Cancer-Causing Chemicals have been detected in a Blue Mountains Dam, causing it to be shutdown and investigation launched.

A water supply dam in the Blue Mountains has been shut down following the discovery of concerning levels of cancer-causing chemicals known as PFAS (per- and polyfluoroalkyl substances). The dam, Medlow Dam, is one of five that supply water to the Cascade water filtration plant in Katoomba, which provides drinking water to more than 41,000 people in the Blue Mountains.

WaterNSW, which manages Greater Sydney’s water catchment, announced the closure in a statement today. “WaterNSW, as Greater Sydney’s catchment manager, is conducting additional, targeted PFAS-related investigations to ensure Sydney Water and NSW Health have up-to-date information on the presence of PFAS in the catchment, so any risks continue to be managed appropriately,” the statement read. It said water is still safe to drink.

Preliminary results published on the WaterNSW website today revealed that Medlow Dam is returning elevated PFAS levels. This means they are higher than the Australian safe levels which are well above US safe guidelines for the cancer causing chemical.

“The WaterNSW investigation, involving specialist water quality scientists, seeks to identify any new localised PFAS contamination sources,” the statement said. “Preliminary results, published on the WaterNSW website, indicate Medlow Dam is the only part of the Blue Mountains dam network returning elevated results,” it said.

Medlow Dam does not supply raw water directly to the public it provides water to the Cascade water filtration plant, which does. WaterNSW said the dam has been disconnected from the supply as a precautionary measure while further investigations are conducted.

WaterNSW said they are investigating the issue, focusing on the Blue Mountains area in the upper reaches of the Greater Sydney catchment, where Sydney Water testing detected PFAS at levels below the Australian Drinking Water Guidelines in the Cascade water filtration plant supply. Despite these findings, Sydney Water said in the statement that the water supplied from the Cascade water filtration plant to local communities is safe to consume and meets the Australian Drinking Water Guidelines.

Australia’s National Health and Medical Research Council is reviewing its guidelines for PFAS following recent conclusions from U.S. authorities and the World Health Organisation that PFAS causes cancer and that no safe level exists. In Australia, the maximum allowable level of PFOA in tap water is 140 times higher than the U.S. limit.

WaterNSW said it is working with NSW Health and Sydney Water to ensure the safety of drinking water and plans to keep the community informed as the investigation progresses. The investigation involves specialist water quality scientists and aims to identify any new localised sources of PFAS contamination.

These developments follow a June investigation by the Sydney Morning Herald, which revealed the presence of carcinogenic chemicals - specifically perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), both part of the PFAS group - in drinking water across parts of Sydney, Newcastle, Canberra, Victoria, Queensland, Rottnest Island, and Norfolk Island. The SMH analysis found dangerous chemicals in the drinking water of up to 1.8 million Australians, including in North Richmond, where testing in the past year revealed some of the highest levels of PFOA contamination in Australia, well above U.S. limits.

In a separate investigation conducted in June, Friends of the Earth, Australia, found that PFAS levels in biosolids (wastewater treatment plant products) were also above safety guidelines. The highest level of PFAS in biosolid sampling sites was recorded at Richmond, with Vineyards also listed in the top 10.

Western Sydney University Associate Professor Ian Wright, a water expert, has warned that the U.S. Environmental Protection Agency has stated there is no safe level for PFOS/PFAS chemicals in drinking water. He explained that these chemicals, resistant to degradation, have been widely used in products like firefighting foams, paints, cosmetics, and non-stick cookware. PFAS contamination in Richmond and Windsor has been linked to the use of firefighting foam at the Richmond RAAF base.

“Humans can readily accumulate PFOS and PFAS chemicals in some of our organs. There is growing evidence that elevated concentrations of these chemicals can be harmful to human health. According to the World Health Organisation, they may be carcinogenic to humans,” he said.