Perfluorocarbons (or PFCs) are compounds derived from hydrocarbons by replacement of hydrogen atoms by fluorine atoms. PFC is 6000 times more effective than carbon-dioxide, entirely toxin-free, and made up of molecules of carbon, fluorine, and/or sulfur. The perfluorocarbons used in the microbubbles of some ultrasound contrast media are liquids at room temperature, but gases at body temperature.
Their stability, inertness, low diffusion rate and solubility increase the duration of contrast enhancement as compared to microbubbles containing air. PFC is also being used in artificial blood.
PFC is being used in refrigerating units and "clean" fire extinguishers. However PFCs are hugely potent greenhouse gases and they are a long-term problem with a lifetime up to 50,000 years. Several governments concerned about the properties of PFCs have already tried to implement international agreements to limit their usage before it becomes a future global warming issue. PFC is one of the gases regulated in the Kyoto Protocol.
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