Some laser printers pose serious health risks and may spew out as much particulate matter as cigarettes, according to an Australian air quality researcher.

The study, set to appear later today in the online edition of the American Chemical Society's Environmental Science & Technology (ES&T) journal, measured particulate output of 62 laser printers, including models from name brands such as Canon, Hewlett-Packard and Ricoh.

Particle emissions, believed to be toner - the finely-ground powder used to form images and characters on paper - were measured in an open office floor plan, then ranked.

Lidia Morawska and colleagues at the Queensland University of Technology, classified 17 of the 62 printers, or 27 percent, as "high particle emitters"; one of the 17 pumped out particulates at a rate comparable with emissions from cigarette smoking, the study said.

Two printers released medium levels of particulates, six issued low levels, and 37 - or about 60 percent of those tested - released no particles at all.

Morawska called the emissions "a significant health threat" because of the particles' small size, which makes them easy to inhale and easily lodged in the deepest and smallest passageways of the lungs. The effects, she said, can range from simple irritation to much more serious illnesses, including cardiovascular problems or cancer. "Even very small concentrations can be related to health hazards," said Morawska. "Where the concentrations are significantly elevated means there is potentially a considerable hazard."

The research also found that office particulate levels increased fivefold during work hours because of laser printers. Generally, more particles were emitted when the printer was using a new toner cartridge, and when printing graphics or photographs that require larger amounts of toner than, say, text.

Morawska recommended that people make sure rooms at work and home with laser printers are well ventilated.