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Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids
Citation:
Kastury, F., R. Karna, Kirk G. Scheckel, AND A. Juhasz. Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 263 part B:114609, (2020). https://doi.org/10.1016/j.envpol.2020.114609
Impact/Purpose:
Exposure to toxic elements in dust or particulate matter (PM) is gaining global attention as a significant health hazard. Adverse health outcomes due to inhalation of elements in dust/PM is felt more acutely in communities near industrial activities, e.g. lead (Pb) mining/smelting, Pb battery recycling, electronic waste recycling, and steel manufacturing. The impact of Pb on childhood cognitive and neurological development is well documented and may occur at low Pb concentrations. Inorganic Pb has been classified as a probable carcinogen to humans by The International Agency for Research on Cancer and the Agency for Toxic Substances and Disease registry with no known level of safe exposure. Although ingestion is considered the major Pb exposure pathway for children, inhalation exposure assessment may be pertinent when PM containing Pb is aerosolized due to resuspension of contaminated dust in arid environments or when Pb is emitted into the atmosphere during industrial activities. Lead speciation is closely tied to bioavailability/bioaccessibility outcomes. X-ray based spectroscopic techniques are considered an ideal Pb speciation method as it does not require sample pre-treatment that may influence speciation. However, Pb speciation in inhalable particle size fractions from mining/smelting regions has received limited attention. Lead speciation in dust/PM and its relationship to bioaccessibility may provide significant insights into the factors influencing Pb exposure via inhalation. Consequently, this study investigated Pb speciation in the < 10 µm particle fraction obtained from five mining/smelting impacted soils in order to elucidate its role in inhalation bioaccessibility via simulating particle deposition in the lung lining fluid and engulfment by alveolar macrophages.
Description:
This study investigated the relationship between lead (Pb) speciation determined using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy in <10 μm particulate matter (PM10) from mining/smelting impacted Australian soils (PP, BHK5, BHK6, BHK10 and BHK11) and inhalation exposure using two simulated lung fluids [Hatch’s solution, pH 7.4 and artificial lysosomal fluid (ALF), pH 4.5]. Additionally, elemental composition of Pb rich regions in PP PM10 and the post-bioaccessibility assay residuals were assessed using a combination of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to provide insights into how extraction using simulated lung fluids may influence Pb speciation in vitro. Correlation between Pb speciation (weighted %) and bioaccessibility (%) was assessed using Pearson r (α = 0.1 and 0.05). Lead concentration in PM10 samples ranged from 782 mg/kg (BHK6) to 7796 mg/kg (PP). Results of EXAFS analysis revealed that PP PM10 was dominated by Pb adsorbed onto clay/oxide, while the four BHK PM10 samples showed variability in the weighted % of Pb adsorbed onto clay/oxide and organic matter bound Pb, Pb phosphate, anglesite and galena. When bioaccessibility was assessed using different in vitro inhalation assays, results varied between samples and between assays, Pb bioaccessibility in Hatch’s solution ranged from 24.4 to 48.4%, while in ALF, values were significantly higher (72.9–96.3%; p < 0.05). When using Hatch’s solution, bioaccessibility outcomes positively correlated to anglesite (r:0.6246, p:0.0361) and negatively correlated to Pb phosphate (r: -0.9610, p:0.0041), organic bound Pb (r: -0.7079, p: 0.0578), Pb phosphate + galena + plumbojarosite (r: -0.9350, p: 0.0099). No correlation was observed between Pb bioaccessibility (%) using Hatch’s solution and weighted % of Pb adsorbed onto clay/oxide and between bioaccessibility (%) using ALF and any Pb species. SEM and EDX analysis revealed that a layer of O–Pb–Ca–P–Si–Al–Fe formed during the in vitro extraction using Hatch’s solution.
URLs/Downloads:
DOI: Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids
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