Fukushima Daiichi nuclear disaster casualties 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, 2011 alone."
Radiation effects from the Fukushima Daiichi nuclear disaster trace amounts of radioactivity would reach California and Mexico around 19 March. These predictions were tested by a worldwide network of highly sensitive radiative isotope measuring equipment, with the resulting data used to assess any potential impact to human health as well as the status of the reactors in Japan. Consequently, by 18 March radioactive fallout including isotopes of iodine-131, iodine-132, tellurium-132, iodine-133, caesium-134 and caesium-137 was detected in air filters at the University of Washington, Seattle, USA. Due to an anticyclone south of Japan, favorable westerly winds were dominant during most of the first week of the accident, depositing