PFAS above drinking water guidelines in global source water

We’re likely underestimating the future impact of PFAS on the environment, a new UNSW Sydney-led study shows.

Per- and poly-fluoroalkyl substances—commonly known as PFAS—are a group of over 14,000 human-made chemicals that have been popular since the 1950s for their diverse abilities to resist heat, water, grease, and stains.

They’ve been commonly found in household products like non-stick frypans, clothing, cosmetics, insecticides, food packaging, and specialty industry products like firefighting foam.

But despite their broad skillset, these chemicals have a dark side. They’re known as ‘forever chemicals’ because once they’re in the environment—or our bodies—they don’t degrade further.

PFAS have been linked to environmental and health issues, including some cancers, but a lot remains unknown about the true scale and potential impacts of the problem – including how much is in our water supply.

A new UNSW-led international study, published today in Nature Geoscience, assessed the levels of PFAS contamination in surface and groundwater worldwide.

Global source water has too much PFAS

It found that much of our global source water exceeds PFAS-safe drinking limits.

“Many of our source waters are above regulatory limits,” says senior author of the study, UNSW Engineering Professor Denis O’Carroll.

“We already knew that PFAS is pervasive in the environment. However, I was surprised to find out that a large fraction of source waters are above drinking water advisory recommendations,” he says. “We’re talking above five per cent, and it goes over 50 per cent in some cases.”

The research team gathered PFAS measurements from sources around the world, including government reports, databases, and peer-reviewed literature. They collated more than 45,000 data points spanning roughly 20 years.

It’s the first study to quantify the environmental burden of PFAS on a global scale.

The study also found high concentrations of PFAS in Australia, with many locations above recommended drinking water levels. This tended to be in areas where firefighting foams had been used in the past, like military institutions and fire training facilities.

Prof. O’Carroll stresses that these traces are found in source water, such as dams, and not drinking water itself – drinking water goes through treatment plants, some of which are designed to reduce the amount of chemicals such as PFAS in our water before it comes out of the tap.

But Prof. O’Carroll says some water providers—for example, Sydney Water—don’t routinely measure the broad range of PFAS potentially in our drinking water.

“Drinking water is largely safe, and I don’t hesitate to drink it,” he says. “I also don’t suggest that bottled water is better because it doesn’t mean that they’ve done anything differently than what comes out of the tap.

“But I certainly think monitoring PFAS levels and making the data easily available is worthwhile.”

A contentious debate: how much is too much?

Most people in Australia – and many places worldwide – are likely to have low levels of PFAS in their bodies.

However, the potential health risks of PFAS chemicals are poorly understood and haven’t been agreed on universally.

According to an Australian Government expert health panel, there is limited to no evidence that PFAS poses clinically significant harm to human health – although further afield, peak bodies in the US and Europe suggest that PFAS is linked to adverse health outcomes, such as lower birth weight in babies, higher levels of cholesterol, reduced kidney function, thyroid disease, altered sex hormone levels, reduced vaccine response, and liver, kidney, and testicular cancers.

In 2023, the World Health Organisation (WHO) declared PFOA, a type of PFAS, a category one human carcinogen.

While PFAS has been linked to many of these health outcomes, they haven’t necessarily been shown to cause them. Given the potential risks and ‘forever’ nature of these chemicals, many regulatory bodies have tightened PFAS use and introduced safe drinking water limits as a precaution.

“Two forms of PFAS initially raised concerns about 20 years ago: PFOS and PFOA,” says Prof. O’Carroll.

“These chemicals are regulated to different extents around the world. In the US, the proposed drinking water limits for PFOS and PFOA are four nanograms per litre.”

A third form of these forever chemicals, PFHxS, is also regulated in Australia. Here, the sum of PFOS and PFHxS is limited to 70 nanograms per litre—well above the four nanograms per litre combined PFOS and PFOA limit in the US.

However, our acceptable levels for PFOA in drinking water are even higher.

“PFOA, on the other hand, is regulated in Australia at 560 nanograms per litre, which is two orders of magnitude higher than in the US,” says Prof. O’Carroll.

While Australia’s limits seem relaxed compared to the US, both countries’ recommended drinking water guidelines pale when compared to Canada’s: rather than limiting only two or three forms of PFAS in drinking water, Canada counts the sum of all 14,000 PFAS and limits the overall number to 30 nanograms per litre.

The study found that 69 per cent of global groundwater samples with no known contamination source exceeded Health Canada’s safe drinking water criteria. In comparison, 32 per cent of the same samples exceeded the US’s proposed drinking water hazard index.

“There’s debate about what level PFAS should be regulated to,” says Prof. O’Carroll. “Australia has much higher limits than the US, but the question is why.

“Both health bodies would have different reasoning for that, and there’s no strong consensus here.”

An underestimated risk

The study suggests that actual PFAS pollution in global water resources could be higher than suspected.

This is, in part, because we only monitor and regulate a limited number of the 14,000 PFAS in existence and because the levels in consumer products are higher than expected.

“There’s a real unknown amount of PFAS that we’re not measuring in the environment,” says Prof. O’Carroll. “Commercial products like garments and food packaging have much more than we realise.

“This means we’re likely underestimating the environmental burden posed by PFAS.”

Prof. O’Carroll and his team are now trying to develop their research by quantifying these levels of PFAS from commercial products in the environment.

They’re also developing technologies to degrade PFAS in drinking water systems and developing predictive models that determine where forever chemicals will go in the environment.

“Part of this is figuring out how PFAS will associate with different parts of the environment and our bodies – proteins, for example,” says Prof. O’Carroll.

These studies will progress over the next two years and aim to be completed by 2026.

In the meantime, Prof. O’Carroll says manufacturers and consumers alike need to be careful and do their due diligence when using products containing PFAS.

“We manufacture and distribute many chemicals without having fully assessed their potential health impacts,” he says.

“We should have judicious use of some of these chemicals. Just because they’re available doesn’t mean we should use them.”