Australia's top neurologists call for chemical regulator to ban ...

Dozens of pre-eminent neurologists in Australia are calling on the chemical regulator to ban paraquat, a controversial herbicide that has been linked to the development of Parkinson's disease.

Paraquat is a widely used weedkiller and has been under review by the Australian Pesticides and Veterinary Medicine Authority for 27 years.

In August, a proposed regulatory decision was released recommending tighter restrictions on the chemical's use, with public consultation closing on October 29.

WA-based neurologist David Blacker has amassed more than 40 signatures from colleagues in clinical neurology, including 31 neurologists, eight movement disorders specialists and 10 professors, joining his submission to the APVMA.

The ABC can also reveal the Movement Disorder Society of Australia and New Zealand (MDSANZ), as well as other world leading-scientists, have made submissions to the review, supporting calls for paraquat to be banned.

Dr Blacker said the quorum of doctors that signed his submission added weight to the growing evidence linking paraquat to Parkinson's disease.

"This is a very highly informed group of people who agree that the medical evidence is now very strong, so that's really, really significant," he said.

Parkinson's is a progressive brain disorder that affects the nervous system. Symptoms generally develop over years and can affect movement, sleep, mental health and cognitive function.

In 2018, Dr Blacker himself was diagnosed with early onset Parkinson's disease, which he suspects could be in part linked to his exposure to agricultural chemicals while growing up in the Western Australian Wheatbelt.

Dr Blacker was diagnosed with early onset Parkinson's disease in 2018, which led him to investigate the origins of the disease. (Supplied)

"People joke about doctors' handwriting — for me, it became very difficult. I could look back in the patient files and see what my writing was like months and years before, and I could clearly see a change," he said.

"It really kicked me when I was examining the movements of Parkinson's patients in the clinic, they were doing better than me."

Dr Blacker's diagnosis led to an intense interest in the suspected origins of the disease.

"The literature over the last few years has really been very suggestive that environmental factors, including exposure to toxins, air pollution and most notably, pesticides, is perhaps playing a key role," he said.

Medical specialists say evidence on paraquat 'warrants immediate action'

In his submission, Dr Blacker and his colleagues have called on the APVMA to take swift action.

"What I would like them to do is listen to the experts in health," he told the ABC.

"It's not just an agricultural problem, it's a health problem, and it's also an environmental problem.

"So I would like them to understand that the medical community is not equivocal about this, we are certain."

MDSANZ president Carolyn Sue is a world renowned expert in movement disorders. In a submission to the regulator, she described the paraquat situation as a critical public health issue.

"The evidence supporting this connection is compelling and warrants immediate action to protect public health," she wrote.

"The health risks associated with this herbicide far outweigh any potential benefits, and alternatives are available that do not pose such severe threats to human health."

Dr Sue told the ABC her organisation felt it was past time to speak up. 

"This is a very clear case where environment exposures in epidemiological studies have brought up the association of their exposure to the development of Parkinson's disease," she said.

The Australian and New Zealand Association of Neurologists (ANZAN) is also supporting MDSANZ call to ban paraquat, calling Australia an "outlier."

Dr Blacker, a clinical professor and noted expert in his own field, said it was reassuring to be backed by these leading peak bodies.

"To have the highest level of expert endorsing this data really means that I'm not acting like a maverick," he said. 

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

Grain growers say risks can be managed

Pete Arkle, interim CEO of Grain Producers Australia (GPA), said the continued used of paraquat was critical to maintain sustainable farming practices in Australia.

"Australian grain farmers are some of the most efficient in the world at turning soil moisture into the food we rely on," he said.

Across key grain growing regions, particularly in the wheat belts of South Australia and Western Australia, paraquat and other chemicals like glyphosate are used to control weeds and preserve soil moisture. (ABC News: Nathan Morris)

Mr Arkle says top soil would be lost if farmers had to revert to ploughing fields to control weeds.

"The last thing we want to see is to go back to that widespread ploughing that we know did lead to dust storms, and did lead to sedimentation of rivers," he said.

Mr Arkle said the industry acknowledged the safety concerns around paraquat, and was determined to see the rules tightened around the safe handling of the herbicide, including high levels of personal protective equipment and closed-looped transfer systems that reduce exposure.

"Four OECD pesticide regulators in the last five years have looked at this question, including the APVMA, and all four of those regulators have concluded that there is no causal link between paraquat and Parkinson's," he said.

"If there is information out there that hasn't been brought to the attention of the APVMA, then this is exactly the time to put that forward."

The leading farm peak body, the National Farmers Federation (NFF), declined the ABC's request for an interview, but said in a statement that it supported the APVMA's process.

"Paraquat is one of many products that allow Australian farmers to grow high quality, safe and sustainable produce in the face of an increasingly volatile climate and growing demand for food and fibre," it said.

"The NFF unequivocally supports the APVMA as Australia’s world-leading independent, science-based regulator, to determine what products they can use and how to use them safely."

In its review of paraquat that was published in August, the APVMA concluded: "There is not a robust association between exposure to paraquat and the development of Parkinson's disease, when used in accordance with the label directions."

The ABC has previously revealed that the science underpinning the APVMA's advice on paraquat's connection to Parkinson's was based on an unpublished paper funded by the maker of the chemical, Syngenta.

US neurologists also pushing for paraquat ban

In the US, Rochester University professors Ray Dorsey and Michael Okun are also lobbying the APVMA to ban paraquat in Australia.

In a letter to the regulator's CEO, Scott Hansen, they warned the health risk was not limited to farmers.

"As you know, farmers who work with paraquat have a 150 per cent increased risk of developing Parkinson's disease," Dr Dorsey and Dr Okun wrote in October.

"It is not just farmers who are at risk. The risk of Parkinson's among individuals who work or simply live near where paraquat is sprayed is doubled.

"These individuals have little protection from the weedkiller's effects."

As Australian farmers have adopted zero-till farming, they have relied more on chemicals to control weeds. (Clint Jasper)

The professors also called on the regulator to consider the tactics of Syngenta, the company that first manufactured paraquat.

"Researchers from around the world have demonstrated that in the laboratory, paraquat produces [in animals] the symptoms (including tremor) and pathology (loss of dopamine-producing nerve cells) of Parkinson's … this research has been conducted by researchers from around the world for the past 25 years," they wrote.

Syngenta maintains that paraquat does not cause Parkinson's disease and is safe to use if the label is followed.

But Dr Dorsey and Dr Okun note that in the 1960s, the company's own researchers "exposed mice, rats, and rabbits to paraquat, and they developed the symptoms and pathology of the disease". 

A 1966 journal article titled The Toxicity of Paraquat, published by scientists from Imperial Chemical Industries, noted rats injected with the chemical exhibited spasms, tremors and "violent forced movements". (Supplied)

"The company … has also sought to discredit scientists investigating paraquat and concealed its own research findings from regulators," Dr Dorsey and Dr Okun wrote.

"These actions beg the question of what else does the company know about paraquat that we do not? Of note, the company's home country and England, where the pesticide is manufactured, have long banned use of the toxic weedkiller."

Dr Blacker told the ABC he doesn't want to be seen as an activist, but as a neurologist representing medical science.

"Future generations are going to look back and think they poisoned themselves," he said.

"[They'll wonder] why did Australia take so long? Why did the United States take so long to join the rest of the world?"

The APVMA declined to comment on this story, but said in a statement it was currently consulting on the proposed regulatory decision for paraquat, adding: "We have public statements and information available and decline to comment further."

The regulator is due to make its final regulatory decision on paraquat by February 28, 2025.