A 2007 study from the Queensland University of Technology in Australia found that some laser printers give off ultra fine particles that could cause serious health problems [source: He, Morawaska and Taplin]. Another study from the National Institute of Public Health also confirmed that laser and ink-jet printers can release volatile organic compounds (VOCs), ozone, and particulates [source: Kagi et al].
Tests so far have shown that concentrations of the released particles return to normal levels after a couple of minutes [source: CBC]. But depending on the size of the specks and exposure time, they have been linked with heart and lung disease [source: Davis]. For that reason, the biggest implication for this finding is in office settings, where someone may sit next to a printer.
Not every printer will do this. In the Queensland study, of the printers tested, researchers found that 40 percent gave off the ultrafine particles and 27 percent of those sent out high concentrations of them. The emissions also varied with the type of printer, its age and toner cartridge.
In response to these findings, companies including Xerox and Hewlett-Packard have publicly denied any health hazards linked to their products. According to Xerox's President of Environment Health and Science, the company continually tests for the health effects of contact with toner particles.
If you're choosing a new printer, Energy Star recommends many types that are better for the environment. Although the Energy Star Web site does not stipulate whether it tests for particle emissions, its endorsed brands do use less electricity.