PFAS in drinking water: which domestic filters tackle 'forever chemicals'?

Many substances that can harm human health are increasingly being found in our drinking water.

Among them are the so-called 'forever chemicals' - per- and polyfluoroalkyl substances (PFAS). These fluorinated compounds break down extremely slowly, can build up in body tissues, and move readily through the environment.

PFAS have been widely used over the past 10 to 20 years in industrial and consumer applications such as non-stick coatings, stain repellents and surfactants. As a result, they have become a major environmental and public health concern.

With the appropriate analytical equipment, PFAS can now be detected almost everywhere, which has intensified questions about what today’s exposure levels could mean for health.

Multiple exposures

Our contact with PFAS comes via drinking water, air and food, and to a smaller extent through absorption via the skin. Reducing exposure through the air is challenging, but cleaning the home more often may help to reduce inhalation of household dust that contains PFAS. That said, this pathway still needs further research.

PFAS can also occur at meaningful levels in food and food packaging. While regulation in this area remains limited, it is especially difficult to reduce exposure by changing what we eat - unless it becomes clear which foods are less contaminated, or unless a large share of products sold in the supermarket are shown to be affected.

Compared with other exposure routes, drinking water is the easiest source to treat when trying to lower overall PFAS exposure. Termeh Teymoorian, a doctoral researcher in chemistry at the University of Montreal, is studying PFAS in water. Her PhD work is co-supervised by Sebastien Sauve, a professor of environmental chemistry at the University of Montreal who specialises in emerging contaminants, and Benoit Barbeau, a professor at Polytechnique Montreal and co-holder of the Industrial Chair in Drinking Water.

We recently published an article in Frontiers in Environmental Chemistry assessing how effective domestic water filters are at removing PFAS.

Drinking water treatment

The most effective approach for drinking water is to modernise water treatment works so they can remove PFAS, ensuring safe tap water for everyone regardless of socio-economic status.

This need is particularly pressing because conventional treatment processes often do not remove these substances effectively. However, targeted PFAS treatment can be expensive and can take time to roll out.

Although switching to bottled water may seem like an easy answer, it is not necessarily affordable for all households. Compared with mains water, bottled water also carries a substantial environmental footprint, notably from transporting bottles and disposing of the packaging.

Boiling water does not effectively destroy PFAS. In some cases, boiling can reduce PFAS concentrations very slightly, but it can also shift some volatile components into the air - meaning the issue is moved rather than resolved.

Residential treatment options

For treatment at home, the most cost-effective solution is typically a filter installed at the main kitchen tap (point-of-use or POU treatment). Treating all the water in the property is unnecessary and costs more. Bathing and showering are not major sources of PFAS exposure.

Residential options include:

1. Nanofiltration and reverse osmosis systems

If these systems are certified for PFAS removal, they are regarded as effective. Their real-world performance depends on water quality and on what other contaminants are present. Under-sink units cost more upfront and need the cartridge or membrane replaced periodically, typically once a year. Installation may require a plumber, and there must be sufficient space under the sink.

1. Pitcher-type filters

These are straightforward, relatively inexpensive and quick to start using. However, standard jug filters are often poor at removing PFAS, particularly newer short-chain compounds. Results also vary depending on water characteristics and the mix of contaminants.

Pitcher filtration performance

We independently tested several brands of pitcher filters to see how well they could remove PFAS, using tap water from two Canadian municipalities.

Our study provides the complete results online; the key findings are summarised below:

• Zerowater pitchers: Certified by the National Sanitation Foundation (NSF) to remove PFAS; in our tests they achieved over 96 per cent removal after 160 L of filtration for both water types.
• Clearly Filtered pitchers: Certified by the Water Quality Association (WQA) for PFAS elimination, with an elimination rate of over 96 per cent after 160 L of filtration in our tests.
• Aquagear pitchers: Despite being considered effective based on a test by an independent laboratory, our testing found a lower elimination rate of 60-77 per cent.
• Brita Elite filter jugs: These jugs are not designed or certified to remove PFAS. Our testing showed only 20-48 per cent elimination, and partial tests indicated poorer performance for the standard Brita filter.

The best residential approach for reducing PFAS in tap water depends on what the user values most. Jug filters are convenient, but their long-term cost can exceed that of adsorption or reverse osmosis systems fitted under the sink. To remove PFAS properly, it is crucial to select products that are certified for PFAS elimination.

Sebastien Sauve, Professor of environmental chemistry, University of Montreal; Benoit Barbeau, Professor, Polytechnique Montreal; and Termeh Teymoorian, PhD student in chemistry, University of Montreal

This article is republished from The Conversation under a Creative Commons licence. Read the original article.