Assessment of uranium and thorium co-contaminant exposure from incidental concrete dust ingestion

Abstract

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-hour exposure period. The RBA values of 238U and 232Th in post-exposure rats' blood were determined as 22.0% ± 0.86% – 30.8% ± 1.01% and 11.8% ± 0.14% – 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 two-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.