A scientist is warning that residues of a harmful agricultural chemical, to which pregnant women and small children should not be exposed, is likely to be lurking in Northland's air, soils and waterways.
Meriel Watts from Pesticide Action Network Aotearoa New Zealand (PAN ANZ) said the results of a scientific study of pesticide in streams had found the most frequently detected one is the organophosphate insecticide chlorpyrifos.
It was found in 87 per cent of samples taken from South Island streams.
"This is devastating news for New Zealand," Dr Watts said.
Even low level exposure to chlorpyrifos can interfere with brain development in the unborn foetus and newborn infants, resulting in altered brain structure, lowered IQ, and behavioural changes, she said.
"The effects reported in studies are regarded by some scientists as comparable to those of lead and tobacco smoke. Chlorpyrifos is also an endocrine disrupter, interfering with androgens, oestrogen and thyroid hormones, and is a risk for breast cancer."
Dr Watts said she did not know if it had been tested for in Northland "but if they've found it in the only place they have looked for it, then it will be everywhere".
"Residues have been found in the air over the Southern Alps, and this latest study found it in pine needles on organic farms where it is not used, indicating both its ability to move away from where it is used and its persistence in the environment."
Chlorpyrifos has been widely used in New Zealand since the 1950s.
There are worldwide efforts to get chlorpyrifos listed under the Stockholm Convention on Persistent Organic Pollutants for a global ban, but in New Zealand the Environmental Protection Authority has recently reassessed its use and given it the green light. PAN ANZ has made submissions opposing its use.