materials, such as water, aspirin, and alcohol, are known to be absorbed from the stomach.
Further details regarding the radon biokinetic model, including the numerical values of the transfer coefficients of the resulting differential equations, are given in appendix A. The equations are solved by assuming that a unit activity (1 Bq) of 222Rn is present in the stomach contents at time zero. The fractions of ingested radon that remain in the body (in the contents of GI tract and in systemic tissues) at various times after intake are shown in figure 4.4. The fraction of the initial activity residing in various tissues as a function of time is shown in figure 4.5. The high radon uptake in the liver shown in figure 4.5 is a direct reflection of the fact that all radon absorbed from the GI tract flows in blood from the GI tract walls to the liver. The importance of adipose tissue as a site of deposition and retention can be seen at later times; beyond about 30 min it is the major site of radon deposition in the body.