present in the intestinal tract. Intestinal tract contents were not separate from the viscera sample. Concentration of 99Sr in the muscle tissue from all fish ranged from 0.2 to 5.7 pCi/kg wet weight. 1.7 pCi/kg wet weight. The mean concentration in muscle tissue. is At this concentration and a consumption rate of 200 « of muscle tissue/d, the resulting mean dose-equivalent rate from 90Sr in the marine fish-food ingestion pathway is less than 0.1 mrem/y. Concentrations o 90Sr associated with muscle tissue are less than 3% of the concentration in the reconstructed whole fish @fable 6). Estimated dose-equivalent rates of 90Sr from muscle only or from whole fish ingestion will differ by orders of magnitude. Therefore, it is misleading to use whole fish (or eviscerated whole fish) concentration data for 90Sr to estimate radiological dose to individuals from 90Sr in the marine fish-food pathway. COBALT-60 IN FISH Between 1958 (the end of nuclear testing at the atoll) and 1984, 60Co levels in the atoll environment decreased by a factor of 5 from radioactive decay alone (t}/2 = 5.26 y). However, measurable concentrations of 60Co arc still found in fish and other aquatic organisms. In fish, 25 to 50% of the total body burden of 60Co is present in the muscle tissue, with most of the remainder distributed among the liver, skin, and viscera (see Table 6). Th levels of ®0Co in the muscle tissue of reef fish from different regions in t! atoll differ somewhat in the same way as that of |37’cs except that fish fro the, southwest portion of the atoll contain concentrations comparable to tho: in fish caught in the northwest quadrant of the atoll. Concentrations of 60 in the muscle tissue of bottom-feeding mullet and goatfish were consistent] higher than levels in other reef species, such as surgeonfish and parrotfisl and in pelagic species caught from the same island of the atoll. This patte is repeated when concentrations in other tissues and organs of the differen Species are compared. | . In Table 9 are shown mean concentrations in the muscle of reef and pelagic fish collected from the lagoon during different periods between 197 and 1984. The mean concentration of 60co in the muscle tissue of fish has been decreasing at a rate faster than that from radiological When appropriate data were found, a comparison was concentrations in specific tissues and organs measured 50005 10 16 made in decay alone. between the the 1977-to-198