Victoria's chief veterinary officer Dr Charles Milne has downplayed concerns about the discovery of toxic chemicals in livestock near Esso's gas plant in Gippsland.

The Department of Agriculture confirmed 45 cattle and 45 sheep, from three properties in Longford, tested positive for elevated levels of polyfluoroalkyl substances (PFAS).

The chemicals were once used in firefighting foam across Australia, including at Esso's Longford gas plant.

There have been similar issues at the nearby East Sale RAAF base.

But Dr Milne said there was no cause for alarm.

"A number of food safety agencies around the world have examined this in detail, including [Food Standards Australia New Zealand] (FSANZ), and concluded the levels that we see in our livestock, the public health risk is negligible," Dr Milne said.

"There is no evidence to date that these levels that we see cause issues for cattle or sheep, or indeed for the human food chain.

"We've tested cattle and sheep on three premises — some 90 animals in all, 45 cattle and 45 sheep — and we've detected levels of PFAS in these animals.

"A few of them actually reached the trigger level set by Food Standards Australia New Zealand, but the majority fell below that level."

The chemicals were once used at Esso's Longford gas plant. ( ABC Gippsland: Kellie Lazzaro )

However, Dr Milne said even those levels were only a guide.

"Nowhere in the world has an authority set a maximum level for these contaminants for food safety. But, having said that, clearly we take this issue very seriously and we look at it from a very cautionary point of view," he said.

"This isn't just a Victorian issue, this is across Australia and indeed across the world."

The chemicals were once used in firefighting foam across Australia. ( Supplied: CRC CARE )

Esso has undertaken peer-reviewed blood serum analysis of livestock, its spokesman Travis Parnaby said.

"Based on the levels of PFAS measured in the livestock, it was found to be very unlikely that there is a risk of harm to a person from eating the livestock," Mr Parnaby said.

'I won't eat them,' farmer says

Victoria's Environment Protection Authority has advised people not to eat ducks, eel and carp from the Heart and Dowd Morass wetlands that have been contaminated by PFAS from the nearby RAAF base.

Ray Shingles farms at Longford, near the Esso plant, and said he has been put off eating his own cattle.

"I won't eat them," he said.

"In fact, I love carp and I won't eat the carp now out of the waterways up here because of the contamination."

He said, while his farm has not yet been tested for PFAS, it is likely to be there.

"Our aquifer up here comes through below Esso, from some of those farms that actually are contaminated, so you live in a situation where you don't know," he said.

"It doesn't do the industry much good as far as I'm concerned and the more we see stuff in the media, it alarms people to actually what is in their food."

Mr Shingles is concerned he may be falsely declaring livestock as free from chemical contamination. ( ABC Open contributor: vikkikay61, file )

Mr Shingles is concerned he and other farmers may be falsely declaring their livestock are free from chemical contamination.

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"We sign a vendor declaration and we have to answer 'yes' or 'no', it's quite clear," he said.

"It's law that when we are signing these documents and ticking those boxes and putting our signatures to them, we are responsible for the husbandry of our cattle."

'Farmers don't need to declare PFAS details'

Mr Shingles said the issue is stressful for farmers, who are already having to contend with drought.

"When these companies can get away with putting this into waterways, as primary producers, at the end of the day, it's got nothing to do with us, but we're the ones that are going to have to foot the cost for it," he said.

Asked if Esso would compensate farmers for contaminated cattle, Mr Parnaby said it was "working with neighbours on a one-to-one basis to provide support where necessary".

But Dr Milne said farmers were in the clear.

"Safe Meat and the integrity systems company who administer the NVDs have advised that farmers do not need to fill in details of PFAS on National Vendor Declarations," Dr Milne said.

But he can understand people's frustration with the issue.

"Yes absolutely, but let me reassure you, what has occurred in these animals is when they're tested, presuming they're below the trigger levels, they can enter the food chain, that's not a problem," he said.

"When the trigger level set by FSANZ are met then a risk assessment is undertaken, and the chief health officer makes a determination as to whether those animals are fit for human consumption or not."

Editor's note (26/6/18): This story has been updated to clarify the advice of Victoria's Environment Protection Authority.