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Abstract:The goal of the study was to determine the concentrations of submicron particulate matter (PM 1 ) and of the mercury contained in it (Hg p ) in the air in two teaching rooms in two Polish cities, Gliwice and Warsaw. The levels of atmospheric particulate matter (PM) differ greatly between these two cities. The relations between the indoor (I) and outdoor (O) 24-h concentrations for each PM 1 and Hg p were determined and, based on the conclusions, an attempt was made to identify the main sources of the indoor Hg p in both cities. During the whole measuring period (April-June 2015), in both Warsaw and Gliwice, the 24-h outdoor PM 1 concentrations were slightly higher than the indoor ones (outdoor and indoor averages were equal to 19.3 µg m −3 and 14.5 µg·m −3 , respectively, in Gliwice and to 13.2 µg·m −3 and 9.5 µg·m −3 in Warsaw). In Gliwice, the indoor concentrations of Hg p (2.4 pg·m −3 to 27.7 pg·m −3 ) were much higher than the outdoor ones (1.1 pg·m −3 to 6.1 pg·m −3 ); in Warsaw the average concentrations of Hg p were equal to 1.4 pg m −3 indoors and outdoors. The 24-h concentrations of Hg p and the 24-h I/O ratios for Hg p varied more intensely in Gliwice than in Warsaw throughout the whole measuring period. In Warsaw, the teaching room Hg p came mainly from the infiltration of atmospheric (outdoor) Hg p . In Gliwice, a part of the indoor Hg p infiltrated into the teaching room with the outdoor PM 1 that most probably was then enriched with gaseous indoor Hg, what resulted in the relatively high indoor Hg p concentrations.

This study assessed inhalation exposure to particulate matter (PM1)-bound mercury (Hgp) and PM1-bound polycyclic aromatic hydrocarbons (PAHs) among university students. For this purpose, simultaneous indoor (I) and outdoor (O) measurements were taken from two Polish technical universities (in Gliwice and Warsaw) located in distinct areas with respect to ambient concentrations and major sources of PM. The indoor geometric mean concentrations of Hgp were found to be 1.46 pg·m−3 and 6.38 pg·m−3 in Warsaw and Gliwice, while the corresponding outdoor concentrations were slightly lower at 1.38 pg·m−3 and 3.03 pg·m−3, respectively. A distinct pattern was found with respect to PAH concentrations with estimated I/O values of 22.2 ng·m−3/22.5 ng·m−3 in Gliwice and 10.9 ng·m−3/11.12 ng·m−3 in Warsaw. Hazard quotients (HQs) as a result of exposure to Hgp for students aged 21 ranged from 3.47 × 10−5 (Warsaw) to 1.3 × 10−4 (Gliwice) in terms of reasonable maximum exposure (RME). The non-cancer human health risk value related to Hgp exposure was thus found to be below the acceptable risk level value of 1.0 given by the US EPA. Daily exposure values for lecture hall occupants, adjusted to the benzo(a)pyrene (BaP) toxicity equivalent (BaPeq), were 2.9 and 1.02 ng·m−3 for the Gliwice and Warsaw students, respectively. The incremental lifetime cancer risk (ILCR) values with respect to exposure to PM1-bound PAHs during the students’ time of study were 5.49 × 10−8 (Warsaw) and 1.43 × 10−7 (Gliwice). Thus, students’ exposure to indoor PAHs does not lead to increased risk of lung cancer.

The research presented herein aimed at recognition of submicrone particulate matter concentration as well as organic (OC) and elemental (EC) carbon bound to it in a lecture room and students’ laboratory. The 24-h variability of PM1, OC and EC concentration in both rooms were also discussed along with I : O ratio. In the analysed period – the turn of spring and summer – independent of the location (Gliwice – students’ laboratory, Warsaw – lecture room) the indoor concentration of elemental carbon EC was conditioned by the intensity of those contaminants migration along with atmospheric air. Because of this, it can be concluded that in neither of the rooms there was an important source of OC and EC. However, it should be noted, that conditions favourable for different contaminant sorption, in particular those belonging to OC bound to particulate matter, vary in time and space. It is expected, that for other measurement period – for instance in winter, when rooms are ventilated seldom and PM has different composition, the cummulation of indoor contaminants, including OC, may be higher than for warm period.