Perfluorocarbons (PFCs) are chemically inactive, nontoxic, and nonflammable compounds that are found in the atmosphere at very low levels. PFCs present no known danger to humans if inhaled or ingested. This study will use very small quantities of PFCs in the low parts per million range, released for 30 minutes only on each test day. To give a better idea of the scale of this release, one part per million is equivalent to half-a-drop of water in a full average-size bathtub.
PFC liquids such as those that will be used in the study are non-reactive and have been used in a number of medical applications. For example, doctors have used perfluorocarbon fluid to assist premature infants’ ability to breathe and to help develop their lung membranes. Perfluorocarbons also are used in eye surgery and as a contrast agent in medical imaging.
Many PFC compounds are commercially available and have been used worldwide for decades as tracers — for example, to detect leaks in electrical transmission lines and natural gas distribution lines. There are no regulatory restrictions on the use or emission of PFT compounds, which have many other research and commercial applications.
Perfluorocarbon tracer technology — which includes the release, sampling, and analysis of PFC compounds — has been used since the late 1970s by scientists studying how materials move and spread in the atmosphere on local, regional, and continental scales. These studies have increased scientists’ understanding of pollutants and other hazardous substances in the atmosphere. They have also helped researchers develop and improve computer models predicting how materials will move in the atmosphere. This research has been applied to critical national and global issues, including homeland security, air quality, and climate change.
Other uses of PFTs as tracers include research on how air enters buildings, tracking flows in oil fields, and ensuring the safety of buildings that house hazardous or radioactive materials. PFTs have also been proposed as tags for identifying explosives and detecting smuggled currency.
This widespread use of PFTs for more than 30 years is based on their demonstrated nontoxic and non-reactive characteristics, their relative scarcity in the atmosphere, and scientists’ ability to detect and track them at incredibly small concentrations — down to just a few parts per quadrillion (one part in 1,000,000,000,000,000 or a thousand million million).