Top Neurologists Say Regulator Ignored Warnings on Weed Killer Decision

Topic: Agricultural Chemicals

Mon 8 Jun 2026 at 4:46am

Neurologist David Blacker wants the Australian regulator to ban the herbicide paraquat.

In short:

Leading neurologists say Australia's chemical regulator has not considered expert warnings about paraquat's links to Parkinson's disease.

The Australian Pesticides and Veterinary Medicines Authority says health and safety are its main concerns.

What's next?

The regulator's review of paraquat has been going on since 1997 and a final decision is expected mid-year.

Australia's top neurologists say they have been ignored by the chemical regulator as it considers the future of a weedkiller linked to Parkinson's disease.

Many movement disorder specialists say the regulator has failed to engage with them during its review.

It has raised fears that 'real-world data' on paraquat's link to Parkinson's disease is being overlooked.

It comes as a final regulatory decision on the herbicide is expected mid-year.

Associate Professor Wesley Thevathasan, a movement disorders specialist, said he and other experts had made submissions to the regulator but had received no further contact.

Dr Thevathasan has treated thousands of patients with Parkinson's disease and says farmers are overly represented.

Dr Thevathasan is a Parkinson's disease specialist and works across several hospitals and research institutes.

He said many scientific bodies and neurologists had made submissions to the regulator but had not been contacted.

Paraquat and diquat are fast-acting weedkillers that farming groups say are essential for controlling resistant weeds.

What is paraquat?

The chemicals have been under review by the regulator since 1997 and are banned in the EU, UK, and China due to their toxicity.

The regulator said the available data was not enough to conclude any link between paraquat exposure and neurotoxicity.

Dr Thevathasan said this position conflicted with the global consensus that exposure to paraquat was linked to Parkinson's disease.

He said the evidence base used by the regulator gave little weight to recent human studies.

Parkinson's disease is a progressive, incurable neurological condition that affects movement and can cause stiffness and uncontrollable shaking.

In this small rural community, Parkinson's disease is common and many fear farm chemicals could be the cause.

Many medical experts and clinicians have raised concerns about the link between paraquat and Parkinson's disease.

Neurologist Dr Kelly Bertram said the regulator's approach was concerning and other countries had made different decisions on paraquat.

The regulator acknowledged concerns about the link between paraquat and Parkinson's disease but said health and safety was its main consideration.

The regulator has hired a public relations company to help with its communications.

A spokesperson for the Assistant Minister for Agriculture said the regulator was using its powers to finalize chemical reviews.

The regulator said Australians could have confidence in its decisions based on the best available science.

Precautionary principle

Parkinson's disease is the fastest-growing neurological disorder in the world in terms of disability and death.

Professor David Blacker said maybe 10 to 15 per cent of Parkinson's cases have a genetic cause, but what about the other 80 to 85 per cent?

Dr Blacker was diagnosed with early onset Parkinson's disease and has been investigating the origins of the disease.

Professor Blacker is a neurologist and movement disorder specialist who also has Parkinson's disease.

He said consideration needed to be given to the precautionary principle.

When you're involved with an activity that raises the risk of harm, precautions can be taken even if you don't have a fully developed cause and effect relationship established.

Professor Blacker also made a submission to the regulator but has received no follow-up.

Farm groups say paraquat is essential

The agriculture industry has come to rely on paraquat for weed control despite long-running health concerns.

Some weeds are resistant to glyphosate and ploughing paddocks can disturb soil structure and moisture.

The National Farmers' Federation said farmers may be forced to return to traditional tillage to manage weeds and resistance without paraquat.

Australian farmers have adopted zero-till farming and rely more on chemicals to control weeds.

NFF president Hamish McIntyre said paraquat was an essential tool for farmers.

McIntyre said there was no like-for-like replacement for paraquat and other options require waiting longer to re-enter a paddock after spraying.

He said the NFF would follow the regulator's lead if it decided to restrict or ban paraquat.

Paraquat 'volatilisation'

The US Environmental Protection Agency said a new vapour pressure study had increased uncertainty about paraquat's potential to volatilise.

The study indicated a higher vapour pressure value for paraquat than was previously used in EPA's risk assessments.

Vapour pressure is a key parameter influencing the extent to which pesticide surface residues may convert into gaseous vapors.

Paraquat is listed as a schedule 7 poison in Australia, which requires a licence to purchase.

The APVMA is reviewing its assessments of the volatility of paraquat before finalizing its regulatory decision.

The regulator said it would consider the updated review and refine its risk assessments if necessary.

The APVMA's latest technical report states that paraquat would not be likely to have a harmful effect on humans if used according to instructions.

The regulator did not answer questions about whether this was still its position following the US EPA's review.

First US state bans paraquat

Vermont became the first US state to ban paraquat, marking a significant departure from federal policy.

The US Environmental Protection Agency continues to allow restricted use of the pesticide despite ongoing health concerns.

Professor Blacker recently attended the World Parkinson Congress in the US and has been following the Vermont ban closely.

He said at least a dozen states were ready to introduce legislation to ban paraquat.

What is epidemiology?

The regulator gives more weight to laboratory experiments than epidemiology, which looks at patterns of disease in human populations.

Dr Thevathasan said real-world exposure data could be just as compelling as laboratory experiments.

Multiple epidemiological studies have shown that people exposed to paraquat have a three times greater risk of developing Parkinson's disease.

A leaked email from the National Farmers Federation directed its members to stay silent on a story linking paraquat to Parkinson's disease.

Dr Thevathasan said the risk was greater with chronic exposure and there was a relationship with dose.

The APVMA has previously stated its analysis of studies and research might result in different conclusions to study authors.

The regulator considered a wide range of studies relating to paraquat, including animal and epidemiological studies.

Mon 8 Jun 2026 at 4:46am

Mon 8 Jun 2026 at 10:02am

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