JANUARY 1982 BIOASSAY FIELD TRIP TO ENEWETAK ATOLL From January 9, 1982 to January 16, 1982, members from the Marshall Islands Ragiological Safety Program at Brookhaven National Laboratory conducted the third annual bioassay mission to Enewetak Atoll. The purpose of this mission was to define current body burdens of 137¢., §0¢5, 20754 990sr and 239pPu in the population that currently resides on Enewetak Atoll. During this time, 399 Marshallese were whole body counted; 24-hour urine samples were collected from 310 individuals and consecutive daily urine and fecal samples were obtained from 10 adult males. Participation in the whole-body counting urine and fecal sampling programs was voluntary and restricted to individuals five years of age and older. Greater than 952% of the population participated in the whole body counting, program and approximately 75% of the population provided the requested urine and fecal samples. This report summarizes the results to date. Data obtained from the analysis of urine and fecal samples will be reported under separate cover. Table 1 is a summary of the population average body burdens for 137¢g, 60¢o, 20754 and potassium. The reported error represents the one sigma standard deviation assactated with the mean for edch population subgroup. The mean potassium body burden for the adult males has returned to the level determined in the baseline study of 1980. reflect a change in diet or living pattern. This is important since it may All other mean potassium body burdens have remained constant since 1980. The mean adult male !3/cs body burden has risen to the level observed at Ujelang Atoll in 1980 and represents a factor of two change in the mean body burden during the past year. Individual results have risen to a high of 0.14 wCi in January 1982 in contrast to 0.026 UCi in 1981. This change in the mean adult male }37cs body burden is assoctated with consumption of food grown at Enjebi Island. The 137¢g body burden in all other population subgroups has remained the same or declined slightly. The nuclides 297n4 and ©%Co were detected in members of the sample population at levels that are at or near the minimum detection limit (MDL) for the radionuclide (0.6 nCi). Results were reported even if less than 0.6 nCi provided that the one sigma standard deviation due to counting statistics did tot exceed the result. This reporting technique will tend to provide less precise information on an individual but will better describe population trends. The nuclide 5% o has been detected in members of each population