SECTION I PHYSICAL DECAY OF SAMPLES FROM ENIWETOK ATOLL IN 1952 INTRODUCTION Previous decay studies (UWFL-53) of the biota and other materials from the Marshall Islands have covered periods up to nearly three years following the detonation of atomic testing devices. The earliest curves (AECD-3446:27) were for oyster, XE-19, and ovary of damselfish, XE-40, whose slopes from 20 to 800 days were -1. 6. Decay of 83 samples from Rongelap Atoll (UWFL-42:46) over a period of from 38 to 500 days following March 1, 1954 averaged ~-1. 4. Coconut milk was most unusual amongthese, having a decay rate of only -Q. 24, Decay data for samples collected in 1952 offer the most comprehensive picture of long-term decay trends that may now be contributed from studies by the Laboratory of Radiation Biology. proximately seven years is involved. A period of ap- These samples number 102, of which 96 were from Eniwetok Atoll collected within 10 days after the Mike test, 6 were within 10 days pre-Mike and would be referred to the Greenhouse series. In addition there were 2 Nevada sand samples lected on November 29, col- 1951, related to the Uncle-Jangle atomic tests, making a total of 104 decay curves. -l-