Bioaccessibility of Uranium in Soil Samples from Port Hope, Ontario, Canada

Abstract

Adequate assessment of human health risk of uranium contamination at hazardous waste sites, which is an important step in determining the cleanup strategy, is based on bioavailability data. Bioavailability of uranium from contaminated soil has not been properly determined yet. Bioaccessibility is an in vitro conservative estimate of bioavailability and is thus frequently used for site-specific risk assessment. Bioaccessibility of uranium was measured in 33 soil samples from the Port Hope area in Ontario, Canada, by the physiologically based extraction test (PBET). Higher bioaccessibility values in the gastric plus intestinal phase, 48.4% ± 16.8%, than in the gastric phase, 20.8% ± 11.7%, are very probably the result of more efficient extraction of uranium from soil by intestinal fluid rich in carbonate ions. The observed variability of measured bioaccessibility values is discussed in light of the results of scanning electron microscope examination of the soil samples. Uranium bioaccessibility values in both gastric (acidic) and gastric plus intestinal (neutral) phases are higher in soil samples with smaller uranium-bearing particles and lower in samples where the uranium-bearing particles are larger. We postulate that the most important reason for variability of measured bioaccessibility values in Port Hope soil samples may be the difference in particle size of uranium-bearing particles.

Internal dose assessment of 238U contaminated soils based on in-vitro gastrointestinal protocol

“…Compared to BRIS, laterite and peat soils, alluvium soil consists of clay which has the tendency to adsorb 238 U, hence increased the formation of complexes with both stage of gut fluids [24]. This compliance with research done by Jovanovic et al [25] that stated difference soil compositions greatly influences the solubility of uranium in simulated physiological fluids. The key results to estimate annual comitted effective dose was summarised in Table 3.…”

Bioaccessibility of U, Th and Pb in solid wastes and soils from an abandoned uranium mine

“…The Physiologically Based Extraction Test (PBET) (Ruby et al, 1993), or subsequent modifications thereof, has been applied to various solids containing uranium (e.g. Frelon et al, 2007;H€ ollriegl et al, 2010;Jovanovic et al, 2012), however, these methods may not accurately reproduce human gastrointestinal digestive processes which has led to the design of improved in-vitro methodologies (summarized by Tokaho glu et al, 2014). In particular, the Bioaccessibility Research Group of Europe (BARGE) developed the Unified BARGE Method (UBM) which has been successfully compared with in vivo studies (Wragg et al, 2011a;Denys et al, 2012) and has been widely applied to metalcontaminated soils (Barsby et al, 2012;Broadway et al, 2010;Farmer et al, 2011;Juhasz et al, 2011b;Pelfrêne et al, 2013).…”

Estimating the Absorption of Soil-Derived Uranium in Humans

“…due to uranium refining, agriculture activities and presumably also as a result of nuclear incidents like the Chernobyl accident in 1986 or the Fukushima Daiichi incident in 2011. [9][10][11] Consequently, soil ingestion leads to a certain internal dose enhancement.…”