POTASSIUM-IODIDE FOR THYROID BLOCKADE IN A REACTOR ACCIDENT - ADMINISTRATIVE POLICIES THAT GOVERN ITS USE

A marked increase in thyroid cancer among young children who were in t he vicinity of the Chernobyl nuclear power plant at the time of the 19 86 accident strongly suggests a possible causal relationship to the la rge amounts of radioactive iodine isotopes in the resulting fallout. A lthough remaining indoors, restricting consumption of locally produced milk and foodstuffs, and evacuation are important strategies in a maj or breach-of-containment accident, stable potassium iodide (KI) prophy laxis given shortly before or immediately after exposure can reduce gr eatly the thyroidal accumulation of radioiodines and the resulting rad iation dose. Concerns about possible side effects of large-scale, medi cally unsupervised KI consumption largely have been allayed in light o f the favorable experience in Poland following the Chernobyl accident: 16 million persons received single administrations of KI with only ra re occurrence of side effects and with a probable 40% reduction in pro jected thyroid radiation dose. Despite the universal acceptance of KI as an effective thyroid protective agent, supplies of KI in the US are not available for public distribution in the event of a reactor accid ent largely because government agencies have argued that stockpiling a nd distribution of KI to other than emergency workers cannot be recomm ended in light of difficult distribution logistics, problematic admini strative issues, and a calculated low cost-effectiveness. However, KI in tablet form is inexpensive and has a long shelf life, and many coun tries have large stockpiles and distribution programs. The World Healt h Organization recognizes the benefits of stable KI and urges its gene ral availability. At present there are 110 operating nuclear power pla nts in the US and more than 300 in the rest of the world. These reacto rs product 17% of the world's electricity and in some countries up to 60-70% of the total electrical energy. Almost all US nuclear power pla nts have multistage containment structures with large steel and concre te shells and multiple redundancy of core cooling mechanisms, These su ccessfully prevented the release of major amounts of radionuclides in the Three Mile Island partial loss-of-primary coolant accident in 1979 . The Chernobyl accident, in a different type of reactor that is commo n in Eastern Europe, did not have effective outer shell containment an d released almost 50 MCi of I-131 compared to the 20 Ci of I-131 relea sed at Three Mile Island. Such accidents have precipitated extensive r e-evaluation of the design and safety devices of all operating reactor s. However, a major contributing factor to the accidents was human err or and considerable efforts must be made to train plant operators so t hey have a better understanding of reactor operation and use of safety mechanisms.