Age dependent concentration of 226Ra in human bone and some transfer factors from diet to human tissues

The concentration of 226Ra in more than 1000 human bone samples, still born infants, fetuses, blood, mixed diet, drinking water and mineral water has been measured. An age dependence of 226Ra concentration in human bone could be demonstrated. Up to an age of 20 yr two maxima of 226Ra concentration in bone occur, coinciding with the increased velocity of skeleton growth. Normally, the main source for uptake of radium by man is food. In Germany the transfer factor from diet to bone is about 0.098. Compared with data from literature for other countries, mainly the U.S.A., the German value is higher by a factor of about 1.5. This difference may be due to the lower calcium uptake in Germany which leads to higher resorption of radium. Two methods for measuring natural radium concentrations is biological material and water samples are briefly described: a gamma-gamma-coincidence method for indirect measurement of 226Ra via the short lived 214Bi(RaC) and an alpha-spectrometric method for direct measurement of the alpha-emission of 226Ra.