re ade U.S. PUBLIC HEALTH SERVICE, DIVISION GF RADIOLOGICAL HEALTH PHOTO FIGURE 6.~Counting a sample of milk for iodine 131. The procedure is quick and simple—the milk is merely poured into a plastic container and set into the counter. In contrast, analysis of milk for strontium 90 may require weeks including radiochemical preparation of the sample. " sures that have hitherto been considered of prime interest for local fallout. However, the total potential doses that may be accrued will require the drinking of the milk over periods of weeks. Up-to-date techniques and equipment now permit a relatively easy and early surveillance of iodine 131 in the milk supply providing an opportunity for whatever action may be appropriate (Figure 6). E. STRONTIUM 90 AND STRONTIUM 89 Background Information Strontium 90 has a half-life of about 28 years. It is selec- tively deposited in the bones. Chemically it is related to calcium. This similarity has led to the use of the ‘strontium unit” defined as one picocurie (2.2 disintegrations per minute) of strontium 90 per gram of calcium. Strontium 90 may become associated with foodstuffs by surface contamination of plants or by uptake of the strontium 14