The world's first map showing areas with the highest levels of glyphosate residues in soils shows Australia isn't a "hotspot" for the controversial herbicide.
A team of agricultural scientists and engineers from Sydney University has produced the map as debate continues to rage around the world about the potential impact of glyphosate on environmental and human health.
Last year in the US the owner of Roundup, Monstanto (now owned by Bayer), was ordered to pay $US2 billion to a couple who said they contracted cancer from the herbicide.
Australia has emerged as the next legal battleground over whether the herbicide is unsafe for humans.
LHD Lawyers is taking a case to the Federal Court with about 150 plaintiffs, with the lead plaintiff western Victorian spray contractor John Fenton, now of Robe, South Australia.
Carbone Lawyers has filed an action with the Victorian Supreme Court with about 100 plaintiffs spearheaded by Victorian livestock producer Nando Maisano.
However both the Australian Pesticides and Veterinary Medicines Authority (APVMA), the national regulator of crop chemicals, and the US Environmental Protection Agency are satisfied glyphosate is safe.
"The scientific jury is still out on whether the chemical glyphosate is a health risk," Professor Alex McBratney, director of the Sydney Institute of Agriculture at the University of Sydney, said.
"But we should apply the precautionary principle when it comes to the health risks.
"And even if no evidence emerges about these risks, it is time for the agriculture industry to diversify our herbicides away from relying on a single chemical."
Lead author of the paper was Associate Professor Federico Maggi from the Sydney Institute of Agriculture and Faculty of Engineering.
"Glyphosate is a ubiquitous environmental contaminant. About 36 million square kilometres are treated with 600,000 to 750,000 tonnes every year - and residues are found even in remote areas," he said.
The paper identified hot spots of glyphosate residue in Western Europe, Brazil and Argentina, as well as parts of China and Indonesia.
Contamination refers to concentration levels above the background level.
"Our analysis shows that Australia is not a hot spot of glyphosate contamination but some regions are subject to some contamination hazard in NSW and Queensland and, to a lesser extent, in all other mainland states," Associate Professor Maggi said.
He said that given the widespread use of the herbicide, soil contamination was unpreventable.
"This is because it is hard to be degraded by soil microorganisms when it reaches pristine environments, or it releases a highly persistent contaminant called aminomethyl-phosphonic acid (AMPA) when it is degraded.
"The researchers emphasise that contamination levels do not necessarily equate to any environmental or health risks as these are still unknown and require further study.
"We found that one per cent of global croplands - about 385,000 square kilometres - has a mid- to high-contamination hazard."
He said contamination was pervasive globally but was highest in South America, Europe and East and South Asia.
It was mostly correlated to the cultivation of soybean and corn and is mainly caused by AMPA recalcitrance and accumulation rather than glyphosate itself.
"While there are controversial perspectives on the safety of glyphosate use on human health, little is known about AMPA's toxicity and potential impacts on biodiversity, soil function and environmental health. Much further study is required," Associate Professor Maggi said.
Professor McBratney said aside from the risks to human health, it is poor long-term agriculture policy to rely on glyphosate as a herbicide.
"Weeds are genetically adapting and building resistance to glyphosate," he said.
"And there is growing evidence that a new generation of precision herbicide application could further improve yields."
Professor McBratney said Australia was well placed to economically benefit from the development of new herbicides.
"In these times of increasing food demand, relying on a single molecule to sustain the world's base load crop production puts us in a very precarious position," he said.
"We urgently need to find alternatives to glyphosate to control weeds in agriculture."
The story World first map shows glyphosate residues are everywhere first appeared on Farm Online.