Letter Cite This: Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/journal/estlcu
Particle Emissions from Laser Printers: Have They Decreased? Lidia Morawska,*,† Meng Xiu,† Congrong He,† Giorgio Buonanno,†,‡ Peter McGarry,† Bastien Maumy,§ Luca Stabile,‡ and Phong K Thai† †
International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4001, Australia Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, via G. di Biasio 43, Cassino, 03043 Frosinone, Italy § EDF Energy R&D UK Centre Ltd, 80 Victoria Street, London SW1E 5JL, United Kingdom ‡
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S Supporting Information *
ABSTRACT: Our work a decade ago demonstrated that approximately 30% of the laser printers tested were high emitters of ultrafine particles (5 and ≤10), and high emitters (ratio >10). Figure 1 presents summary statistics of the ratios and
outside the chamber, and sampling using 50 cm long tubes connected through the holes in the walls of the chamber. Particle deposition on the walls of the chamber during the tests was considered to be negligible.10 PN concentrations and PM2.5 inside the chamber were measured before and during printing. For each printer, 50 single pages were printed with 5% black and white toner coverage, with a printing speed/ quality according to the standard setting. 2.4. Data Analysis. According to He et al.,1 for the office testing, the ratios of the peak concentration values after printing to the background values of PN, PM2.5, and VOC were calculated for each printer. Based on these ratios, the printers were assigned into four different classes: nonemitters (ratio ≤1), low emitters (ratio >1 and ≤5), medium emitters (ratio >5 and ≤10), and high emitters (ratio >10). To compare the office tested printers with those tested in the chamber in Cassino, a somewhat different approach had to be developed. This was because PN concentrations and PM2.5 measured in the chamber after printing were 1−2 orders of magnitude higher than those after office printing due to the lack of particle dispersion in the enclosed chamber. To enable comparison with the printers tested in the offices, the ratios calculated for the printers tested in the chamber were adjusted by applying an adjustment factor (α): α = R max /R max (1) ′ where Rmax and Rmax′ are the maximum values of the ratios for the printers tested in Cassino in the offices and in the chamber, respectively. Thus, the adjusted ratios (Ri) for the printers tested in the chamber were calculated according the following equation: ratio = αR i
(2)
All the statistical analyses (t test, one-way ANOVA) were conducted using a statistical analysis software package: SPSS for Windows version 10 (SPSS Inc.)
3. RESULTS AND DISCUSSION 3.1. Printers. There were 188 printers identified at the QUT GP campus, of which 46 printers were not accessible due to access restrictions to the offices/laboratories in which they were located, and 3 printers were installed before 2007. Therefore, 139 printers (73.9% of all the printers) were investigated at the QUT GP campus. All the printers (27) in the library of UQ were tested. In total, 166 printers from 7 manufacturers (and of 29 models) were tested in Brisbane, and included 102 ApeosPort printers, 21 Konica Minolta, 16 DocuPrint, 14 Xerox, 6 HP LaserJet, 3 Dell, 2 Lexmark, and 2 Ricoh. In Cassino there were 131 printers investigated, of which 107 printers (of 79 models) were tested in the chamber (81.7%) and 24 (of 24 models) in the offices. The printers tested in the chamber belonged to 7 manufactures, comprising 39 HP LaserJet, 31 Samsung, 16 Epson, 11 Xerox, 4 Brother, 3 Canon, and 3 Lexmark, while the printers tested in the offices comprised 7 HP LaserJet, 7 Xerox, 5 Ricoh, 2 Canon, 2 Samsung, and 1 Epson. There was a large variation in models and manufacturers between the printers used and tested in Brisbane and in Cassino. While some printer manufacturers were represented in both places, such as HP or Ricoh (however the models were different), the majority of the printers came from different manufactures.
Figure 1. Box plot for printers classified as nonemitters and low, medium, and high particle number emitters in Brisbane and Casino.
printer classification obtained for the printers tested in Brisbane and in Casino. Overall, 57% of the investigated printers were nonemitters, and of the 35% that were emitters, 4% were classed as high emitters (Figure S1a). The distributions of the printers between different classes in the two cities were very similar, except for the medium emitters, with the percentage in Cassino higher than that in Brisbane (Figure S2). 3.1.2. Particle Mass Emissions. While PM2.5 measurements in Brisbane were abandoned to simplify the protocol when we found out that there was no increase in PM2.5 concentrations as a result of operation of the printers, such measurements C
DOI: 10.1021/acs.estlett.9b00176 Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
Letter
Environmental Science & Technology Letters
Figure 2. Relationship between the size of the printers and their emission levels in Brisbane: (a) particle number emissions; (b) VOC emissions.
