In an unpleasant surprise for firefighting foam investigators, the toxic chemicals have now been found in the drinking water of a Rangitikei town.
Photo: 123RF
The Health Ministry said the chemicals were at levels well below maximum safety guidelines and Bulls water was still safe to drink.
The fact the chemicals were in the water beneath Bulls was mystifying investigators, however.
Ōhakea airbase had levels in at least one test well that were very, very high, and surrounding groundwater and the drinking water of at least seven properties had concentrations above safety maximums.
However, Rangitikei mayor Andy Watson said the town's bores were upstream and across the river.
"We didn't expect to find any trace of contaminants, and nor did the Ministry of Defence," Mr Watson said.
"The information that we had been given was that any water movement would tend to be out towards the coast."
Meanwhile, the water supplies in nearby Sanson were yesterday cleared of any contamination from the PFOS or PFOA chemicals.
In Bulls, though, four out of five bores have the chemicals in them. Mr Watson said the fifth clear bore was the largest source of drinking water, and was being cranked up to supply more as the second round of tests was carried out.
He said one theory was the contamination might be linked to firefighting at a Skyhawk crash site in the 1980s. The chemicals are very long lasting.
The highest test results were at 11 parts per billion (ppb). The guideline maximum is 70.
The Defence Force said it was "highly unlikely" the chemicals came from Ōhakea, and retesting was under way.
Backlog for testing
There is now a backlog at New Zealand's only lab accredited to perform the incredibly sensitive tests for these toxic chemicals.
Marlborough District Council does not expect to get its second round of tests on Blenheim's town water supply until next month. The first round cleared the town supply.
New Zealand's guideline maximum of 70 is the same as the US Environmental Protection Agency guideline and of several US states, but much lower than Alaska's and West Virginia's, twice as high as Minnesota (35ppb for PFOA) and four times higher than New Jersey (14ppb).
Safe limits have tended to drop worldwide since 2009.
The latest health advice from the US Environmental Protection Agency - where the research is probably the most advanced - about exposure to the PFAS class of chemicals, including those found in firefighting foam, was cause for concern.
"There is evidence that exposure to PFAS can lead to adverse health outcomes in humans".
"Studies indicate that PFOA and PFOS can cause reproductive and developmental, liver and kidney, and immunological effects in laboratory animals. Both chemicals have caused tumors in animal studies.
"The most consistent findings from human epidemiology studies are increased cholesterol levels among exposed populations, with more limited findings related to: infant birth weights; effects on the immune system; cancer (for PFOA); and thyroid hormone disruption (for PFOS)."
New Zealand's drinking water guideline maximum for PFOA is eight times higher than for PFOS.