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An inhalation-ingestion bioaccessibility assay (IIBA) for the assessment of exposure to metal(loid)s in PM10
Citation:
Kastury, F., E. Smith, R. Karna, K. Scheckel, AND A. Juhasz. An inhalation-ingestion bioaccessibility assay (IIBA) for the assessment of exposure to metal(loid)s in PM10. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, , 92-104, (2018).
Impact/Purpose:
Metal(loid) inhalation from ambient particulate matter (APM) is increasingly becoming recognised as a significant exposure pathway associated with potentially adverse human health outcomes. According to the USEPA, the fraction of APM that enters the respiratory system and deposits in the fluid lining the human lung has an aerodynamic diameter (Dae) of <10µm (PM10). High metal(loid) concentrations in PM10 are often reported near areas with current or historic industrial activities, such as mining, smelting and manufacturing. The overarching aim for this study was to develop a conservative bioaccessibility assay that provides the maximum metal(loid) dissolution using an SLF simulating a human inhalation scenario. To achieve this aim, PM10 from three environmental matrices were used to study the effect of S/L ratio, type of agitation, fluid composition and extraction time on the bioaccessibility. The parameters that provide the highest metal(loid) solubility were used in conjunction with simulated gastro-intestinal fluids to reflect the passage of PM10 via the gut. This novel approach is the first investigation to study metal(loid) bioaccessibility combining both inhalation and oral exposure pathways. In this study, a certified reference material and PM10 from three environmental matrices with elevated concentrations of multiple metal(loid)s due to mining/smelting activities were used to investigate the effects of methodological parameters on inhalation bioaccessibility. Additionally, the assay was extended to include gastrointestinal solutions to simulate a scenario where PM10 is cleared from the lung and swallowed. The main findings were used to develop an optimised, two-stage inhalation-ingestion bioaccessibility assay (IIBA), which provides the most conservative exposure via this pathway. During stage one, PM10 should be leached in Hatch’s solution for 24 hours at 37°C using an S/L ratio of 1:5000 and end over end rotation (45 rpm). After 24 hours, PM10 should then be separated from SLF by centrifugation, reserving the solution for metal(loid) analysis. During step two, PM10 should be further leached in simulated gastrointestinal solutions according to (Juhasz et al., 2009). The highest cumulative metal(loid) dissolution should be used as the final inhalation bioaccessibility result.
Description:
Although metal(loid) bioaccessibility of ambient particulate matter, with an aerodynamic diameter of <10 μm (PM10), has recently received increasing attention, limited research exists into standardising in-vitro methodologies using simulated lung fluid (SLF). Contradictions exist regarding which assay parameters should be adopted. Additionally, potential continuation of metal(loid) dissolution once PM10 is cleared from the lungs and passed through the gastro-intestinal tract (GIT) has rarely been addressed. The objective of this study was to assess parameters that influence inhalation bioaccessibility in order to develop a conservative assay that is relevant to a human inhalation scenario. To achieve this aim, the effect of solid to liquid (S/L) ratio, extraction time, agitation and five major SLF compositions on the bioaccessibilities of arsenic (As) and lead (Pb) was investigated using PM10 from three Australian mining/smelting impacted regions. Using the biologically relevant parameters that resulted in the most conservative outcomes, bioaccessibility of metal(loid)s in PM10 was assessed in SLF, followed by simulated GIT solutions. Results from this study revealed that fluid composition and S/L ratio significantly affected metal(loid) dissolution (p < 0.05). The highest Pb bioaccessibility resulted using simulated lung-gastric solution, while that of As resulted using simulated lung-gastric-small intestinal tract solutions. Compared to SLF alone, metal(loid) dissolution using the inhalation-ingestion bioaccessibility assay (IIBA) was significantly higher (p < 0.05) for all PM10 samples.
URLs/Downloads:
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https://www.sciencedirect.com/science/article/pii/S004896971830737X