Radioactivity in milk and human diet - levels in the UK during 1979

The National Radiological Protection Board assumed responsibility for the national milk monitoring scheme from the Agricultural Research Council in January 1979. This joint report presents the results of analyses by both organisations of the samples collected during 1979. The activity concentrations of 90Sr and 137Cs in milk during 1979 differed little from those measured in recent years and lay in the range expected from measurements of deposition of fallout. The average ratio of 90Sr to calcium in 1979 (0.10 Bq g-1Ca) was less than one tenth of the maximum value measured in 1964 after the nuclear tests of the early 1960s. The average activity concentration of 137Cs (0.17 Bq 1-1) was only 3 per cent of the peak value. The measured values of these nuclides in milk were used to calculate the effective dose equivalent incurred in 1979 from total diet consumed. The values in that year of 1.2 and 1.6 μSv from 90Sr and 137Cs respectively are in agreement with values previously calculated and reflect the continuing low level of fallout. (author)