Katherine residents are being warned not to eat local seafood and other home-grown produce after an interim report into PFAS contamination identified them as potential health risks.

The Department of Defence released details of an interim human health risk assessment for the Northern Territory town on Monday outlining potential exposure pathways to the community.

Most of the town is in the investigation area.

The chemicals, an ingredient in firefighting foam once used at the nearby Tindal RAAF Base, have seeped into Katherine's bores used for drinking water and irrigation.

The interim report said initial findings indicated a number of activities could pose a risk to residents:

Drinking contaminated bore water or water from the Katherine river downstream of the Stuart Highway

Drinking contaminated bore water or water from the Katherine river downstream of the Stuart Highway Eating eggs from poultry that have been watered with contaminated bore water

Eating eggs from poultry that have been watered with contaminated bore water Young children eating large amounts of fruit and vegetables in the dry season that have been irrigated with contaminated bore water

Young children eating large amounts of fruit and vegetables in the dry season that have been irrigated with contaminated bore water Eating seafood from Tindal Creek and Katherine river, including as far south as the Daly river

Eating seafood from Tindal Creek and Katherine river, including as far south as the Daly river Swimming in pools with bore water above recreational values

"We did find that in the fish samples that we've taken they have triggered what they call the trigger values in the food standard Australia and New Zealand thresholds," Steven Grzeskowrak from Defence said.

"That means it's appropriate to start looking at limiting intake of, in this case, fish from Katherine river."

Many people catch black bream and cherabin from the Katherine River and surrounding waterways. ( Supplied: Chaoshu Zeng )

The trigger value for PFOS in fish flesh is 5.2 micrograms a kilogram and is based on a child between two and six years old eating 500 grams of fish a week.

Compared to the trigger value, barramundi that were tested returned between 12 and 42 micrograms, up to six times the safe level.

Cod and catfish contained between 6.2 and 88 micrograms, up to 17 times the value.

Other fish had the broadest range, between 9.5 and 350, a maximum of 70 times the trigger value. When asked what fish were included in the last group, a Defence representative said it was varied but could not provide detail on which particular fish had the highest concentration.

Mr Grzeskowrak said in terms of vegetables, the concentration of PFAS was higher in leafy greens.

"The uptake into fruits has been very low or nil in many cases," he said.

"The uptake into leafy green vegetables tends to be higher."

Map Defence Force toxic chemical contamination sites

The Department also noted the testing was done during the dry season, when bore water use is at its peak, so it could give results that were "worst case scenario".

It also recommended that people avoid or minimise their contact with the activities or, in the case with fruit, vegetables and seafood, combine it with goods from a non-contaminated source.

But the Department said their testing of incidental exposure from digging in soil or coming into contact with dust contaminated with PFAS was not considered an exposure pathway.

Similar advice was given to Darwin residents in 2016 when the chemicals were found in shellfish in Ludmilla and Rapid Creek, but were later found to be safe for consumption.

Warning signs similar to those at Rapid Creek will be put up along the Katherine River. ( ABC News: Xavier La Canna )

Defence also said the report informed a recent decision to offer a $5.7 million support package to Katherine residents, which included voluntary blood testing, funding for counselling services, and an epidemiological study.

Local and State Government representatives lobbied to have the services available in the town for months, including the Chief Minister writing to the Prime Minister asking for blood tests.

The Department did not detail for how many years residents may have been consuming the toxic chemicals, which have been linked to a number of conditions in animal studies including some types of cancer and low birthweight.

The United States Environmental Protection Agency has said there may be a correlation between PFAS consumption and adverse health effects in humans, but Australian authorities maintain there is currently no consistent evidence that exposure to PFOS and PFOA causes adverse health effects.

Loading...