Aerosol cans have been around for nearly a century; they were first used for non-painting applications, such as applying pesticides and other liquids. In 1949, Edward Seymour invented canned spray paint and a new industry was born.
Over the years, some changes have reduced the side effects of aerosol use, but it still has a long way to go to become "green." The original propellants used in aerosol spray paints were chlorofluorocarbon gases (CFCs); they were banned from use in the US in 1978 when it was discovered that they depleted the ozone layer. Hydrocarbon propellants were then widely used until the 1980s when they were found to contribute to smog by reacting with nitrous compounds in the air. Today we have 1, 1, 1, 2,-tetrafluoroethane as the main propellant. It's a mouthful just to say it, and not very green by any stretch of the imagination.
Handy to Use
Aerosol spray paint is very convenient to use: You pop the top, give it a few shakes and you're on your way. The finish dries quickly, leaves no brush marks and there are no brushes or other equipment to clean afterward. What you do have, however, is an empty metal can, which usually cannot be recycled and is often considered hazardous waste.
New Latex Formulations
The standard for aerosol spray paint is solvent or oil-based, but now we can choose from a handful of manufacturers that produce latex and water-based aerosol spray paints. While these have lower VOCs (volatile organic compounds) than their more toxic cousins, they still produce emissions that are hazardous and most people would find unpleasant. According to Krylon, its H2O aerosol spray paint releases 55 percent less smog-generating chemicals into the air than the average solvent-based spray paint, and VOC emissions are reduced by 25 to 30 percent.
Think Outside the Spray Can
Obviously, the greenest option would be not to use aerosol spray paint in the first place. If necessary, however, choose a water-based product or use a solvent-based one sparingly. The best way is to use them outdoors or in a well-ventilated area. To provide additional protection to the user, a respirator that is rated for this type of product is recommended. Unfortunately, a giant respirator is not handy for Mother Earth, and a dedicated air-handling room or facility is not an option for the home user. A better option would be to use an air sprayer or HVLP type of painter with a low or no-VOC paint. These systems use air to move the paint through the spray nozzle and therefore do not use chemical propellants.
That can of aerosol spray paint on the shelf at your local hardware store may change the color of some deck chairs in no time, but think about ways to use other painting techniques first. You can often avoid the environmental impacts of aerosol spray paint with a simple brush and can. I'm sure you and Mother Earth can live with a few brush marks if your technique is a little off.