Biological variability influencing lung dosimetry for inhaled 222Rn and 220Rn decay products

Particle deposition, clearance and dosimetry of inhaled short-lived 222Rn and 220Rn decay products in the human respiratory tract have been modeled by a stochastic compartment system, based on an already existing deterministic model (Ho82a). In order to allow for statistical uncertainties and biological variabilities, input parameters and transfer coefficients were described by truncated lognormal frequency distributions. Applying Monte Carlo techniques, a set of parameter values is selected randomly in an iterative manner from these prespecified distributions, yielding finally basal-cell doses as probability density distributions instead of single mean doses. The resulting highly skewed dose distributions illustrate the fact that a small percentage of individuals in an exposed population receives considerably higher doses than indicated by a deterministic mean value.