Firefighters and air-traffic controllers are being tested after high levels of toxic PFAS chemicals were found in drinking water at a major Victorian airport.

The contamination has forced the closure of the fire station at Avalon Airport, which takes domestic and international flights.

United Firefighters Union aviation branch secretary Wes Garrett says about 30 firefighters are anxiously awaiting blood test results after PFAS was detected at levels well beyond safe drinking limits.

The air-traffic control tower is also affected, but not the terminal itself.

Man-made PFAS chemicals are often referred to as forever chemicals because they are very slow to break down and accumulate in human bodies.

They have been associated with a range of serious health issues.

Some of the worst types were used in fire fighting foams.

They were banned in Australia more than a decade ago, but by that time had already created serious contamination issues at sites where the foam was used.

“The drinking water standard currently sits at 70,000 parts per trillion,” Mr Garrett told AAP.

“We know that the air traffic control tower was receiving 5.1 million parts per trillion, and we know the fire station was receiving at 3 million and 80 thousand parts per trillion.”

He said Airservices Australia is responsible for the safety of firefighters who work at Avalon, but allowed them to continue showing up for a week after the contamination was detected 10 days ago.

The station has since been shut down.

Airservices Australia says it has “temporarily ceased” providing its Aviation Rescue and Fire Fighting Service at the airport to support affected staff at the leased site.

“The source of the PFAS is unknown at this stage. Airservices has never used fire fighting foam containing PFAS at Avalon,” it said on Monday.

Civil Aviation Safety Authority and customers have been advised of the closure.

“Fire Rescue Victoria will service the airport during the temporary closure. Airport users will make their own determination on operating at the airport,” Airservices Australia said.

The fire station is being connected to a new water supply and the site will undergo deep cleaning.

Airservices said its highest priority was the wellbeing of its 30 aviation rescue fire fighters and two air traffic controllers.

“[They] have been offered expert health advice and free blood testing.”

Airservices has advised other stakeholders including Victoria’s Environment Protection Authority, and Barwon Water, which provides water to the airport precinct.