Aerosol

Aerosol technically refers to airborne liquid droplets or solid particles (also called dust or particulate matter (PM)). In casual language, aerosol refers to an aerosol spray can or the output of such a can.

The term aerosol, derives from the fact that matter "floating" in air is a suspension (a mixture in which solid or liquid or combined solid-liquid particles are suspended in a fluid). To differentiate suspensions from true solutions, the term sol evolved—originally meant to cover dispersions of tiny (sub-microscopic) particles in a liquid. With studies of dispersions in air, the term aerosol evolved and now embraces both liquid droplets, solid particles, and combinations of these. An aerosol may come from sources as various as a volcano or an aerosol can.

Workplace exposure
Concentrated aerosols from substances such as silica, asbestos, and diesel particulate matter are sometimes found in the workplace and have been shown to result in a number of diseases including silicosis and black lung. Respirators can protect workers from harmful aerosol exposure. The [[National Institute for Occupational Safety and Health] certifies respirators through the National Personal Protective Technology Laboratory to ensure that they protect workers and the public from harmful airborne contaminants. {cite web url= http://www.cdc.gov/niosh/npptl/ |title= NPPTL|accessdate=2007-10-03|publisher=United States National Institute for Occupational Safety and Health}

Effect on climate
Anthropogenic aerosols, particularly sulfate aerosols from fossil fuel combustion, exert a cooling influence on the climate. The cooling effect of aerosols, however, does not seem to directly counteract the warming induced by greenhouse gases such as carbon dioxide, methane and water vapor and is accounted for in climate models, despite some claims that "global dimming" by aerosols may counteract global warming.