A look into the PFAS issue

So-called 'per- and polyfluoroalkyl substances' (or PFAS for short) include a large group of more than 6,000 man-made products that do not occur in nature. PFOS (perfluorooctanesulfonic acid) and PFOA (perfluorooctanoic acid) are the most well-known PFAS and are used in all kinds of products like textiles, carpets and frying pans for their water-, grease- and dirt-repellent properties. By using these products, however, PFAS have found their way into our environment, through factory emissions, incidents and even just by extinguishing fires with foam. To confound matters, they do not break down, spread easily and can accumulate in the cells of animals and plants, and, yes, in human cells too. Hence their nickname: 'forever chemicals'.

Apart from places where PFAS are produced or used, like in the galvanising industry and the production of Teflon™, there is also a large chance of PFAS being released into the environment wherever foam is used to extinguish fires. Other processing industries like the textile, paper and packaging industry, varnish and paint sector, landfill sites, water purification plants and waste burning facilities are considered potential high-risk locations as well, though to a lesser extent.

After being released, PFAS can slowly dissolve in the soil (through a process called 'leaching'), get into the groundwater and spread further. Or they can spread through the air to then be deposited in the soil or surface water. Lastly, they can spread through polluted silt, earth or dredging and the transformation of their precursors in the environment to perfluoroalkyl acids (PFAAs).

Whenever an exploratory soil survey or technical report is put together in Flanders for land deemed to be high-risk for the release of PFAS into the environment, they must always be considered as suspect substances. For all other exploratory soil surveys and technical reports, the recognised soil remediation expert decides whether PFAS should be considered as a class of suspect substances or not.

It is important to avoid potentially PFAS-contaminated soil from spreading by human activity in an uncontrolled way. This is why the general principles for earthworks, developed and supervised by the Waste Agency of Flanders OVAM always apply.

Soil dug from potentially PFAS-contaminated land, for example, as is the case with the Oosterweel Link, should be reused as much as possible on the land it came from. However, reusing polluted soil outside of the cadastral working zone (as it is recorded in the Belgian land registry) is discouraged in order to tackle the uncontrolled spread of PFAS in residential areas, for instance.

If the chance of PFAS being released into the environment is deemed 'high' because the project involves groundwater, e.g. land drainage, infiltration of precipitation, and such like in areas where these substances are present already, it may be advisable to take groundwater samples and analyse them for PFAS, and PFOS and PFOA in particular. An exploratory soil survey may be important at any rate, as PFAS (as well as other substances) were rarely considered suspect substances in the past. For these reasons, OVAM could prioritise an exploratory soil survey of previously non-surveyed high-risk soil within the zone the groundwater work will affect to contain uncontrolled spreading of these substances But this is not yet the case unfortunately.

When a firefighting foam tank was removed during demolishing work on a former General Motors (GM/Opel) site, a limited quantity of the foam was spilled on the ground. The incident prompted an analysis for PFOS (and subsequently PFAS too) in the soil and groundwater.

This showed the PFOS/PFAS pollution at the site was so severe it could not possibly be down to the calamity with the firefighting foam tank. For this reason, OVAM asked Antea Group to do an extra soil survey to assess the presence of PFOS/PFAS in the soil and groundwater. The results were already included in a first phased descriptive soil survey in 2018. Last year, we also set up a first phased soil remediation project which was approved on 29 June 2020 and started at the end of the year.

Together with our clients, OVAM and Port of Antwerp, we resolved to reuse the PFAS-contaminated soil at the location it came from after physico-chemical purification, as this technique does not guarantee complete removal of all PFAS from the soil. However, by reusing it at the original location, the soil would at least be kept away from the usual earthworks circuit and only traces of PFAS will remain at the site.