One New South Wales community is taking on the government after cancer-causing chemicals were found in their local water supply.

A group of 450 people living in Williamtown's "Red Zone" - a collection of 650 properties within five kilometres of the local air force base - have launched a class action seeking compensation after claiming their homes have been rendered worthless by the contamination.

The suit was sparked by revelations in 2015 that the RAAF's 40-year use of a toxic fire-fighting foam had contaminated the area's water supply.

The foam included PFAS chemicals, which are suspected carcinogens.

The UN Persistent Organic Pollutants Review Committee to the Stockholm Convention has linked PFAS chemicals to six diseases, including cancer.

Residents were told to not use the bore water connected to their properties, and to avoid eating home-grown vegetables, eggs, dairy and livestock.

Gaylene Brown had breast cancer.

The "Red Zone" around Williamtown's RAAF base.

The RAAF provided bottled water for homes that needed it.

However, residents are living in fear with a spate of cancer cases in the area.

Along the 4km Cabbage Tree Road, at least 39 people have battled cancer in the past 15 years.

One resident, Gaylene Brown, considered herself fortunate that her breast cancer was caught early, and she originally did not link the disease to the water contamination.

However, in her street alone there have 10 known cases of breast cancer, eight of prostate cancer, five of bowel cancer, three of stomach cancer, three non-Hodgkin’s lymphomas, two leukemia diagnoses and two of live cancer, among others.

"There's not actually a lot of properties on this street," Ms Brown said.

Locals claim the only medical assistance being offered are blood tests which measure PFAS levels in their blood.

These tests have proved devastating for some families, with couples claiming their infant children are returning unusually high levels.

Samantha and Jamie Kelly said they had taken every precaution with their young son William.

"We had stopped eating chicken's eggs, we'd stopped eating all the vegetables, William had never set foot on the lawn outside our home," Mrs Kelly said.

Mark and Karen Grant's daughter Audrey was tested just minutes after she was born, and they say she had accrued a contamination level which was above the average for children in the two- to six-year-old group.

The RAAF used a toxic fire-fighting foam for 40 years.

At least 39 cases of cancer in the past 15 years have been found among residents of one street.

They said they had also followed the Environmental Protection Agency's guidelines during pregnancy.

However, they were told it would take decades living away from the exposure before Audrey's PFAS levels would recede.

Both families decided they had to move - but here they encountered new obstacles.

They have been unable to sell their homes, with property values plummeting after the water contamination was announced.

This has prompted the class-action suit, to allow residents to start a new life elsewhere.

"We want to be able to get people out of the area, people that are trapped, the young families that have children with high blood levels and who are trapped because their properties are worthless and they can't sell them," long-time resident Lindsay Clout said.

A recent independent review into the contamination has also found that the Department of Defence knew about the problem years before it told residents - potentially as early as 2003.

Residents around the military base in Oakey, Queensland, have launched a similar class action, and a similar contamination has surfaced around a RAAF base near Katherine in the Northern Territory.

Residents are launching a class-action suit for compensation.

Williamtown residents are angry with the government.

The federal government has issued a statement saying it is "working closely" with residents of Williamtown and Oakey to help respond to the "complex issue".

In June last year, the government announced a $55 million package to address the issue of PFAS contamination at a number of Defence bases.

"This package included a number of initiatives specifically for the communities of Williamtown and Oakey including an epidemiological study that is investigating the potential health effects of these chemicals, dedicated mental health and counselling services, appointment of Community Liaison Officers in both communities, a voluntary blood testing program for eligible residents and workers, and connection of properties to reticulated town water," the statement read.