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TI-099Matter1930s

You are radioactive

A typical adult body contains enough potassium-40 and carbon-14 to undergo several thousand nuclear decays every second.

Established2 min read

Potassium is essential, and about one atom in 8,500 of natural potassium is the isotope K-40, with a half-life of 1.25 billion years. A 70-kilogram person holds roughly 140 grams of potassium and therefore a few thousand becquerels of K-40 — a few thousand decays a second — plus a smaller contribution from carbon-14. Bananas are radioactive for the same reason, and you are a large banana.

The dose is part of natural background, small beside radon and medical imaging. The point is not danger. The point is that a living body is a weak radioactive source by chemistry, not by contamination. Life runs on elements that were never perfectly stable.

Caveats

  • The count depends on body size and diet. ‘A few thousand per second’ is the right order for an adult.
  • This is not a reason to fear potassium. You would die without it, of other causes, much faster.

Sources

  1. 1UNSCEAR. Sources and Effects of Ionizing Radiation. United Nations, 2000.

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