119 Radiation doses and cancer risks in the Marshall Islands @ S. L. Simon ET AL. first tests and would have received approximately equal doses regardless of the birth year. Wefound that our estimates of total organ radiation were greatest in the years with large yield nucleartests, Le., 1954, 1956, and 1958. Fig. 3 shows the temporal pattern of total dose (external plus internal) received on an annualbasis to the thyroid gland of children born in 1953 in each of four population groups (Majuro resi- absorbed doses (sum of external and internal) varied by year of birth. Persons who were adults at the beginning of the testing period (born in 1930 or earlier) received relatively low thyroid doses from the large tests in 1954 compared to those who were very young at the time of dents, Kwajalein residents, Utrik community, and Rongelap Island community). Children born in 1953 would havereceived the largest doses of any birth cohort. those tests (Table 8). Among the four representative population groups, cumulative thyroid doses ranged from 33 mGyfor adults who lived on Majuro at the time of testing to as high as 23,000 mGyfor infants on Rongelap Island at the time of the Bravotest. The dose contributions from the six tests that re- Uncertainties of estimated doses. Estimated doses and the uncertainties associated with those estimates varied by location, fallout event, calendar year, and age at time of exposure. The precision of our dose reconstruction is better for exposures received on Rongelap and Ailinginae than on Utrik, primarily because of the availability of historical urine bioassay data and large amounts of environmental monitoring data (both historical and contemporary), and both are more reliable than the estimated doses for persons exposed on the midlatitude and southern atolls. Of the exposure pathways examined, determination of dose from external sources was the mostdirect and, therefore, the most precise. An analysis was conducted to evaluate the uncertainty in the annual doses from external irradiation for each year of testing. Annual and sulted in the highest total doses (external plus internal) to adults of the four representative atolls and for the four organs and tissues that are considered (RBM, thyroid, stomach wall, and colon wall) are provided in Table 9. Bravo was by far the most important contributor to the total dose for the Utrik and Rongelap Island communities, but less important than Yankee, Yoke, Koon, Romeo, and Flathead for the Kwajalein residents, and less important than Koon and Romeo for the Majuro residents. For purposes of cancer risk projection (Land etal. 2010), the annual organ doses are required. Annual doses Table 8. (Continued) Utrik community Rongelap Island community Birth year RBM Thyroid Stomach Colon RBM Thyroid Stomach Colon <1931 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 160 160 160 160 160 160 160 160 160 160 160 190 190 200 200 200 200 200 200 200 200 200 210 210 93 32 18 13 10 890 890 890 890 890 890 890 1,000 1,000 1,000 1,000 1,000 1,100 1,100 1,100 1,100 1,100 1,500 1,500 1,500 1,500 1,500 2,000 2,000 550 31 21 16 11 170 170 170 170 170 170 170 170 170 170 170 190 200 200 200 200 200 210 210 210 210 200 230 230 85 24 14 10 8.2 340 340 340 340 340 340 340 360 360 360 360 380 420 430 430 430 430 460 460 460 460 460 600 600 130 34 21 17 13 1,600 1,600 1,600 1,600 1,600 1,600 1,600 1,600 1,600 1,600 1,600 2,000 1,900 1,900 1,900 2,000 2,000 1,900 1,900 1,900 1,900 1,900 2,100 2,100 500 30 30 35 30 9,200 9,200 9,200 9,200 9,200 9,200 9,200 11,000 11,000 11,000 11,000 12,000 12,000 12,000 12,000 12,000 12,000 17,000 17,000 17,000 17,000 17,000 23,000 22,000 5,600 38 Al 40 31 2,100 2,100 2,100 2,100 2,100 2,100 2,100 2,200 2,200 2,200 2,200 2,900 2,500 2,900 2,500 2,500 2,900 2,600 2,600 2,600 2,600 2,600 3,100 3,100 630 26 27 29 26 4,400 4,400 4,400 4,400 4,400 4,400 4,400 4,700 4,700 4,700 4,700 5,000 5,600 5,600 5,600 5,600 5,600 6,000 6,000 6,000 6,000 6,000 8,200 8,200 960 37 40 44 38