PFAS is the new “It” organic chemical contaminant.  You hear about it in newspapers, in magazines, at environmental conferences and wherever environmental professionals gather to talk.  PFAS is not just one organic chemical but a whole suite of related organic chemicals and the acronym stands for per- and poly-fluoroalkyl substances.  There are dozens of these chemicals but in water only the per-fluoralkyl substances are important.

          The per-fluoroalkyl substances are chain like structures composed of a series of bonded carbon and fluorine atoms attached to a charged ion.  Scientists call the carbon and fluorine atoms the “tail” and the charged ions the “head”.  There are two main types of per-fluoroalkyl substances:  per-fluoroalkyl acids and per-fluoroalkyl sulfonamides.  Scientists, seemingly in order to confuse everyone, have given the per-fluoroalkyl acids the acronym PFAAs. 

          The two PFAAs which give us the most trouble are per-fluoroalkyl carboxylic acid and per-fluoroalkane sulfonic acids.  Of the per-fluoroalkyl carboxylic acids the one’s that are detected most in water are PFOA or per-fluorooctanoic acid and its cousin per-fluorooctanoate.  Of the per-fluoroalkane sulfonic acids, the ones that are detected most often are PFOS or per-fluorooctane sulfonate and per-fluorooctane sulfonic acid.    

          I know this is a jumble of acronyms and chemical names.  Here’s a handy cheat sheet to keep them all straight.

          Really the only chemicals you need to remember are PFOA and PFOS, because they are basically non-degradable.  Yes that’s right, they are not degradable.  They are with us forever. Scientists even call them “terminal PFAS” or “terminal degradation products”.  The carbon fluorine bond is so strong that it is impossible to break it apart through natural degradation processes existing in our environment.  There are plenty of other PFAAs too.  But they are not generally found in water as they degrade into the “terminal PFAS.”  Ditto for the poly-fluoroalkyl substances. 

          There are lots of different PFAS that have been manufactured over the last 80 years.  As a result, PFOA and PFOS are found everywhere.  They are in the air, the soil, the water, the fish, the plants, and your blood.  In one study in 2015 supported by the Red Cross (authored by G.W. Olsen and others) a set of 616 blood donor’s plasma samples, representing the general U.S. population, was analyzed for PFAS.   Researchers reported PFOA levels of 1.1 micrograms per liter in the blood donor’s plasma and 4.3 micrograms per liter of PFOS.   Why in the world would anyone produce something like this and why in the world is it so ubiquitous in the environment?  This stuff is even found in the Arctic and Antarctic.    

          PFAS are chemicals that repel oil and water and reduce friction.  They have been used in non-stick cookware and in protective sprays to prevent spills and stains on carpets and upholstery.  They are also used in firefighting and firefighting training at airports and military bases because they can put out a jet fuel fire.  PFAS have been manufactured since the 1940’s.  The chemicals were never reviewed under the Toxic Substances Control Act (TSCA) because the law which was written in 1976 only required review and approval of new chemicals.  TSCA was rewritten to fix this loophole in 2016.  The U.S. Environmental Agency (U.S. EPA) worked with companies to phase out the manufacture of the problem PFAS chemicals back in 2002 so presumably new contamination sources no longer exist.

          The “terminal PFAS” – PFOA and PFOS – have a wide distribution in the environment because of the chemical nature of PFAS.  Remember the “tail” of bonded carbon and fluorine?  That tail acts to repel water and oil.  Remember the “head” of charged ions?  It mixes with water.  How crazy is that?  But these are the properties that this chemical was made for; it’s why those no stick pans in your kitchen work so well and clean up like a breeze.  But where this chemical has been spilled or disposed of in our environment, it results in all sorts of weird activity.   Where it is found in the vadose zone (the unsaturated area of soils and rock before groundwater is encountered) the “tail” properties cause it to attach to organic carbon and other organic contaminants in the soils.  At the same time, its negatively charged “head” repels the negatively charged soils.  This makes the “head” free and available for mixing with water.  During and after a rainfall, water percolating through the vadose zone attaches to the “head” and drags the chemical down into the groundwater zone below with it.  Unless you get rid of the PFAS in the vadose zone, you have an ever present source for water contamination.

          Once PFAS moves into the groundwater, it moves fast because PFAS’s chemical properties give it high solubility and low retardation in the aqueous environment.  Groundwater can discharge into surface water, and before you know it, PFAS is down the river.  If you have a private or public well into groundwater near a PFAS spill or disposal area then it can get into your drinking water.  Drinking PFAS is not good for your health.  In 2016, the U.S. EPA set a drinking water health advisory for PFAS.  It is 70 parts per trillion.  This is a very, very small number and is based on protection of fetuses and breast fed infants.  Fortunately the EPA surveyed 4064 public water supplies individuals in the U.S. and found only a small number to be contaminated with PFAS.  Most of these systems are near manufacturing plants where PFAS was made and released into the environment or near military bases and airports where firefighting training has occurred.

          Quite a bit of research has been conducted over the past 10 years on PFAS and its’ interactions in the environment, including on-going studies into the complexities of the chemical’s interactions in the natural environment.  I’m always floored by the fact that scientists are doing the research on these interactions years after a chemical was first developed and put into use.  This is not the first time this has occurred.  Fifteen years ago the “It” organic chemical contaminant was MTBE or Methyl tert-Butyl Ether.  MTBE replaced lead in gasoline as far back as 1988.  What nobody bothered to look at back then was what chemical properties MTBE might have that would interact in a poor manner with the environment after it leaked from underground storage tanks at gas stations.  Like PFAS, MTBE is highly soluble in water.   And like PFAS it forms big plumes moving from the source of contamination through the groundwater to reach drinking water wells and surface water.  MTBE though, unlike PFAS, is readily degradable in the environment.   

          Failure to examine a chemical’s interactions with the environment prior to its widespread use has resulted in an entire industry of environmental remediation where costly soil removals and large scale groundwater recovery systems have to be installed and maintained.  The costs of such remediation can be exorbitant and the desire to recover these costs as well as damages for the contamination has led to lawsuits against chemical manufacturers and corporations using the chemicals.