Roundup is for the first time being tested for nationwide in groundwater - which is used to supply up to half of the country's drinking water.

The controversial weed killer made global headlines earlier this year after former school groundskeeper Dewayne Johnson successfully sued Monsanto, on the basis that its product contributed to his cancer. The 46-year-old was awarded US$289 million in damages.

The International Agency for Research on Cancer (IARC) found in 2015 that glyphosate (commonly known as Roundup) was "probably carcinogenic to humans". Despite IARC's evidence, Monsanto still claims it's safe and does not cause cancer.

New Zealand's Environmental Protection Authority also believes it is still safe to use.

"There is no change to the science behind our current position, which is products containing glyphosate remain safe to use when you follow the instructions on the products label," EPA's Dr Fiona Thomson-Carter said in August.

The Institute for Environmental Science and Research confirmed to the Herald that Roundup or Glyphosate - will be tested for in a "separate suite of analysis" as part of its 2018 groundwater pesticide survey. The survey is conducted every four years.

Up to 50 per cent of the community drinking water supplies around the country were reliant on groundwater. A significant number of individual rural households also relied on groundwater for their drinking water supply.

ESR's principal scientist, Murray Close, said most of the groundwater wells that are tested as part of the survey are not community drinking water supplies.

He said the research is carried out for the regional councils - the ones which sign up to it - for the sake of assessing the quality of groundwater as a resource. Bay of Plenty and West Coast regional councils did not participate in 2014.

Andrea 't Mannetje, an associate professor at Massey University's Centre for Public Health Research, said it was great ESR was testing for it.

"It's used a lot, a lot, a lot.

"[I] definitely expect they will find some," she said.

University of Canterbury Associate Professor Sally Gaw agreed that Roundup was a "sensible one to include" in testing, given the huge public interest in the weed killer right now.

She said it would be informative to know where it is and how much is out there.

Along with glyphosate, a long list of new, what are called "emerging contaminants" or chemicals where the risks to human health and the environment were not yet fully understood, had also been added to this year's survey.

They include Bisphenol-A or BPA - which yesterday the Herald revealed had been found throughout the Waiwhetu Aquifer which is used to supply the Wellington region's drinking water - pharmaceuticals, including Ibuprofen, Triclosan - which was banned in hand soaps in the United States in 2017 - insect repellent, caffeine, nicotine and others.

Testing was expected to be completed by late November or early December, with the results expected back by the end of January or early February 2019.

It's far from the first time Glyphosate has been tested for and found in drinking water in the world. The first time it was tested for in drinking water, back in 2002, was in the United States. Researchers from the US Geological Survey collected 154 water samples across nine Midwestern States, finding Glyphosate in 34 per cent of them.

That led to the US Environmental Protection Agency setting a drinking water maximum contaminant level of 700,000 nanograms per litre (ng/L) for glyphosate. Maximum levels vary in other parts of the world - in Europe it's 100 ng/L, in Canada it's 280 ng/L, in the UK it's 100 ng/L and in Australia it's 1,000,000 ng/L.

New Zealand's Environment Protection Authority regulates the manufacture, importing, use, storage, and transportation of hazardous substances, such as glyphosate, for environmental, and health and safety purposes.

The EPA has approved this herbicide for use in New Zealand.

The Ministry for Primary Industries monitors and controls the use of glyphosate.

Its sale and use is regulated under the Agricultural Compounds and Veterinary Medicines Act 1997 and the Hazardous Substances and New Organisms Act 1996.

MPI sets maximum residue levels for pesticides, including herbicides, in foods. It also monitors food production for residues and tests raw milk and crops for glyphosate.
No glyphosate has been detected.