‘The Parkinson’s Plan:’ A Neurologist on How Toxins Drive Risk — and What to Do

Parkinson’s may now be the world’s fastest-growing brain disorder. But Neurologist and author Dr. Ray Dorsey believes this disease may be preventable. In his new book The Parkinson’s Plan: A New Path to Prevention and Treatment (PublicAffairs, 2025), co-written with Dr. Michael Okun, Dorsey outlines how pesticides, industrial chemicals, and exposure to other environmental toxins are fueling Parkinson’s and offers practical steps to reduce risk and improve treatment.  

A professor of neurology at the University of Rochester, Dorsey has testified before Congress, advised the World Health Organization, and was recognized by the White House as a Champion for Change. He now directs the Center for the Brain & Environment at Atria Health and Research Institute. He also co-authored Ending Parkinson’s Disease: A Prescription for Action (2020).

In this conversation with Being Patient founder Deborah Kan, Dorsey explains why most Parkinson’s cases appear to stem from environmental rather than genetic factors — and what individuals can do to reduce risk, protect brain health, and seek better treatment.

Being Patient: Can you tell us what we know about that relationship between Lewy body dementia and Parkinson’s?

Dr. Ray Dorsey: There are multiple causes of dementia, and dementia means problems with memory and other aspects of thinking. Alzheimer’s disease is the most common cause, but two of the other top causes are dementia with Lewy bodies and Parkinson’s disease. Dementia with Lewy bodies [has] three main features: difficulties with thinking; slowness of movement, tremor like you see in Parkinsonism; and hallucinations. 

Many of these diseases are not natural consequences of aging — they’re unnatural consequences. The drivers of these diseases — whether Alzheimer’s, Parkinson’s, or dementia with Lewy bodies — in a small proportion are due to changes in our genetics (a large proportion for Alzheimer’s disease), but for most individuals, it’s due to factors in our environment. Parkinson’s disease classically does not have dementia early in the course, and that only develops later.

“Many of these diseases are not natural
consequences of aging — they’re unnatural
consequences… For most individuals, [they’re] due to
factors in our environment.”

Being Patient: So technically, can we call Parkinson’s a dementia?

Dorsey: It can be a dementing condition, and if people live long enough, most will develop some level of cognitive impairment. But we’ve seen people serve in the Senate with Parkinson’s disease. We’ve seen people serve as attorney generals with Parkinson’s disease. So, with Parkinson’s, people can live long, productive lives. It does have cognitive impairment associated with it, but not to the degree or extent that dementia with Lewy bodies or Alzheimer’s does.

Being Patient: So would you say we could talk about Parkinson’s in two different ways — one affiliated with Lewy body, so it’s Lewy body dementia with Parkinson’s symptoms, is that correct? And then Parkinson’s, which sits on its own. Is that a fair way to look at it?

Dorsey: The term scientists like to use is “Lewy body disorders,” because when you look under the microscope, you see clumps of a protein called alpha-synuclein that are in these garbage bags called Lewy bodies within the cells of people with Parkinson’s disease and with dementia with Lewy bodies.

In Alzheimer’s disease, you see another protein called beta-amyloid. But for Parkinson’s and dementia with Lewy bodies, you see these Lewy bodies in the nerve cells.

One great scientist, Dr. Per Borghammer, in 2019 said there are two real forms of these Lewy body disorders: one that begins in the gut — predominantly, in most cases, dementia with Lewy bodies — and one that begins in the nose — predominantly seen in Parkinson’s disease — giving us a clue that the origins of these so-called brain disorders lie not actually within our brain, but outside of it, perhaps beginning in the gut (especially dementia with Lewy bodies) and in the nose (especially Parkinson’s).

Being Patient: Would you say most causes can be equated with environmental factors?

Dorsey: For Parkinson’s disease, a large-scale genetic study came out in 2024 in the Brain journal. They looked at 8,000 people with Parkinson’s disease — many of them Americans — and of those 8,000, only 13 percent carry a genetic cause or risk factor. Said another way, 87 percent of Americans with Parkinson’s disease have no known genetic cause or risk factor.

