Perfluorocarbons (PFCs)
Perfluorocarbons (PFCs) are chemical compounds consisting solely of carbon and fluorine atoms, created when hydrogen atoms in hydrocarbons are replaced by fluorine. The most recognized true PFCs include tetrafluoromethane (CF4) and hexafluoroethane (C2F6), along with several synthetic gases generated as by-products of industrial processes such as aluminum smelting and semiconductor manufacturing. Known for their chemical inertness, PFCs exist both as clear, dense liquids and gases. They have been investigated for various applications, including use in medical procedures and as potential artificial blood substitutes.
PFCs are classified among greenhouse gases (GHGs) and play a role in Earth's climate system, though their impact is less pronounced than that of gases like carbon dioxide and methane. They can remain in the atmosphere for hundreds or thousands of years, contributing to long-term climate effects, such as rising sea levels and increased severity of weather events. Due to their persistence, PFCs have raised concerns regarding environmental and human health, leading to regulatory actions such as bans on their use as food additives and designations as hazardous substances. The complex relationship between PFCs, climate change, and public health underscores the need for continued research and monitoring.
Perfluorocarbons (PFCs)
Definition
Perfluorocarbons are chemical compounds that are formed when some hydrogen atoms in hydrocarbons are replaced by fluorine atoms. True perfluorocarbons (PFCs) contain only carbon and fluorine atoms and generally include only CF4 and C2F6; PFC derivatives may have other chemical groups attached to them. PFCs are chemically inert. They exist in a clear and colorless liquid form that has two times the density of water because of its high molecular weight. There are also five PFC gases: tetrafluoromethane, hexafluoroethane, octafluoropropane, perfluoro-n-butane, and perfluoro-iso-butane. These gases are formed synthetically and are by-products of aluminum smelting, uranium enrichment, and semiconductor manufacturing, as well as refrigerant blends. They have also been used as substitutes for CFCs in manufacturing.
PFCs are used in medical procedures, such as eye surgery and certain types of imaging procedures. They are being investigated for use as artificial blood, though this application is not yet feasible. However, PFCs are also suspected as agents in human disease and damage, such as breast, liver, prostate, and testicular cancer; hypothyroidism; and other developmental damage associated with toxic chemicals.
Significance for Climate Change
PFCs affect the warming and cooling cycle of the Earth, as do the other addressed by the Kyoto Protocol. PFCs are part of the class of fluorinated gases, which—along with carbon dioxide (CO2), methane, and nitrous oxide—are considered to be the major GHGs listed in the Kyoto Protocol. However, they do not affect the atmosphere to the extent that other gases, such as water vapor, CO2, or methane, do. PFCs also do not affect the as some other gases do, and they were introduced as an alternative to ozone-depleting substances.
As light from the Sun enters the atmosphere, some of that light is scattered by molecules in the air or reflected from clouds back into space. Some of the light that reaches the Earth is also reflected back into space by surfaces such as snow or ice. Much of the light that reaches the Earth is absorbed and retained as heat. The Earth’s surface warms and emits infrared photons, which make several passes between the Earth and the atmosphere, warming the atmosphere and the Earth as they go back and forth. Eventually, these infrared photons return to space.
The GHGs, whose molecules are all composed of three or more atoms, are able to absorb infrared photons as they pass, transferring the energy from the photons to the gases’ molecules and trapping the thermal energy associated with them. Eventually, this absorption of energy effects a net change in the Earth’s energy balance. The extent of the net change depends on the radiative force associated with the gas, as well as the lifetime of the gas. These two factors are expressed together by the gas’s global warming potential. PFCs can stay in the atmosphere for hundreds or thousands of years. Thus, they continue to affect Earth’s atmosphere and climate far longer than other GHGs.
Many GHGs are emitted as a result of human energy use, such as when fuel is used to generate electricity. Though human-made gases, such as PFCs, only account for approximately 2 percent of total GHG emissions, some scientists believe these emissions are enough to tip the delicate balance of the Earth’s warming and cooling patterns. PFCs can be removed from the atmosphere through and precipitation or by chemical reactions. However, because of their long lifetimes, they tend to accumulate more quickly than they can be dispersed.
Because of PFCs’ effects on the global climate, the retention of these gases in the atmosphere could lead to melting of glaciers and polar ice caps, increased severity of flooding and droughts, rising sea levels, increases in the of freshwater, more devastating tropical cyclones and tidal waves, and coastal erosion. These effects on the global climate could also help increase food production. As the Earth becomes warmer, growing cycles lengthen, more land becomes available for food production, and more and different varieties of food are able to be grown. Climate change from the GHGs, including PFCs, could also lead to more insect-borne disease spreading further throughout the world. As mosquitos and other pests are able to survive in more and different areas, malaria, dengue fever, and cholera could spread further.
In 2106, the Food and Drug Administration banned the use of three long-chained PFCs as food additives. Later that year, the organization banned the remaining two long-chained PFCs used as food additives. Additional state-level bans of PFCs were put in place throughout the 2010s and 2020s. In 2024, the Biden-Harris administration officially designated two widely-used PFAS chemicals, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).
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