that for a high VOC and low PN emitters, conditions are not favorable for particles to form at a high rate. 3.4. Relationship between the Size of Printers and Their Emission Levels. Figure 2 presents a summary of the relationship between the size of the printers and their PN and VOC emission levels in Brisbane. It can be seen from Figure 2a that over 20% of high PN emitters were the desktop printers, but none of the large printers were in this class. The high emitters included DocuPrint, Phaser, and Dell printers (see Table S1). Figure 2b demonstrates that the distribution of the VOC emitters was different. Low VOC emitters dominated among both small and large printers; however, there was a shift toward higher VOC emitters among the large printers. In our previous study we concluded that the difference between high and low PN emitting printers was dependent on the speed and sophistication of the temperature control.2 We speculate that large printers tend to have a better performance on the temperature control than desktop printers, leading to lower level of emissions from large printers. 3.5. Relationship between the Model of the Printers and Their Emission Levels. Overall, for the sample of the printers investigated, we did not identify any statistically significant relationships between the emission levels and the brand or model of the printers for low emitters; however, the sample size of medium and higher emitters was not sufficiently
were conducted during office testing in Cassino. In summary, the ratios ranged from 1.03 to 2.28, with the mean value of 1.42, indicating that in general the printers were low PM2.5 emitters. This is because the majority of the particles resulting from printer operation are secondary, mainly in the ultrafine range, and therefore of very small mass.2 Similar observations were reported before. For example, McGarry et al.,10 who measured PN concentrations 1 m away from printers, which were high PN emitters, reported that the PM2.5 peak concentration values were not distinguishable from the background values and were not linked with the print events. Also the measurements of hardcopy devices demonstrated that there was no substantial release of particles larger than 500 nm.11 3.3. VOC Emissions. Figure S1b presents classification of the printers based on the VOC emission ratios. In Brisbane, 72% of printers were found to be nonemitters and low VOC emitters, with 10% classified as high emitters. Among the high VOC emitters, only one small printer was a high PN emitter. It can be concluded that even nonemitters or low particle emitters do emit VOC, and they can be high VOC emitters. Previous studies concluded that particles originating from printer operation are formed by condensation of VOC released during the heating phase of the toner.2,11,12 Thus, it is likely D
DOI: 10.1021/acs.estlett.9b00176 Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
Letter
Environmental Science & Technology Letters
Figure 3. Comparisons of particle number emissions of small and large printers between this study and He et al.1
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large to enable such analysis. This does not mean that such relationships do not exist, but to uncover them would require a large sample size and a study design specifically focused on this aspect. It can be seen (Table S1) that the same model of a printer can be a nonemitter or an emitter, such as ApeosPortIV C3370, ApeosPort-IV C3375, ApeosPort-IV C4470, ApeosPort-IV C4475, DocuPrint C5005d, and Phaser 3435. Moreover, printers can be emitters of both PN and VOC, or both nonemitters of PN but emitters of VOC. 3.6. Comparison with the 2007 Study. In 2007, out of 62 printers, 60%, 10%, 3%, and 27% were PN nonemitters and low, medium, and high emitters, respectively.1 This work demonstrated that 10 years later the respective percentages were 56.6%, 34.7%, 4.7%, and 4.0% (Figure 1a). This comparison shows that there has been a shift, with more printers being low emitters and fewer high emitters. The results of PN concentration ratios show on average a ratio of 2.25 in Brisbane and 2.58 in Cassino, which means that, overall, the 297 printers are mainly low emitters. Based on a comparison of the emissions of large printers between He et al.1 and the current work, as illustrated in Figure 3, it can be seen that now very few large printers are high PN emitters. If we rely on the results of PNC ratios, since 2007, the big commercial printer manufacturers have improved their products. However, for small/desktop printers (Figure 3), the proportion of nonemitters and high emitters decreased, while those of low and medium emitters increased, when compared with the situation in 2007, suggesting that there has been no obvious improvement since then. Emissions of VOCs were not investigated in the previous work; however, this study demonstrated that there was not always a direct relationship between the VOC and PN emissions of individual printers. Therefore, printer VOC emissions should be further investigated in future studies.
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AUTHOR INFORMATION
ORCID
Lidia Morawska: 0000-0002-0594-9683 Phong K Thai: 0000-0003-0042-3057 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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REFERENCES
The assistance of officers from the QUT Printing Services, especially Darryl Dibble, is gratefully acknowledged. Members from ILAQH, in particular Chantal Labbe, are thanked for their assistance with this project. Dr. Peter McGarry is employed by the Queensland Government’s work health and safety regulator as the Chief Safety Advisor Asbestos. Dr. McGarry also works for the same organization in the area of occupational hygiene.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.estlett.9b00176. Additional data and printer emission investigation results (PDF) E
DOI: 10.1021/acs.estlett.9b00176 Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
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DOI: 10.1021/acs.estlett.9b00176 Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
