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The aim of this study was to evaluate the nanoparticle emissions from a laser printer in a chamber in conjunction with emissions from printers in a print room (PR) and to characterize the processes that lead to increased nanoparticle concentrations, as well as to estimate the human particle dose of the printers’ users. Measurements were conducted in a small stainless steel environmental chamber under controlled conditions, where the evolution of particle size distributions (PSDs) with time and printed pages was studied in detail. Printer was generating nanoparticles (vast majority ˂ 50 nm with mode on ~ 15 nm) primarily during cold startup. Previously, 1-week sampling was also done in a PR at the Technical University of Crete, where the tested laser printer is installed along with three other printers. Similarly, as it was observed in the chamber study, printers’ startup on any given day was characterized by a sharp increase in particle number (PN) concentrations. Average measured PN concentrations during printing hours in PR (5.4 × 10 3 #/cm 3 ) is similar to the one observed in chamber measurements (6.7 × 10 3 #/cm 3 ). The ExDoM2 dosimetry model was further applied to calculate the deposition of particles in the human respiratory tract. More precisely, the increase in particle dose for an adult Caucasian male was 14.6- and 24.1-fold at printers’ startup, and 1.2- and 5.2-fold during printing in the PR and experimental chamber, respectively, compared to the exposure dose at background concentrations (BCs).

Aerosolized black carbon is monitored worldwide to quantify its impact on air quality and climate. Given its importance, measurements of black carbon mass concentrations must be conducted with instruments operating in quality-checked and ensured conditions to generate data which are reliable and comparable temporally and geographically. In this study, we report the results from the largest characterization and intercomparison of filter-based absorption photometers, the Aethalometer model AE33, belonging to several European monitoring networks. Under controlled laboratory conditions, a total of 23 instruments measured mass concentrations of black carbon from three well-characterized aerosol sources: synthetic soot, nigrosin particles, and ambient air from the urban background of Leipzig, Germany. The objective was to investigate the individual performance of the instruments and their comparability; we analyzed the response of the instruments to the different aerosol sources and the impact caused by the use of obsolete filter materials and the application of maintenance activities. Differences in the instrument-to-instrument variabilities from equivalent black carbon (eBC) concentrations reported at 880 nm were determined before maintenance activities (for soot measurements, average deviation from total least square regression was −2.0 % and the range −16 % to 7 %; for nigrosin measurements, average deviation was 0.4 % and the range −15 % to 17 %), and after they were carried out (for soot measurements, average deviation was −1.0 % and the range −14 % to 8 %; for nigrosin measurements, the average deviation was 0.5 % and the range −12 % to 15 %). The deviations are in most of the cases explained by the type of filter material employed by the instruments, the total particle load on the filter, and the flow calibration. The results of this intercomparison activity show that relatively small unit-to-unit variability of AE33-based particle light absorbing measurements is possible with well-maintained instruments. It is crucial to follow the guidelines for maintenance activities and the use of the proper filter tape in the AE33 to ensure high quality and comparable black carbon (BC) measurements among international observational networks.

The aim of this study was to develop an experimental self-etch dental adhesive (SE) by synthesizing graphene oxide–functionalized zirconia (GO-ZrO2) and hydroxyapatite–functionalized zinc (HA-Zn) as inorganic powders together with bis-GMA (0–2) (bisphenol A-glycidyl methacrylate) oligomers as main components of the organic matrix. The adhesive was compared to the current gold standard adhesive Clearfill SE Bond 2 (CSE) using cytotoxicity assays, shear bond strength (SBS) tests, and resin–dentin interface analyses. Cytotoxicity assays with human gingival fibroblasts (HGF-1) revealed reduced cell viability at early time points but indicated favourable biocompatibility and potential cell proliferation at later stages. SBS values for the experimental adhesive were comparable to CSE after 24 h of storage while aging did not significantly affect its bond strength. However, SBS exhibited more consistent resin tag formation and higher Weibull modulus values post-aging. A scanning electron microscopy (SEM) analysis highlighted differences in resin tag formation, suggesting the experimental adhesive relies more on chemical bonding than micromechanical interaction. The experimental adhesive demonstrated promising potential clinical properties and bond durability due to the integration of GO-ZrO2 and HA-Zn fillers into the adhesive.

