By David Imhoff*
Note: As of the time of writing, it is not clear what effect the incoming administration will have on climate policy and the phase-out of hydrofluorocarbons in the United States.
In the late 1800s, mechanical refrigeration was beginning to revolutionize food processing and transportation.  These early refrigerators generally used ammonia, sulfur dioxide, or methyl chloride as refrigerants.  Unfortunately, all of these compounds are toxic, and methyl chloride is highly flammable.  In 1928, the search for a safer substitute resulted in the synthesis of the first chlorofluorocarbons (CFCs).  These chemicals were inexpensive, non-toxic, non-flammable, and highly stable.  For decades, they were employed in an ever expanding range of applications including refrigeration, fire suppression, aerosol cans, polymer foam manufacturing (foam blowing), and many other industrial processes. 
By the mid-1980s, it had become apparent that CFCs catalyzed the destruction of stratospheric ozone.  This realization led to the 1987 adoption of the Montreal Protocol (currently ratified by all UN member states), which resulted in the rapid phase out of CFCs globally.  In many applications, CFCs were replaced with a new class of chemicals, hydrofluorocarbons (HFCs).  Similarly to the CFCs they replaced, HFCs are non-toxic and have favorable properties for many of the same applications.  Unfortunately, HFCs are also potent greenhouse gasses.  One of the most commonly used, HFC-134a, has a global warming potential 1,430 times that of carbon dioxide.  Many others have similar or larger global warming potentials.  This adds up to a large impact. If no action were taken, HFC emissions would have the potential to produce an additional 0.5oC of warming by the end of the century. 
In October of 2016, the parties to the Montreal Protocol took action, agreeing to an amendment to phase out HFCs while meeting in Kigali, Rwanda.  Unlike the Paris climate agreement, the Kigali amendment is legally binding and enforceable.  Developed countries (including the United States) will be required to begin reducing consumption of HFCs in 2019, with consumption being reduced to 15% of 2012 levels by 2036.  Developing countries will be required to freeze HFC consumption by 2024, with reductions to follow.  This combination of robust targets and legal enforceability makes the Kigali Amendment one of the strongest actions taken to date to address climate change.
Even before the Kigali Amendment, the United States had initiated actions to reduce HFC emissions in accordance with the President’s 2013 Climate Action Plan. These consist of both voluntary, industry-led measures and regulatory action through the EPA’s Significant New Alternatives Policy (SNAP) program.  Article 612 of the Clean Air Act of 1990 provides that:
Within 2 years after November 15, 1990, the Administrator shall promulgate rules under this section providing that it shall be unlawful to replace any class I or class II substance with any substitute substance which the Administrator determines may present adverse effects to human health or the environment, where the Administrator has identified an alternative to such replacement that—
(1) reduces the overall risk to human health and the environment; and
(2) is currently or potentially available.
The Administrator shall publish a list of (A) the substitutes prohibited under this subsection for specific uses and (B) the safe alternatives identified under this subsection for specific uses. 
The SNAP program implements this section. While HFCs are not class I or II substances, they are frequently used as substitutes for class I or II substances and thus are subject to regulation under this section.  Under SNAP, the EPA publishes lists of chemical compounds that are acceptable for specific industrial uses including refrigeration, foam blowing, and fire suppression.  In response to concerns regarding the global warning potential of HFCs, the EPA has issued a series of rules to reduce HFC consumption.  The most recent of these is Rule 21, which was published in the Federal Register on December 1, 2016.  Rule 21 will dramatically reduce the range of applications in which HFCs are acceptable and permit the utilization of a range of substitutes.  Specifically, high global warming potential HFCs will be phased out in most refrigeration applications between 2021 and 2024.  They will also be phased out in many foam blowing applications between 2020 and 2021. 
These mandatory HFC reduction steps come on top of voluntary actions in the private sector. In September 2014, 22 U.S. private sector entities agreed to voluntary reductions in HFC consumption.  These reductions are expected to prevent HFC emissions equivalent to 700 million metric tons of CO2 through 2025.  The combination of robust international action, strong domestic regulatory action, and voluntary private actions make HFC reduction one of the most successful initiatives to date in mitigating the impacts of climate change.
The views and opinions expressed in this blog are those of the authors only and do not reflect the official policy or position of the Michigan Journal of Environmental and Administrative Law or the University of Michigan.
*David Imhoff is a Junior Editor for MJEAL. He can be reached at email@example.com
 See James W. Elkins, Chlorofluorocarbons, esrl.noaa.gov (last visited Jan. 25, 2017), https://www.esrl.noaa.gov/gmd/hats/publictn/elkins/cfcs.html [hereinafter CFCs]
 Id. See also Methyl Chloride Safety Data Sheet, Airgas (May 20, 2015), https://www.airgas.com/msds/001036.pdf
 CFCs, supra note 1.
 Id. See also Halocarbon R-12 Safety Data Sheet, Airgas (May 21, 2015), https://www.airgas.com/msds/001018.pdf
 CFCs, supra note 1.
 See Id.
 See Protection of Stratospheric Ozone: New Listings of Substitutes; Changes of Listing Status; and Reinterpretation of Unacceptability for Closed Cell Foam Products Under the Significant New Alternatives Policy Program; and Revision of Clean Air Act Section 608 Venting Prohibition for Propane, 81 Fed. Reg. 231, 86778, 86781 (Dec. 1, 2016) (to be codified at 40 CFR Part 82) [hereinafter Rule 21]
 See Halocarbon 134a Safety Data Sheet, Airgas (May 27, 2016), https://www.airgas.com/msds/001055.pdf
 See Rule 21, supra note 9, at 86786.
 UNEP/OzL.Pro.28/CRP/10 Further Amendment of the Montreal Protocol, Twenty-Eighth Meeting of the Parties Dec. XXVII/1 Annex F (2016) [hereinafter Kigali Amendment]
 Press Release, The White House, FACT SHEET: Nearly 200 Countries Reach a Global Deal to Phase Down Potent Greenhouse Gases and Avoid Up to 0.5°C of Warming (Oct. 15, 2016)
 Kigali Amendment, supra note 13.
 See Id.
 Id, Article 2J.
 Press Release, The White House, FACT SHEET: Obama Administration and Private-Sector Leaders Announce Ambitious Commitments and Robust Progress to Address Potent Greenhouse Gases (Oct. 15, 2015) [hereinafter Private Sector Fact Sheet]. See also Rule 21, supra note 9, at 86786.
 42 U.S.C. §7671k
 Rule 21, supra note 9, at 86787.
 See Id at 86788.
 Id at 86787 – 88.
 Id at 86778.
 See Id at 86883 – 95.
 Id at 86889 – 93.
 Id at 86885 – 89.
 Private Sector Fact Sheet, supra note 19.