Retrospective measurements of airborne 129iodine in Austria

The knowledge about the distribution of anthropogenic (129)I is crucial for a successful establishment of transport mechanisms, fate and behaviour in the environment. In present study, the historical record of dry deposition of (129)I in Austria over four decades back to the 1960s is reconstructed. The (129)I/(127)I isotopic ratio of the order of 10(-9)-10(-7) in airborne particles revealed a prominent anthropogenic (129)I signature. The time profile of airborne (129)I follows directly the pattern of the gaseous emissions from European reprocessing plants. Furthermore, temporal variations of (129)I were traced monthly over two years. The potential risks of internal exposure to (129)I are associated with both inhalation and ingestion. Since dose via inhalation was found insignificant, the thyroid equivalent dose from the internal exposure of (129)I using a value of 10(-8) for the isotopic ratio (129)I/(127)I in the thyroid and ICRP reference man was calculated. The corresponding thyroid cancer risk factor of 10(-11) for an adult from life-time exposure is one order of magnitude higher than for a 1-year old child. Due to low radiation toxicity of (129)I the annual dose is 8 × 10(4) times lower than the dose limit of the National Research Council, USA which is 0.04 mSv y(-1) to whole body or any organ for a combined beta and photon emitting radionuclide.