A public health statement summarizes information about a hazardous substance. The information is taken from a toxicological profile developed by ATSDR’s Division of Toxicology and Human Health Sciences (DTHHS). A toxicological profile is a thorough review of a hazardous substance.This toxicological profile examines uranium. This public health statement summarizes the DTHHS findings on uranium, describes the effects of exposure to it, and describes what you can do to limit that exposure.

Toxicological profile for uranium

MATHEMATICAL models are used in many countries to predict the dissolution of radioactive waste in underground vaults and the subsequent transport of radionuclides through the geosphere and biosphere. It is important to understand the interactions between radionuclides and various media along the path to the biosphere, whether disposal is in deep or shallow rock caverns or in shallow overburden facilities. The preliminary or screening assessments of the safety of these disposal concepts is usually carried out using generic data; in other words, a specific site has not been chosen. This precludes the use of parameter values measured in situ and relegates assessment modellers to using generic data that may not approximate real conditions (Till and Meyer 1983). Although such generic values are not necessarily useful in predicting absolute impact, standardization of generic data is useful. Our research, using a soil transpon model for the assessment of our disposal concept, shows that only four parameters are essential to accurately predict soil concentrations from either contaminated ground water or inigation water (Sheppard and Bera 1984). These four parameters, in order of decreasing importance, are: soil retention, annual precipitation, soil texture, and depth to the water table. The soil retention parameter in most assessment models is the soil solid/liquid panition coefficient, Kd, (Till and Meyer 1983; Isherwood 1981 ). This empirical parameter lumps all operating retention mechanisms into one value (Ames and Rai 1978). The Kd model assumes that the liquid and solid phases are at equilibrium and that there is a linear relationship between solute concentration in the solid ( Cs) and liquid ( C1) phases (Sheppard 1985; Sheppard and Evenden 1988), as expressed by the equation:

Default soil solid/liquid partition coefficients, Kds, for four major soil types: a compendium.

Proposal for new best estimates of the soil-to-plant transfer factor of U, Th, Ra, Pb and Po.

The migration of radionuclides from waste repositories to the biosphere potentially leads to a contamination of soil. Due to the importance of food production, the mobilisation and accumulation behaviour of long-lived radionuclides in the soil plays a key role in performance assessment studies. In this paper, the main features and processes that control radionuclide behaviour in soil, such as pH, redox potential and sorption to organic and inorganic soil components, are discussed for the radionuclides 36Cl, 79Se, 129I, 99Tc, 237Np and 238U, that are usually most relevant in long-term safety assessments of nuclear waste. The interaction of radionuclide behaviour in soil with environmental factors, such as temperature and humidity as well as farming practices are discussed. The possible impact of future soil development on long-term behaviour in soil are taken into consideration. Due to the physiological constraints of plant growth, appropriate soil conditions for growth will probably not be substantially different from current requirements, bearing in mind that sustainable agriculture strives for optimal plant growth. Against this background, present-day parameters may in general be considered appropriate for roughly estimating the behaviour of radionuclides in the soil-plant system.

Considerations on the behavior of long-lived radionuclides in the soil.

A pathway analysis computer code called RESRAD has been developed for implementing US Department of Energy Residual Radioactive Material Guidelines Hydrogeological, meteorological, geochemical, geometrical (size, area, depth), and material-related (soil, concrete) parameters are used in the RESRAD code This handbook discusses parameter definitions, typical ranges, variations, measurement methodologies, and input screen locations Although this handbook was developed primarily to support the application of RESRAD, the discussions and values are valid for other model applications

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Data collection handbook to support modeling the impacts of radioactive material in soil

The objectives of this study were to compare the effects of technetium and uranium on the yield and uptake, and to identify the organ of accumulation, of an edible leafy vegetable growing in sandy and peaty soils. In sand, where the soil's sorption capacity is negligible, technetium uptake is four orders of magnitude higher than from peat, suggesting no plant mediation of uptake and thus a constant concentration factor (greater than 50) in an oxidizing environment where technetium is continuously supplied. The technetium is predominantly translocated to the shoots. When soil fixation occurs, as in peat, this becomes the controlling factor in the plant uptake of technetium. In the case of uranium, plant mediation is more significant. Uranium uptake by Swiss chard is up to 80 times higher from sand than from peat. The uranium is restricted to the root system and may only be precipitated on the outer root membrane and may not accumulate in the roots.

Thibault Dh

Papers

Technetium and uranium: sorption by and plant uptake from peat and sand.