Some beaches in the south of France present high levels of natural radioactivity mainly due to thorium (Th) and uranium (U) present in the sand. Risk assessment after internal exposure of members of the public by either inhalation or ingestion of black sand of Camargue was performed. This evaluation required some information on the human bioavailability of U and Th from this sand. In vitro assays to determine the solubility of U, Th and their progeny were performed either in simulated lung fluid, with the inhalable fraction of sand, or in both simulated gastric and intestinal fluids with a sample of the whole sand. The experimental data show that the bioavailability of these radionuclides from Camargue sand is low in the conditions of the study. Prospective dose assessment for both routes of intake show low risk after internal exposure to this sand.