Bioaccessibility of metal (loid)s from fine particulate matter (PM2.5) varies by artificial lung fluid type, season, and location in Mexico City

Particulate matter pollution has been particularly linked to respiratory diseases. Particles ≤ 2.5 µm in aerodynamic diameter (PM_2.5) easily penetrate the lower airways of the lungs and release constituents that produce local or systemic effects by translocation. Bioaccessibility refers to the availability of metals when dissolved in body fluids in vitro. Given that the biological composition of lung fluids facilitates the bioaccessibility of PM_2.5 components, we identified the soluble elements in the following artificial fluids: Gamble´s solution, artificial interstitial fluid (AIF), simulated epithelial lung fluid (SELF), artificial lysosomal fluid (ALF), and deionized water. We collected PM_2.5 from three sites in Mexico City (CDMX), Pedregal (PED), Universidad Autónoma Metropolitana Iztapalapa (UIZ), and the Laboratory of Environmental Analysis (LAA), during two seasons, dry-hot (dh) and dry-cold (dc). The PM_2.5 was sonicated and incubated in each fluid for 24 h at 37 °C and then centrifuged. We measured the metal (loid) content in the supernatant by ICP-MS. Bioaccessibility, in terms of element concentration and number of elements detected, was (from higher to lower) as follows: LAA > UIZ > PED; dh > dc; and ALF > SELF > Water > AIF > Gamble´s solution. The metal (loid)s with the highest levels were Zn, As, Cr, and V. In conclusion, metal (loid)s are differentially soluble in various solutions, and the time it takes to read the solutions affects the bioaccessibility results from each fluid when the samples are not acidified (no digestion).