VEC explains PFCs, PFOA, PFOS

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VEC explains PFCs, PFOA, PFOS

Thu, 09/15/2016 - 12:04pm -- tim

Vermont Environmental Consortium Recently, there have been many news reports documenting contamination of drinking water sources with "emerging contaminants" such as perfluorinated compounds (PFC) above USEPA and individual state health advisory levels. PFOS (perfluooctanesulfonic acid) and PFOA (perfluorooctanoic acid) were the PFCs reported above drinking water wells in several Vermont communities this year (particularly in Bennington). These compounds have also been found in public water systems in New York, New Hampshire and Rhode Island. PFCs are utilized in many industrial and commercial products such as non-stick cookware, non-stain fabrics, water repellant coatings, fast-food packaging and fire-fighting foams. PFC are comprised of carbon chains of various lengths (3 to 12 carbon atoms long) with an acid group on one end. The carbon chain has all of its available bonding sites attached to fluorine atoms as shown below. 

 This structure makes for extremely stable, water soluble compounds that do not degrade biologically or chemically making them very persistent in the environment once released from a source such as a manufacturing facility, fire using fire-fighting foam, or landfill containing PFC wastes. Since the chemical structure is so soluble, there is very little adsorption to soil.  Though not volatile, many PFCs can remain airborne for extended periods of time.  These characteristics have resulted in the near ubiquitous distribution of PFCs around the globe.

PFCs have been shown to bio accumulate.  Once exposure to or intake of PFCs has ceased, the estimated "half life" for excretion from humans is 3 to 4 years.  Studies have also shown a correlation - but not a cause-and-effect relationship - between levels of PFCs in the blood and high blood pressure, decreased birth weight, some immune system effects, thyroid disease, kidney cancer and testicular cancer.  However, studies to date have been limited and insufficient data exists to determine safe exposure levels in soil, surface water or drinking water.  Currently, the EPA has set a long term exposure advisory concentration for drinking water of 70 nanograms per liter (parts per trillion) for PFOA and PFOS combined.  The State of Vermont Department of Health, has set a more stringent health advisory of 20 parts per trillion combined PFOA and PFOS based on potential toxicity to infants.   Formal adoption of the VTDOH health advisory as a groundwater enforcement standard is in process.

Due to their physical properties, PFCs can migrate great distances in the environment. This has led to groundwater plumes many miles long in both soil (overburden) and bedrock aquifers.  In Vermont, hundreds of private drinking water wells have been impacted by releases of PFCs from more than a decade ago.   The plumes are so extensive that, even with "source area" remediation, they will continue to expand and persist for decades to come.  The current state of remedial technology is generally limited to contaminated soils removal and groundwater plume control through pumping.  Drinking water treatment methods are also limited to granular activated carbon filtration.  Though effective, PFCs do not bind to the carbon efficiently and frequent changing/regeneration of the carbon is necessary to achieve the part per trillion water quality levels necessary.  Recently, some advances in resin filtration have appeared promising but are not available for commercial use at this time.

Use of long chain PFCs has been voluntarily phased out by manufactures at the EPAs request for the past several years.  This has reduced the risk of "new" sources of PFCs arising.  However, the risk of contaminants migrating to, and impacting water supplies above the health advisory levels will remain for decades.


North Bennington wells test positive for PFOA

Governor says PFOA testing will be broadened across state

Testing results from Pownal show some PFOA in public water system

Final PFC testing site in Shelburne shows results below limits

Source: VEC Sept 2016 Newsletter, Rutland

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