vo The 137Cs concentrations in drinking coconut meat and fluid on Rongelap Island are about 20% of those on Eneu Island, and about 2% of those on Bikini Island. However, treatment of coconuts and other food crops on Rongelap Island with potassium-rich fertilizers should reduce the 137Cs uptake to about 10% of current levels and reduce the estimated dose from theterrestrial food chain by a similar amount. Thus, the . estimated maximum annual effective dose and 30-y integral effective dose for Rongelap, including both internal and external exposure, would then be about 0.12 mSv (12 mrem) and 0.0026 Sv (0.26 rem), respectively. If a reasonable agricultural program is implemented that includes periodic use of fertilizer, the dose from 137Cs through the food chain will be greatly reduced, and the growth and productivity of some plants and food crops will be enhanced. Environmental Half-Life of 137Cs Fraction of currently estimated dose There are natural processes operating at the atolls that also will reduce the estimated doses presented in this paper. For example, 137Csis found in the ground water 3 to 4 m surface. The only way for the 137C§ pelow the soil to get to the ground water is by transfer down soil column during rainy seasons when suffifient rainfall occurs to produce a recharge of the Fround water lens. This is the mostlikely i of 137Cs from the island. Another system, and/or make it unavailabl plants can be defined in t environmental half-life (T,/2 en¥i analogous to half-life for radioactive decay (T1;2 radiologi loss of 137Cs from the environment , therefore, a radioactive sum of two components: the loss processes. decay and the loss by environme Thus, an effective decay constargt, A,, can be defined, which is equal to Arddiological + environmental, Where the decay fonstant A = 0.693/T1,/2. The significance of the environmental half-life is shownjin Figure 5, 0.80— 0.70= 0.56 0.40— 0.30 = 0.10 = 50 66 70 80 90 100 Environmental halt-life, y Figure 5. Percentage reduction in estimated doses to residents of Rongelap Islandas a fiinction of the environmental half-iife.