137Cs into food crops and/or el it from the soil column would substantially] reduce the Similarly, the mean 30-y integral effective dose of 0.0059 Sv (0.59 rem) estimated for Rongelap Island is only 12% of the 0.05 Sv potential exposure of the Rongelap peopleliving on RongelapIsland. The external gamma exposur€ is next in significance and contributes about] 40% of the 30-y integral effective dose. The p source of exposure from the external pathwayis (5 rem) Federal guidance for the general public for a 30-y period (EPA, 1987; FRC, 1960a,b). It is 20% of 0.03 Sv (3 rem), which is the equivalent of 1 mSv y-! (100 mrem y-!) summed over 30 y. In view of the fact that there is some question as to whether such guidanceis really relevant for a situation such as the Marshall Islands, it is useful to develop other reference criteria. For perspective, the annualeffective background dose in the United States is 137Cs. In the first year, 1995, 137Csl contributes more than 99% of the 0.11 mSv y-1 (1 mrem y-!) external gamma dose rate; °Co a than 0.08%. ts for less By the year 2000,[137Cs will essentially accountforall of the ext gamma dose rate. The annual external effective dose rates, the cumulative effective ddse, and the compared in Table 15 to the total maximum annual effective dose, including natural and contributions of 137Cs and 69Co man-made sources, at Rongelap Island. Thetotal maximum annual effective dose at Rongelap Island of 2.66 mSv (266 mrem) is 89% of the annual background effective dose of 3 mSv (300 mrem)in the United States. Appendix C. The inhalation pathway is age listed in ntially the most significant exposure pathway for the transuranic radionuclides. For this pathway, 239+240Py and 241Am are about 3 t@ 4 orders of magnitude more significant than 7Cs, 90Sr, or Relative Contributions of Exposure Pathways 60Co. The transuranic radionuclidés contribute less through the ingestion pathway The ingestion dose calculation fq@r Pu and Am includes a 100 mg d-! consumption surface soil The relative contribution of each of the exposure pathwaysis presented in Table 16. The dose from the terrestrial food-chain pathway accounts for about 60% of the total estimated 30- every day of one's life. We feef this model probably overestimates the ann soil, but chose it as a conservativ y integral effective dose; 137Cs accounts for about 96% of this dose and %Sr for about 2%. Any the problem. We also used recommended ICRP gut-transfer fa organically bound transuranic r procedure that would either block the uptake of Table 16. The 30-, 50-, and 70-y integral effective dose for the various exposure pathwayA) Effective integral equivalent dose, Sv (rem Exposure pathway Oy Oy ny Terrestrial food External gamma Marine food 0.0034 (0.34) 0.0024 (0.24) 1.6 x10-5 (0.0016) 0.0047 (0.47) 0.0033 (0.33) 3.5 x10-5 (0.0035) 0.0056 (¢.56) 0.0039 (9.39) 6.0 x10-¥ (0.0060) Inhalation Totala 4.8 x 10-5 (0.0048) 0.0059 (0.59) 1.2 x 10+ (0.012) 0.0082 (0.82) 2.0 x 10-F (0.020) 0.097 (07) Cistern and ground water 5.1 x 10- (0.00051) 7.8 x 10-6 (0.00078) a The total dose mayvary in the second decimal place due to rounding. 33 1.0 x 10- (0.0010)