Fight Parkinson’s position on paraquat and Parkinson’s disease
Sep. 06, 2024
Fight Parkinson’s is committed to supporting advocacy and providing information, education and services based on robust clinical evidence. All information offered to the Parkinson’s community is based on scientific research as referenced throughout this page.
Our commitment to the continuous development of evidence-based best practices ensures the community can trust that the information we provide is current and reliable.
About Parkinson’s disease and its impact
Parkinson's disease is a chronic neurological condition with a range of complex symptoms unique to each individual. The most common symptoms include stiffened muscles, slowing movement, and changing posture. Many people also experience tremors when resting.
The movement symptoms of Parkinson’s disease are well known. However, non-motor symptoms can also be part of the condition including pain, depression, anxiety, speech changes, and loss of facial expression. Medication and support from health care professionals can help manage these symptoms, however there is no way to slow progression or cure Parkinson's disease.
Neurological disorders are now the leading cause of disabilities in the world and Parkinson’s disease is the fastest growing neurological syndrome1. The cause is still unknown. It's estimated that 57,000 Victorians are living with Parkinson's disease, and 219,000 nationally2.
Parkinson’s disease poses a significant challenge to our healthcare systems and is estimated to cost the Australian community more than $15 billion annually3.
What causes Parkinson's disease?
Science has shown that Parkinson’s symptoms are caused by the breakdown of nerve cells in the brain that produce the chemical messenger dopamine. The exact reasons for the death of these dopamine-producing cells remain unknown.
A significant factor in the onset of Parkinson’s disease is the build-up of the protein alpha-synuclein, forming structures known as Lewy bodies within these cells. However, it is still unclear whether Lewy bodies cause the death of nerve cells or if they are formed as a protective response.
Our understanding of Parkinson’s disease is increasing through progressive research, but there is still much that doctors and scientists do not know about its causes.
It is likely that for most cases, there is a complex interplay between genetic and environmental influences in the causation of Parkinson's disease4.
Studies worldwide have considered pollution, pesticides, herbicides and plastics as environmental factors that may increase the risk of developing Parkinson’s disease.
Understanding the distinction between correlation and causation is important in interpreting research findings. A correlation indicates a relationship between two things but doesn't prove one causes the other.
Risk does not necessarily imply causation but rather indicates how likely an event is to happen given certain conditions.
Position on paraquat
A number of scientific studies have established a clear association between the herbicide paraquat and development of Parkinson's disease9.
Paraquat is a non-selective herbicide which kills most green plant tissue on contact through inhibition of photosynthesis and can also desiccate crops5. Paraquat is also used as an alternative for weeds that are resistant to glyphosate, another common herbicide6.
There is evidence in Australia and around the world, showing a correlation between heightened incidence of Parkinson’s disease in environments where paraquat is used7,8.
International research has provided evidence that paraquat dichloride exposure is associated with a greater risk of developing Parkinson’s disease9. Some studies have shown that the greater the exposure, the greater the risk8,10,11.
There is currently no definitive ‘scientific proof’ that paraquat causes Parkinson’s disease in an individual. As Parkinson's disease is thought to be influenced by a combination of genetic and environmental factors, it is difficult to isolate a single cause, such as exposure to a specific herbicide.
Animal models have however provided evidence of the biological mechanisms through which paraquat could cause Parkinson’s disease14,15,16.
There is also no clear way of proving a causal rather than correlative link between paraquat exposure and Parkinson's disease in humans in a reasonable timeframe and in an ethical way.
Here are some current key findings from the scientific literature:
- Epidemiological findings:
- Numerous credible studies have shown an increased risk of Parkinson's disease among individuals exposed to paraquat. For example, agricultural workers who handle paraquat or live near treated areas exhibited a higher incidence of Parkinson's disease9,12,13.
- Molecular Mechanisms:
- Animal studies have shown that paraquat is known to be toxic to nerve cells. It can damage mitochondria (the ‘powerhouse’ of the cell) and can cause oxidative stress, damaging cellular components including DNA, proteins, lipids and can cause cell death14,15,16.
The European Union, United Kingdom, Canada, China and many more countries have banned the use of paraquat to mitigate potential risks.
The use of paraquat is currently permitted in Australia – a decision that is now under review.
Based on the evidence and the actions of the international community, Fight Parkinson’s supports a ban of paraquat in Australia.
Regulatory review
Currently, the use of paraquat does come with cautions and safe use guidelines including protective gear and health warnings however exposure guidelines established by Safe Work Australia provide limited information on what is considered safe exposure limits to paraquat17,18.
In Australia, paraquat is currently a listed chemical under review under the Australian Industrial Chemical Introduction Scheme's reconsideration program.
As part of the review process, a report has been undertaken by the Office of Chemical Safety at the request of the Australian Pesticides and Veterinary Medicines Authority (APVMA) and published July 202419.
The APVMA are inviting written submissions on a proposed course of action by 29 October 2024.
When the risk assessments have been completed, the proposed regulatory decisions will be drafted. The process is forecasting a decision in February 202519.
Conclusion
Given the body of current evidence, Fight Parkinson’s supports a ban of paraquat to mitigate risk to farmers and their families and the wider Australian community.
