Correlation of Lead-210 with Strontium-90 in Human Bones

Abstract

THE radioactive gas radon-222, produced by the decay of radium-226, diffuses from the ground and is transported by atmospheric turbulence far from its origin through the troposphere and into the stratosphere¹. The radioactive decay of radon-222 and its short-lived descendants produces measurable quantities of lead-210 in the atmosphere^1–3. Lead atoms so formed become attached to dust particles and eventually return to the Earth's surface, principally in rainfall^1,4,5. Hill's⁴ report of a correlation coefficient of 0.87 between the quantity of rainfall and the concentration of lead-210 in grass clearly indicates a linear relationship. Holtzman⁶ reported a relationship between the concentration of lead-210 in the human skeleton and in the atmosphere. Whether the lead-210 enters the body principally through precipitation on foodstuffs that are later eaten⁵ or through direct inhalation, or by both means⁷, is at present uncertain. It is therefore feasible to view the occurrence of lead-210 as a “natural fall-out” product, similar, in this respect, to fission product fall-out, artificially produced from a nuclear detonation. In fact, very strong similarities between lead-210 and fission product activities have been reported with respect to their behaviour in the atmosphere¹, to their rate and mode of deposition^1,5, and to their concentration in grasses⁴. The similarities between lead-210 and fission product activities do not imply any relationship in their production. The formation of lead-210 in nuclear weapons explosions is improbable, and if any were so formed it would be negligible in comparison with the amount formed by natural processes⁸. The observed similarities between lead-210 and fall-out are caused by their similar behaviour in the atmosphere.