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It has been the subject of nationwide protests, billion-dollar lawsuits in the United States, and recently Japan turned away New Zealand honey because of it. What is glyphosate, and should we be worried about its use in New Zealand? Katy Jones reports.

Glyphosate is the world’s most commonly used herbicide. In New Zealand, it is used to kill weeds in places ranging from orchards, crops and vineyards, to private gardens, roadsides and public parks.

The herbicide is contained in hundreds of products globally, and used in about 90 products in this country, with Roundup arguably the most recognised brand.

Glyphosate now underpins much of New Zealand’s – and the world’s – food production.

Why do we use glyphosate? Glyphosate was discovered to be a herbicide in 1970, by a chemist at American agrochemical corporation Monsanto.

The chemical works by blocking an enzyme present in plants (not in animals), which plants need to survive.

Monsanto brought glyphosate to the market in 1974, under the Roundup trade name.

It was quickly adopted in the agriculture sector, as it enabled farmers to kill weeds without killing their crops.

Ecologists are now among those who use it for land restoration projects.

But glyphosate has been mired in controversy over the past six years after it was linked to cancer.

Courts in the United States have subsequently ordered Monsanto to pay millions of dollars in damages to people who claimed the weedkiller caused their non-Hodgkin’s lymphoma.

WHAT DO THE SCIENTISTS SAY?

In 2015 the World Health Organisation’s International Agency for Research on Cancer (IARC) classified glyphosate as ‘‘probably carcinogenic in humans’’, prompting several countries to ban, or restrict its use.

But that wasn’t the end of it. Subsequent reviews by international bodies either contradicted that, or were inconclusive.

The European Food Safety Authority found that glyphosate was unlikely to pose a carcinogenic threat to humans.

And in 2016, the WHO and Food and Agriculture Organisation joint committee on pesticide residues said the use of glyphosate formulations did not necessarily constitute a health risk, and gave an acceptable daily intake.

WHAT IS NEW ZEALAND’S POSITION ON GLYPHOSATE?

In line with regulatory authorities in the US, European Union, Australia and Canada, New Zealand’s Environmental Protection Authority (EPA) said in 2016 that glyphosate was safe to use, when the rules around its use were followed.

An amount of glyphosate residue is permitted in food.

The highest level allowed in food, grown in New Zealand, is 0.1 parts per million (ppm). This is apart from in fruit, which has a limit of 0.01ppm.

Residues of up to 30ppm are allowed in some imported foods, such as cereal grains.

But the use of glyphosate remains hotly contested by campaigners and some scientists, because of health and environmental concerns.

Last month, the EPA called for information about the manufacture, importation, and patterns of use of the weedkiller in this country, ahead a review of the classification of glyphosate in Europe.

The EPA said that would ensure it was better prepared to assess the findings of the review, due to be released in mid-2022, by the European Chemicals Agency (ECHA) and the European Food Safety Authority (EFSA).

‘‘We want to understand whether products containing glyphosate may be damaging the environment or human health, despite the clear rules in place,’’ Dr Chris Hill, EPA general manager hazardous substances and new organisms, said.

WHY DO LOCAL AUTHORITIES USE GLYPHOSATE?

Many councils use glyphosate to kill weeds in public spaces, including parks and playgrounds, to keep them tidy.

GETTY IMAGES Glyphosate, manufactured by Monsanto, is the world’s most commonly used herbicide.