We hope the APVMA will follow the lead of the countries who have placed a ban on paraquat use.
Parkinson’s disease has been described as a global pandemic1 and as the fastest growing neurological condition1. The APVMA is in the position to create change and prevent more people from paraquat exposure that may contribute to them developing Parkinson’s disease.
A ban would be Australia’s first preventative measure to reduce the risk of Parkinson’s disease.
Fight Parkinson’s vision is for a world free of Parkinson's disease and until a cause, prevention or cure is found, we aim to empower those living with Parkinson's disease to lead full and active lives.
The review under the Australian Industrial Chemical Introduction Scheme's reconsideration program provides an opportunity to make submissions with our community.
References
1. Dorsey, E. R., Sherer, T., Okun, M. S., & Bloem, B. R. (2018). The Emerging Evidence of the Parkinson Pandemic. Journal of Parkinson's disease, 8(s1), S3–S8. https://doi.org/10.3233/JPD-181474
2. Fight Parkinson’s, Parkinson’s Prevalence retrieved from: https://www.fightparkinsons.org.au/about-us/media-release/parkinsons-prevalence/
3. Bohingamu Mudiyanselage, S. et al. (2017). Cost of Living with Parkinson's Disease over 12 Months in Australia: A Prospective Cohort Study. Parkinson's disease, 2017, 5932675. https://doi.org/10.1155/2017/5932675
4. Warner, T et al. (2003). Genetic and environmental factors in the cause of Parkinson's disease. Ann Neurol 2003;53 (suppl 3):S16–S25
5. Environmental Protection Agency, Paraquat Dichloride: Interim Registration Review Decision Case Number 0262” (Washington, D.C.: Environmental Protection Agency, July 13, 2021), https://www.federalregister.gov/documents/2021/08/02/2021-16344/pesticide-registration-review-interim-decision-for-paraquat-dichloride-notice-of-availability.
6. Paulo Prada, Paraquat: A Controversial Chemical’s Second Act, Reuters, April 2, 2015, retrieved from: https://www.reuters.com/article/brazil-pesticide-paraquat/paraquat-a-controversial-chemicals-second-act-idUSL2N0WY2V720150402.
7. Ayton, D. et al. (2019). Parkinson's disease prevalence and the association with rurality and agricultural determinants. Parkinsonism & related disorders, 61, 198–202. https://doi.org/10.1016/j.parkreldis.2018.10.026
8. Tanner, C. M. et al, (2011). Rotenone, paraquat, and Parkinson's disease. Environmental health perspectives, 119(6), 866–872. https://doi.org/10.1289/ehp.1002839
9. Paul, K. C. et al. (2024). Agricultural paraquat dichloride use and Parkinson's disease in California's Central Valley. International journal of epidemiology, 53(1), https://doi.org/10.1093/ije/dyae004
10. Yaun, Y et al, (2022). High Pesticide Exposure Events and Dream-Enacting Behaviors Among US Farmers, Movement Disorders, Vol. 37, No. 5, 2022
11. Darweesh, Sirwan K.L.et al. (2022) Exposure to Pesticides Predicts Prodromal Feature of Parkinson’s Disease: Public Health Implications, Movement Disorders, Vol. 37, No. 5, 2022
12. Costello, S. et al. (2009). Parkinson's disease and residential exposure to maneb and paraquat from agricultural applications in the Central Valley of California. American Journal of Epidemiology, 169(8), 919-926
13. Gu, Q., et al. (2024). Unraveling paraquat-induced toxicity on mouse neural stem cells: Dose-response metabolomics insights and identification of sensitive biomarkers for risk assessment. Environmental pollution (Barking, Essex : 1987), 355, 124211. https://doi.org/10.1016/j.envpol.2024.124211
14. Sun, J. M., et al. (2023). Cryptotanshinone protects against oxidative stress in the paraquat-induced Parkinson's disease model. Environmental toxicology, 38(1), 39–48. https://doi.org/10.1002/tox.23660
15, Peng, Jun et al., (2004) The Herbicide Paraquat Induces Dopaminergic Nigral Apoptosis through Sustained Activation of the JNK Pathway, Journal of Biological Chemistry 279, no. 31: 32626–32,
16. AIRR Apparent Pty Ltd, ‘Safety Data Sheet - Apparent Paraquat 250 Herbicide,’ 1 June 2021, retrieved from: https://apparentag.com.au/documents/msds/66103_APPARENT_PARAQUAT_250_HERBICIDE_MSDS_1.pdf
17. Work Safe Australia, April 2024 ‘Workplace exposure standards for airborne contaminants’ retrieved from: https://www.safeworkaustralia.gov.au/doc/workplace-exposure-standards-airborne-contaminants-2024
18. Australian Pesticides and Veterinary Medicines Authority, Paraquat Technical Review Report (July 2024) retrieved from: https://www.apvma.gov.au/chemicals-and-products/chemical-review/listing/paraquat
19. Australian Pesticides and Veterinary Medicines Authority, Paraquat chemical review: https://www.apvma.gov.au/chemicals-and-products/chemical-review/listing/paraquat.