Particle number (PN) and mass (PM) concentrations were measured in four offices in a HVAC building, one of them corresponding to a printer room. On-line monitoring of the indoor PM concentrations was accompanied with monitoring of the outdoor concentration. In addition, black carbon was measured in two of the selected offices. PN concentrations were measured with a variety of instruments (SMPS,NanoScan, P-Trak) covering a range between 10 nm and 9 μm, whereas PM 10 mass concentrations were measured with several DustTraks. Cleaning activities and printing were identified as the most significant indoor sources for ultrafine particles with the latter resulting in a substantial increase of indoor PN <1 concentrations in the printer room during workdays. Moreover, indoor transport of fine particles from the printer room was found to have an important contribution to both indoor PN <1 and PM 10 concentrations in two of the rest three offices. The physical presence of the occupants had an impact on particles >2.5 μm during workdays due to particle resuspension. However, when the offices were not occupied (night, weekend) the outdoor environment was a strong contribution to indoor concentrations. Lastly, black carbon preserved low concentrations in both under study offices and was not associated with printer emissions suggesting that black carbon is not an appropriate measure for assessing printer emissions.

The presented doctoral dissertation deals with the estimation of emission rates from varines acrosol sources, which may occur in a wide range of indoor workplace environments. Moreover, substantial increase in particle number and mass concentration may lead to high exposure levels of possibly harmfial airborne contaminants. Thus, respiratory protection and human dose are also essential parts of this research. In the first part of Chapter 4, particle number concentration and size distribution along with PM and TVOC were measured during emissions from painting materials (turpentine oils) inside an indoor microenvironment (laboratory room of 54 m3). New particle formation events were observed in all 10 experiments. The nucleation events lasted on average less than one hour with an average growth rate 33.9 ±9.1 nm/h and average formation rate 21.1 8.7 cm-3s-1. After the end of the nucleation event, a condensational growth of indoor particles followed with average growth rate 11.6 +2.8 mm/h and duration between 1.4 and 4.1 h. High concentrations up to 3.24 ppm were measured for the indoor TVOC concentrations during the experiments. High nucleation rates indoors were observed in conjunction with high TVOC concentrations originating from painting materials which resulted to high exposure concentration levels of particle number concentration The next part of this study evaluates the nanoparticle emissions from laser printers in a print room (PR) and an office. Printing was identified as the most significant indoor source of nanoparticles (100 nm) resulting in a substantial increase of indoor PN concentration in the PR during the workdays. Average particle concentration during opened hours was measured to be 5.4 × 103 #/cm3 and similarly, as it was observed in the chamber study, printers startup on any given day was characterized by a sharp increase in particle concentrations (on average 4.4 × 105 #cm3). Printer from the PR examined in a chamber (7.6 m3) was generating nanoparticles (vast majority 50 nm with mode on ~15 mm) primarily during cold startup (1.9 × 104 to 1.6 x105 cm2). Dust resuspension may significantly contribute to increased mass concentration in an indoor environment. Therefore, PM and number concentration were measured during walking experiments inside a laboratory. The different dust loadings were used (25, 35, 5, 1 g/m2) in order to evaluate the impact of surface loading on the indoor PM mass concentration and on the resuspension rate. Moreover, the experiments involved two different walking patterns (rectangular and line). The average resuspension rate was calculated to be equal to 10-2 - 10-3 h-1. No impact on suspension rate was observed for different walking patterns or walking speed. On the other hand, the measured mass concentration inside the room was increased when using higher dust loading on the floor The objective of the last part of Chapter 4 was to determine the emission rates from two are welding processes (SMAW and TIG) and cutting processes in a simulated confined workspace of experimental chamber. All 3 investigated processes generated high particle member concentrations ranging from 24 to 3.6 106 #/cm3 and were the highest during TIG welding. Among all 3 processes, PM10 from cutting reached the highest mass concentrations (11 and 22 mg/m3), while SMAW had the highest contribution of fine particles (~4.1 mg/m3), consisting mostly of PM1-2.5.Chapter 5 deals with penetrations and the most penetrating particle size (MPPS) of 47 mm filters from CE-marked filtering facepiece respirators (FFRs) These were then compared to identical FFR models tested in manikin-based chamber tests. These two experimental methods were in good agreement (R2-0.91). Penetrations were evaluated size-selectively using 9 sizes of charge-neutralized monodisperse aerosol (20-400mm CMD). Comparison of the penetrations at MPPS from all the examined filters and FFRa showed within-respirator variations in all three filtering classes. The MPPS in this study was found to be in the range of 25-65 am (CMD) in all measurements. It is concluded that the EN 149 method underestimates particle penetration (especially for particles <100 mm) due to the inadequate penetration test method for respirator certification Human dose from aforementioned aerosol sources was assessed in ExDoM2 model and the results are presented in Chapter 6. During emissions from painting materials, the average increase of total dose represented 4.6 and 1.3-fold at emission and post-emission period, respectively, compared to the exposure dose from BC Increase of total dose in the PR represented 13.4 and 1.2-fold at printers startup and printing. respectively. Cumulative deposited and retained dose were also estimated for 4 different scenarios for resuspended dust, and arc welding. Results revealed that: (1) in both emission cases, the find scenario staying in the polluted workspace for the entire time period without a use of FFR, was the \"worst case' scenario; and that (2) It would be more beneficial in respect to total deposited dose if the exposed simulated subject not wearing FFR st the duration of emission, would leave the polluted workspace immediately after the end of emission. Due to very small contribution of fine particles in the resuspended dust, only -4% of total dose were deposited in the thoracic region. On the company. retained dose in the thoracic region was the highest for arc welding processes (~20%).

