Steve - I think you'll find that the toner powder issue is no worse than the general air pollution issue in the developed world (& of far less concern than that in developing countries). Particulate Matter (PM) is quite a big issue for public health, but arises from a great many sources. IMHO, toner powder in a domestic environment is fairly low in the list of PM 'baddies'.
If you want to look into the health implications of laser printers, you shouldn't, however, ignore the ozone they produce. Ozone is incredibly chemically reactive and affects lung function in particular. (If you thought that ozone was something that the planet was short of, that's only high up above the troposphere or thereabouts.) Strangely, very tiny amounts of ozone can be beneficial, but humans shouldn't be exposed in the long-term to more than 60 parts per billion in the air they breathe. (I think that's the WHO recommended level, although there's controversy in the US over this as industry doesn't want to pay for the cost of cleaning up their operations.)
Large commercial laser printers (& copiers) have carbon-based filters which convert most of the ozone into normal oxygen but the cheaper domestic models don't usually have them as they're rarely used as intensively.
The bottom line is that domestic laser printers should always be located in a reasonably ventilated area. If you are printing a lot of pages & can smell that characteristic laser/photocopier smell, that's ozone & I would suggest that you open the window and keep away from the printer as much as practicable. This applies especially if you are asthmatic or have other breathing issues.
To read more about this, the University of Edinburgh has published a useful Health Hazard Guide.