Interlaboratory Comparison of the Effects of Radon on L5178Y Cells: Dose Contribution of Radon Daughter Association with Cells

The cytotoxic and mutagenic effects of radon and its progeny were compared in murine lymphoblast L5178Y-R16 cells after exposure at three institutions. The cells were exposed to²²² Rn at Case Western Reserve University (CWRU) and Pacific Northwest Laboratories (PNL) and to²¹² Bi, a decay product of²²⁰ Rn, at the University of Chicago (UC). The dose to the cell nucleus was calculated using a dosimetric model which addressed both the contribution of the dose from the radioactivity in the medium and that associated with the cells. The dose-response curves for cell survival showed$D_{0}\text{'}{\rm s}$ of 0.30 Gy at CWRU, 0.20 Gy at PNL, 0.37 Gy for chelated²¹² Bi, and 0.13 Gy for unchelated²¹² Bi. Induced mutant frequencies at the thymidine kinase locus at the 37% survival level were$1470\times 10^{-6}$ at CWRU, 1518 at PNL, and$2414\times 10^{-6}$ at UC using combined results for chelated and unchelated²¹² Bi. The variation between institutions was greater than obtained in a previous interlaboratory comparison of the effects of radon on CHO cells. Since less radioactivity was associated with CHO cells than L5178Y cells, we have concluded that the variation between institutions in the case of L5178Y cells is caused by the differences in cell-associated radioactivity and errors related to the measurement of this parameter.