Evaluating chromosome damage to estimate dose to tracheal epithelial cells

Chromosome aberration frequency has been widely used to estimate dose in radiation accidents when no physical dosimetry was available. Basal and secretory cells are thought to represent the major cells at risk in the upper respiratory tract for induction of cancer. Using an in vivo/in vitro approach, we have evaluated chromosome aberrations to determine radiation sensitivity of basal and secretory cells and to estimate the dose to tracheal epithelial cells following radon inhalation. Tracheal epithelial cells were isolated, sorted by flow cytometry into populations of basal and secretory cells, grown in serum-free medium, and exposed to graded doses of x rays. Chromosome aberration frequency was determined in both types of cells. A 2-Gy dose of x rays induced 0.52 ± 0.07 or 0.55 ± 0.07 aberrations/cells in the basal and secretory cells, respectively. These data suggest that the radiation sensitivity is similar for the two cell populations and, because these are the cells that divide, the measured aberration frequencies can provide an estimate of radiation dose. After evaluating the response to x rays it was essential to determine the dose-response relationship for tracheal epithelial cells exposed to alpha particles. Tracheal cells were isolated from the trachea, allowed to attach to a 3-μm Mylar film, exposed to a 238Pu source, and grown in culture. The frequency of chromosome aberrations was then determined. One gray of alpha exposure produced 0.55 ± 0.06 aberrations/cell as well as 0.11 ± 0.04 dicentrics plus rings/cell. This provides a benchmark against which radon-induced aberrations in the trachea cells exposed to radon can be compared. In other experiments, two groups of F-344/N rats inhaled radon and its progeny at concentrations and times to produce total exposures of either 900 or 1000 working level months (WLM)