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  • 1 Instituto de Radioproteção e Dosimetria/CNEN Av. Salvador Allende, s/no, via 9-Barra da Tijuca CEP 22780-160 Rio de Janeiro Brazil
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Abstract  

This study is a comparison between bioassay data of thorium-exposed workers from two different facilities. The first of these facilities is a monazite sand extraction plant. Isotopic equilibrium between232Th and228Th was not observed in excreta samples of these workers. The second facility is a gas mantle factory. An isotopic equilibrium between232Th and228Th was observed in excreta samples. Whole body counter measurements have indicated a very low intake of thorium through inhalation. As the concentration of thorium in feces was very high we concluded that the main pathway of entrance of the nuclide was ingestion, mainly via contamination through dirty hands.The comparison between the bioassay results of workers from the two facilities shows that the lack of Th isotopic equilibrium observed in the excretion from the workers at the monazite sand plant possibly occurred due to an additional Th intake by ingestion of contaminated fresh food. This is presumably because228Ra is more efficiently taken up from the soil by plants, in comparison to228Th or232Th, and subsequently,228Th grows in from its immediate parent,228Ra.