Radioactivity contents in dicalcium phosphate and the potential radiological risk to human populations

Potentially harmful phosphate-based products derived from the wet acid digestion of phosphate rock represent one of the most serious problems facing the phosphate industry. This is particularly true for dicalcium phosphate (DCP), a food additive produced from either sulphuric acid or hydrochloric acid digestion of raw rock material. This study determined the natural occurring radionuclide concentrations of 12 DCP samples and 4 tricalcium phosphate (TCP) samples used for animal and human consumption, respectively. Metal concentrations (Al, Fe, Zn, Cd, Cr, As, Hg, Pb and Mg) were also determined. Samples were grouped into three different clusters (A, B, C) based on their radionuclide content. Whereas group A is characterized by high activities of U-238, U-234 (similar to 10(3) Bq kg(-1)), Pb-210 (2 x 10(3) Bq kg(-1)) and Po-210 (similar to 800 Bq kg(-1)); group B presents high activities of U-238, U-234 and Th-230 (similar to 10(3) Bq kg(-1)). Group C was characterized by very low activities of all radionuclides (<50 Bq kg(-1)). Differences between the two groups of DCP samples for animal consumption (groups A and B) were related to the wet acid digestion method used, with group A samples produced from hydrochloric acid digestion, and group B samples produced using sulphuric acid. Group C includes more purified samples required for human consumption. High radionuclide concentrations in some DCP samples (reaching 2 x 10(3) and 10(3) Bq kg(-1) of Pb-210 and Po-210, respectively) may be of concern due to direct or indirect radiological exposure via ingestion. Our experimental results based on Pb-210 and Po-210 within poultry consumed by humans, suggest that the maximum radiological doses are 11 +/- 2 mu Sv y(-1). While these results suggest that human health risks are small, additional testing should be conducted. (C) 2009 Elsevier B.V. All rights reserved.