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Describe chemicals used to substitute for chlorofluorocarbons (CFCs).

Reducing Ozone Depletion

The Montreal Protocol 🕶️ is the world's primary treaty regulating ozone depleting substances (ODS) and the Clean Air Act 💨 is one way the United States enacts the measures specified in the Montreal Protocol 🕶️. It is important that you understand both pieces of legislation, as they are an integral part of reducing ozone depletion and are required for the AP exam.

Click through the tabs below to learn about both of these important pieces of legislation and how they protect the ozone layer:

Montreal Protocol 🕶
Clean Air Act 💨

Montreal Protocol 🕶

What is it?

When we realized that Ozone Depleting Substances (ODS), such as chlorofluorocarbons (CFCs) and halons, were linked to holes in the ozone layer, the nations of the world came together to protect the ozone layer. The result was the Montreal Protocol 🕶, which is an international treaty designed to control the production and consumption of CFCs and other ODSs. The Montreal Protocol 🕶 was signed by 194 nations. As you can see in the map below, it has now been signed by all countries of the world - proof that we CAN work together to protect our planet!

The Protocol 🕶 had the goal of scaling back CFC and other ODS production by 50% by 2000.

Old devices that still used ODS were allowed to operate, but if they were serviced, the technician was required to track the chemicals and siphon the chemicals into an ODS recovery device.

Most of these devices are old air conditioners in businesses, cars, and houses. The theory is that as these devices need service, the ODS will be removed from use. If cars are involved in a wreck or scrapped, they must be checked for ODS before they can go to the junk yard.

There are other measures in place, such as the Green Chill program, which helps businesses reduce ODS emissions, that discourage the use of ODS.

Once we realized CFCs were more heavily implicated in destroying the ozone layer, the target date was moved up to 1996.

Is It Working?

As a result of the broad compliance with the Montreal Protocol 🕶 and its Amendments and Adjustments as well as industry's development of "ozone-friendly" substitutes to replace CFCs, the total global accumulation of ODSs in the atmosphere has slowed and begun to decrease. The graph below shows the annual changes in the concentrations of ODS in the atmosphere from the period 1986-2021:

Since the signing of the Protocol 🕶 in 1987, the ozone layer has seen substantial recovery. According to NASA scientist Pawan Bhartia, “The Antarctic hole is stabilizing and may be slowly recovering. Our focus now is to make sure that it is healing as expected.” In the image below, blue represents the ozone layer and each of the global views shows the total ozone over the southern hemisphere in 1979 (top left), 1987 (top right), 2006 (bottom left), and 2011 (bottom right).

Graph of projected total ozone levels. 4 globes represent different years to signify changes in ozone concentration — ***The ozone hole is slowly recovering - proof that we can work together to protect our planet.***

Production of this ODS was completely stopped worldwide in 2010 but rogue emissions of the gas still caused a latent increase in the atmosphere until the latter part of 2018. In the graph below, you can see our current and future progress in the reduction of chlorine concentrations in the stratosphere as an outcome of the Montreal Protocol🕶:

The data provided in the graphs above shows that the world can make progress when everyone on Earth gets on board with a specific effort, in this case, saving the ozone layer. Similar efforts are being made to reduce climate change but that’s another lesson for another day!

Clean Air Act (CAA) 💨

What is it?

The Clean Air Act (CAA) 💨 is a comprehensive federal law in the United States that regulates air emissions from both stationary and mobile sources. It was initially enacted in 1963 and has been amended several times, most notably the Title VI Amendments in 1990. It plays a crucial role in protecting the ozone layer through several key provisions and programs.

Title VI specifically addresses stratospheric ozone protection. It requires the Environmental Protection Agency (EPA) to develop and implement regulations for managing ozone-depleting substances (ODS) in the United States.

ODS Regulation (click to reveal)

- - - - The CAA 💨 has several programs regulating the use of ODS:
        
        Phaseout: bans the production and import of Class I ODS and phases out the production and import of Class II ODS.
        
        Exemptions: allow specific uses of ODS to be excluded from the phaseout, such as for certain medical devices and agricultural uses.
        
        Imports and Exports: establishes recordkeeping, reporting, and other requirements for importing virgin and used Class I and Class II substances.
        
        Destruction: sets acceptable practices for destroying ODS in the United States.
        
        Nonessential Products Ban: bans the sale and introduction into interstate commerce of certain products manufactured with or containing ODS.
        
        Labeling: establishes labeling requirements for ODS containers or products manufactured with ODS.

Stationary Refrigeration and Air Conditioning Program (click to reveal)

- - - - Establishes service practices, technician certification, sales restrictions, and other requirements for these appliances and systems.

Motor Vehicle Air Conditioning Program (click to reveal)

- - - - Sets servicing, technician certification, small can sales restrictions, and other requirements for air-conditioning systems in vehicles.

Halon Program (click to reveal)

- - - - Establishes installation, handling, and emissions requirements for halon fire suppression systems.

Significant New Alternatives Policy (SNAP) Program (click to reveal)

- - - - Identifies and evaluates substitutes for ozone-depleting substances, listing them as either acceptable, acceptable with use restrictions, or unacceptable for specific uses.

ODS Alternatives

The Montreal Protocol 🕶️ and the Clean Air Act 💨 have helped us reduce ODS emissions, but what do we use as refrigerants instead? You still probably have a refrigerator and air conditioning in your house and car - we do at my house!

As a replacement for CFCs, we introduced hydrofluorocarbons (HFCs) because they do not deplete the ozone layer. However, as you've noticed by this point in environmental science, there is no perfect environmentally friendly alternative to anything. There will always be side effects - we just need to decide which products have the least undesirable side effects and use those.

So, what are the problems with HFCs?

While HFCs are better for the ozone layer, they are potent greenhouse gases with a high global warming potential (GWP), which is a measure of how much heat a greenhouse gas traps in the atmosphere compared to carbon dioxide (CO₂). Some HFCs can be thousands of times more potent than CO₂ in terms of their GWP.

To address the issue of HFCs contributing to global warming, the Kigali Amendment to the Montreal Protocol 🕶️ was adopted. This amendment aims to gradually reduce the production and consumption of HFCs and eventually phase them down, similar to the approach taken with CFCs.

Essential Knowledge

Ozone depletion can be mitigated by replacing ozone-depleting chemicals with substitutes that do not deplete the ozone layer. Hydrofluorocarbons (HFCs) are one such replacement, but some are strong greenhouse gases.

AP Exam Tip

Both the Montreal Protocol 🕶 and the Clean Air Act 💨 are two of the 11 pieces of legislation you NEED to know for the AP exam.

You should know the benefits and drawbacks of CFC alternatives.

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