RESUMO
PM2.5 (i.e., particles with aerodynamic diameters less than 2.5 µm) and the associated water-soluble, dissolved, and labile fractions of heavy metals (Cu, Pb, Mn, Ni, Co, Zn, Cr, and Cd) were determined in indoor air of twenty workplaces in Alexandroupolis (Northeastern Greece). PM2.5 concentrations exhibited significant variance across the workplaces ranging from 11.5 µg m-3 up to 276 µg m-3. The water-soluble metal concentrations varied between 0.67 ± 2.52 ng m-3 for Co and 27.8 ± 19.1 ng m-3 for Ni exhibiting large variations among the different workplaces. The water-soluble metal fractions were further treated to obtain the labile metal fraction (by binding with Chelex 100-chelating resin) that might represent a higher potential for bioaccessibility than the total water-soluble fraction. The largest labile (chelexed) fractions (48-67% of the corresponding water-soluble concentrations) were found for Cd, Mn, Cu, and Ni, while the labile fractions of Pb, Cr, Co, and Zn were relatively lower (34-42% of the corresponding water-soluble concentrations). Water-soluble and labile concentrations of heavy metals were further used to calculate cancer and non-cancer risks via inhalation of the PM2.5-bound metals. To our knowledge, this is the first study estimating the health risks due to the inhalation of water-soluble and labile metal fractions bound to indoor PM.