Scientists at the Queensland University of Technology in Australia found that the office laser printer can be hazardous to your health:
An investigation of a range of printer models showed that almost a third emit potentially dangerous levels of toner into the air. [...]
Conducted in an open-plan office, the test revealed that particle levels increased five-fold during working hours, a rise blamed on printer use.
The problem was worse when new cartridges were used and when graphics and images required higher quantities of toner.