The global chemical company Monsanto is describing its weedkiller Roundup as safer than household bleach, with a lower toxicity than table salt.
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The company has been ordered to pay more than $NZ400 million to a Californian man after a jury found the herbicide containing glyphosate had given him non-Hodgkin's lymphoma.
He is among more than 5000 similar plaintiffs across the US.
Pharmaceutical group Bayer, the German company which owns Monsanto, denied the herbicide causes cancer and it intends to appeal the verdict.
The New Zealand government has asked the Environmental Protection Authority (EPA) to consider adding the Roundup product - which has other ingredients as well as glyphosate - to a list of hazardous substances.
Glyphosate is already on the chief executive's reassessment list.
The EPA, which operates independently of ministerial direction, said Roundup was safe as long as it was used as directed.
Harvey Glick from Monsanto's Singapore office told Morning Report the chemical does not cause cancer.
"When we are faced with these kinds of questions we only have really one solution, and that is to rely on expert interpretation of the existing scientific data.
"And that has been done by many experts in many countries and they've all come to the same conclusion - that it is safe."
Mr Glick said appropriate safety precautions should be taken while preparing and using the product.
Many household cleaning products, such as bleach, have a higher toxicity warning than glyphosate, he said.
"Roundup has a lower toxicity, based on [laboratory toxicity testing] than many, many products, including table salt."
Mr Glick said the reason Roundup was such a popular product worldwide was because it had such a large scientific body of evidence of its safety and efficacy.
"The concern is that if this safe product gets taken off the market for whatever reasons, that is going to create a real challenge for farmers.
"It might lead to them using many other products instead, which have even higher toxicity.
"I'm hoping that as we go forward from this ruling we continue to rely on the scientific evidence ... and not fall into knee-jerk reactions driven by the legal community," Mr Glick said.
NZ authority on dangerous chemicals maintains Roundup safe
Wayne Temple is largely responsible for glyphosate's lingering position on the EPA's worry list.
Dr Temple headed the National Poisons Centre for years and since retiring, has been a consultant in the field of dangerous chemicals.
He cleared the chemical in a report for the EPA two years ago, but said it should still be watched in case new information comes to hand.
"Based on a weight of evidence approach, taking into account the quality and reliability of the available data, glyphosate is unlikely to be genotoxic or carcinogenic to humans and does not require classification as a carcinogen or mutagen," Dr Temple wrote in his report.
But he said that was not the end of the matter, and further observation was prudent.
"With any chemical that is being used, there needs to be post-market surveillance to see if any adverse health effects arise," Dr Temple said.
He said this practice applied with medicines, where there was a monitoring system to check on any adverse reactions from patients.
"The same thing applies with pesticides - we have to look them and build up a profile (later) because things may be missed with (earlier) studies."
Dr Temple said he found glyphosate was not a danger at levels used in New Zealand when he reviewed it, and studies in Europe and the US found the same thing.
But that was still not the end of the matter.
"Regulatory authorities review various chemicals as a matter of course, and I would think glyphosate is in a similar position."
What is glyphosate and is it dangerous?
Glyphosate was introduced by Monsanto in 1974, but its patent expired in 2000, and now the chemical is sold by various manufacturers. In the US, more than 750 products contain it.
In 2015, World Health Organisation's cancer agency - the International Agency for Research on Cancer - concluded that glyphosate was "probably carcinogenic to humans".
However, the US Environmental Protection Agency insists it is safe when used carefully, and the European Food Safety Authority said the chemical was unlikely to cause cancer in humans.
- RNZ / BBC
