2011 Tōhoku earthquake and tsunami
It was reported that radioactive iodine was detected in the tap water in Fukushima, Tochigi, Gunma, Tokyo, Chiba, Saitama, and Niigata, and radioactive caesium in the tap water in Fukushima, Tochigi and Gunma. Radioactive caesium, iodine, and strontium were also detected in the soil in some places in Fukushima. There may be a need to replace the contaminated soil. Many radioactive hotspots were found outside the evacuation zone, including Tokyo. Food products were also found contaminated by radioactive matter in several places in Japan. On 5 April 2011, the government of the Ibaraki Prefecture banned the fishing of sand lance after discovering that this species was contaminated by radioactive caesium above legal limits. As late as July 2013 slightly elevated levels of radioactivity were found in beef on sale at Tokyo markets.
Iodine-123
I is the most suitable isotope of iodine for the diagnostic study of thyroid diseases. The half-life of approximately 13.13 hours is ideal for the 24-hour iodine uptake test and I has other advantages for diagnostic imaging thyroid tissue and thyroid cancer metastasis. The energy of the photon, 159 keV, is ideal for the NaI (sodium iodide) crystal detector of current gamma cameras and also for the pinhole collimators. It has much greater photon flux than I. It gives approximately 20 times the counting rate of I for the same administered dose. The radiation burden to the thyroid is far less (1%) than that of I. Moreover, scanning a thyroid remnant or metastasis with I does not cause "stunning" of the tissue (with loss of uptake), because of the low radiation burden of this isotope. (For the same reasons, I is never used for thyroid cancer or Graves disease "treatment", and this role is reserved for I.)