Workers face a potential health threat from office laser printers that emit large amounts of tiny particles into the air, an Australian research team has found.

Potential effects range from respiratory irritation to effects on the cardiovascular system and cancer, said Prof. Lidia Morawska of the Queensland University of Technology.

The researchers do not know the chemical makeup of the particles and how they are released. But they recommend good office ventilation to minimize the chances of particles entering the airways.

Morawska and colleagues will publish their results online later this week in the American Chemical Society journal Environmental Science & Technology.

The researchers classified 17 of the 62 printers as "high particle emitters."

And Morawska, author of the journal study, said one printer released particles, under experimental conditions, at a rate comparable to the particle emissions from cigarette smoking.

But 37 of the printers were non-emitters.

The study found printers emitted more particles when the toner cartridge was new, and when printing images and graphics, as these require greater amounts of toner.

Morawska, director of the International Laboratory for Air Quality and Health, said that when inhaled, the ultrafine particles can travel to the deepest parts of the respiratory tract and enter the bloodstream.

Morawska said the findings were made by chance while her team was investigating the efficiency of ventilation in protecting office workers from outdoor pollution.

The researchers tested a large open-plan office in the Brisbane central business district, surrounded by busy roads and about 120 metres from a freeway.

"We really didn't expect to find anything from indoor sources [but] we soon discovered that the indoor sources of pollution were far higher than the outdoor sources," she said.

The study shows the average particle number concentration inside the test office is five times higher during working hours than non-working hours.

And at its highest levels, indoor particle concentration was about three times higher than the outdoor rate.

Morawska said that in offices with poor ventilation, higher concentrations of particles can "prevail for the whole day."

She said the health risks will be "quite high" for workers that "sit in an office like this for days and months."

Researchers suggest government regulation

Her research team is calling on governments to consider regulating emission levels from laser printers.

But Morawska said more research is needed into the chemical makeup of the emissions and how the particles are released to back any such move.

Her paper includes a list of the brands and models studied, and their rating by amount of particles emitted.

A total of 12 models of Hewlett Packard printers and one Toshiba printer are listed as high emitters of tiny particles.

Morawska said that until governments move to regulate printer emissions, office managers should consider buying printers classified as low emitters.

She said what's most important, however, is to locate the printer "where the air flow doesn't distribute the particles to the whole office."

The National Industrial Chemicals Notification and Assessment Scheme and Hewlett Packard were unable to comment in time for the story.