In 2003, a really smart German pathologist named Heiko Braak said that when he looks at the brains of people with Parkinson’s disease, he sees the pathology beginning in one of two locations. One, the smell center — the olfactory bulb — and second, in the cell bodies of the neurons that go to the gut, called the vagus nerve. 

He thought that Parkinson’s disease might be due to neuroinvasion from some kind of infectious particle that would lead to the misfolding of a protein, alpha-synuclein, that would spread from nerve cell to nerve cell.

We know there are a few viruses that increase risk, but for the vast majority, it’s not viruses — it’s chemicals. When we ingest chemicals — certain pesticides; well water; dry-cleaning chemicals that can contaminate up to 30 percent of groundwater — we predispose to misfolding of alpha-synuclein beginning in our gut and then spreading up to the brain. Those individuals get early constipation, early sleep disturbances, then Parkinsonian symptoms. They also tend to be more likely to get dementia with Lewy bodies.

Some individuals — especially those with Parkinson’s disease — the pathology begins in the smell center of the brain, perhaps due to inhaling pesticides from golf courses or from dry cleaners, or outdoor air pollution, a major risk factor for Alzheimer’s disease as well.

“87 percent of Americans with Parkinson’s disease have no known genetic cause or risk factor.”

Being Patient: What do we know in terms of linking these chemicals to Parkinson’s directly? Has there been credible research? How do we know that?

Dorsey: In 2011, Dr. Caroline Tanner — a Parkinson’s specialist with a PhD in epidemiology — showed that farmers who work with a weed killer called paraquat, which damages the energy-producing parts of cells called mitochondria, have a 150 percent increased risk of Parkinson’s disease.

In 2023, two other women, Drs. Beate Ritz and Kimberly Paul at UCLA, showed that simply living or working near where paraquat is sprayed is associated with a doubling of risk. 

In about 1998, my colleague Dr. Debbie Cory-Slechta, a neuroscientist at the University of Rochester, showed that when you expose laboratory animals to paraquat, they develop the clinical and pathological features of Parkinson’s disease, including slow movement and tremor. 

About two years ago, she showed that when laboratory animals inhale paraquat, it gets back to all the parts of the brain examined, including the substantia nigra — the part of the brain impacted in Parkinson’s.

Being Patient: Is paraquat widely used today still?

Dorsey: Over 70 countries, including China, have banned it, but the United States has not. The U.S. continues to spray a weed killer that China has banned on cornfields, soybean fields, cotton fields, and vineyards throughout the United States, and, according to reporting from The Guardian, use has tripled in the last eight years.

Being Patient: How do people protect themselves from environmental risk? 

Dorsey: On page 237 of our book, we give you the Parkinson’s 25: 25 actions you can take in your everyday life to reduce your risk of ever getting Parkinson’s disease or, if you’re among the 1.5 million Americans who already have the disease, what you can do to possibly slow your rate of progression.

One is: what are we eating? How do we reduce chemical exposure? Buy organic. Wash your fruits and vegetables, even organic ones. When the Department of Agriculture determines a safe residue of a pesticide on an apple, for example, they do so after that apple’s been held under cold water for 15 to 20 seconds. That’s what the government is doing with food. Think about what you should be doing — washing with water and a vegetable wash, or salt or vinegar. 

If you get your water from a well, you should test that water for pesticides and industrial chemicals, and you should add a water filter. 

I think almost everyone should have an air purifier, especially if you live in an area with high levels of air pollution. In New York City, we have an air purifier in our living room and bedroom. 

There’s a great study from the Nurses’ Health Study that looked at nurses who had normal cognition at 70 and followed them for about five to eight years. Nurses who lived in areas with less air pollution had slower rates of cognitive decline than people who lived in polluted areas. 

If you’re dry cleaning, make sure you use a green dry cleaner. Find a green dry cleaner that does not use a chemical called perchloroethylene (PERC) which has a chemical structure very similar to trichloroethylene. 

Make sure you’re not poisoning yourself in your home and your environment. Many pesticides are nerve toxins — that’s how they kill insects. If something’s killing off insects, it may not be good for your nervous system either.

