A team of mainly Wellington scientists want a partial ban on the use of the herbicide Glyphosate.
A protest in Europe against Glyphosate. Photo: AFP
They also want the Environmental Protection Authority (EPA) to cancel an earlier report clearing Glyphosate of serious health risks.
They say the methodology of the EPA report was not of a sufficient standard to overturn earlier findings that Glyphosate was probably carcinogenic.
The scientists were led by Professor Jeroen Douwes, of the Centre for Public Health Research at Massey University in Wellington.
Their paper is being publised in the New Zealand Medical Journal today.
Glyphosate is a widely used herbicide found in approximately 90 products, of which the best known is Monsanto's weedkiller, Roundup.
It is used in farming, and in gardens, streets and parks.
This controversy began with analysis of Glyphosate by the International Agency for Research on Cancer (IARC), a branch of the World Health Organisation (WHO) based in Lyon, France.
Seventeen scientists recruited by the IARC concluded there was "limited evidence" of carcinogenicity for humans because the available research on this subject was also limited.
But there was "sufficient evidence" of carcinogenicity in experimental animals.
The scientists then went on to combine the animal findings with other data, and the limited human research that was available, and concluded that glyphosate was "probably carcinogenic to humans".
The EPA then conducted its own research.
In part, the EPA report defended Glyphosate on economic grounds.
It argued there was a need to look at all aspects of a project to achieve what it called its net benefit.
"We need to consider everything otherwise it is not the net benefit approach," the paper said.
"We go to all sources because there is an economic implication with the use of Glyphosate.
"We agree that at high exposures and dosages, cancer could occur, but we don't have those high exposures and dosages in New Zealand."
But Professor Douwes said this report failed to exonerate Glyphosate.
"As an analogy, if someone neither smokes nor is exposed to asbestos, this does not mean that tobacco and asbestos are not carcinogenic," he said.
"Both are recognised human carcinogens: most lung cancer and virtually all mesothelioma cases are attributable to these exposures, even though most people are not exposed."
Dr Douwes had a blunt message for the EPA:
"There is a strong reason to do a reassessment and follow the advice that IARC has provided and reject the current report," he said.
In the meantime, there should be restrictions on the use of the substance.
"I don't think an outright ban would be justified, but I do believe some signage on the packaging would be useful so that people are aware of what they are using and can protect themselves.
"I don't think we need Glyphosate for private use and so a ban (on private gardens) could be introduced."
Professor Douwes added a ban could be considered on the use of Glyphosate by local councils but added it could be too soon to ban the herbicide from farms.
Auckland Council announced last October it would review the use of Glyphosate.
A council official said while the use of chemical was restricted where possible, official policy by the council would defer to the EPA.