How did cancer-causing ‘forever chemicals’ contaminate Brisbane water?

It remains unclear exactly how a cancer-causing chemical contaminated one of the city’s biggest drinking water treatment plants – but Seqwater thinks it has a pretty good idea.

Brisbane Times revealed last month known carcinogen PFOA had been identified in tests at Mount Crosby over four years at levels above US legal limits, but below the level permitted in Australia.

Seqwater says it believes the chemical may have leached from industrial or agricultural facilities bordering the Brisbane water catchment, potentially through runoff after heavy rain.

Seqwater Mount Crosby EastBank, one of several sites where PFAS chemicals were detected. The highest levels were detected at the nearby Mount Crosby WestBank.

“[The basin] spans more than 13,000 square kilometres and includes residential and industrial areas and agricultural activities which include intensive irrigation and grazing,” a spokesperson for Seqwater told Brisbane Times this week.

“PFOA has been widely used in industrial activities and as a contaminant in feedstock ... as a result runoff can enter the waterways.

“Through its wide use in domestic, industrial and agricultural products, PFAS is widely present throughout our environment and water catchment and weather conditions can impact the presence of PFAS.”

Perfluorooctanoic acid – or PFOA for short – is among the family of PFAS chemicals mass produced by US conglomerate 3M, beginning in the late 1940s. They are prized for their water-resistant and heatproof properties.

PFOA also causes cancer. In 2023, the World Health Organisation’s International Agency for Research on Cancer designated it a known carcinogen.

Documents obtained by this masthead through a Right to Information application reveal the chemical has been identified at multiple treatment centres at seven times the level considered safe by the US Environmental Protection Agency, but within the range currently considered acceptable in Australia.

PFOA was recorded at 36 parts per trillion in Mount Crosby Westbank raw water in 2023, and at only slightly lower levels after treatment. The plant is part of a complex, about 25 kilometres west of the CBD, that produces the majority of Brisbane’s drinking water.

It has also been recorded above the US limit of four parts per trillion – usually significantly so – in the Lowood treatment plant, Camerons Hill, Mount Crosby Eastbank, Lockyer Catchment and Tingalpa Creek Channel since testing began in 2018.

“It’s very alarming and really big news,” Western Sydney University water scientist Ian Wright told Brisbane Times when shown the documents.

“I haven’t seen anything quite like this … it’s hot data.”

The documents suggest water testing at Mount Crosby followed detection of PFAS chemicals in nearby soil, supporting the theory it may have leached in through runoff after heavy rain.

“Increase of PFAS detection at these assets could be related to climatic differences over the years, such as the period of extended wet weather in 2023 and 2024,” an internal memo said.

Seqwater confirmed it is increasing the frequency of its PFAS testing to twice a year, with the next round to begin in January, 2025.

“Seqwater is always exploring emerging and innovative water quality treatments and options,” a spokesperson said.

“Increasing our testing and monitoring regime will help inform our risk profile and what treatment technologies should be explored.”

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