A New Zealand scientific review has said that the weedkiller glyphosate is "unlikely" to be carcinogenic and should not be classified as a mutagen or carcinogen under the HSNO Act.
Poisons expert Dr Wayne Temple and his colleague from the National Poisons Centre, Michael Beasley, carried out the review, which was commissioned by the Environmental Protection Authority (EPA).
Glyphosate is the active ingredient in chemical company Monsanto's Roundup and underpins much of New Zealand's - and the world's - food production. It is also widely used in parks and gardens.
Last year the scientific community became divided over the issue, after one World Health Organisation agency said glyphosate was "probably carcinogenic to humans" but another said it was unlikely to pose any health risk to humans.
In June this year the European Commission had to intervene to grant a reprieve to users of the chemical, after countries became locked in disagreement.
The Commission extended the approval for the popular weedkiller until the European Chemicals Agency issues its opinion on whether the chemical is hazardous. The extended approval will last until the end of 2017.
Federated Farmers president Dr William Rolleston welcomed the report, saying glyphosate was safer than other more toxic chemicals which would have to be used in its place.
He said the farming community would have been surprised if the report had found differently. Activist groups wanted to portray the chemical in a negative light.
"Monsanto is a leader in making genetically modified plants - they're bad. Monsanto makes Roundup - it's bad. It's part of a campaign to undermine the company and its products," Rolleston said.
He said the WHO agency that found glyphosate was "probably carcinogenic to humans" had identified it as "hazard" and not as a "risk".
Green MP Steffan Browning also welcomed the report, which he said showed the EPA was taking people's concern about glyphosate seriously. He is campaigning to stop its use in parks, gardens and schools.
EPA manager of hazardous substances and new organisms Asela Atapattu, said the reason behind commissioning the report was concern from several city councils about the use of glyphosate.
"Councils have options to manage weeds, what we wanted to do was to provide them with some real science," Atapattu said.
The Auckland Council has decided to review its use after a 3696-strong public petition was presented last month.
Glyphosate has been approved for use in New Zealand since 1976. There are no figures for the precise volume used in New Zealand, but there are 94 trade name products registered containing the ingredient.
