But the study which has not been made public and only came to light on Wednesday has been slammed as truly meaningless and a complete farce by Labor, following revelations around 80 per cent of the population it sampled do not even live in the contaminated zone.

Some of the 12,500 people it sampled live as far away as Karuah, while sparsely populated Cabbage Tree Road is the most heavily polluted road in the red zone and consists of a smattering of acreages and hobby farms.

At least 18 of the 50 cancer cases uncovered by Newcastle Herald investigation last year were excluded because NSW Health only looked at cancer incidences between 2005 and 2014. It also failed to include people interviewed by the Herald who lived in the area and moved away.

Member for Paterson Meryl Swanson had grave concerns about the flaws in the study.

I also have grave concerns that the NSW Government would commission what seems to be an irresponsibly ad-hoc study, she said.

NSW Health itself has been quick to point out the very great limitations of this study.

It would be hasty, dismissive and potentially dangerous for anyone to conclude from these findings that there is no evidence of a cancer cluster in Williamtown.

She argued the extraodinary situation on Cabbage Tree Road deserved careful and detailed analysis.

I am led to believe this will be part of the ANUs epidemiological study and I am mystified that NSW would go it alone when the Turnbull Government has an expert health panel and an epidemeological study already underway.

President of the Williamtown and Surrounds Residents Action Group Cain Gorfine ridiculed the study as an embarassment.

This analysis is so severely flawed from a scientific and medical point of view the conclusions drawn [are] completely useless, he said.

The timing of NSW Healths announcement has also raised eyebrows.

Labor MPs were suprised to learn of the study in a one-line statement tabled in State Parliament this week.

The statement came in reply to a question put by Shadow Health Minister Walt Secord late last year. Mr Secord had raised concerns about the parallels between the situation on Cabbage Tree Road and a cancer cluster at Fiskville in Victoria, linked to the same chemicals.

In his response, Minister for Regional Water Niall Blair said NSW Health was currently reviewing statistical analyses of cancer data in the Williamtown area, with the assistance of the NSW Chief Health Officer's Environmental Health Expert Advisory Panel.

On Wednesday morning, Labor MPs grilled bureaucrats about the study at a meeting of the Williamtown Elected Representatives Reference Group. The meeting was told the study was still underway and the results would be released next week.

But late on Wednesday evening a few hours after inquries were made by the Herald NSW Health released a statement saying the study had found no evidence of a cancer cluster.

"NSW Health has considered data on reported cancer rates by census-defined regions between 2005-2014, a spokesperson said.

This is a standard practice when suspicions of a cancer cluster are first raised by members of the public.

This is a useful initial analysis and we note a further study has been planned by the federal government on the health impacts of PFAS.

However it is unclear whether the federal study will look specifically at Cabbage Tree Road, which intersects with a network of open drains carrying contaminated run-off from the Williamtown RAAF base.

Historically, when the alarm has been raised about potential cancer clusters elsewhere, much smaller sample groups have been examined.

Studies which confirmed cancer clusters at Kooragang Island, the Fiskville fire training ground in Victoria and at the ABC studios in Brisbane all looked at groups of between 550 and 850 people.

People have lost heart and theyve lost faith, said Cabbage Tree Road resident Jenny Robinson, diagnosed with breast cancer in 2016.

People are getting around here with face masks on when they mow their lawns they can do all the studies they like, it doesn't make me trust the studies any more.

Member for Port Stephens, Kate Washington, descibed the study as truly meaningless and a complete farce.

The NSW Health spokesperson said it was highly unlikely for exposure to a specific chemical to be responsible for a variety of different types of cancer.

However the studies which confirmed clusters at Fiskville and Kooragang Island both found a variety of cancers among victims. Member for Paterson Meryl Swanson blasted that argument as ludicrous.

Overseas research into the PFAS family of chemicals indicates that it impacts the immune system and, as such, can manifest in a myriad of forms, she said.