DOI: 10.17344/acsi.2016.2269 Acta Chim. Slov. 2016, 63, 327-334 327 Scientific paper Indoor Nanoparticles Measurements in Workplace Environment: The Case of Printing and Photocopy Center Irena Grgic,1* Jožica Bratec1,2 and Marija Bester Rogač2 1 Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia 2 University of Ljubljana, Faculty of Chemistry and Chemical Technology, Večna pot 113, SI-1000 Ljubljana, Slovenia * Corresponding author: E-mail: irena.grgic@ki.si Received: 20-01-2016 Abstract In recent studies, laser printers and photocopy machines have been identified as important sources of indoor air pollution with fine and ultrafine particles. In this work, the indoor pollution of a printing and photocopy center in Ljubljana, Slovenia was investigated. The particle number concentration time series and the particle size distributions were measured continuously for a period of one month by a scanning mobility particle sizer (SMPS). Our measurements clearly showed that during operating hours the total number concentration of nanoparticles (size between 15 and 750 nm) increased in both working rooms with laser printers as well as in a room with photocopy machines. In rooms with laser printers the bimodal particle size distribution was frequently observed (i.e. max. at ca. 20 or 30 nm and at ca. 100 nm), with the aged particles persisted in the room over the night and over the weekend. In the photocopy room the situation was different, again with a sharp increase in concentration of small particles (ca 20 nm) and their growth to bigger sizes, but after closing a decrease to the background concentration. The results undoubtedly proved that the fast increase in na-noparticles (size below 50 nm) was associated with processes, the intense laser printing and photocopying activity. Our study also confirmed that the ventilation of the room is a very important factor which affects the life time of aged nano-particle in the indoor environment. Keywords: Indoor air quality, indoor environment, ultrafine and fine particles, laser printer emissions, photocopier emissions 1. Introduction Nowadays we spend the majority of our lifetime, professional and private, in different indoor environments. In addition to the influence of outdoor pollution, which can penetrate into the buildings, various different sources can contribute to indoor pollution. Electronic devices, such as personal computers, printers, photocopy machines, which are nearly vital in our lives, can importantly influence the indoor air quality. Therefore, the emissions from such devices are of big health concern. Many studies have reported that laser printers and photocopy machines emit besides volatile organic compounds (VOCs) and ozone, also fine and ultrafine particles.1-6 It is also known that the major fraction of particles emitted during operation of laser printers represents ultrafine particles (i.e. nanoparticles) with the size range below 100 nm with an average size of about 30-50 nm.7,8 The studies on indoor pollution due to the emissions of nanoparticles from laser printers and photocopy machi- nes are mostly related to the particle concentrations and size distributions1'9'10 and to possible formation mechanisms.810 Measurements on particle emissions in the real-room environment710 and studies on modeled office environment can be found as well;5 the influence of different parameters, such as fuser roller temperature on the emissions of laser printers was also studied.711 The majority of particles emitted from laser printers is volatile and of secondary nature, i.e. formed in the air through the reactions of VOCs and semi volatile organic compounds (SVOCs) originating from paper and/or hot toner with ozone.8 In addition, Barthel et al.12 reported on elemental analysis of fine and ultrafine particles, and the elements identified (e.g. Si, S, Cl, Ca, Ti, Cr, Fe) were mainly connected with toner and paper. Further, the studies have also pointed out the potential health hazards associated with nanoparticles emitted during laser printing and photocopying operation.13-15 For example, it has been shown that already short-term expo- Grgic et al.: Indoor Nanoparticles Measurements in Workplace 328 Acta Chim. Slov. 2016, 63, 327-334 329 sures (i.e. 6 h) to modest concentrations (5,000-30,000 particles cm-3) of nanoparticles emitted during photocopying induced statistically significant increases in systemic oxidative stress and upper airway inflammation.14 In addition, occupational and consumer risk for nanoparticles from laser printers have been estimated16 and their toxico-logical effects have been recognized by World Health Organization as well.17 In this work, the indoor pollution with fine and ultrafine particles in a company for spatial informatics and graphic design from Ljubljana, Slovenia dealing with different services, among which are also printing and photo-copynig, was investigated for the first time. The particle number concentrations and the particle size distributions were measured continuously in a period of one month in three working rooms (in each for about 10 days) where different hardcopy devices were in use. 2. Experimental 2. 1. Instrumentation A Scanning Mobility Particle Sizer spectrometer (SMPS 3936L75, TSI) was used for continuous measurements of submicrometer particle number concentrations and size distributions in the range from 15 nm to 750 nm (scan up time 180 s; retrace time 15 s). The SMPS consists of an Electrostatic Classifier with a long Differential Mobility Analyzer (DMA, 3081), negatively charged high voltage controller and Impactor nozzle (0.071 cm), which is coupled to a Condensation Particle Counter (CPC 3775). The solvent for the CPC was n-butanol (Reagent Grade). The SMPS was set to measure every 5 minutes during period from February 25 to March 28, 2014. A sample flow rate of 0.3 L min-1 was used with a sheath flow of 3 L min-1. 2. 