Being Patient: I’m curious about the genetics of Parkinson’s. In Lewy body dementia, it could be genetic, or they’ve found variants linked to it, but not all cases are. What about Parkinson’s disease? Although environmental factors appear to be significant, are people with certain genes more susceptible?

Dorsey: I think this is a great myth — that these diseases are natural consequences of aging. I was taught that Parkinson’s disease was due to aging, bad genes, and bad luck. I don’t think that’s the case for the vast majority of people. 

These diseases are not natural consequences of aging. John Adams, 200 years ago, was writing letters at age 90 to Thomas Jefferson at age 83. Neither had Alzheimer’s disease, Parkinson’s disease, or dementia with Lewy bodies. We’ve had old people around for long periods of time, and these diseases — Parkinson’s not described until 1817; Alzheimer’s not described until 1906; dementia with Lewy bodies not described until 1976. I find it hard to believe neurologists and physicians were missing millions of people with these brain diseases. 

We know from the Lancet Commission that 45 percent of Alzheimer’s disease might be preventable. There are cardiovascular risk factors, diabetes, hypertension. Air pollution is an enormous, understated risk factor for Alzheimer’s disease. Chemicals in our food, water, and air are fueling the rise of disease. Alzheimer’s has a modest genetic contribution — ApoE being the biggest — but diseases like Parkinson’s are among the least heritable of all diseases. I told you only 13 percent of people carry a genetic risk factor. The most common is a mutation in a gene called GBA, also possibly implicated with dementia with Lewy bodies. 

Our colleague, Dr. Ethan Brown, showed that people who carry this mutation might have increased susceptibility to the effects of pesticides. Some of these genetic changes might explain why some individuals exposed to toxicants get the disease and some don’t. But for the vast majority with Parkinson’s, if you are not exposed to these chemicals, you’re highly unlikely to get Parkinson’s. There are exceptions, but you’re highly unlikely if you’re not exposed to these pesticides, dry-cleaning chemicals, and air pollution.

“But for the vast majority with Parkinson’s, if you are not exposed to these chemicals, you’re highly unlikely to get Parkinson’s.”

Being Patient: You’ve talked about how we can protect ourselves, but your book is “The Parkinson’s Plan”. What is the plan? What’s available to people in terms of treatments? 

Dorsey: If you already have Parkinson’s disease, what are the three things you should be doing? Number one: stop being exposed to toxicants. Research shows people with Parkinson’s disease exposed to high levels of pesticides have a faster rate of progression across almost every domain measured, and individuals exposed to high levels of air pollution have a greater risk of being hospitalized for their Parkinson’s disease. 

If you have dementia with Lewy body disease, be vigilant about protecting the remaining nerve cells. Stop being exposed to toxicants, control and manage diabetes, and minimize exposure to air pollution. I think air pollution, especially for Alzheimer’s disease, is completely underestimated in its contribution. 

Second: exercise. Exercise vigorously enough to make you sweat. It releases growth factors in the brain that might protect damaged or dying nerve cells, let them recover, and let your body’s processes improve and repair the nerve cells that have been damaged. 

Third: get really good care. Good care makes a difference. In the United States, less than one out of every 10 individuals with Parkinson’s see a Parkinson’s specialist. My colleague, Dr. Allison Willis, demonstrated that individuals who do not get care from a neurologist are more likely to fracture their hip, more likely to be placed in a skilled nursing facility, and more likely to die. Good care is really important for people with Parkinson’s disease — and likely dementia with Lewy bodies and Alzheimer’s disease.

Being Patient: Talk to me about what types of drugs people are put on in the case of Parkinson’s or Lewy body. Are they different? Is it managing the symptoms? What medications are out there?

Dorsey: In Parkinson’s disease, we’ve known for about 60 years that people have low levels of dopamine in their brain. That led neurologists to give first dopamine — which didn’t work — and then a precursor to dopamine called levodopa — just an amino acid you can take as a pill — highly effective.

Unfortunately, that same medication, when given to people with dementia with Lewy bodies, doesn’t appear to help their Parkinsonian symptoms as well. As I mentioned, one of the three core features of dementia with Lewy bodies is hallucinations, and levodopa can predispose individuals to hallucinating. You’re stuck in a tight spot with treating individuals with dementia with Lewy bodies. So levodopa can be effective, but more problematic, and usually not as robust a response as with Parkinson’s.

