The herbicide paraquat, banned in over 70 countries, will remain legal in Australia despite Parkinson’s groups, scientists and neurologists arguing there is a strong correlation between direct exposure and the incidence of the disease.

The Australian Pesticides and Veterinary Medicines Authority (APVMA) announced its final decision on Tuesday following a decades-long review of the highly toxic paraquat and a related chemical, diquat. Both are widely used in Australian agriculture.

The regulator will continue to allow their use, but with stricter conditions to reduce the exposure risk for farm workers, birds and mammals.

Paraquat is used in broad-acre farming, particularly for grains, sugarcane, cotton and horticulture.

The APVMA chief executive, Scott Hansen, said that while the regulator would have liked to find a clear answer as to what caused Parkinson’s, the review of hundreds of scientific papers and long-term data had not established a causal link between paraquat and the debilitating neurological disease.

Tuesday’s ruling was not a surprise, given it had been flagged in an earlier draft. It’s unlikely to end the controversy regarding paraquat and diquat – and Australia’s approach to regulating agricultural chemicals.

About 70 countries have banned the highly toxic paraquat. The European Union and the UK banned it in 2007 after a lawsuit found the manufacturer, Sygenta, had not established the safety of the herbicide, and its initial assessment was flawed.

The EU and many other nations apply what is known as the precautionary approach to licensing the use of chemicals. They require manufacturers to establish that their products are safe.

Australia uses a risk-based assessment where actual risk must be established.

However, establishing how risky a herbicide might be is not easy, especially given that the regulator relies on evidence from the manufacturer at the registration stage.

Chemical giant feared weedkiller’s link to Parkinson’s

A Guardian investigation in 2022 uncovered internal documents that showed Sygenta had reservations in the 1970s about paraquat’s chronic effects – despite the company’s public statements to the contrary.

Other countries have approved the continued use of paraquat, too. The US Environmental Protection Agency reviewed paraquat in 2021 and has allowed its ongoing use with stronger controls. Some states, such as Vermont, have unilaterally moved to ban it amid concerns over links to Parkinson’s. New Zealand also allowed paraquat to be used.

Hansen said an extensive review of scientific studies failed to establish a causal link with Parkinson’s disease. But there was evidence regarding potential impacts on farmworkers from exposure and the impact on birds and mammals in the path of spraying, he said on Tuesday.

“Both chemicals remain available for use with significant new restrictions on application rates and permitted uses.

“To protect users from acute exposure, new restrictions will phase out backpack sprayers and require enclosed mixing and loading systems for all uses, and enhanced personal protection equipment.

“Overall, the maximum rate of application on paraquat and diquat will be 231 grams per hectare, when it was previously 1,150 grams per hectare.”

A higher application rate will be permitted when using technology-assisted spot spraying, limited to 30% of a total area.

Parkinson’s researchers insist Australia is out of step with the prevailing scientific evidence.

The Melbourne neurologist Prof Wes Thevathasan told the ABC on Tuesday that the “global consensus” in his field was that exposure to paraquat was closely linked to the development of Parkinson’s disease. He said the APVMA had failed to engage with researchers in the field.

“There are now multiple epidemiological studies or real-world exposure studies that have suggested that paraquat increases the risk of Parkinson’s disease by around threefold,” Thevathasan said.

‘Are the lives of Australians less valuable?’

The Parkinson’s Australia CEO, Olivia Nassaris, said she was disappointed with the outcome of the review.

“Seventy countries have banned the use of paraquat,” she said on Tuesday. “Are the lives of Australians less valuable?”

Nassaris said her organisation would continue the fight to ban paraquat in Australia.

The APVMA lost much of its expertise when the then-agriculture minister Barnarby Joyce announced it would move from Canberra to his home town of Armidale in 2013. Several critical reports have concluded it was a disaster for the regulator.

The paraquat review took about 30 years despite it being declared a priority for “reconsideration” in 1994. The work program for the review was settled in 2015, with an interim report released in 2024.

Australia does not have a system of regularly reviewing approved products and does so only when a chemical comes to international attention.

The paraquat decision could focus attention on whether the regulatory scales here are tipped in favour of big agriculture.

Paraquat quickly kills foliage it touches and is used to control grasses and weeds around crops, as well as removing foliage from crops like cotton and potatoes before harvest.

Industry has fought to keep the herbicide available, arguing it is key to no-till farming practices, which are in turn essential for retaining soil moisture and preventing erosion.

The National Farmers’ Federation president, Hamish McIntyre, on Tuesday acknowledged “community concern around paraquat”.

“It is absolutely critical that the products farmers use are safe for both people and the environment,” he said, adding that Australian agriculture operated under strict controls.

‘Science-based safeguards protect farmers and workers’

“These are science-based safeguards designed to protect farmers, their workers and the environment.”

The ACT independent senator David Pocock, who has taken up the cause of Parkinsons’ sufferers, said on Tuesday: “This seems like yet another example of vested interests winning out over community interest.”

Sygenta Australia said: “With a number of crop use cases removed from the label as part of this decision, Syngenta is assessing the impact on the product portfolio under these restricted conditions.”

The company said paraquat had played a “unique and important role in Australian agriculture”.

“Many farmers consider it an essential tool for conservation agriculture and integrated weed management.”