result with the annual effective dose received from natural background radiation today, as shown in Figure C.2.
As seen in Figure C.2, the external dose received by residents of Guam from the test was about 20% of the annual effective dose received from natural background radiation in the continental United States and about 50% of the annual effective dose received from current values of natural background in Guam.
To gain an appreciation of the fallout received from other tests, we used data from the ground-based monitoring stations. At each station, 24 hour samples of airborne dust were collected on 30 × 30-cm sheets of adhesive (gummed film). All samples were mailed to the Health and Safety Laboratory in New York City for analysis, where they were ashed and counted for gross beta activity. The total activity on the sample at the time of collection was determined; a power function decay with a coefficient of 1.2 was assumed.
Operation Castle began in 1954. There were 16 tests in 1954, 17 tests in 1956, and 33 tests in 1958. No tests were conducted in 1955 and 1957. Results from the gummed-film data collected at Guam are shown in Figure C.3. The ordinate is the sum of monthly data reported as the deposition of strontium-90 (90Sr) on the surface of the gummed film (Harley et al., 1960).
As mentioned above, there were more than 100 gummed-film stations around the globe. Monthly data from each station have been compiled for the 5-year period of atmospheric testing from 1954 to 1958. The 5 year accumulation of