An Auckland councillor is calling for the council to stop spraying Roundup in parks and roadsides around the city, following a landmark US ruling finding the weedkiller may have caused cancer.

The chemical glyphosate - the active ingredient in Roundup - is the world's most widely used weedkiller and is sprayed extensively around parks, verges and roadsides across New Zealand.

But with three landmark court verdicts in the US finding the product may have caused cancer, questions have been raised about whether it should continue to be used in New Zealand.

Most recently, in mid-May Roundup's manufacturer Bayer was told to pay US$2billion ($3bn) to a couple who extensively used Roundup Ready, and both contracted non-Hodgkin's lymphoma.

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Auckland Councillor John Watson says the use of the weedkiller is "indefensible" and believes the council should follow the example of several councils in Sydney which are reviewing or banning use of the chemical in public places.

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The safety of Roundup has been the subject of much controversy after the World Health Organisation's International Agency for Research on Cancer (IARC) classified it as "probably carcinogenic to humans" in 2016. That finding led to Christchurch City Council cutting back on its use.

But critics of the IARC decision argued it didn't take into account the amount of glyphosate exposure or how it was used. (For context, the IARC has says red meat is "probably carcinogenic to humans".)

New Zealand's Environmental Protection Authority (EPA) has not changed its stance is that glyphosate products are safe as long as the user follows the instructions on the label.

In a statement Watson said the Sydney councils were concerned future court action could be aimed at them.

While Auckland Council is a heavy user of glyphosate, some parts of the city do not use the chemical. Watson said Biosafe was used in inner city suburbs while on the North Shore hot water is used.

He called the use of glyphosate "indefensible".

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"Over the years I've regularly dealt with complaints from people who've been exposed to spraying, some with extreme chemical sensitivity who've become ill as a consequence," he said.

"They, like me, struggle to understand the contradiction that while some communities in Auckland enjoy being chemical free, most others are awash with the stuff.

"There are contractors in Auckland who have the latest chemical-free technology and who for the last 20 years have won contracts on the basis of price yet there is still this organisational determination to persevere with glyphosate."

Roundup is used on streets and verges to control weeds in towns and cities around New Zealand. Photo / File
Roundup is used on streets and verges to control weeds in towns and cities around New Zealand. Photo / File

Auckland Council's head of operational maintenance and management Agnes McCormack said the council followed EPA guidelines. If those changed - or if the Ministry for the Environment changed its stance - the council would respond appropriately, she said.

McCormack said Auckland's temperate climate made the city especially vulnerable to weeds and pest plants.

Different methods were used to control weeds depending on the type of weed, where it was found and how bad the infestation was, she said. These included herbicide, hand pulling, mechanical control, organic weedkiller, biological control and hot water.

There were different approaches across Auckland because councils that existed prior to the Super City had made different arrangements, she said.