Ozone in the stratosphere or stratospheric ozone protects the earth and its inhabitants. But at ground level, ozone can be unhealthy—in fact it’s a component of what has become known as “smog.” Smog formation requires three ingredients:
- 1) Nitrogen oxides, which come almost entirely from anthropogenic (man-made) sources such as automobile exhaust and power plants;
- 2) Sunlight; and
- 3) Volatile organic compounds (VOCs), both naturally occurring and man-made. “Volatile” means evaporating, and virtually anything that gives off an odor or quickly evaporates into the air is a source of VOCs.
The U. S. EPA estimates that of the major man-made sources of VOCs, 58 percent are from industrial facilities, 37 percent are from vehicle emissions and 5 percent are from consumer products. The portion of these products packaged in aerosol containers accounts for only a fraction of that amount (and is largely composed of the least reactive—or least smog- forming—type of VOCs.
Natural sources—flowers, trees, decaying organic matter, animals and even humans—account for at least as much VOC emissions as anthropogenic sources and probably more. However, all sources of VOCs—including paints, solvents, textiles, household products, cosmetics and personal care products— are being examined in an effort to clean up our air.