- a ~~ 22 . Pom Dat ationsniyp wh _— ~ ? (ad) Unexplained Episodes: ‘Firure l reveals two other isolated periods (4 and 6) of slightly elevased isolated radioiodine concentrations in the PMY that nave not been previously discussed. From Novenber 30 to Decenber 8, 1965, eleven milxsheds in the southeastern U. S. (Baltimore, Md. to Tampa, Fla. to Little Rock, Ark.) reported concentrations between 14 and 36 pCi/l. Reanalysis of the gamme spectra for the detectable values during the | November 30 - December 8, 1965 period confirmed the presence of radioiodine as originally reported. ‘The Savannah River and Oak Ridge Atomic Energy Commission installations lie in this area and mere proximity suggests them as possible sources. However, neither their local monitoring results nor reported zis releases, if any, implicate either plant. The other period, July 1966, followed the South Pacific atmospheric tests. of 60 pCi/L was observed at Palmer, Alaska, on July 19, 1966. A value But itis . deemed unlikely that an Alaskan milkshed would be contaminated by a source at 22°S. There is, however, no independent evidence for accepting or rejecting southern hemisphere nuclear tests for the several elevated yi3l milk concentrations in 1966. In addition to the two unexplained periods in November-December 1965 and July 1966, there are others diring which the radioiodine concentrations exceeded 10 pCi/l but failed to reach 30 pCi/1l, most lying close to the lower value. These concentrations do not, a of course, ? appear on Fig. l. in all of these latter cases the geographical and temporal distribution or milxsheds appears to ve almost random. These relatively few concen- trations above 10 pCi/l might be expected as statistical fluctuations .because of the routine handling and analysis of the many thousands of sanoles. Commerison of PMN with State milk network , In addition to the PMN, about 40 states monitor zist in milk. In 1963 only 11 states reported to the FHS, which publishes their results in the Radiological Health Data and Reports (21). reporting had increased to fifteen. By 1968 the number of states Many of the state networks collect and analyze milk samples on @ monthiy basis wnile some collect more frequently. Neill and Snavely (22) summarized the criteria used by the states in their milk samvling < gS programs. gr :