Researchers Investigate Whether Laser Printers Emit Pathogenic Toner Particles into the Air

Could the humble laser printer be responsible for poor health among office workers? These printers, it has been said, could be to blame for the release of tiny particles of toner-like material into the air. These particles would then be inhaled by consumers deep into their lungs, triggering health-related problems. Now scientists investigating this preconception have come up with surprising results.

Researchers at the Fraunhofer Wilhelm Klauditz Institute (WKI) in Braunschweig, Germany, have teamed up with scientists from the Queensland University of Technology (QUT) in Brisbane, Australia, to investigate the controversial topic of whether laser printers emit pathogenic toner particles into the air. Their results are not what anyone expected.

Past studies have shown that indoor particle levels in office air increased as much as five-fold during work hours due to printer use. It was assumed that printers emitted more particles when operating with new toner cartridges, and when printing graphics and images that require greater toner quantities.

Contrary to earlier reports, the team discovered that laser printers released hardly any particles of toner into the air. Professor Tunga Salthammer, WKI department head, said: 'What some printers do emit are ultra-fine particles made of volatile organic-chemical substances. One essential property of these ultra-fine particles is their volatility, which indicates that we are not looking at toner dust.'

This discovery spurred them on in their search for the source of these ultra-fine particles. To do this, they developed a process that allowed them to resolve and compare the quantity, size and chemical composition of the emitted particles. To assist them in their research, they turned to the German Association for Information Technology, Telecommunications and New Media (BITKOM), which provided the team with financial and technical support.

What the researchers also discovered was that the latest generation of printers that 'print' without paper or toner also produce these particles. 'The amazing thing is that the ultra-fine particles are still produced even in this case. The cause is the fixing unit - a component that heats up as high as 220°C during the printing process in order to fix the toner particles on the paper,' WKI scientist Dr Michael Wensing explained.

To test their results and to ensure no outside contamination, the printers used were housed in a test chamber measuring 1 or 24 cubic metres. Particle analysers were then used to count the particles and measure their size distribution.

The researchers found that the high temperatures that were generated caused volatile substances, such as paraffins and silicon oils, to evaporate; these would then accumulate as ultra-fine particles. Similar particles are also created in comparable conditions in the kitchen, the team said. Simple household activities like cooking, baking, or even making toast were responsible for the proliferation of these particles.

While filters are available to reduce the particles from escaping from printers, the scientists question their effectiveness. 'Our investigations show that the various external filters on offer for printers operate in very different ways. As the ultra-fine particles are not emitted from a specific part of the printer, but also from the paper output, for instance, a filter can only have a limited effect,' Dr Wensing said.

Source: Cordis

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