Assessment of Uranium and Thorium Co-contaminant Exposure from Incidental Concrete Dust Ingestion

Abstract

Potential health risks of contaminated media linked to bioavailability and hematotoxicity of uranium-238 (²³⁸U) and thorium-232 (²³²Th) remain uncertain. This study investigates the relative bioavailability (RBA), histopathological, and hematological effects of acute oral exposure to ²³⁸U and ²³²Th in co-contaminated concrete dust using 174 female Sprague Dawley (SD) rats. In order to create a range of ²³⁸U and ²³²Th concentrations, concrete was spiked with uranyl and thorium nitrates (~ 50, 100, and 200 mg kg⁻¹). Spiked concretes were then crushed, ground, sieved (≤ 75 µm), and blended uniformly to create co-contaminated concrete dust. SD rats’ diet pellet was amended with co-contaminated concrete dust and orally ingested over a 48-h exposure period. The RBA values of ²³⁸U and ²³²Th in blood samples from rats’ post-exposure were determined as 22.0% ± 0.86% to 30.8% ± 1.01% and 11.8% ± 0.14% to 13.7% ± 0.29%, respectively. Compared to ²³²Th, ²³⁸U blood levels of SD rats fed with co-contaminated concrete dust-amended diets were ~ 100-fold higher due to solubility differences, and ²³⁸U-RBA values were approximately 2-fold greater, revealing that their absorption rates in the gastrointestinal tract were affected by compound solubility. Post-acute ²³⁸U and ²³²Th ingestion from co-contaminated concrete dust demonstrate noticeable histopathological and hematological alterations, implying that intake of ²³⁸U and ²³²Th in co-contaminated concrete dust can lead to erythrocytes damage and elevated hematological attributes. Our study would be beneficial for an adequate understanding of the health implications caused by the acute oral exposures of ²³⁸U and ²³²Th in co-contaminated concrete dust, especially in the bioavailability and toxicity assessment.