Laser printers can dirty the air

The smaller an air-pollution particle is, the more likely it will be inhaled deep into the lungs, where it can trigger disease. A new study finds that office laser printers can spew especially small particles.

Lidia Morawska of the Queensland University of Technology in Brisbane, Australia, says that her team stumbled onto the finding while attempting to evaluate the effectiveness of office ventilation by comparing indoor and outdoor pollution. In the office building studied, airborne concentrations of nanoscale specks were higher than they were near a busy expressway.

Using air monitors, the physicists tracked down the major indoor culprits: 13 of the building's 62 laser printers were high emitters of fine particulates, another 2 were mid-level emitters, and 7 were low emitters.

During workdays, at least, the building's ventilation system couldn't remove all the printers' combined pollution. For the dirtiest printers, emissions climbed as the amount of toner incr