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.
According to the map, iodine levels over 3 million becquerels per sq. meter were detected 5 km from the plant, but equally high levels were also found in areas 20 km northwest of it, including in the municipalities of Katsurao and Namie.
The patterns are consistent with other fallout projections delineating severely contaminated areas.
Iodine-131 accumulates in the thyroid gland and can cause cancer in young people. Treatment usually requires that the gland, which controls the body’s hormone levels, be removed.
Via a health monitoring program in the prefecture, 12 minors were diagnosed with thyroid cancer and 15 others are suspected. The program covers about 175,000 people up to age 18. Thyroid cancer makes up about 1 percent of all cancer cases and is usually appears in those in their 50s, 40s and 30s, with women more than three times likely to develop it, according to Aichi Cancer Center Hospital.
Japan’s medical experts have not yet linked the youth cancer cases in Fukushima to fallout from the stricken power plant. According to the National Cancer Institute at the U.S. National Institutes of Health, however, the median age for thyroid cancer diagnosis in the U.S. was 50 from 2006 to 2010. The incident rate for Asians in the U.S. during that time frame was 5.3 cases per 100,000 men and 17.9 cases per 100,000 women.
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