Mineralogy Controlled Dissolution of Uranium from Airborne Dust in Simulated Lung Fluids (SLFs) and Possible Health Implications

Abstract

The recent increase in cardiovascular and metabolic disease in the Navajo population residing close to the Grants Mining District (GMD) in New Mexico is suggested to be due to exposure to environmental contaminants, in particular uranium in respirable dusts. However, the chemistry of uranium-containing-dust dissolution in lung fluids and the role of mineralogy are poorly understood, as is their impact on toxic effects. The current study is focused on the dissolution of xcontaining-dust, collected from several sites near Jackpile and St. Anthony mines in the GMD, in two simulated lung fluids (SLFs): Gamble's solution (GS) and Artificial Lysosomal Fluid (ALF). We observe that the respirable dust includes uranium minerals that yield the uranyl cation, UO 2 2+ , as the primary dissolved species in these fluids. Dust rich in uraninite and carnotite is more soluble in GS, which mimics interstitial conditions of the lungs. In contrast, dust with low uraninite and high kaolinite is more soluble in ALF, which simulates the alveolar macrophage environment during phagocytosis. Moreover, geochemical modeling, performed using PHREEQC, is in good agreement with our experimental results. Thus, the current study highlights the importance of site-*

Simulated biological fluids – a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres

“…Mineralogy was also found to influence the dissolution and pH preferences. In a study of U-bearing dusts, those low in uraninite and high in kaolinite were more soluble in ALF, while those rich in uraninite and carnotite more soluble in Gamble's solution (Hettiarachchi et al 2019). For Ag NPs, the greater quantity of nitrogen donors, especially when modified to contain DTPA, lead to a greater Ag þ concentration in modified Gamble's solution than ALF, even though pH is neutral (Zhong et al 2019).…”

New Insights into Health Risk Assessments for Inhalational Exposure to Metal(loid)s: The Application of Aqueous Chemistry Modelling in Understanding Bioaccessibility from Airborne Particulate Matter

“…Moreover, it is known that the metal and metalloid components of the particulates are also associated with these health effects [1,2]. Upon inhalation, fine particulate fractions, i.e., those with an aerodynamic diameter less than 4 µm, are most likely to deposit in the alveoli [3], whereas larger particulates may become impacted upon the mucous-lined surfaces of the nasopharynx and tracheobronchial regions of the respiratory tract [4]. These different deposition locations determine the residence time of the particle in the lungs and the composition of the lung fluid into which bound contaminants, such as metals/metalloids, might be extracted [5].…”

“…The chemical nature of the PTE components of the deposited particles also plays a significant role in its bioaccessibility, with several studies reporting the role played by mineralogy and speciation [3,13,14,16]. Such observations, for example that particles containing Pb in the form of galena (PbS) give lower inhalational bioaccessibilities than those containing Pb as anglesite (PbSO 4 ) [13], imply that bioaccessibility is likely to be highly source dependent.…”

“…Sources may also change, in terms of metal speciation, over time because of weathering; this is particularly relevant to particulates generated from mining [16][17][18] and smelting [19] wastes. Other factors that have been considered to affect bioaccessibility are dissolution kinetics [17], surface reactions and complexation [20,21], redox reactions [3], particle size and shape [15,19] and the solid to liquid ratio (S/L ratio) [8,14]. Of these factors, S/L ratio and the potential for surface complexation are likely to have the most significant influence on the % bioaccessibility.…”

“…There are literature examples of aqueous chemistry modelling being applied to a range of related environmental scenarios, such as in the prediction of speciation and solubility of metals and metalloids during leaching from smelter fly ash [19,[22][23][24] and mine tailings [16,17], and in assessing the impact of acid rain on weathering and Al 3+ release in Swedish conifer forests [25]. Specific applications involving bioaccessibility modelling have included the simulation of speciation and solubility of PTEs from mine tailings in simulated lung and gut fluids [16] and the dissolution of uranium from particulates in simulated lung fluids [3]. Most of these studies have used the PHREEQC geochemical modeler [26], with either the MINTEQ [3,17,19,22,23,27] or WATEQ4F [18] thermochemical databases [27,28].…”