Citation:

Kastury, F., E. Smith, Ranju R. Karna, Kirk G. Scheckel, AND A. Juhasz. Methodological factors influencing inhalation bioaccessibility of metal(loid)s in PM2.5 using simulated lung fluid. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 241:930-937, (2018). https://doi.org/10.1016/j.envpol.2018.05.094

Impact/Purpose:

Epidemiological studies have consistently linked chronic and short term exposure to fine particulate matter with an aerodynamic diameter of < 2.5 µm (PM2.5) to adverse health outcomes. The main constituents of PM2.5 include sulphate (20%), crustal materials (soil, sand, road and desert dust; 13.4%), equivalent black carbon (11.9%), NH4NO3 (4.7%), sea salt (2.3%), trace element oxides (1%), water (7.2%) and residual matter (40%). An increase of 10 µg PM2.5 m3 was linked to increase in respiratory illness related hospital admission frequencies and 1.04% in mortality. Recent research highlighted that metals in PM2.5 (e.g. Cu, Fe, Mn and Ni) collected at traffic intersections may have considerable oxidative capabilities. Additionally, metals in aqueous extracts of PM2.5 was demonstrated to cause lung inflammation and injury, oxidative stress, lipid and protein damage and cardiovascular injury in mouse and rat models. Instead of using total meta(loid) concentration for human exposure assessment, it is more relevant to use the concentration of metal(loid)s in PM2.5 that may potentially dissolve in the lung fluid and be absorbed into the blood. Although the bioavailable fraction (metal(loid)s absorbed into the systemic circulation) remains the most appropriate, exposure assessment refinement using the bioaccessible fraction (metal(loid) extracted using simulated lung fluid (SLF)) is often more desirable as a rapid and cost effective approach. Additionally, significant knowledge gaps exist in methods currently used to determine metal(loid) bioaccessibility in PM2.5. For example, the solid to liquid (S/L) ratio used ranges significantly (1:100 –1:1163) or not reported because a part of the filter paper with which the particles were collected was used directly in assays; agitation ranges from occasional, continuous or ultrasonic; and extraction time varies from 1 to 120 h. The overarching aim of this study was to develop a conservative method to assess inhalation bioaccessibility of metal(loid) in PM2.5 from environmental samples. To achieve this aim, the effect of solid to liquid (S/L) ratio, agitation, SLF composition and extraction time on metal(loid) bioaccessibility in PM2.5 was assessed using SLF and compared to the extraction efficiencies using GIT solutions. Seven metal(loid)s (Al, As, Cd, Fe, Mn, Pb, Zn) from three environmental matrices and a certified reference material were used to develop a standardized inhalation bioaccessibility assay for metal(loid)s in PM2.5.

Description:

In this study, methodological factors influencing the dissolution of metal(loid)s in simulated lung fluid (SLF) was assessed in order to develop a standardised method for the assessment of inhalation bioaccessibility in PM2.5. To achieve this aim, the effects of solid to liquid (S/L) ratio (1:100 to 1:5000), agitation (magnetic agitation, occasional shaking, orbital and end-over-end rotation), composition of SLF (artificial lysosomal fluid: ALF; phagolysosomal simulant fluid: PSF) and extraction time (1–120 h) on metal(loid) bioaccessibility were investigated using PM2.5 from three Australian mining/smelting impacted soils and a certified reference material. The results highlighted that SLF composition significantly (p < 0.001) influenced metal(loid) bioaccessibility and that when a S/L ratio of 1:5000 and end-over-end rotation was used, metal(loid) solubility plateaued after approximately 24 h. Additionally, in order to assess the exposure of metal(loid)s via incidental ingestion of surface dust, PM2.5 was subjected to simulated gastro-intestinal tract (GIT) solutions and the results were compared to extraction using SLF. Although As bioaccessibility in SLF (24 h) was significantly lower than in simulated GIT solutions (p < 0.05), Pb bioaccessibility was equal to or significantly higher than that extracted using simulated GIT solutions (p < 0.05).

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