Radioactive fallout in Norway in 1964

Scholastic achievement of Norwegian children born in 1965 has been analysed in relation to date of birth and school address, in order to examine a possible effect of radioactive fallout during their fetal period. The Western regions of the country had an order of magnitude higher fallout contamination than the Eastern region. There was in the Western region a pronounced seasonal variation in e.g. 137Cs content of milk. The results indicate a deficiency in scholastic achievement in the West cohort corresponding to the coincidence of the most sensitive fetal period (8-15 weeks post conception) with the 1964 late summer increase in 137Cs content of milk. The dose from fallout is several orders of magnitude too low to explain the observed deficiency quantitatively in consonance with the Hiroshima-Nagasaki findings. It is suggested that the explaination may be found be way of a repair induction lag hypothesis, related to the microdosimetric conditions at background dose rate level. (author)