The Japan Atomic Energy Agency disclosed a radiation map Thursday showing how iodine-131 likely spread in the early stages of the March 2011 Fukushima meltdowns, a development that could help doctors locate unsuspecting cancer victims.

While estimates on how cesium spread have been available for years, government inaction notwithstanding, it hasn't been clear whether iodine spread any differently, and a map of iodine-exposed areas could help health officials raise awareness of thyroid cancer risks.

Because iodine-131 has such a short half-life — only eight days — collecting data was difficult. Thanks to atmospheric radiation data collected in 2011 by U.S. Department of Energy flights from March 17 to April 5, however, JAEA was able to develop a new method to calculate surface levels of iodine-131 in consultation with international experts.