The Sensitivity of three Diploid Human Cell Lines to Alpha-Irradiation

Abstract

The inhalation and retention of alpha-emitting radionuclides may pose a serious threat to the health and safety of those individuals who have been exposed. Higher levels than normal could arise from the increased use of plutonium in the nuclear power industry, and could lead to an increased risk of lung cancer. A study of the sensitivity of three lines of human, diploid lung cells of fibroblast-like morphology to irradiation by 238Pu alpha particles was conducted. Measurements were made to assess the probability of cell death and the incidence of chromosomal aberration as a function of absorbed dose. Cell survival as a function of dose could be described by a single exponential curve within the limits of experimental error. Values of Do ranged from 33 to 42 rad. The inactivation cross-sections calculated from the alpha-particle fluences required to reduce the survival to 37% (2.0–2.6 × 106 alpha per cm2) varied between 38 and 48 μm2. Thus for a mean lethal dose, an average of about four alpha particles pass through each cell nucleus. All unstable chromosome aberrations were scored. Of these, only the dicentric yields were analyzed in detail. The yield as a function of dose was found to be linear in the range 0–1.5 Gy (0–150 rad): in each case the slope was about 5 × 10−3 dicentrics per surviving cell per rad. These results indicate that the diploid, human cells are about twice as sensitive to radiation-induced effects as hamster cells. These findings support the supposition that the cell nucleus is the critical volume of interest and indicate that sensitivity could be a function of chromosome number.