Methodological Aspects of In Vitro Assessment of Bio-accessible Risk Element Pool in Urban Particulate Matter

In vitro tests simulating the elements release from inhaled urban particulate matter (PM) with artificial lung fluids (Gamble’s and Hatch’s solutions) and simulated gastric and pancreatic solutions were applied for an estimation of hazardous element (As, Cd, Cr, Hg, Mn, Ni, Pb and Zn) bio-accessibility in this material. An inductively coupled plasma optical emission spectrometry (ICP-OES) and an inductively coupled plasma mass spectrometry (ICP-MS) were employed for the element determination in extracted solutions. The effect of the extraction agent used, extraction time, sample-to-extractant ratio, sample particle size and/or individual element properties was evaluated. Different patterns of individual elements were observed, comparing Hatch’s solution vs. simulated gastric and pancreatic solutions. For Hatch’s solution, a decreasing sample-to-extractant ratio in a PM size fraction of <0.063 mm resulted in increasing leached contents of all investigated elements. As already proved for other operationally defined extraction procedures, the extractable element portions are affected not only by their mobility in the particulate matter itself but also by the sample preparation procedure. Results of simulated in vitro tests can be applied for the reasonable estimation of bio-accessible element portions in the particulate matter as an alternative method, which, consequently, initiates further examinations including potential in vivo assessments.