"Multiple epidemiological studies, supported by laboratory and animal research, have identified a consistent correlation between paraquat exposure and Parkinson’s Disease (PD). Whilst correlation does not equate to causation, this absence of definitive proof should not be mistaken for evidence of safety. Public health and environmental regulation often require decisions to be made based on the best available evidence rather than absolute certainty.

When a substantial body of scientific data repeatedly points to a potential risk, particularly for a serious and incurable condition such as PD, regulators should apply the precautionary principle. In circumstances where uncertainty remains but credible evidence of harm exists, the responsible approach is to err on the side of caution and prioritise the protection of human health while further research continues."

"The APVMA decision is not a finding that paraquat is harmless. Paraquat retains registration under substantially tighter conditions, including lower general application rates, closed mixing and loading, enclosed-cab requirements, stronger protective equipment and the phase-out of backpack spraying. Importantly, these restrictions were driven mainly by acute risks to handlers and risks to birds and mammals, rather than by a demonstrated safe threshold for Parkinson’s disease.

From a neuroscience perspective, the evidence is that Paraquat causes oxidative injury, and experimental systems show effects relevant to Parkinson’s disease, including damage to dopamine-producing neurons and altered alpha-synuclein biology. Human observational studies and meta-analyses report increased Parkinson’s risk associated with paraquat exposure, including recent studies using pesticide-application records rather than recall alone. However, exposure measurement, co-exposures and study design limit causal certainty, and some large cohorts have not found a robust association. 

That uncertainty should not be confused with evidence of no risk. The lack of conclusive evidence points to an urgent need for funded research into the neurological risks and the cancer risks. In fact, the lack of safety data is an argument for taking far more caution until the serious issue is resolved, much as we would not approve drugs until rigorous safety is shown. I support time-limited registration and ultimately cessation in the absence of clear evidence of safety. We need independent neurological review, national exposure and health surveillance, and rigorous auditing of compliance. Australia should also fund a planned transition to safer alternatives. If chronic neurological and cancer safety cannot be demonstrated under real-world conditions, paraquat should be phased out."

"From an environmental science perspective, the discussion around paraquat should not focus solely on application rates, but also on the broader question of long-term exposure and environmental persistence. While reducing application rates may lower immediate exposure, scientific assessment of risk must also consider how frequently the chemical is used, how long exposure occurs, and its behaviour in the environment over time.

One of the key scientific challenges with paraquat is that it binds very strongly to soil particles, particularly clay minerals. This can reduce its immediate mobility, but it also means that residues may remain in soils for extended periods following repeated applications. Consequently, understanding the long-term environmental fate of paraquat remains an important area of research.

There is also strong scientific evidence that paraquat is highly toxic to aquatic organisms if it enters waterways through runoff, erosion, or accidental releases. Therefore, protecting sensitive ecosystems requires continued attention to application practices, environmental monitoring, and risk management measures.

The science surrounding paraquat is complex, and it is important that regulatory decisions continue to be informed by emerging evidence. Ongoing research into long-term environmental behaviour, exposure pathways, and ecological impacts will be critical to ensuring that agricultural productivity is balanced with protection of human health and the environment."

"The decision is deeply concerning and should be for all Australians because it represents a failure of Australia’s chemical regulatory frameworks in their supposed core vision of safeguarding human and environmental health. This decision is at its core emblematic of the alarming outcomes that can be expected from a system that in its evaluation of a chemical asks 'how can we approve this chemical with adequate safe use recommendations?' rather than 'should we approve this inherently dangerous compound and are any usage instructions applicable when the intention is to release it into the environment where we can’t predict its fate or action?'.

The former is a risk-based approach to evaluation that the Australian Pesticides and Veterinary Medicines Authority (APVMA) adheres to, and which the EU has rejected as not being appropriate for chemical evaluation. Rather, they have adopted a Hazard-Based approach that seeks to eliminate the use of inherently toxic compounds. Paraquat is likely the worst example of a dangerous pesticide that remains approved in Australia, but our recent study showed that 84% of Australia’s highest use pesticides (i.e. those used >100t per year) were already banned overseas. The fact that Australia is consistently out of step with international decision-making on pesticides warrants societal concern and an evaluation of regulatory processes."

Australia’s pesticides regulator, the Australian Pesticides and Veterinary Medicines Authority (APVMA) has released its long-awaited regulatory review into paraquat, after public consultation and considering the latest data from the United States. As expected from the preliminary report in 2024, the review retains the use of paraquat.

However, standard maximum broadacre application rates have been slashed by 80% to reduce the risk of acute human toxicity and environmental risks to wildlife. Higher rates are permitted solely for technology-assisted spot spraying. Furthermore, the types of applications that are allowed are greatly restricted to improve safety. While paraquat is known as a Schedule 7 poison, most commentary has focused on potential links to Parkinson’s disease.

Parkinson’s disease is a devastating, progressive movement disorder. Over time, people develop muscle rigidity, become less able to move, experience tremors, and become unsteady on their feet. While agricultural workers have a higher risk of Parkinson’s, tying this to any specific chemical exposure has been elusive.

The APVMA has concluded that the weight of evidence does not show that paraquat exposure increases the risk of developing Parkinson's disease. This conclusion is certain to be controversial.

But it is warranted. Experimental animals exposed to paraquat through typical routes of exposure (inhalation, oral consumption) do not develop Parkinson’s. Industrial workers exposed to high levels of paraquat have not developed Parkinson’s. Systematic reviews of epidemiologic studies have failed to find a definitive link.

Regardless, the new exposure and application limits will improve human and environmental safety.

This is a very concerning decision for rural communities. We already know that Parkinson’s disease is more prevalent in rural and regional areas, and while the APVMA claims the causal link with paraquat has not been conclusively shown, it seems they have ignored submissions from experts in the field on the growing epidemiological evidence for this link.

In our research, we have found that this increased prevalence is also compounded by the low level of local services available for patients in rural and regional areas, such as specialists, physiotherapists and allied health professionals, meaning that many patients must travel long distances to access their care.

The recent announcement of the continued approval for the use of the herbicide paraquat by the Australian Pesticides and Veterinary Medicines Authority (APVMA) is a blow for the Parkinson's disease community in Australia, who have actively campaigned to bring Australia into line with countries that have banned the use of this chemical.

This is because there is strong evidence that exposure to paraquat, particularly over a period of time or high doses, increases risk for this common neurological disease. While there is as yet no definitive proof that paraquat causes Parkinson's disease, as this would be extremely hard to prove in humans, the evidence suggests it would be wise to err on the side of caution.

Decreasing exposure by wearing protective clothing or using alternative weed-control chemicals would appear to be wise until we have a better understanding of this risk. While the use of paraquat has not been banned in Australia, it will now be used under stricter controls, including at lower diseases, and this may decrease possible risks to the community.