“…Many years ago it was shown by Russel (1965) that the mutation yield per unit dose was higher at low doses of radiation than at high doses. Similar results were obtained by studying radiation-induced cytogenetic damage (Luchnik and Sevankaev, 1976;Pohl-Rulling et al, 1983;Lloyd et al, 1988;Zaichkina et al, 1997), transformation (Oftedal, 1990), and cell survival (Joiner, 1994;Joiner et al, 1996). Joiner et al (2001) showed that most cell lines have hyperradiosensitivity to very low radiation doses, which is not predicted by backextrapolation of the cell survival curve from higher doses.…”