It wasn't until the 1970s that the public became worried about the possibility that their hairspray might actually be helping along massive global climate change. The first person to even try to measure the concentration of CFCs in the troposphere was Jim Lovelock, who was actually just using them to track global air currents. While hitching a boat ride form Britain to Antarctica and back, Lovelock used a self-made device to check the distribution of these particles. His machine measured in units of parts per trillion, and Lovelock found CFC concentration to be a few to a couple dozen in certain areas, causing him to decide that "the presence of these compounds constitutes no conceivable hazard." (Source: Gribbin, The Whole in the Sky). Unfortunately, Lovelock was wrong in one major detail: while CFCs are not dangerous in small concentrations in the troposphere, they become extremely hazardous when they accumulate and drift up to the stratosphere.
One of the first scientists to notice something potentially harmful in the release of CFCs into the atmosphere was Sherry Rowland, a chemist who specialized in radioactive isotopes. The first thing that struck Rowland as odd was something told to him by another scientist, Lester Machta. In 1971, before Lovelock had gone on his trip to Antarctica, Machta had been in a conference with Lovelock and the head of a Du Pont lab that created types of CFCs. In conversation, the Du Pont chemist mentioned the amount of CFC's his labs estimated were in the atmosphere. A year later in 1972, when Lovelock had already gone to Antarctica, Machta mentioned this conversation to Rowland, who realized something significant: the numbers given by the Du Pont chemist were actually the same as the concentration found by Lovelock. If this was the case, nothing was destroying them in the troposphere. However, they could not all simply stay in the troposphere- where were they going?
The answer was up. The CFCs had nowhere to go but drift into the stratosphere, where they were broken up by high-energy ultraviolet rays. What made the CFCs so dangerous was what had initially made them so appealing to manufacturers: they were incredible stable. Because they were so chemically stable, they were affected by absolutely nothing when they remained in the troposphere. Whereas most types of aerosols are washed out of the atmosphere, and dissolve in the water cycle, CFCs pretty much just hang out until they get around to heading upwards. The amount of time this process takes is quite long. For example, Trichlorofluoromethane (CCl3F) and dichlorofluoromethane (CCl2F2), were the most popular CFCs used by Du Pont, and take several decades to finally decompose; F-11 (a type of Freon) survives for seventy-five years, while F-12 survives for a full century.
Okay, so what? Why did anyone care about some tiny particles drifting from your deoderant can to the second level of the atmosphere?
Well, like most Hollywood movies, the real action starts when stuff starts to break other stuff up. The stratosphere is full of powerful 200-220 nanometer ultraviolet rays, which are not present in the troposphere, due to ozone protection. These UV rays break the chemical bonds of the CFCs in a decompostion reaction, ending with a harmful product (Source: Gribbin, A Hole in the Sky). Lets take a look at this reaction:
CCl3F + UV = Cl + CCl2F
CCl2F2 + UV= Cl + CClF2
Chlorine product breaks apart Ozone molecules:
Cl + O3 = ClO + O2
ClO + O = Cl + O2
Ultimate effect:
O + O3 = O2 O2
So What Happened??