For many years now, there has been talk about our depleting ozone layer. Do you always understand what people are talking about when they bring up terms like "CFCs," and "ODP"? If not, read on and learn a little more about our depleting atmosphere in a free science lesson.

Why do we care about ozone? Ozone is a gas that is composed of three atoms of oxygen. It is harmful to breathe, but nearly 90 percent of the Earth's ozone is located in the stratosphere, which is referred to in common parlance as the "ozone layer." The ozone layer serves a important purpose. It absorbs a band of ultraviolet radiation called UVB, which is particularly harmful to living organisms, such as humans. A healthy ozone layer prevents most UVB from reaching us, however.

Chlorofluorocarbons, or CFCs are compounds that consist of chlorine, fluorine, and carbon. While CFCs are stable in the troposphere, they are broken down by strong ultraviolet light in the stratospheric level, or "ozone layer" and end up releasing chlorine atoms that can then deplete the ozone layer.

The combination of UVB in the ozone and CFCs in the same area creates a cause and effect cycle. The UVB is absorbed by the ozone layer, which prevents it from harming us. However, the CDCs come along, break down in the ozone layer due to the presence of the UVB, and then release chlorine atoms as they are "dying." The chlorine atoms, in turn, deplete the ozone layer, which allows for more UVBs to escape through it. Sounds like a nasty situation, doesn't it?

CFCs are commonly used as refrigerants, solvents, and foam-blowing agents. There are more than one kind of CFC, with the most common being called CFC-11, CFC-12, CFC-113, CFC-114, and CFC-115 (they do have longer, multi-syllable and multi-consonant chemical names, as well). Each of these CFCs has a different effect on the ozone, or a different "ozone depletion potential" (ODP). CFCs may be a major contribution to the depletion of the ozone layer, but they are not the only bad guys out there. Halons, methyl bromide, carbon tetrachloride ,and methyl chloroform, among others, also act as "ozone-depleting substances," or ODSs. Some ODSs release bromine atoms, as opposed to chlorine like CFCs, when they are breaking down in the ozone layer. Unfortunately, bromine atoms have the same effect of eating away the ozone as chlorine atoms.