.5 % of Japan 's total rice production in 2010 . Ibaraki prefecture is the country 's second-largest producer of Koshihikari , a gourmet variety of rice . According to the Food and Agriculture Organization of the United Nations , Japan 's rice-growing season starts in April ( depending on the region ) and this year 's crop could remain unaffected , depending on how much radiation is released and in which direction , as well as how long it takes to clear farmland of contaminated soil . Jim Walsh , CNN consultant and international security expert at the Massachusetts Institute of Technology , warned that should a reactor suffer a meltdown and radiation reach ground water , the situation would be much worse , as it would be impossible to tell where the contamination starts and stops . So , how does food become contaminated ? According to the World Health Organization , the surface of foods like fruits and vegetables or animal feed can become radioactive by the deposit of radioactive materials falling on it from the air or through rainwater . Over time , radioactivity can also build up within food , as radionuclides are transferred through soil into crops or animals ( and thereby tainting milk ) , or into rivers , lakes and the sea , where fish and shellfish could take up the radionuclides . Radionuclides are elements in an unstable form that emit radiation . The severity of the risk depends on the radionuclide mix and the level of contaminant released . The health organization says packaged food is not susceptible to radiation contamination as long as the food is sealed . The organization warned that `` food contaminated with radioactive material will not appear spoiled , but consuming such food will increase the amount of radioactivity a person is exposed to and could increase the health risks associated with exposure . '' It went on to recommend that people avoid consumption of locally produced vegetables and milk , as well as fishing , hunting and slaughtering animals . As of right now , Japan appears to have adequate stockpiles of staples such as rice , but getting food to some of the hardest-hit regions is proving difficult . If current radiation levels hold , the farming community , while affected , could be spared . With the situation being so fluid , however , it 's impossible to tell what impact this disaster will have on an already devastated population .
The central province is the top producer of fruits , vegetables , fish . Its fish haul is among China 's largest . Contaminated rice , spinach , so far .