f Exposure to External and Internal Radiation Evaluation of Hazards from Tritium--Dominant Lethal Project Title: Mutations in Mice 13. oo RX-01-01-(c) Publications: Elias, J. M,, Conkling, K., and Makar, M. oe effect on displacement of tritiated thymidine. oo a 14. Cold fuelgen hydrolysis; Stain Technol. it (in press). Pa3g Scope: ‘A) 200 Word Summary: With the increasing number of power reactors, there is a growing concern as to the genetic and somatic effects resulting from exposure to radioactive reactor effluents, Critics contend that the present radiation safety Standards, enough, from a genetic and long-term somatic standpoint, are not stringent The objective of these studies is to ascertain if dominant lethal mutations are induced in mice by exposure to 1-100 times the present maximum permissible concentrations (MPC's) of tritium in water. B) Supplement to 200 Word Summary: Parent (P,}) animals are fed on tritiated water commencing at four weeks of age. Four weeks later, when their tissues are nearly in equilibrium with HOH-3, they are mated. The offspring (F,) are maintained on tritiated water “ ™, throughout the remainder of the experiment. At eight weeks of age they are divided into three experimental groups and mated as follows: group one, : consisting of tritiated males mated to tritiated females; group two, consist-- ing of tritiated males mated to untreated females; and group three, consisting of tritiated females mated to untreated males. This allows an estimate of the effect on the male and female germ cells separately and also detection of any interaction if it exists. Initially each experimental group, receives 100 times the MPC. An additional group of untreated controls also is exam- ined. Histological examination of pre-implantation zygotes is made on a sufficient number of animals to establish that pre-implantation and early post-implantation deaths are due to chromosome abnormalities of the type characteristic for dominant lethal mutations. Serially sectioned ovaries from the F,; mice are microscopically analyzed to enumerate the number of surviving ova. For comparison, additional groups of x-irradiated animals will be studied, meas ae concentration of tritium in body water and DNA of cells is, .» The complete tritium analysis includes determination of the amoulg.0 f activity in the wet tissue, dried residue (freeze dried), DNA, RNA, histones, and residual chromosome associated protein. From these data the dose to ova and testes will be calculated, probable effects estimated, and these compared to observed effects in order to determine if there is any unique and unexpected effect from tritium in germ cells. (See Continuation Sheet) Pi Tglss RX-25