I Exposures from Dietary Sources

Although radioiodine released into the biosphere in North America and Europe reaches people chiefly through cow s milk, the stable iodine content of cow s milk is only about 0.2 ng g (0.004 to 2 /tg g )(NAS-NRC, 1956). The iodine content of milk varies greatly with 

Marine Ush and invertebrates contain more stable iodine than other human foods. However, because average seafood consumption in the U.S. is small, the impact of these foods in the tJ.S. on iodine metabolism is generally insignificant. Concentrations of iodine in fresh-water biota are about 1% of those in marine biota. The main Sources of dietary stable iodine in the U.S. are bread made with iodate dough conditioners, milk, and iodised Salt (Kidd et al., 1974). 

Because of insufficient experimental data, many Of the physical and biologic characteristics of must be based on observations of other iodine isotopes. For example, studies of short-term iodine behavior have utilized fallout radioiodine from nuclear explosions, principally in particulate form, and releases of elemental vapor forms of in field experiments or associated with nuclear power generation. However, little information is available concerning the changes in bioenvironmental concentration processes that might result from alterations in form and availability of in the long term. Analyses of behavior and potential accumulation of released to the environment must therefore be based on studies of 1 as a model for shortterm behavior, and stable iodine for long-term behavior. 

The transfer of iodine among the various portions of the environment depends on its chemical and physical form (Holland, 1963 Perkins, 1963). Inorganic vapor is the most chemically reactive form of iodine, but iodine associate with particles and organic compounds, such as methyl iodide (CH3I), is readily metabolized (Morgan et al., 1967). 

In the following discussion, factors used for the transfer of from soil to plants and from animal feeds to animal products are those assembled by Soldat for the study of the potential doses to people from a nuclear power complex in the year 2000 (Fletcher and Dotson, 1971). Although a number of models for the environmental transport of radioiodine exist in the scientific and technical literature (many of them for the atmosphere — vegetation - cow — milk — person pathway for 1), the concepts and values from the many other available models are similar to those presented in the Fletcher and Dotson report. 

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