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A new study of office laser printers by Australian researchers suggests selected toner and printer combinations release emissions of small particles that are potentially harmful to respiratory health.

The study, which was led by a research professor at the Queensland University of Technology, looked at the ways laser printers emit small particles when used under regular office circumstances.

To get a snapshot of printer behaviour in the office environment, the researchers measured the emissions of 62 Hewlett-Packard, Mita, Ricoh, Canon and Toshiba laser printers in an office building in Brisbane.

Specifically, the study counted the size and number of particles released by the printers and their levels of submicrometre particulate matter emissions - tiny, microscopic particles that are easily inhaled into the lungs.

Tim Takaro, a professor of health sciences at Simon Fraser University, said the study raises questions about the specific types of particles being emitted and what chemicals they contain.

"We don't know exactly what [those particles]are, but they almost certainly contain some carbon black - most inks do - and that's a respiratory irritant," Prof. Takaro said in an interview yesterday.

"My concern would be mainly for people who have pre-existing respiratory conditions," he said.

Particle counters were mounted above each of the printers in the study to assess their local emissions contribution.

The researchers concluded that the recorded levels of printers' general emissions were high enough to significantly affect the level of local emissions in an office - and by extension, the air quality in their local vicinity.

The researchers also concluded that more than a quarter of the printers studied would be considered high emitters - which they defined as increasing the amount of small particle emissions tenfold of what the expected background level would be. Those "high emitters" included 10 different Hewlett-Packard models and a Toshiba printer.

Tannis Baldock, a spokesperson for Hewlett-Packard, said in an e-mail that the company is reviewing the study and that HP engineered its printers to meet strict international health and safety standards. A spokesperson for Toshiba Canada declined to comment on the report.

Brian McCarry, a professor of environmental chemistry at McMaster University, said in an interview yesterday that the study showed printer emissions to be an air-quality hazard that was completely unknown until someone decided to measure it.

"It's pretty clear that some of these printers are pretty dirty," Prof. McCarry said, referring to the study.

It is his guess, based on the variations in emissions between printers of the same make or model, that manufacturers have likely not considered emissions hazards when designing them until this point.

The study is to be released publicly today and will be published in the online version of the American Chemical Society's Environmental Science & Technology publication.