BBC News is reporting that laser printers can emit particles into the air similar to second hand smoke. From the article:
Almost one-third were found to emit ultra-tiny particles of toner-like material, so small that they can infiltrate the lungs and cause a range of health problems from respiratory irritation to more chronic illnesses.
While this is the first study of its kind, it should not surprise anyone that has worked in an office. When printing using a laser printer, there is often a sandy substance left by the printer on the print dock (more so when there are a lot og graphics/blackspace involved . It would not be difficult for that to get into the air and your lungs.