crnerat SUMMARY Results of routine monitoring of fallout in air, rain and milk samples during the third quarter 1969 are tabulated in this heport, presented graplically in Fig. and 1969, 2, These results are summarized on a quarterly basis and are together with results from previous Quarterly Reports during 1968 Additional information on sumple collection and evaluation, comparison of levels of environmental radioactivity and health hazard assessment is given in the Annual Summary Heport for 1968 “ENVIRONMENTAL RADIOACTIVITY IN NEW ZEALAND, Report No.NRL-F33" which also tneludes the results of extended monitoring of fallout from the French nuclear tests in the Pacific. TOTAL BETA ACTIVITY ~ INDIVIDUAL STATIONS As already noted in the reports NRL-F31i to NRL-F35, increased levels of fission products in air and rainwater were measured during the third quarter 1968. These levels resulted from the 1968 series of nuctear tests conducted by France in the Pacific Area between & July and 9 September. This series included for the first tine the detonation of two hydrogen bombs. ‘The expected decrease in levels, which - hadi been evident during the months following the previous tast series of 1966 and 1967, occurred more stowly following the 1968 nuclear testa. ‘The greater delay in the reduction of fission product levels following the 1968 nuclear tests undoubtedly resulted from the injection of fission debris into higher altitudes when the hydrogen bonbs were tested. The subsequent depasition of ‘the debris was thus extended over a longer period . , During the second and third quarters 1969, however, there were significant decreases in the levels of total beta activity of air and rainwater, . The ayerage levels in air during the third quarter 1969 were-0.08 pCi/n? at Auckland, 0.06 pci/m at Wellington and 0.05,pCi/m at Christchurch, During the corresponding period dn 1968 the levels were 0.23 pCi/m’ at Auckland and Wellington, and 0,16 pCi/m’ at Christchurch, The total, deposition in rain during the third quarter 1969 was 9.1 ca /am* at Greymouth, and 0.4 mci/ 112.8 mCi/km” at Christehurch. During the corresponding period in 1968 the deposition was at Greymouth, and 16.4 mCi/km” At Christchurch, SPECIFIC RADIONUCLIDES - COUNTRY-WIDE AVERACES 1, STRONTIUM~90 IN RAIN The average deposition in rain increased slightly from 0.27 mei/km” ‘during the second quarter 1969 to 0.30 mCi/km* during the third quarter 1969. This level is less than one quarter of the highest level previously recorded, i.e., during the first quarter 1965, 2, STRONTIUM.89 IN RAIN The average deposition reached a maximum of 5.1 met/tan® during October 1968, about one month after the cgnclusion of the 1968 nuclear tests,, During the third quarter 1969 levels were about 0.1 mCi/km per month, 3. STONTIUM-90 IN MILK The average level has increased from 6.8 Strontium second quarter 1969 to 7.9 Strontium Units during the third quarter 1969. previously recorded was 15,9 Strontium Units during July-August 1964, The the twelve months ending Septenpey 1969 (6.6 Strontium Units) is about 2.5% level" for the whole population\ Units during the The highest level average level for of the "permissible 4, CAESIUM-137 IN MILK The average level has decreased slightly from 27 pci/g K during the second quarter 1969 to 24 pCi/g K during the third quarter 1969, The highest level for the twelve rionths ending Sept gyre 1969 (27 pCi/g K) is less than 0.4% of the "permissible level" for the whole population (1) See "POTENTIAL HEALTH HAZARD" -~ Page 3, TTi - 20