Medlow Dam: Blue Mountains waterway shut down after cancer-linked ‘forever chemicals’ found in Sydney’s water supply

A dam has been shut down after being identified as the source of so-called ‘forever chemicals’ which have contaminated the water supply of 41,000 residents.

WaterNSW on Wednesday revealed the presence of the per- and polyfluoroalkyl substances (PFAS) in the Blue Mountains water supply came from Medlow Dam at Medlow Bath, west of Sydney. 

In 2023, the World Health Organization declared perfluorooctanoic acid (PFOA), which is one of the roughly 14,000 known variants of PFAS, is a class one human carcinogen.

PFOA was one of the forever chemicals detected in Medlow Dam.

‘This dam does not supply raw water directly, but as a precautionary measure has been disconnected from supply while further investigations are conducted,’ a WaterNSW statement read. 

Water from Medlow Dam joins water from other sources in supplying the Cascade water filtration plant.

A WaterNSW spokesperson told the Sydney Morning Herald that the water supplied from the Cascade plant to local communities is safe to consume and meets Australian drinking water guidelines.

But the amount of PFAS allowed in drinking water are the subject of new limits in the US, where the laws are far more restrictive than Australia’s. 

Earlier this month, a senior policy advisor for the International Pollutants Elimination Network claimed that Australia is falling behind other countries rgearding drinking water safety. 

A dam in the Blue Mountains west of Sydney has been shut after it was identified as the source of so-called ‘forever chemicals’ which have contaminated the water supply of 41,000 people in the area. Stock image

‘Australia cannot continue to use drinking water guidelines that are an international embarrassment,’ Dr Mariann Lloyd-Smith told ABC’s Radio National.

‘Australian standards … are out of date, out of touch and totally are not usable for protecting human health. We really do need to move on these chemicals quickly. 

‘And particularly when it’s in drinking water, something that everybody has to consume. It just is totally unacceptable.’

WaterNSW has been working for months to find the source of elevated PFAS levels in the Cascade filtration plant, which provides drinking water to the millions of people who visit the world heritage area every year, as well as Blue Mountains locals. 

The levels found in the plant were about 300 times higher than that of Warragamba Dam- Sydney’s main drinking water source.

The sampling results released on Wednesday showed the contaminants’ source is probably high levels of PFAS in Medlow Dam, which exceeded  national safety standards.

WaterNSW said all dams will be monitored and that preliminary sampling indicated Medlow Dam is the only one in its network with elevated readings.

‘WaterNSW will keep the community informed as the investigation progresses and work closely with NSW Health and Sydney Water to ensure drinking water remains safe,’ the statement added.

In Australia, PFAS chemicals have been used widely in firefighting foam in Defence Force bases due to their resistance to heat and flames.

Dveloped in the 1940s and 1950s, the chemicals are also known for their resistance to water and stains and are used in products such as rain coats and non-stick frying pans.

Dr Nick Chartres, of the University of Sydney’s medicine and health faculty, said they are ‘the most mobile, persistent and toxic chemicals in the world’.

‘We know that they can get into the Arctic ice caps, they can get into the ice in Antarctica, they get into the deep-sea floor soil sediment. They basically travel everywhere,’ he said.

PFAS’ in drinking water led to the new, stricter regulations in the US.

Most Australians are likely to already have very low levels of PFAS in their bodies from using sunscreen and cosmetics.

But prolonged exposure, which could happen through drinking contaminated water over a long period, can lead to immune and heart problems, and can also affect fetal and infant growth.

Dr Chartres said the US Environmental Protection Agency found ‘based on the best available evidence that we have … there is actually no safe level (of exposure to PFAS)’.

‘So if you get exposed across a lifetime, at any level, your risk of these diseases starts going up incrementally based on the level of exposure.’

He said that the US law change should be a wake-up call for Australia.

‘We now have to look to that and say, how do our standards (compare)? … And if there’s any type of divergence with the Australian (laws), why is there a divergence?’

On Wednesday WaterNSW revealed the presence of the per- and polyfluoroalkyl substances (PFAS) in the Blue Mountains water supply came from Medlow Dam (pictured) in Medlow Bath, 108km from Sydney

On Wednesday WaterNSW revealed the presence of the per- and polyfluoroalkyl substances (PFAS) in the Blue Mountains water supply came from Medlow Dam (pictured) in Medlow Bath, 108km from Sydney

In the US, the maximum level allowed for PFOA and another variant, perfluorooctane sulfonate (PFOS), in drinking water is four parts per trillion.

But in Australia, PFOS and perfluorohexanesulfonic acid (PFHxS) – yet another PFAS variant – are allowed up to a level of 70 parts per trillion.

PFOS and PFHxS were both also found in Medlow Dam. 

Dr Lloyd-Smith cautioned against buying bottled water to use instead of tap water, though.

‘We’ve found PFAS in bottled water too, so that’s not the solution,’ she said.

Filtration systems can lower PFAS levels in drinking water, but they are expensive and unaffordable for many people.

Dr Lloyd-Smith cautioned against buying bottled water to use instead of tap water, though. Stock image

Dr Lloyd-Smith cautioned against buying bottled water to use instead of tap water, though. Stock image

Dr Lloyd-Smith said people should try to reduce their exposure to PFAS beyond its presence in drinking water.

She advised people to check labels and read the ingredients in the make-up products they use.

People should also research how their clothes, food and food packaging are made, and what chemicals they could contain.

‘Australia must … assess (PFAS) as a class and aim to restrict and eliminate all uses of PFAS,’ Dr Lloyd-Smith said.

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