INVESTIGATION OF LUNG-TUMOR INDUCTION IN BALB CJ MICE FOLLOWING PATERNAL X-IRRADIATION

Evidence of an enhanced incidence of lung tumours (benign adenomas and adenocarcinomas) was sought in the BALB/cJ mouse following paternal g erm cell X-irradiation. Tn a series of replicate studies spanning appr oximately 1 year, males were exposed to single, acute X-ray doses of 0 , 250 and 500 cGy. In each of the 2 consecutive weeks immediately ther eafter they were placed with two females to generate progeny that were derived from irradiated post-meiotic cells (spermatozoa to late sperm atids). These animals were then examined at 8 or 12 months for lung tu mours. While the proportion of fertile females and mean litter size wa s affected by the radiation, showing a dose-dependent, dominant lethal response, and while cases of mutant offspring were detected, the pate rnal radiation did not affect lung tumour incidence in the offspring. The incidence did not vary significantly between germ cell stages irra diated (week of mating), sex of offspring, or radiation dose. However, significant differences between lung tumour incidence (mostly represe nting benign adenomas) were found between different replicates, these being high at the start of the study, declining and then rising to yet higher levels at its close. The finding that lung tumour incidence in BALB/cJ mice is not affected by paternal germ cell irradiation does n ot accord with Nomura's reports using other strains of mice. This, in turn, weakens biological support for a causal association between the raised incidence of childhood leukaemia and non-Hodgkin lymphoma near Sellafield and the father's recorded radiation exposure during employm ent by the nuclear industry.