PFAS risk management in drinking water: an overview
Known as the "forever chemicals," the presence of PFAS in water and food has raised the concerns of health and environmental authorities, who are already working to build a solid regulatory framework, while advancing knowledge about their risks.
Per- and polyfluoroalkyl substances, better known as PFAS, are a group of synthetic chemicals that, due to their thermal resistance and stability, have been used for different industrial and consumer applications since the 1940s.
Their chemical characteristics – ideal, for example, for the manufacture of water- and oil-repellent products – means they are persistent and bioaccumulate in food chains, something that has raised the concerns of health and environmental authorities. Exposure to them through drinking water and food, and knowledge about their toxicity to the environment and health have led in the last decade to accelerated measures to curb their use.
As far as water is concerned, PFAS can reach it in several ways: through improper disposal in the form of spills and/or waste containing PFAS, direct release into the air or water when they are used, or firefighting foams. In addition, upon release, they may infiltrate into the soil and eventually reach groundwater aquifers, where they can persist for many years, as they are resistant to degradation and they can adhere to sediments. Thus, the presence of PFAS in groundwater is a major concern, as there is a high likelihood that such water will be withdrawn for agricultural or other uses and eventually consumed by humans.
In Europe and the UK, a mapping project carried out in February 2023 by The Guardian and Watershed with data obtained from water companies and the Environment Agency revealed high concentrations, of more than 1,000 nanograms per litre of water at approximately 640 sites and above 10,000 ng/l at 300 locations. The map shows Belgium is home to the highest levels of pollution, where PFAS were found in groundwater in concentrations of up to 73 million ng/l near a PFAS manufacturing site. The map also shows that drinking water sources in the UK have been contaminated, yet water companies say that a specialised treatment process is used to remove PFAS so that they do not end up in tap water.
Water utilities are already taking steps to minimise the risks associated with PFAS with a relatively new regulatory framework
In this regard, PFAS risk management in drinking water is a complex issue involving multiple stakeholders, especially the industrial sector, including water companies, which are already taking steps to minimise the risks associated with a relatively new regulatory framework for PFAS.
A regulatory framework is still under construction, but determined
The World Health Organization (WHO) classifies perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) as suspected carcinogens, suspected reprotoxic and harmful to vulnerable populations. In addition, the Strategic Approach to International Chemicals Management (SAICM), a policy framework to promote chemical safety worldwide that is part of the UN Environment Programme, considers them as emerging contaminants.
However, the global regulatory framework to control PFAS is still under construction. While the regulations that have been implemented in the last decade, especially in the United States and Europe, are increasingly committed and strict, there is still a long way to go.
Regulations are taking an increasingly rigorous approach, particularly in the U.S. and Europe, but there is still some way to go
Thus, these compounds were included in 2009 in the list of restricted chemicals of the Stockholm Convention on Persistent Organic Pollutants, but it was not until 2016, in a review of the Review Committee of this convention, that a consensus was reached stating that PFOA could cause significant adverse effects on human health and the environment.
At the global level, there is a draft background document for the development of WHO Guidelines for drinking water quality
The United States was a pioneer in 2012 in including PFASs and PFOS among the contaminants to be monitored in water systems, as well as establishing a PFAS Strategic Roadmap through the Environmental Protection Agency (EPA) in 2021. In addition, the Biden-Harris Administration proposed the first national drinking water standard for six per- and polyfluoroalkyl substances in 2023, a major step forward to protect the public health of Americans. On top of this, the EPA announced $2 billion from the Bipartisan Infrastructure Law to address emerging contaminants in drinking water across the country, including PFAS.
While chemicals are essential to the well-being and comfort of modern society, many of them have hazardous properties that can damage the environment and human health. This is why the European Commission published the Chemicals Strategy for Sustainability in 2020, in line with the objectives of the European Green Deal, which aims to better protect citizens and the environment and drive innovation for safe and sustainable chemicals. This includes phasing out the use of PFAS in the EU, "unless proven essential for society".
The difficulties of dealing with PFAS stem from the fate and prevalence of these substances, so that a holistic approach is required
From it derived a Restrictions Roadmap, published in April 2022, to prioritise these substances for restrictions under the Regulation on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). "We have come a long way regulating chemicals in the EU. But the ambition of our European Green Deal is that we all live in a truly toxic-free environment. We cannot afford to expose our health and our nature to harmful chemicals," Virginijus Sinkevičius, European Commissioner for Environment, Oceans and Fisheries, said at the time.
In addition, Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the quality of water intended for human consumption establishes values and measures concerning PFAS, binding for Member States, to be implemented by January 2026 to ensure that water intended for human consumption complies with the parametric values, 0.50 μg/l for the totality of per- and polyfluoroalkyl substances, and 0.10 μg/l for the sum of these same substances considered a concern as regards water intended for human consumption, listed in its Annex III. However, Member States are free to introduce stricter legislation at the national level.
One of the main strategies used to reduce PFAS exposure in drinking water is through various water treatment processes
It should be noted that this is in addition to regulations from food safety authorities, such as the European Food Safety Authority (EFSA), which establishes a safety threshold for the main types of PFAS that accumulate in the body.
Thus, the growing concern about the negative effects of PFAS on both public health and the environment is leading more and more countries around the world to adopt measures to regulate these substances in water, although there is neither a consensus on what levels are dangerous for the population nor corresponding legislation. According to Medical News Today, in some regions of the world, such as Asia, restrictions have not yet been imposed.
There is, however, a draft background document for the development of WHO Guidelines for drinking water quality. Although the process of developing guideline values is still ongoing, the WHO advises its Member States to: (i) strive to achieve concentrations in drinking water that are as low as reasonably practical; (ii) minimise contamination of water sources, including preventing new sources of contamination; (iii) stop nonessential uses of PFAS; and (iv) balance the risks from PFAS with other risks in the water supply, including not having adequate supplies of drinking water.
Technology and innovation to remove PFAS from water
Exposure to PFAS through drinking water has become a major concern for the water industry. The difficulties of dealing with PFAS stem from the fate and prevalence of these substances, so it requires a holistic approach that includes research, characterisation, analysis, testing and technology development.
Water companies clearly have the willingness, the commitment and the knowledge necessary to address this new challenge
Thus, not only is it important for environmental authorities and companies involved to identify and eliminate the sources of PFAS contamination, but it is also key to research what are the best ways to address the risk from PFAS in water and develop new treatment methods. "The water sector must be aware of this issue and be proactive about it," noted Isle Utilities’ chairman Dr Piers Clark in a January 2021 webinar organised by the Water Action Platform.
In this regard, one of the main strategies used to reduce PFAS exposure is through various water treatment processes. Among the technologies that have been tested and have proven most effective are activated carbon, ion exchange, reverse osmosis, electrodialysis, photocatalysis and advanced oxidation, which are more or less efficient depending on the class, species and chain length of each PFAS substance.
Although the concern about PFAS risk management in drinking water is still recent and the technologies focused on it are still beginning, water companies have the willingness, commitment and knowledge necessary to address this new challenge.