Health body warns over weed killer

The World Health Organisation has warned that a weed killer common on WA farms and in homes is a probable carcinogen.

The WHO International Agency for Research on Cancer classified glyphosate, used to make Roundup, as a potential threat.

The IARC warning came amid a landmark legal battle involving two Kojonup neighbours over the growing of canola genetically modified to survive Roundup use.

The Roundup Ready gene technology used in the canola is owned by Monsanto, which said the IARC conclusions were not supported by scientific data.

"All labelled uses of glyphosate are safe for human health and supported by one of the most extensive worldwide human health databases ever compiled on an agricultural product," Monsanto executive Phillip Miller said.

An IARC working group of 17 experts from 11 countries has reviewed scientific evidence and evaluated the carcinogenicity of five insecticides and herbicides, including glyphosate.

In findings on glyphosate published in The Lancet, it said there was "limited evidence of carcinogenicity" in humans for non-Hodgkin lymphoma.

"The evidence in humans is from studies of exposures, mostly agricultural, in the US, Canada and Sweden published since 2001," it said. "In addition, there is convincing evidence that glyphosate also can cause cancer in laboratory animals."

The IARC also noted: "The agricultural use of glyphosate has increased sharply since the development of crops genetically modified to make them resistant to glyphosate."

Monsanto said the IARC was at odds with the findings of regulatory bodies worldwide.

Three Supreme Court judges have reserved judgment after a appeal in a damages case involving organic farmer Steve Marsh and neighbour Mike Baxter.

Justice Kenneth Martin earlier rejected an $85,000 claim based on allegations Mr Marsh lost organic certification because GM canola from Mr Baxter's farm blew on to his property.