Contamination from banned chemicals in firefighting foam at levels above safe drinking water guidelines has been found in streams around Palmerston North airport.
Seven surface water samples have all tested above the guidelines for the banned chemical PFOS.
People are being advised to not gather eels or watercress at Mangaone Stream, Richardsons Line Drain or streams near the airport flowing through the Madison Avenue and Jefferson Crescent area, Clearview Park and McGregor Street.
Streams around Palmerston North airport are contaminated with firefighting foam chemicals at between three and 12 times the safe drinking water guidelines.
But Palmerston North City Council said ecological toxicity limits were not exceeded in the streams.
None of the waterways were used for the city's supply and drinking water bores on the city supply tested all-clear of PFOS in April, the city council said.
"This means everyone on the Palmerston North water supply can be reassured it is not contaminated and is safe for consumption," chief executive Heather Shotter said.
However, anyone with a private bore near the airport was being urged to contact authorities.
Swimming and showering in potentially affected water is not considered to pose a significant risk.
Two dozen soil and sediment samples were also tested from the former fire training area, north of the main runway and around the Rescue Fire Station site. It is unclear what the results of those tests are.
The airport has admitted using the foam up till last December despite it being banned in 2006.
About 250 litres of firefighting foam concentrate had been used since the late 1980s for testing fire truck foam systems, the airport said.
However, the chemical, and other man-made chemicals from the long-lasting and damaging per- and poly-fluoroalkyl substances (PFAS) family, are extremely long-lasting.
They build up in the body with repeated exposure over time. Research into their health impacts is so far inconclusive, although in Europe and parts of the US they are considered possibly cancer-causing, or an actual risk to unborn babies.
A group with representatives from Palmerston North Airport, Horizons Regional Council, Palmerston North City Council, and MidCentral DHB Public Health Services has been set up to handle the PFOS contamination.
The airport was working on a disposal plan of PFOS foam, which would be replaced with fluorine-free firefighting foam, airport chief executive David Lanham said.
More bores will begin to be drilled next week for more tests, to assess if contaminated groundwater was moving off the airport site, Mr Lanham said.
The regulation of PFASs has been weak.
Several airports including Auckland, have admitted using or storing the PFOS foam until recently despite it being banned in 2006, as has the petrochemical industry in Taranaki.
Regional councils have been ordered to identify potentially contaminated sites but little investigating has been done, with councils saying they are waiting for more guidance from the Environment Ministry.
The Defence Force is exempt from fines under the Resource Management Act over its contamination of groundwater at several bases.
"There are no formal requirements for landowners or regulatory authorities to notify [the public of] the results of investigations," the ministry said in a statement today.
"A landowner could, however, be required to report potential contamination when seeking resource consent."
PFASs were not included in the drinking-water standards, only in interim guidelines, so district health boards and the Ministry of Health do not need to be told if they were found, it said.
Port Taranaki found high levels of PFOS beside a tank farm near New Plymouth in July 2017 but did not tell anyone else for a year.
"Currently there is no consistent evidence that environmental exposures at the low levels New Zealanders are generally exposed to will cause harmful health effects," the ministry said.
"The interim guidance levels for PFOS and PFOA in drinking water were derived from effects found at certain doses in animal studies.
The guidance levels are based on a person weighing 70 kg drinking 2 litres of water every day over a lifetime without any significant risk to health.
Although there is no consistent evidence that the effects in animals also occur in humans, the Ministry of Health recommends that an alternative drinking water source is used to protect health if the interim guidance levels are exceeded."
- By Phil Pennington