Alan Taylor
Banning the world's most common herbicide will have major effects on both farming and urban weed control, Whanganui cropping farmer Alan Taylor says.
Glyphosate is the active ingredient in Roundup and hundreds of other weedkillers. It's so commonly used worldwide that traces have been found in breast milk, urine and bread.
In March 2015 it was deemed "probably carcinogenic" by the World Health Organisation's cancer research agency. A few countries have banned it and others are considering doing so.
Since then it has also been assessed by the European Food Safety Authority and deemed unlikely to cause cancer in humans through exposure in food.
In Auckland there's a petition to ban it from public places. New Zealand's Environmental Protection Authority considers it safe, provided instructions are followed.
Any restrictions on its use would be a headache for a lot of people, Mr Taylor said.
"It would make some forms of farming really, really difficult and add considerable cost. It would also reduce efficiency and reduce the quality of product that you can turn out.
"For councils it would make their maintenance operations more expensive."
In 40 years of use there had never been anyone proven to be badly affected in any peer-reviewed scientific paper, he said. He had some advice for people worried about the use of glyphosate.
"I suggest that they try to read balanced literature about it and if they're worried not expose themselves to it."
He's been using glyphosate to kill weeds and grasses prior to cultivating and planting crops for nearly 40 years. It can also be used two weeks before grain harvest, to kill green weeds and add to the drying of grains.
He said he followed the instructions and had no irritation or other ill effects. Alternative weedkillers were less effective and more damaging, he said.
In parts of Australia, rye grass has developed a resistance to glyphosate. To avoid that, Mr Taylor changes weed control methods every third year. He uses other chemicals, burns straw or ploughs seeds under.
Glyphosate was pioneered by a chemist at Monsanto, a multinational agrochemical company. It was initially under patent, and has been much cheaper since other companies have had access to it.
Mr Taylor said it had cost from about $220 to $16 per hectare to apply.
It works by inhibiting an enzyme that stops the plant producing proteins. Plants are killed from tip to roots, and the substance is said to break down in the soil.
In March last year, the WHO International Agency for Research on Cancer found glyphosate was "probably carcinogenic" on limited human evidence and more convincing animal evidence.
Members of the European Union, the world's strictest regulators of chemicals, are now deciding whether to approve its use for another 15 years.
It has been approved for use in New Zealand since 1976, and is sold here in 89 different forms.