Naturally occurring 226Ra concentrations in bone at various ages and alpha doses in adults.

Radium-226 concentrations of bone from the fetus and stillborn and from subjects aged 0 to 87 y, especially those older than 15 y, were determined by alpha spectrometry after an ion exchange separation. The median and mean 226Ra concentrations in bone of the adults, 20 to 69 y, were 0.35 and 0.42 Bq (kg bone ash)-1, respectively, and those for ages 15 to 87 y were 0.35 and 0.41 Bq (kg bone ash)-1, respectively. For fetal bones, mean content was 0.29 Bq (kg bone ash)-1. Annual dose equivalents in cells near bone surfaces and active red bone marrow, received from alpha radiation emitted from 226Ra and its decay products in mineral bone, were estimated using the ICRP dosimetric model for bone and assuming masses of source and target tissues for a Japanese Reference Man.