An inhalation-ingestion bioaccessibility assay (IIBA) for the assessment of exposure to metal(loid)s in PM₁₀

Although metal(loid) bioaccessibility of ambient particulate matter, with an aerodynamic diameter of <10microm (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.