Division of Nuclear Medicine, University Medical Centre Ljubljana, Ljubljana, Slovenia.
Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
Radiol Oncol. 2024 Oct 4;58(4):459-468. doi: 10.2478/raon-2024-0051. eCollection 2024 Dec 1.
During a nuclear accident, numerous products of nuclear fission are released, including isotopes of radioactive iodine. Among them is iodine-131, with a half-life of 8.02 days, which emits β radiation. For decades, it has been effectively and safely used in medicine. However, in the event of a nuclear accident, uncontrolled exposure can have harmful biological effects. The main sources of internal contamination with iodine-131 are contaminated air, food and water. The most exposed organ is the thyroid gland, where radioactive iodine accumulates via the Na+/I- symporter (NIS). NIS does not distinguish between radioactive iodine isotopes and the stable isotope iodine-127, which is essential for the synthesis of thyroid hormones. Exposure to radioactive iodine during a nuclear accident is primarily associated with papillary thyroid cancer, whose incidence begins to increase a few years after exposure. Children and adolescents are at the highest risk, and the risk is particularly significant for individuals living in iodine-deficient areas.
Ensuring an adequate iodine supply is therefore crucial for lowering the risk of the harmful effects of exposure to radioactive iodine at the population level. Protecting the thyroid with potassium iodide tablets significantly reduces radiation exposure, as stable iodine prevents the entry of radioactive iodine into the thyroid. Such protection is effective only within a narrow time window - a few hours before and after the exposure and is recommended only for those under 40 years of age, as the risks of excessive iodine intake outweigh the potential benefits in older individuals.
在核事故中，会释放出大量的核裂变产物，包括放射性碘的同位素。其中碘-131 的半衰期为 8.02 天，会发射β射线。几十年来，它在医学上被有效地安全使用。然而，在核事故发生时，不受控制的暴露会产生有害的生物学效应。碘-131 内污染的主要来源是污染的空气、食物和水。最易受影响的器官是甲状腺，放射性碘通过钠/碘同向转运体（NIS）积聚在那里。NIS 不能区分放射性碘同位素和稳定碘同位素 127，后者对于甲状腺激素的合成是必需的。核事故期间暴露于放射性碘主要与甲状腺乳头状癌有关，其发病率在暴露后几年开始增加。儿童和青少年的风险最高，而在缺碘地区的个体风险尤其显著。
因此，确保充足的碘供应对于降低人群水平暴露于放射性碘的有害影响的风险至关重要。用碘化钾片保护甲状腺可显著降低辐射暴露，因为稳定碘可防止放射性碘进入甲状腺。这种保护仅在几个小时的狭窄时间窗口内有效，即在暴露前后的几个小时内，并且仅推荐给 40 岁以下的人群，因为过量摄入碘的风险大于老年人的潜在益处。
