Toxicity of soil iodine to terrestrial biota, with implications for 129I

The environmental impact of 129I has traditionally been assessed by its radiological effects on human health; however, protection of human health does not ensure protection of other biota. Because of the very long half-life of 129I, there is a relatively high molar concentration of I associated with any specified level of radioactivity. The potential exists for chemical toxicity to non-human biota to exceed radiological toxicity in importance. The authors reviewed the literature and conducted laboratory bioassays to obtain information on the chemical toxicity of inorganic I to terrestrial biota. Levels as low as 5 mg I kg-1 soil may have detrimental effects. If this were as 129I, the corresponding radiological effects to non-human biota may not be as important as the chemical toxicity. However, because of the very low risk factor applied to protect humans, levels of 129I in the environment acceptable for human health appear to be acceptable for other biota at the higher risk levels commonly used for them. (author)