Reactor accidents. Public health strategies and their medical implications.

In a reactor accident with release of radioactivity, the major potential public health risks are likely to result from radioiodines, particularly iodine 131, which can be readily volatilized and dispersed. They are rapidly absorbed and concentrated by the thyroid, which could result in substantial thyroidal radiation. Although some forms of radiation can cause thyroid cancer in humans, 131I has not been shown to do so, and 40 years of safe experience with this radionuclide in routine clinical thyroid testing and treatment has been reassuring. Nevertheless, since 131I has been shown to cause thyroid neoplasms in animals, efforts to minimize unwarranted exposure seem advisable. Potassium iodide, administered at an appropriate time, will effectively block thyroid uptake, but it has potential toxicity and may be difficult to distribute effectively and safely on a large scale in an emergency. Evaluation of the risks and benefits of potassium iodide use is essential to establishing sound public health policy but awaits additional scientific information.