The ubiquitous office, laser printer has been a fixture in many offices for years. According to a news report from the BBC, researchers have found that they emit particles that may infiltrate your lungs.
Australian researchers at QUT have found that 1/3 of the 60 laser printers they tested emitted tiny particles of toner. They also suggested regulations on indoor air quality and keeping the printers in ventilated areas. Think about this when you go to work in an office and see what you can do to minimize the risk. TreeHugger has a more in-depth article with links.