Inhalation bioaccessibility of polycyclic aromatic hydrocarbons from reference combustion-derived particles: Methodological aspects and toxicological impact on bronchial epithelial cells.

Combustion-derived particles are a significant concern due to their nanometric sizes and complex chemical compositions, which can negatively impact health. These particles contain polycyclic aromatic hydrocarbons (PAH) and their oxygenated derivatives (OPAH), which can dissolve in biological lung fluids. As a result, they form complex mixtures whose toxicity is often poorly studied. Therefore, evaluating inhalation bioaccessibility is crucial for accurately assessing the health risks associated with these particles. We determined the inhalation bioaccessibility fractions (IBAF) of 16 PAH and 5 OPAH from particles generated under controlled conditions. Several critical parameters were evaluated, including simulated lung fluids (SLF), extraction times, and solid-to-liquid (S/L) ratios. Our results indicated that eight compounds - NAP, ACY, FLU, 9-FLUO, PHE, ANT, FLT, PYR - were systematically extracted by the different SLF, namely Gamble's solution (GS), artificial lysosomal fluid (ALF), modified GS (MGS), and simulated epithelial lung fluid (SELF) after 24 h of extraction time with an S/L ratio of 1/2000. The evaluation of the toxicological response, based on cytotoxicity and the AhR-dependent pathway, demonstrated variability in the toxicological profiles, depending on the extraction conditions used. Notably, the extraction condition yielding a biological response equivalent to that assessed with the total particulate fraction was the use of MGS as the extraction fluid under our experimental conditions. From a toxicological perspective, these approaches appear relevant for assessing the toxicity mechanisms of PAH mixtures, closely mimicking the in vivo conditions found in the human respiratory tract. This study outlined that understanding whether the bioaccessible fraction of particulate-bound PAHs is a reliable predictor of toxicity is central to advancing inhalation risk assessment.