Residents near the Richmond Air Base should reduce their intake of locally caught fish and locally grown eggs and red meat because of PFAS contamination, the Department of Defence has warned.

The Air Force started phasing out the use of the firefighting chemical in 2004 and is now undertaking a national review of its impact on the environment around bases.

In June, the Air Force announced a 10-square-kilometre plume of PFAS contamination had been found in the ground water below and around the Richmond Air Base, 50 kilometres north-west of Sydney's CBD.

Twenty-five surface water test sites were also found to have had PFAS contamination above safe drinking levels, including Rickabys Creek and Bakers Lagoon. It was also found at low levels in the Hawkesbury River.

At the time, the assistant secretary of PFAS Investigation and Management, Luke McLeod, said there was no need to advise anyone to not use or swim in the water, and no-one used the surface water for drinking.

The RAAF Richmond base, where a 10-square-kilometre plume of contamination was found. ( Supplied: Airforce )

However, the Human Health Risk Assessment released today says people living in the area should limit their intake of locally grown eggs and red meat, and locally caught fish to reduce their exposure to the chemical.

The report said people living in the investigation area around the air base should not eat more than 24 eggs per month, 50 serves of red meat per month or 12 servings of fin fish per month that have been grown or caught locally. That amount is smaller for children.

Joanna Pickford lives in Richmond and has been told not to eat her chicken's eggs.

"Each chook egg had a different level of PFAS in it. Some of them were above the level that you should eat and some of them were considered to be edible by adults," Ms Pickford said.

"I was really distressed, particularly because I'd been feeding them to my grandchildren — one of whom is under six.

"I just wish they would be honest and open with the public and say, look, we made a mistake and we're going to do something about it."

An ecological risk assessment also released today found unacceptable risks of contamination for animals and the environment on and around the base.

The report says there is moderate to high potential for exposure to PFAS for animals and birds on the Richmond base, while the risk is moderate at nearby Bakers Lagoon.

There is also some exposure risk for animals and birds in the Hawkesbury River, the assessment found.

According to NSW Health, PFAS does not break down in the environment and can accumulate and persist for a long time in humans and the environment.

An independent health panel told the Government earlier this year that while health effects could be ruled out, there was limited or no evidence to link exposure to PFAS chemicals with human disease.

They noted that scientific studies showed a "possible link" with an increase risk of testicular and kidney cancer.