2. Sampling Sites Measurements were performed in a company for spatial informatics and graphic design from Ljubljana, Slovenia in three different working rooms dealing with different kind of services (e.g. digital printing, graphic design, scanning, photocopying). From a schematic illustration (Figure 1) it can be seen that in the first working room (Room 1, size: 5.5 m x 7.2 m x 3.2 m) the SMPS stand on a table at 0.75 m from the ground with the sampling tube at a distance of about 2 m to the laser printer (Konika Minolta C7000); in this room was also one bigger inkjet plotter (Inkjet Cannon iPF8000S) at the distance of about 3 m to the SMPS. In the second room (Room 2, size: 10 m x 7.3 m x 3.20 m) the SMPS was about 3 m from the laser printer (Laser Xerox Colour 560) (Figure 1); there were also four bigger inkjet plotters of different producers (Roland Versa CAMM, Sure-Colour S 30610, Hp designjet 5500 and UV-160 UV printer Mimaki). In the third room (Room 3, size: 5.2 m x 7.5 m x 3.2 m) there were two photocopy machines (Ducacolors 252 and Kyocera mita, KM4530). The SMPS was in the corner on the shelf at about 0.75 m from the ground with the sampling tube at about 2-3 m to the machines (Figure 1). Figure 1: Schematic illustration of three investigated working rooms in a company for spatial informatics and graphic design in Ljubljana, Slovenia with denoted positions of SMPS in each room as well as printers and copiers. L: laser printer, P: photocopy machine and I: inkjet plotter. The continuous measurements were performed for one month, the first 10 days in Room 1 with one laser printer, then the SMPS was moved into Room 2 with one laser printer as well, and the last 7 days the measurements were performed in Room 3 with two photocopy machines (Figure 1). The ventilation in Room 1 and Room 3 was carried out only by opening the windows when necessary, mostly in the morning; while in Room 2 there was no window at all, the only access of fresh air, better said the mixing of the air was possible through the door between the two rooms. The working time from Monday to Thursday was from 8:00 to 17:00, on Friday from 8:00 to 16:00, while during the weekend the company was closed. 3. Results and Discussion 3. 1. Results of SMPS Measurements in Room 1 The continuous measurements of fine and ultrafine particles in the company for spatial informatics and graphic design from Ljubljana were started in the Room 1 (Figure 1) at 16:00 on February 25 and finished at 14:00 on March 6, 2014. The typical particle number size distribu- Grgic et al.: Indoor Nanoparticles Measurements in Workplace ... Acta Chim. Slov. 2016, 63, 327-334_ 329 tions for all days including the weekend are shown in Figu- immediately after 8:00. In most cases a bimodal size distri-re 2. In general, it is evident that the concentration of nano- bution was observed: first one is a mode with particles of a particles significantly increased during working hours, i.e. diameter at around 30 nm and the second one with partic- Figure 2: Number concentration (particle cm-3) and size distribution of the particles continuously measured in Rooml of the company of spatial informatics and graphic design in Ljubljana, Slovenia from February 25 to March 6, 2014. White color represents the concentrations above 10 X 103 particle cm-3. Grgic et al.: Indoor Nanoparticles Measurements in Workplace ... 330 Acta Chim. Slov. 2016, 63, 327-334 329 les between 50 and 150 nm (maximum at around 100 nm). Strong emissions of smaller particles can be undoubtedly seen especially on February 26, March 3 and March 4, 2014. Although the concentration of particles decreased during the nonworking time it is evident that they persisted in the room during the night and also during the weekend (March 1 and 2, 2014); these were mostly aged particles with the average particle size of around 100 nm. The characteristic total number concentration of particles between 15 and 750 nm measured on March 5, 2014 (Figure 3 a) show a clear diurnal variation; it can be seen that the concentration raised steeply after 8:00 in the morning, reached the highest concentration during the high load of work between 8:00 and 12:00, and decreased to below 3.0 x 103 particle cm-3 at 15:00. In the Room 1 the average total number concentration for all working days during the working hours (from 8:00 to 17:00) was around 5.1 x 103 particle cm-3, while the highest measured concentration during printing was around 17 x 103 particle cm-3 determined at 12:30 on March 6, 2014. Our measurements also reveal that the concentration of particles (i.e. background concentration) during nonworking time (no printing) was about 2 x 103 particle cm-3. Obviously, the elevated concentrations did not decrease always to the background concentration as it can be seen from the results over the night and also from the results for the weekend when the average concentration for Saturday March 1 was about 3.7 x 103 particle cm-3 and for Sunday even higher (ca. 4.6 x 103 particle cm-3). However, it can be assumed that these were aged particles of the size of about 100 nm (Figure 2) expressing higher concentrations after 18:00 in the evening until the next day morning. Observed situation can be ascribed to the absence of any ventilation during the weekend. In any case, the average number particle concentration in the Room 1 during working time was more than 2 times higher than during nonworking time, and the maximal measured number particle concentrations were more than 5 times higher than the background concentrations. 3. 2. Results of SMPS Measurements in Room 2 The SMPS was afterward moved into the Room 2 (Figure 1) where the continuous particle measurements were conducted from March 7 to March 17, 2014. From Figure 4 representing size-resolved particle number concentration time series for 10 days, it is evident that in general the indoor pollution with particles was similar as in Room 1, but still with some important differences. As in Room 1 the concentration of nanoparticles raised immediately in the morning when the laser printer and other electronic devices were turned on. During working days the bimodal size distribution was frequently observed, i.e. particles with a diameter below 50 nm (maximum at around 20 or 30 nm) and particles between 50 and 200 nm with maximum at around 100 nm (e.g. March 10 and 12, 2014 in Figure 4). The aging of particles was evident every working day; for example very clearly at around 14:00 on 4> o t ro Cl t E u [O 1 2E+ 04 c