Iodine in biology
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for iodine in 2000. For people age 14 and up, the iodine RDA is 150 μg/day; the RDA for pregnant women is 220 μg/day and the RDA during lactation is 290 μg/day. For children 1–8 years, the RDA is 90 μg/day; for children 8–13 years, 130 μg/day. As a safety consideration, the IOM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. The UL for iodine for adults is 1,100 μg/day. This UL was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone. Collectively, the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
Nuclear Regulation Authority
On 19 July 2013, the NRA updated its guidelines for the distribution and use of stabilized iodine tablets. Under the old rules designed in 2002 by the former regulator, the NSA, iodine tablets were recommended for those up to the age of 40. These former guidelines were based on studies done on the health of the atomic bomb survivors of Nagasaki and Hiroshima. Later studies however showed that although older people had less risk of developing cancer, the risk was not zero. Therefore, the age limit of 40 was abandoned. Because tablets were needed for approximately 4.8 million people who live within 30 kilometers of a nuclear reactor, implementation may take some time with only one pharmaceutical firm in Japan available for the production. Distribution would be started soon, and local governments were ordered to hold briefings for their residents. The NRA also warned that the use of iodine tablets could cause hypothyroidism, a slow-functioning thyroid gland.