We've updated our Privacy Policy to make it clearer how we use your personal data. We use cookies to provide you with a better experience. You can read our Cookie Policy here.


Testing London’s Water for PFAS

A glass being filled with tap water.
Credit: Andres Siimon/Unsplash
Listen with
Register for free to listen to this article
Thank you. Listen to this article using the player above.

Want to listen to this article for FREE?

Complete the form below to unlock access to ALL audio articles.

Read time: 4 minutes

British water is in need of some good publicity. The country’s water companies have been mired in controversy in recent years following reports of mismanagement, widespread leaking pipes, sewage-saturated seas and record fines. In a recent survey, only 34% of respondents trusted their local water company to prevent sewage from entering rivers and seas.  

So, the last thing these companies would want right now is a trending story about another dangerous contaminant in the country’s water systems. But such a headline may just be around the corner…

London trawling: looking for forever chemicals in the Thames

Per-and polyfluoroalkyl substances (PFAS) are a growing concern around the world. The group of surfactants were first mass produced in the mid-20th century to waterproof consumer products like pans, paints and packaging. They’re now known as “forever chemicals” because they have an almost-unbreakable highly-fluorinated alkyl chain backbone that makes them extremely chemically stable and difficult to degrade naturally.

This robustness has helped the chemicals reach as far the Arctic and the base camp of Mount Everest. So it’s no surprise they’re in British rivers, too.

What may be more shocking is the level of PFAS that might persist in the nation’s drinking water, particularly as a recent wave of research has linked the compounds to health concerns like cancer and low birth weights.

A recent report from the Royal Society of Chemistry found that more than a third of tested water courses in England and Wales contained medium- or high-risk levels of PFAS. The river Thames in London was one of the most polluted sites the team sampled; the capital’s waterway contained a combined PFAS concentration level of 4,931.1 nanograms per liter (ng/l) – nearly 50 times the Royal Society’s proposed limit (100 ng/l) of all forever chemicals in drinking water.

So, the pertinent question is: how many of these PFAS compounds are making their way through the river’s filtration network and into London’s drinking water?

To work that out, researchers would need to gather tap water samples from across the city, which is exactly what one team is about to do.

“We want to quantify how much PFAS is coming out of the taps in people’s homes,” said Dr. Alexandra Richardson, a researcher at Imperial College London’s School of Public Health. Richardson is heading up the university’s Investigating the Toxicological Assessment of PFAS (ITAPS) project, which is partly funded by the Royal Society of Chemistry.

“There are guidelines for what PFAS levels are suitable once it leaves the drinking water treatment plant, but there's a lot of piping between the treatment plants and our kitchen taps,” said Richardson. “In the US, that there are quite a few studies looking at what's coming out the taps in the various states in the USA, but nothing really in the UK. So that's what this project is about.”

To gather the required data, Richardson and her colleagues have already recruited 40 participants, and hope to enlist more from across the city after the Easter break.

“From an experimental and scientific standpoint, a scatter [of data] across London is what we’re trying to achieve – good representation from almost every from every London borough,” said Richardson. “Because we genuinely do not know if the PFAS concentrations vary across the city at all, or one region, or if a region with old infrastructure is better or worse affected than a newer build area. We genuinely don't know.”

More PFAS, more research

If the team do end up detecting high levels of PFAS in one particular area, they’ve vowed to notify all relevant participants.

“We want to give back to the community in some ways,” Richardson continues.
“We are planning on giving them the concentrations of PFAS in line with the current drinking water spectra guidelines, which I've hoped would be below the lowest tier. If a house does trigger a concern, then we will investigate that further. But it's a balance, as we don't want to fear monger.”

This balance between safety and excessive scrutiny is something that, according to Richardson, hasn’t always been struck when it comes to recent PFAS regulation, particularly in the US.

“I think the US has gone a bit overboard in some ways with it,” she said. “PFAS and PFOA [perfluorooctanoic acid] are nasty compounds. There are definitely indications there might be cancer risk caused by them. But asking labs to routinely test down to four PPT [parts per trillion], it's a very big ask, analytically.”

In 2022, the US Environmental Protection Agency (EPA) issued its interim PFOA and perfluorooctanesulfonic acid [PFOS] limit of 4 ng/l for single samples. In comparison, the European Union’s collective limit for 20 PFAS chemicals is 100 ng/l. While there are no firm limits for PFAS in England and Wales, there are “wholesomeness” guidelines to keep 47 individual PFAS compounds to 100 ng/l.  

While the Royal Society of Chemistry isn’t as ardent as the EPA, it has proposed more stringent PFAS limits for the UK (100 ng/l for all collective compounds) to bring the country’s regulations in line with the continent. In its report last year, the society also called on the UK government to enforce stricter limits on PFAS industrial discharge and ensure that many hundreds of sources of PFAS are captured and documented in a national lab for record-keeping.

In principle, Richardson agrees that more PFAS research can only be a good thing for public health policies.

“I hope that research along this route will continue,” she said. “It doesn't necessarily have to be the same model as the ITAP study. It’s like the early days of understanding the health effects of air pollution. We know these things are in the environment. We know they can cause effects. But we don't know the human dose at the moment. Because we don't know how much we ingest in food or tap water. Therefore, it's very hard to put a toxicology value on it and to determine effect. So, I definitely hope that PFAS research into human health exposures and human health effects will definitely continue because I do think it's something that is important.”

Richardson hopes the ITAP study will have produced its first round of results by the end of this year.

About the interviewee

Dr. Alexander Richardson is a research associate within the Epidemiology and Biostatistics (EBS) and Emerging Chemical Contaminants (ECC) groups at Imperial College London.

Dr. Alexander Richardson was speaking to Leo Bear-McGuinness, Science Writer for Technology Networks.