The New South Wales Water Board temporarily closed a dam in the Blue Mountains after tests found high levels of PFAS chemicals in untreated water.
The state's water department said it had disconnected Medlow Dam from the local water supply as a precaution while further investigations were conducted.
Medlow Dam does not directly supply raw water – the water is pumped through other dams in the network to the Cascade Water Treatment Plant, which supplies treated drinking water to the Blue Mountains region.
Sydney Water has confirmed that the water supplied to the community from Cascades Power Station is safe to drink and meets Australian drinking water guidelines.
The NSW Water Board said in a statement it was conducting focused research in the Blue Mountains region, upstream from the Sydney metropolitan area, to ensure other agencies had up-to-date information on the presence of PFAS.
PFAS (per- and polyfluoroalkyl compounds) are sometimes called “forever chemicals” because they are difficult to destroy.
There are about 12,000 PFAS, but only two main types, PFOA and PFOS, have strong evidence of adverse health effects, including links to cancer.
The International Agency for Research on Cancer classifies PFOS as a possible carcinogen, but notes there is “insufficient” evidence that it directly causes cancer.
Anne Expert Health Commission Report A report on PFAS submitted to the Australian government stated that “Currently, there is no evidence to suggest an overall increased cancer risk from these chemicals.” Research on PFHxS is ongoing, and the evidence on their health effects is not as comprehensive as that for PFOA and PFOS.
Tests of Medrowdam's untreated water found the combined concentration of PFOS and PFHxS was 0.09 micrograms per litre.
This is slightly above the level set for treated water in Australian drinking water guidelines (0.07 micrograms per litre). Once the Medrowdam water is treated at the Cascade plant, the levels of PFOS and PFHxS in the drinking water will remain within safe standards, Water NSW said.
“Preliminary results published on the NSW Water website show that Medlow Dam is the only dam in the Blue Mountains dam network to have a high reading,” the department said in a statement.
“The dam does not directly supply raw water but as a precautionary measure the supply has been stopped whilst further investigations are carried out.”
After leaving Medrow Dam, the water passes through Greaves Dam, the Upper, Middle and Lower Cascade Dams before reaching the Cascade Filtration Works.
Testing found that the concentrations of PFAS in the raw water reaching the filtration facility were within Australian drinking water guidelines.
Professor Stuart Khan, a water expert and dean of the school of civil engineering at the University of Sydney, said generally speaking, if contaminants were found in water, it was appropriate for authorities to identify the source and carry out remediation where necessary.
“But at the moment… the message that Sydney Water is trying to get across is that exposure [to PFAS] “It's at a safe level and there's no need to worry,” he said.
Mr Khan said he did not believe there was a need to close Medlow Dam and that at some stage the dam's water supply would need to be re-introduced.
“It sends a message that there is a problem when in fact it is not as serious as it is being portrayed in the media,” he said.
Khan said he was concerned that some media reports were “doing significant damage to public confidence in the water supply,” creating “fear where there shouldn't be and there is a risk that water supplies will be cut off.” [regulators] It's a case of getting your priorities wrong.”
