The Cancer Council is urging global chemical giant Monsanto to come clean on any potential links to cancer with one of its popular weed killers following a major lawsuit in the US.

Key points: A US jury has found the weed killer glyphosate contributed to a former school gardener's non-Hodgkin's lymphoma

A US jury has found the weed killer glyphosate contributed to a former school gardener's non-Hodgkin's lymphoma Monsanto denies the link and will appeal the decision, saying its product is safe to us

Monsanto denies the link and will appeal the decision, saying its product is safe to us The Cancer Council in Australia is concerned Monsanto is concealing information on cancer links and urges precautions

The agribusiness was ordered to pay $US289 million ($396 million) to a former school gardener who is dying of cancer, after a jury in California found the company's Roundup weed killer contributed to his illness.

However, Monsanto has denied the link between Roundup's active ingredient, glyphosate, and cancer, and will appeal the decision.

Professor Sanchia Aranda, CEO of the Cancer Council in Australia, said there was a probable link between glyphosate, Monsanto's Roundup weed killer's key ingredient, and cancer. ( ABC News: Jennifer Douglas )

Cancer Council Australia's chief executive officer Professor Sanchia Aranda said the International Agency for Research on Cancers has classified glyphosate as a probable carcinogen.

"Studies — which are of variable quality — are mixed. But some definitely show an association with cancer called non-Hodgkin's lymphoma in people who use these chemicals frequently," Professor Aranda said.

"There's some suggestion in the US court case that they have more information than what they're letting on.

"We would also be concerned by the concealment of evidence that might support this man's case."

'Glyphosate … did not cause Mr Johnson's cancer,' says Monsanto

Monsanto issued a statement saying they were sympathetic to the former groundskeeper Dewayne Johnson and his family, but denied glyphosate caused his cancer.

"Today's decision does not change the fact that more than 800 scientific studies and reviews — and conclusions by the US Environmental Protection Agency, the US National Institute of Health and regulatory authorities around the world including Australia — support the fact that glyphosate does not cause cancer, and did not cause Mr Johnson's cancer.

"We will appeal this decision and continue to vigorously defend this product, which has a 40-year history of safe use and continues to be a vital, effective, and safe tool for farmers and others."

In 2017, the Australian Pesticides and Veterinary Medicines Authority assessed glyphosate as safe to use if label instructions were followed.

Dewayne Johnson was awarded $US289 million in compensation after a jury in California found Roundup contributed to his cancer. ( News Video )

Take precaution using the weed killer, say Cancer Council

Professor Aranda said The Cancer Council suggested "anyone using them [the product] regularly to take precautions, such as masks and protective clothing".

"The work health and safety aspects of these kinds of exposures aren't quite as tight as we'd like them to be," she said.

The lawsuit in California was the first to go to trial among hundreds filed in state and federal US courts claiming Roundup causes non-Hodgkin's lymphoma.

Jurors in California's Superior Court determined that Roundup contributed to Mr Johnson's cancer and said the company should have provided a label warning of the potential health hazard.

Dr Ian Musgrave, a pharmacologist at the University of Adelaide, said those concerned about the cancer link were "somewhat exaggerating the evidence".

He cited an American epidemiological study that found "no apparent" association between glyphosate and non-Hodgkin's lymphoma and its subtypes.

"Science is not besotted by court cases and the actual scientific evidence we have shows that that link is not apparent at the concentrations humans use, under the conditions human use it."

Roundup needs to be reviewed, says lawyer

Public liability lawyer at Maurice Blackburn, Dimi Ioannou, said the findings of the US case would make glyphosate "a long-standing issue".

Ms Ioannou said if the effects of glyphosate ever matched something like asbestos, it could lead to thousands of compensation claims in future.

"It is a significant development for any Australians that have been impacted by cancer as a result of Roundup," she said.

"If they fail to mitigate the risk and fail to warn their consumers that it could potentially lead to cancer then they are liable and negligent.

"It is the most widely used weed killer in Australia. Councils and other authorities need to review and revisit the use of this chemical … if they breach their duty of care they could potentially find themselves in a lawsuit."

Ms Ioannou said there had been no cases at their office.

"Workers could potentially sue their employers if they developed a significant injury as a result of their exposure to Roundup."

She said the product "desperately needs to be reviewed as a result of the risks involved".