241Am distribution in foetal haemopoietic organs of Balb/c mice

Developing haemopoietic organs and the fetal skeleton are considered target organs after internal contamination of the mother with actinides. Pregnant Balb/c mice were injected with 14 kBq 241Am citrate at day 14 of gestation, at the time haematopoiesis rises in the foetal liver. The 241Am retention was measured between one day after injection until 3 months after birth. The activities of 241Am in carcass and liver were measured by gamma-counting in a NaI (Tl) well-type crystal, skeletal parts and intestinal tract were measured by alpha-counting in a ZnS counter. Liver and skeleton concentrated 241Am but in the skeleton the 241Am concentration varied considerably between various parts: e.g. mandible and calvarium showed a 5 fold higher 241Am concentration compared to the femur. Comparison was made between mice which stayed with their mother till 3 weeks after birth and mice which received a foster-mother, this allows to calculate the importance of the maternal contamination via milk to the dose of the young mice. The retention data were used to calculate initial dose rates and absorbed radiation doses in function of time in the organs at risk. 15 refs.; 1 figure; 2 tabs