From Chemical and Engineering News:
Office workers now have reason to think twice before printing out that report the boss is waiting for. In a recent office study, researchers in Australia found that nearly one-third of laser printers emitted high levels of nanoparticles into the air, and on average, particle counts during working hours were five times higher than during nonwork hours (Environ. Sci. Technol., DOI: 10.1021/es063049z.). Inhaling these ultrafine particles may pose a health hazard, experts caution.