Chlorofluorocarbons (CFCs) are synthetic compounds of carbon, chlorine, and fluorine, once used in aerosols, refrigerants, and foams, that both deplete stratospheric ozone and act as the greenhouse gas with the highest global warming potential (GWP) on the AP Enviro exam.
Chlorofluorocarbons (CFCs) are human-made compounds built from carbon, chlorine, and fluorine atoms. For decades they were everywhere, in aerosol spray cans, refrigerators, air conditioners, and foam-blowing agents, because they were cheap, stable, and nontoxic. That stability turned out to be the problem. CFCs don't break down in the lower atmosphere, so they drift up into the stratosphere, where UV radiation knocks chlorine atoms loose. Those chlorine atoms tear apart ozone molecules, thinning the protective ozone layer (EK STB-4.A.2).
Here's what makes CFCs special for AP Enviro. They're the rare term that's a villain in two completely different stories. They cause stratospheric ozone depletion (Topic 9.1), AND they're one of the five principal greenhouse gases (EK STB-4.C.1) with the highest global warming potential of all of them, beating nitrous oxide and methane (EK STB-4.D.1). Because they were phased out under the Montreal Protocol and replaced with substitutes like hydrofluorocarbons (HFCs), they're also the centerpiece of the exam's favorite environmental success story.
CFCs live mostly in Unit 9 (Global Change), where they support three learning objectives at once. For 9.1.A, they're the main anthropogenic cause of stratospheric ozone depletion. For 9.3.A and 9.3.B, they're a principal greenhouse gas with the highest GWP. For 9.2.A, their replacement by HFCs is the textbook case of mitigating ozone depletion. They also connect back to Unit 4 (Topic 4.4), because you can't explain why CFCs are dangerous without knowing the atmosphere's layers. The damage happens specifically in the stratosphere, where the ozone layer sits. If the exam asks about ozone, greenhouse gas potency, or international environmental policy, there's a good chance CFCs are the answer.
Keep studying AP Environmental Science Unit 4
Montreal Protocol (Unit 9)
The 1987 Montreal Protocol phased out CFC production worldwide, and it's the exam's go-to example of international environmental cooperation actually working. If a question asks which chemical was phased out under the Montreal Protocol, the answer is CFCs.
Hydrofluorocarbons (HFCs) (Unit 9)
HFCs replaced CFCs because they don't contain chlorine, so they don't destroy ozone. The catch, and the exam loves this catch, is that some HFCs are strong greenhouse gases. Solving one problem created another.
Global warming potential (GWP) (Unit 9)
GWP compares a gas's warming power to carbon dioxide, which is set at 1. CFCs sit at the top of the GWP ranking, above nitrous oxide and methane. Memorize that order; it's a straight MCQ point.
Earth's Atmosphere (Unit 4)
The whole CFC story depends on location. Ozone in the stratosphere is the good ozone that blocks UV radiation, and that's exactly where CFCs do their damage. Knowing the atmospheric layers from Topic 4.4 is what makes the ozone story make sense.
CFCs show up most often in multiple-choice questions, and they're usually the correct answer rather than a distractor. Common stems include identifying the greenhouse gas with the highest global warming potential per molecule (CFCs), naming the anthropogenic compound primarily responsible for stratospheric ozone depletion (CFCs), and identifying the chemical phased out under the Montreal Protocol (CFCs again). You'll also see the reverse question, asking which substitute for ozone-depleting substances is itself a potent greenhouse gas, where the answer is HFCs. For free-response questions, CFCs are useful in any answer about ozone depletion, UV radiation and human health (skin cancer, cataracts), or proposing solutions, since the Montreal Protocol gives you a concrete, named policy to cite when an FRQ asks for a realistic mitigation strategy.
CFCs contain chlorine; HFCs don't. That one atom is the whole difference. The chlorine in CFCs is what destroys stratospheric ozone, so chlorine-free HFCs were introduced as the safe substitute. But HFCs aren't harmless. Some are strong greenhouse gases. So remember it this way. CFCs are bad for the ozone layer AND the climate. HFCs spare the ozone layer but can still warm the climate.
CFCs are synthetic compounds of carbon, chlorine, and fluorine that were once used in aerosols, refrigerants, and foam-blowing agents.
The chlorine in CFCs breaks apart ozone molecules in the stratosphere, making CFCs the main anthropogenic cause of ozone depletion.
CFCs have the highest global warming potential of any greenhouse gas, followed by nitrous oxide, then methane, with carbon dioxide as the baseline of 1.
CFCs are one of the five principal greenhouse gases, alongside carbon dioxide, methane, water vapor, and nitrous oxide.
The Montreal Protocol phased out CFCs, and HFCs replaced them, but some HFCs are themselves strong greenhouse gases.
Less stratospheric ozone means more UV radiation reaches Earth's surface, which raises rates of skin cancer and cataracts in humans.
CFCs are synthetic compounds made of carbon, chlorine, and fluorine that were used in aerosol propellants, refrigerants, and foam-blowing agents. On the AP exam they matter for two reasons. They deplete stratospheric ozone, and they're the greenhouse gas with the highest global warming potential.
Both, and that's exactly what the exam tests. CFCs are one of the five principal greenhouse gases (EK STB-4.C.1) with the highest GWP of all of them, and they're also the main human-made cause of stratospheric ozone depletion.
No, CFCs were phased out under the 1987 Montreal Protocol, which is the exam's standard example of successful international environmental policy. They were replaced by hydrofluorocarbons (HFCs), though some HFCs are strong greenhouse gases.
CFCs contain chlorine, which destroys stratospheric ozone; HFCs are chlorine-free, so they don't deplete ozone. The trade-off is that some HFCs are potent greenhouse gases, so they helped the ozone layer but not necessarily the climate.
They contribute to both. Chlorine from CFCs destroys ozone in the stratosphere, increasing UV exposure that causes skin cancer and cataracts, and CFCs also trap heat as a greenhouse gas with a higher GWP than nitrous oxide, methane, or carbon dioxide.