Airborne black carbon particles are monitored in many networks to quantify its impact on air quality and climate. Given its importance, measurements of black carbon mass concentrations must be conducted with instruments operating in a quality checked and assured conditions to generate reliable and comparable data. According to WMO (World Meteorological Organization) and GAW (Global Atmosphere Watch), intercomparisons against a reference instrument are a crucial part of quality controls in measurement activities (WMO, 2016). The WMO-GAW World Calibration Centre for Aerosol Physics (WCCAP) carried out several instrumental comparison and calibration workshops of absorption photometers in the frame of ACTRIS (European Research Infrastructure for the observation of Aerosol, Clouds and Trace Gases) and the COST Action COLOSSAL (Chemical On-Line cOmpoSition and Source Apportionment of fine aerosoL) in January and June 2019. The experiments were conducted to intercompare filter-based particle light absorption photometers, specifically aethalometers AE33 (Magee Scientific), which are operated by research institutions, universities or governmental entities across Europe. The objective was to investigate the individual performance of 23 instruments and their comparability, using synthetic aerosols in a controlled environment and ambient air from the Leipzig urban background. The methodology and results of the intercomparison are presented in this work. The observed instrument-to-instrument variabilities showed differences that were evaluated, before maintenance activities (average deviation from total least square regression: 1.1 %, range: −6 % to 16 %, for soot measurements; average deviation: 0.3 %, range: −14 % to 19 %, for nigrosin measurements), and after they were carried out (average deviation: 0.4 %, range: −8 % to 14 %, for soot measurements; average deviation: 1.1 %, range: −15 % to 11 %, for nigrosin measurements). The deviations are in most of the cases explained by the filter material, the total particles load on the filter, the performance of the flow systems and previous flow check and calibrations carried out with non-calibrated devices. The results of this intensive intercomparison activity show that relatively small unit-to-unit uncertainties of AE33-based particle light absorbing measurements are possible with functioning instruments. It is crucial to follow the guidelines for maintenance activities and the use of the proper filter tape in the AE33 to assure high quality and comparable BC measurements among international observational networks.

The aim of this study was to develop an experimental self-etch dental adhesive (SE) by synthesizing graphene oxide–functionalized zirconia (GO-ZrO[sub.2]) and hydroxyapatite–functionalized zinc (HA-Zn) as inorganic powders together with bis-GMA [sub.(0–2)] (bisphenol A-glycidyl methacrylate) oligomers as main components of the organic matrix. The adhesive was compared to the current gold standard adhesive Clearfill SE Bond 2 (CSE) using cytotoxicity assays, shear bond strength (SBS) tests, and resin–dentin interface analyses. Cytotoxicity assays with human gingival fibroblasts (HGF-1) revealed reduced cell viability at early time points but indicated favourable biocompatibility and potential cell proliferation at later stages. SBS values for the experimental adhesive were comparable to CSE after 24 h of storage while aging did not significantly affect its bond strength. However, SBS exhibited more consistent resin tag formation and higher Weibull modulus values post-aging. A scanning electron microscopy (SEM) analysis highlighted differences in resin tag formation, suggesting the experimental adhesive relies more on chemical bonding than micromechanical interaction. The experimental adhesive demonstrated promising potential clinical properties and bond durability due to the integration of GO-ZrO[sub.2] and HA-Zn fillers into the adhesive.