the japanese government estimates the total amount of radioactivity released into the atmosphere was approximately one-tenth as much as was released during the chernobyl disaster. significant amounts of radioactive material have also been released into ground and ocean waters. measurements taken by the japanese government 30–50 km from the plant showed caesium-137 levels high enough to cause concern, leading the government to ban the sale of food grown in the area. tokyo officials temporarily recommended that tap water should not be used to prepare food for infants. in may 2012, tepco reported that at least 900 pbq had been released "into the atmosphere in march last year [2011] alone" although it has been said staff may have been told to lie, and give false readings to try and cover up true levels of radiation.