In the early 2000s I had a leading role in the technical review of perfluorooctane sulfonate (PFOS) for the United Nations Environment Programme. We concluded that it was toxic to some species in the environment and that its use should be restricted to situations where no suitable replacement was available. This recommendation was adopted by the Stockholm Convention on Persistent Organic Pollutants. Another PFAS substance - perfluorooctanoic acid (PFOA) - is going through the Stockholm process right now and I expect it will be banned or restricted, too, and for the same reasons
 
PFOS is the major substance of the PFAS family that has been released to the environment, mainly through its use in fire fighting foams. Like so many of the substances we have banned or restricted - think DDT, for example -  PFOS is especially effective in the uses it was designed for. But of course, like DDT, it has bad effects on environmental species, and these impacts came to light only long after the substances were introduced.
 
While the evidence for environmental harm was sufficient to see PFOS dealt with under the Stockholm Convention the evidence for harm to people is not strong. Small quantities can be found in the blood of most of us, but nobody seems to have been exposed to high enough concentrations to enable health professionals to identify a cause-and-effect relationship. Even so, there is justification for a cautious approach and for ways to minimise exposure to possible contamination.
 
The PFAS contamination is carried by water. Living near a defence site is not especially risky unless you are exposed to surface water or ground water that has been contaminated. PFAS foams were used at other places, too, such as the areas where fire-fighters were trained, such as the Fiskville site, to west of Melbourne.
 
Treating contaminated water with activated carbon (sometimes referred to as granulated activated carbon, GRAC) removes PFAS by adsorbing it onto the carbon. The carbon can then be safely buried in a secure landfill, or - more likely - burned at high temperatures to destroy it and the PFAS. PFAS-contaminated soil can be heat-treated to destroy the PFAS and some facilities of this type are already operating in Australia.
 
A national environmental management plan for PFAS is being developed by the EPAs of the states and territories, together with the Commonwealth, and should be completed by the end of this year.

PFAS contamination in groundwater is widespread in many parts of the world. We’re only just starting to understand how widespread it is in Australia, but there is evidence that large parts of urban Australia are contaminated. The ‘hot spots’ tend to be where fire-fighting foams have been used intensively and over long periods of time. This includes large and small airports, defence sites and firefighting training sites.

When firefighting foams have been used in these locations, they have often been subsequently washed into waterways, or just left on the ground to soak into the soil. These chemical have practically indefinite persistence in the environment, meaning that there is effectively no natural degradation or remediation process. Furthermore, they are highly mobile, meaning that they will eventually reach groundwater tables, and then travel with the groundwater from one location to another.

These characteristics make PFAS quite different to many other environmental contaminants, which either break-down over time, or tend to become stuck to soil, this remaining largely at the site of the contamination.
 
It is possible to treat PFAS in drinking water, but the treatment processes are expensive and highly energy intensive. The most common processes are reverse osmosis membrane filtration and some emerging ion-exchange processes. The problem with both approaches to PFAS treatment, is that neither actually breaks-down or destroys the PFAS molecules. They merely concentrate the PFAS into a waste solution, which then requires disposal. Opportunities for safe disposal of that waste solution are currently very limited, so there is really no established sustainable remediation technique. The current techniques predominantly involve shifting the contamination from one location to another.
 
The vast majority of drinking water treatment plants in Australia are largely ineffective for PFAS removal. For this reason, it is very important that we manage the PFAS problem at the source, rather than hope to manage it at the water treatment plant. This means that we must pay much greater attention to managing our catchments and preventing chemical contamination from occurring in the first place. This will require much more significant measures for risk management to be instituted for all industrial and government operations undertaken in current or potential future drinking water catchments.