Radioactive iodine in food is of immediate concern, but it has a relatively short half-life and will naturally decay over a short time frame.
食品中的放射性碘直接引起人们的关注，但是它的半衰期相对较短并将在短时间内自然衰变。
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Most famously, uranium-238 decays into lead-206 with a halflife of 4.5 billion years, though radioactive rubidium and samarium are also useful for dating things billions of years old.