Radon Retention in Radium-Injected Beagles

Abstract

The fraction of radon (Em222) produced inside the body and disintegrating therein, increases with time after radium (Ra226) injection. For beagle dogs this fraction may be expressed as F = 0.057 t-20 where "t" is the number of days after injection. Within the range of values tested, fractional radon retention seems independent of the injected radium dose (1.9 -10.8 [mu]c/kg) and age at injection (1.7-75 months). Fractional radon retention is similar in rats, dogs, and humans at the same times after injection and is similar from bone to bone in a given animal, but retention in the teeth is only half that in the skeleton. Radon retention is chiefly due to the difficulty of diffusion of radon atoms out of mineral bone. The increased radon retention with time after radium deposition is attributed to increasing mineral density, increasing bone crystal size and decreasing diffusion coefficient of radon in mineral bone as the bone crystals mature.