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Environmental Toxins and Parkinson’s Disease

Can pesticides and air pollution cause Parkinson’s disease? Learn about environmental factors linked to Parkinson’s and how reducing harmful chemicals may help prevent the disease.

The prevalence of Parkinson’s has doubled over the past 25 years and is projected to double again by 2050. Over the same 25-year period, disability due to Parkinson’s disease has increased by 80% and Parkinson’s-linked deaths have increased by 100% — outpacing every other neurologic disorder globally. With the skyrocketing impact of this disabling disease on millions of people worldwide, research into prevention and cures is critical.

We hosted a discussion with Ray Dorsey, MD, David M. Levy Professor of Neurology and director of the Center for Health and Technology at the University of Rochester Medical Center, to discuss one surprising and under-researched possible cause of Parkinson’s disease: toxic environmental factors like pollution and pesticides.

Reframing Parkinson’s as a Preventable Disease

Since the completion of the Human Genome Project in 2003, researchers have seen leaps forward in early diagnosis for a number of brain diseases linked to genetic causes. However, Dorsey notes that diseases like Parkinson’s do not seem to be strongly linked to genetics and are not likely to be inherited.

“Only about 15% of people with Parkinson’s have a family history of the disease, and only about 15% of people with Parkinson’s have an identifiable genetic risk factor,” says Dorsey. “[Additionally], most people who carry those genetic risk factors will not go on to develop Parkinson’s disease. So what is causing Parkinson’s?”

Dorsey thinks that while genes may play a small role in Parkinson’s risk, the disease is largely caused by environmental factors within human control. Specifically, exposure to high levels of pollution as well as chemicals like certain pesticides and industrial cleaning products play a large role in a person developing Parkinson’s disease.

This means Parkinson’s disease could be preventable if we can reduce exposure to these chemicals and other environmental risk factors. For this reason, Dr. Dorsey argues we should be putting many more resources into prevention — both in researching how environmental toxins like pesticides contribute to the development of Parkinson’s and in reducing and ultimately eliminating the use of these harmful chemicals. 

Air Pollution and Neurologic Disorders

Recent research studies have linked air pollution with brain disease, but Dorsey argues this is still an under-researched topic with serious implications for our understanding of multiple diseases, including Parkinson’s. He notes that the rise in Parkinson’s cases over the past century has often corresponded with increased pollution in large urban areas. In fact, the earliest descriptions of Parkinson’s by English researchers in the early 1800s coincided with a drastic increase in the amount of smog and air pollution in London. 

“Areas of the world that are undergoing the most rapid industrialization, like China and India, have the fastest increasing rates of Parkinson’s disease,” says Dorsey. “The areas of the world that are most industrialized, like the United States and Canada, have the highest rates of Parkinson’s disease, while the areas that are least industrialized, like sub-Saharan Africa, have the lowest rates of the disease.”

Even with current clean air and emissions laws, studies have found that 40% of people in the U.S. still breathe unhealthy air, and 95% of the global population is exposed to pollution levels above WHO guidelines. 

Additionally, events like the wildfires in Canada last year can also spread harmful levels of pollution across many miles of airspace. “In fact, air pollution in New York City this summer reached the levels of 1800 London [due to the Canadian wildfires],” says Dorsey. 

Pesticides and Other Harmful Chemicals Linked to Parkinson’s

In addition to air pollution, Dorsey identifies two types of chemicals that have been strongly linked to Parkinson’s: pesticides like paraquat, and cleaning chemicals like trichloroethylene (TCE).

Paraquat and Parkinson’s

Paraquat is a pesticide that has been linked to a 150% increased risk of Parkinson’s disease. It has been banned in over 30 countries but is still in widespread use in the U.S. Additionally, studies have shown that farmers exposed to pesticides have an increased risk of developing Parkinson’s.

An investigation published by The Guardian in 2022 found that manufacturers of paraquat identified links between the pesticide and Parkinson’s as far back as the 1960s. Specifically, animal trials in 1966 showed that high doses of paraquat in rats and mice resulted in “stiff gait or tremors” — the primary physical symptoms of Parkinson’s disease. Nearly 20 years later, a research study reported an extremely high correlation between levels of pesticide exposure and Parkinson’s. 

Despite this, says Dorsey, “use of paraquat in the U.S. has more than doubled in the past five years for which data is available, despite its known risks.”

TCE and Parkinson’s Risk

TCE is a cleaning chemical used in a variety of products, including household cleaners, and across a wide range of industries, from dry cleaning to manufacturing. Researchers have linked exposure to TCE with a 500% increased risk of Parkinson’s disease. A very similar chemical called perchloroethylene (PCE) is used in many of the same types of products and applications.  

Because it is so widely used across many different industries, it is difficult to estimate the total number of people in the U.S. who have been exposed to toxic levels of TCE. Dorsey notes that even if people do not work in an industry that uses TCE, the chemical is so widespread that many are exposed to contaminated groundwater or toxic TCE levels in the air. 

“TCE contaminates up to 30% of groundwater in the United States,” says Dorsey. “Once contaminated, it forms underground plumes that can migrate a mile or more, and then from these underground plumes, much like radon, TCE can evaporate from groundwater into people’s homes, schools, and workplaces.”

Prioritizing Parkinson’s Research and Prevention

Dorsey argues that in order to effectively address the growing rate of Parkinson’s, the scientific community needs to embrace a new approach to brain diseases like Parkinson’s — one that emphasizes research and prevention, not just treatment.

“For each dollar Medicare is spending on caring for people with Parkinson’s, the NIH is spending one cent on research related to it — that’s just not going to get the job done,” says Dorsey. “It’s really hard to make big therapeutic breakthroughs when you don’t know the cause of a disease.”

Research is key to better understanding how environmental toxins like pollution, pesticides, and chemicals like TCE contribute to the formation and progression of Parkinson’s. Additionally, insights gained from this research will shed light on related neurodegenerative diseases. 

“These environmental toxins that are associated with Parkinson’s disease aren’t just limited to Parkinson’s — they likely apply to other brain diseases, especially Alzheimer’s disease and ALS,” says Dorsey. “The greatest gift we neurologists can give to future generations is a world where Parkinson’s disease, Alzheimer’s disease, and ALS are increasingly rare, not increasingly common.”

You can view the full webinar discussion with Dr. Dorsey here.

The American Brain Foundation knows that when we find the cure to one brain disease, we will find cures to many others. Learn more about the brain disease research we fund, or donate today to support the cures and treatments of tomorrow.