Pyrite-driven reactive oxygen species formation in simulated lung fluid: implications for coal workers’ pneumoconiosis

Abstract

The origin of coal worker's pneumoconiosis (CWP) has been long debated. A recent epidemiological study shows a correlation between what is essentially the concentration of pyrite within coal and the prevalence of CWP in miners. Hydrogen peroxide and hydroxyl radical, both reactive oxygen species (ROS), form as byproducts of pyrite oxidative dissolution in air-saturated water. Motivated by the possible importance of ROS in the pathogenesis of CWP, we conducted an experimental study to evaluate if ROS form as byproducts in the oxidative dissolution of pyrite in simulated lung fluid (SLF) under biologically applicable conditions and to determine the persistence of pyrite in SLF. While the rate of pyrite oxidative dissolution in SLF is suppressed by 51% when compared to that in air-saturated water, the initial amount of hydrogen peroxide formed as a byproduct in SLF is nearly doubled. Hydroxyl radical is also formed in the experiments with SLF, but at lower concentrations than in the experiments with water. The formation of these ROS indicates that the reaction mechanism for pyrite oxidative dissolution in SLF is no different from that in water. The elevated hydrogen peroxide concentration in SLF suggests that the decomposition, via the Fenton mechanism to hydroxyl radical or with Fe(III) to form water and molecular oxygen, is initially inhibited by the presence of SLF components. On the basis of the oxidative dissolution rate of pyrite measured in this paper, it is calculated that a respirable two micron pyrite particle will take over 3 years to dissolve completely.

Metal-sulfide mineral ores, Fenton chemistry and disease – Particle induced inflammatory stress response in lung cells

“…It is possible that the dissolution and release of iron is limited in the more complex fluids used in the cellular studies, similar to earlier results with pyrite, which showed a reduction in dissolution rate (Harrington et al, 2012a). Furthermore, at a neutral pH, ferric iron-hydroxide coatings dominate the surface of arsenopyrite and sulfur, not iron, is readily released into solution (Asta et al, 2010).…”

“…An excessive particle burden can cause an array of pulmonary issues, ranging from chronic inflammation and fibrosis, to the development of tumors (Oberdorster, 1995). Once inhaled, a mineral particle might undergo surface-mediated reactions, including dissolution reactions (Fubini, 1997; Ghiazza et al, 2011; Harrington et al, 2012a; Schoonen et al, 2006). The reactivity of an inhaled particle is a function of its stability in the lung environment, its solubility, and modifications of its surface, such as the presence of defects or surface coatings (Fubini, 1997; Ghiazza et al, 2011; Schoonen et al, 2006).…”

“…The approach developed by Harrington et al (2012) takes into account the possible complexity of immune responses to foreign materials in the body by capturing the immediate and short-term inflammatory stress response (ISR) generated by exposure to a contaminant (Harrington et al, 2012b). The ISR is the normalization of the cellular upregulation of ROS with respect to the cell viability.…”

Bioaccessibility, release kinetics, and molecular speciation of arsenic and lead in geo-dusts from the Iron King Mine Federal Superfund site in Humboldt, Arizona

“…The simulated lung fluid (SLF) method used a modified Gambles' solution developed by Takayka (7)(8)(9)(10)(11)(12)(13). Bioaccessibility is determined based on metal release normalized to total metals determined from Aqua Regia extraction.…”

An improved pyrite pretreatment protocol for kinetic and isotopic studies

“…Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation [9][10][11][12][13][14][15][16], the isotopic fractionations associated with these reactions [17][18][19][20][21][22], the microbiological processes involved [23][24][25], and the effect of pyrite surface reactivity and hydroxyl radical formation on human health [26][27][28][29]. Common to many of these studies is the pretreatment of pyrite to prevent experimental artifacts and inaccuracies.…”