Authorities have stressed that drinking water in Sydney is safe after levels of PFAS, commonly dubbed 'forever chemicals', were detected across several catchments.
The data, tested by Sydney Water and published on its website, showed low levels across water filtration plants in June, including Warragamba, North Richmond and the Cascade Dam in the Blue Mountains, which had the highest levels.
These PFAS levels fall within Australia's safe drinking water guidelines, but are four to five times higher than those in the United States, according to Dr Nicholas Chartres, a senior research fellow at the University of Sydney's Medicine and Health faculty.
Chartres has worked with the US's Environmental Protection Agency (EPA) on its chemical policy.
"Their evaluation has been extraordinarily rigorous," he said.
But he stressed the issue goes far beyond the types of PFAS that were recently detected in Sydney's water supplies.
"We're talking about two of around 15,000 chemicals that are out there being used," he said.
"There's a lot we don't know about them."
What do we know about PFAS chemicals?
PFAS (per and polyfluoroalkyl substances) are generally described as a group of thousands of synthetic, human-made chemicals.
They have been used widely for industrial and consumer purposes due to being heat, stain, grease and water-resistant.
"Common consumer products include stain and water protection for carpets and upholstery, paper coating, cosmetics and sunscreen," Sydney Water says on its website. "Some PFAS have also been used in fire-fighting foams."
In recent decades, they're also used in things like pesticides and food packaging, Chartres said.
"They're really used broadly for a series of different consumer products. We're exposed in lots of different ways to them."
PFAS are a group of chemicals that can be added to household products to make them heat, stain, grease or water resistant. Source: SBS News
What do we know about possible health effects?
PFAS are often dubbed 'forever chemicals' due to their half-life.
"They take several decades to break down - they can be in the environment for hundreds of years. Not only are they persistent, they are also bioaccumulate and they're toxic," Chartres said.
"It's only been the last 15 or 20 years that we've been able to conduct studies to see what they do to us - and now we're catching up with the science and we're starting to see there's myriad health effects."
According to the Australian government, many scientific studies have investigated potential health effects from PFAS exposure - but the results have been "mixed".
Increased exposure to these chemicals has been associated with adverse health effects, including higher cholesterol, lower birth weights and kidney and testicular cancer, according to the Agency for Toxic Substances and Disease Registry based in Atlanta, Georgia.
The EPA states the latest science shows there is "no level of exposure to these contaminants without risk of health impacts, including certain cancers".
The Australian government's expert health panel - set up in late 2017 - acknowledged reviews and scientific research to date have provided "fairly consistent reports of an association with several health effects". But it said these are generally small associations within normal population ranges.
"There is also limited to no evidence of human disease or other clinically significant harm resulting from PFAS exposure at this time."
Where have PFAS chemicals recently been detected?
Sydney Water undertook sampling of treated water from nine water filtration plants in June this year. This followed the Sydney Morning Herald reporting evidence of past contamination of Sydney's tap water.
Repeat samples were taken from one site, the Cascade Water Filtration Plant at Katoomba and Blackheath, the following month due to results being higher than other sites.
At Blackheath, in the Blue Mountains, detection showed perfluorooctane sulfonate (PFOS) at 0.0155 ug/L (micrograms per litre) or 15.5 ppt (parts per trillion). Levels of another PFAS type, PFHxS, were 0.0136 ug/L 13.6 ppt.
There were low levels of PFOS and PFHxS found at North Richmond and Orchard Hills, while Warragamba and Prospect had low levels of PFHxS.
Source: SBS News
In contrast, the US's recently reviewed enforceable limits are now 4 ppt each for PFOS and PFOA, which is another PFAS type.
"They [the US] have said there is no safe level for these chemicals," Chartres said.
In a statement, Sydney Water said it is required to meet the Australian guidelines "and all samples are well below these guidelines".
"Monitoring of drinking water uses a risk-based approach, and Sydney Water regularly tests for PFAS, including monthly monitoring, in potentially impacted areas.
"There is regular consultation between Sydney Water, WaterNSW and NSW Health to assess any potential risk of PFAS or any other contaminant to Sydney’s drinking supply."
Locations across Sydney where water testing was recently conducted. Source: SBS News
"Sydney Water and other utilities regularly monitor for various parameters in drinking water to ensure it's safe and to identify risks - and that's what has happened here," he said on Tuesday.
"The levels in Sydney water are in the safe [Australian] guidelines."
A spokesperson for the federal Department of Health and Aged Care said drinking water monitoring, including PFAS, is the responsibility of state and territory health departments, regulators and local health authorities.
At a Commonwealth level, the National Health and Medical Research Council (NHMRC) is currently reviewing its 2018 "health-based guideline values for PFAS" in the drinking water guidelines.
"The process for developing these NHMRC guidelines has a number of stages to ensure high quality, trusted guidelines," they said. "NHMRC has expedited their review process, with public consultation expected to commence in October 2024."
What don't we know?
Beyond the recent findings, Chartres' biggest concern is the "ubiquitous nature" of the PFAS family.
"There's 15,000 variants and they're everywhere," he said.
"We have minimal data on whether these other PFAS variants are harmful to us or not, but we're all being exposed to them."
Professor Denis O'Carroll from the University of New South Wales' Water Research Laboratory agreed, saying this is an active area of research.
"In Australia there are only three PFAS that are regulated in drinking water, but there's over 14,000 PFAS, we really don't know where those other PFAS are, if they're acceptable in our waters, in the environment," he said.
"We're trying to figure out all of that."
Chartres said while the focus is now on water, the public needs to be armed with knowledge about the products they're buying, and whether they might be exposed to PFAS.
"But with that being said, that's not how we should as the public be expected to take care of our health."
With additional reporting from Hannah Kwon.
