AIR POLLUTION: CHEMISTRY AND HEALTH RISKS Indoor concentrations of PM 2.5 and associated water-soluble and labile heavy metal fractions in workplaces: implications for inhalation health risk assessment Efthalia Kogianni 1 & Athanasios Kouras 1 & Constantini Samara 1 Received: 24 September 2019 /Accepted: 29 December 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract PM 2.5 (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). PM 2.5 concentrations exhibited significant variance across the workplaces ranging from 11.5 μgm -3 up to 276 μgm -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 PM 2.5 -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. Keywords PM 2.5 . Indoor air . Workplaces . Water-soluble metal fraction . Labile metal fraction . Bioaccessibility . Risk assessment Introduction Taking into account that people in modern society spend most of their time in indoor environments (Amoatey et al. 2018; Simoni et al. 2003; Szigeti et al. 2014), indoor air pollution has become one of the biggest threats for public health in most of the places all over the world. Many diseases, like cardiore- spiratory problems and pulmonary or lung cancer, are con- nected to inhalation of indoor air pollutants, whereas long- term exposure to them can also cause mortalities (Pope III et al. 2004; Amoatey et al. 2018). A great majority of those pollutants contribute to such negative effects on humans’ health due their particulate nature, especially when the diam- eter of the particles tends to be very small, as they have higher accessibility deeply inside the lung. Indoor PM 2.5 (i.e., parti- cles with aerodynamic diameters less than 2.5 μm) appear to be a risk factor for cardiovascular disease mortality (Pope III et al. 2004; Brook et al. 2010; Pope III and Dockery 2006), whereas a significant positive correlation between their con- centrations and lung cancer mortality has been found (Huang et al. 2017; Cao et al. 2018). However, the size of particulate matter (PM) particles is not the unique risk factor, since their composition also plays a determinative role in their toxic effects. Among PM compo- nents, heavy metals have been widely studied in several in- door environments (Taner et al. 2013; Satsangi et al. 2014; See Responsible editor: Gerhard Lammel Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-019-07584-8) contains supplementary material, which is available to authorized users. * Efthalia Kogianni ekogiann@chem.auth.gr Athanasios Kouras akouras@chem.auth.gr Constantini Samara csamara@chem.auth.gr 1 Environmental Pollution Control Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-07584-8