Iodine-131 (I), also called radioiodine (though many other radioactive isotopes of this element are known), is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical. It also plays a role as a major radioactive hazard present in nuclear fission products, and was a significant contributor to the health effects from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a threatening presence today in the Japanese nuclear crisis...