3.12 Monthly Sr?° Levels in Liquid Milk from New York City Beginning in June 1954, a quart of liquid milk was purchased five days a week from a store near HASL. The labeled brands were varied to avoid sampling milk from particular farms. The daily samples were combined, evaporated to dryness, ashed and analyzed as a weekly sample. Since January 1957, the daily samples have been combined to form a monthly composite. Table 9 summarizes data in ype sr90/g Ca. graphed in Figure 9, The data are The values through May 1956 represent monthly averages of weekly analyses. Since January 1957, the values represent averages of replicate analyses made on monthly composites. In both cases, the error term represents one standard deviation from the mean. From June through December 1956, no liquid milk samples were analyzed. This program was resumed after it was recognized that the powdered milk samples from Perry, New York did not represent the New York City milkshed,. - 60 -