Being Patient: Is there any other medication given? And when we see focused ultrasound treatments — using ultrasound to open the blood-brain barrier and aim medication at the brain — is that levodopa that’s happening, or is there another medicine out there?

Dorsey: The FDA-cleared indication for focused ultrasound today is to treat disabling tremor on one side of the body. Focused ultrasound works by delivering high-energy ultrasound waves that damage — kill off — a part of the brain that might be inappropriately overactive in people who have Parkinson’s disease or another tremor-related condition called essential tremor. You only do it on one side of the body, so it only gives you benefits on the opposite side. 

There are research studies looking at using ultrasound to disrupt the blood-brain barrier to allow medications to more effectively cross; those are still in early stages. For people with dementia with Lewy bodies, I think your audience knows about acetylcholinesterase inhibitors. These likely offer benefits to people with dementia due to Parkinson’s or due to dementia with Lewy bodies, and can decrease hallucinations, so they’re often used. 

But I think a lot of dementia with Lewy bodies — the root cause — is toxicants people have ingested. Time and time again, when I see people with dementia with Lewy bodies, I ask what they were drinking or eating when they were young. Did they grow up with well water? Did they have a contaminated water supply? I get really concerned about what people are drinking or eating, especially early in childhood — when they were teenagers — setting them up for getting these diseases years or decades later.

Being Patient: What is the typical age for Parkinson’s?

Dorsey: It triples every decade. It’s extraordinarily rare before 30 or even 40, but the number of people with young onset — before 50 — appears to be rising, and it triples every decade in your 50s, 60s, and 70s.

Being Patient: What do you recommend? Diagnosis can be very difficult, especially on the Lewy body side. What should people do if they’re starting to question symptoms — maybe tremors, hallucinations? What is the best thing they can do, and what questions should they be asking to get a more accurate diagnosis?

Dorsey: First, find a really good neurologist or specialist. That’s true for any chronic, serious disease. It’s important to find someone who is good and specialized. 

Second, ask why you have the disease. Why do I have this disease? Why is that important? If you know why, you can take actions to slow progression. You can take actions to treat more effectively, you get a lot closer to a cure, and you can prevent your kids, grandkids, and others from getting the disease.

If we view Parkinson’s, Alzheimer’s, and dementia with Lewy bodies as natural consequences of aging, when they’re unnatural for most individuals, we’re only going to allow one in three Americans at age 85 to get Alzheimer’s disease; we’re only going to allow dementia with Lewy bodies to be the second leading cause of dementia in the United States; we’re only going to continue to allow Parkinson’s to be one of the world’s fastest-growing brain diseases. These are not natural consequences of aging for most individuals. These are unnatural consequences. The sooner we recognize that, the sooner we clean up our air, food, and water, the sooner we create a world where these diseases are increasingly rare instead of increasingly common.

Being Patient: Is there one particular treatment in the pipeline being tested now — stem cell therapy, something — that you’re keeping a close eye on? 

Dorsey: There’s lots of hope, and our book is hopeful and optimistic. Chapters eight and nine — my colleague Dr. Michael Okun writes on what treatments are most promising in the short term (next five years), midterm (five to 10), and longer term. 

For Parkinson’s, the levodopa pumps — like insulin pumps for diabetes — can be very effective. The surgical treatments — Dr. Okun’s one of the world’s experts in surgical treatments for Parkinson’s, like deep brain stimulators — are really powerful. The immunotherapies being used to reduce amyloid in Alzheimer’s disease are being studied to reduce the amount of a misfolded protein called alpha-synuclein in Parkinson’s disease. I think those have a lot of hope. 

I think we can be the first generation to create a world where these diseases are less common. We’ve received a world where polio is largely absent, where drinking and driving is socially unacceptable, where the incidence of HIV is falling, not rising. These are gifts we’ve received from previous generations. It’s time for our generation to reciprocate and create a world where diseases like dementia with Lewy bodies, Alzheimer’s disease, autism, ALS, and Parkinson’s disease are increasingly rare.