RADIOSTRONTIUM IN SOIL, GRASS, MILK, AND BONE IN THE UNITED KINGDOM, 1956 RESULTS” F. J. Bryant, A. C. Chamberlain, A. Morgan, and G. 8S. Spicer, Atomic Energy Research Establishment, Harwell ABSTRACT The results of Sr’® analysis of soil, grass and sheep bone from twelve stations in England and Wales are given. The Sr®° in the top 4 inches of undisturbed soil in July, 1956 ranged from 1.9 to 10.0 mc/km*, depending on the rainfall. The Sr*? activity of herbage and of sheep bone showed a Wider range, samples from acid hill soils being relatively more active. Milk from Somerset had a median activity of 4.4 uuc of Sr®*® per gram of Ca in 1956, compared with 4.1 in 1955. Human bone specimens obtained in 1956 showed Sr” activity depending on age. The average level in children under 5 was 0.7 puc of Sr*’ per gram of Ca, and the average bone dose 2 mrad/ year. 1 INTRODUCTION The fission products formed in nuclear explosions are carried round the world in the upper air and fall to earth in rain (Eisenbud and Harley, 1953, 1955, 1956; Stewart et al., 1955, 1956; Libby, 1956). The fission product of greatest biological hazard is Sr*® (Medical Research Council, 1956, para. 236). The routes by which Sr°® enters the human body are shown diagram- matically in Fig. 1. The work described here is concerned with the Sr*® contamination of agricultural produce, and with the resulting trace contamination of human bones. As strontium and calcium are chemically related the amount of Sr*® in biological materials is usually expressed in terms of the specific activity relative to calcium. The strontium unit,t or 8.U. is defined as: Strontium unit = 107" curie Sr*® per gram calcium. 2 METHODS The analytical methods used have been described in detail in an AERE report (Bryantet al., 1956). After addition of carrier strontium, sample material is treated to bring the alkaline earths into solution. Radiostrontium (Sr® and Sr*°) with the strontium carrier is separated from calcium as nitrate in strong nitric acid solution. Ferric hydroxide and barium chromate scavenges are included to remove contaminating activities. The separated strontium is stored with *This paper was received from The Atomic Energy Research Establishment as Report A.E.R.E. HP/Ro 2353, dated August 1957. +The unit was referred to in the past as the ‘‘Sunshine Unit.’’ 209 senigtren