BY RAY DORSEY, MD, AND MICHAEL S OKUN, MD

Parkinson’s disease was the last thing on Steve Phillips’s mind when he was a carefree teenager surfing the waves of Long Beach, California, in the 1960s.

When his older brother married into a cotton-farming family in West Texas, teenage Steve jumped at the chance to earn some money and experience a summer on the farm.

In 1969, at age seventeen, he traded the beach for the dusty fields of Pep, Texas—population seven.

There, he had a “chance to make a ton of money.” But the price would be high. With no formal training or proper protection, Steve was responsible for mixing chemicals, including the weed killer paraquat.

He would load the toxic weed chemicals into fifty-five-gallon drums that were placed on the back of a tractor. Steve did not wear gloves, goggles, or a respirator. He did not have a protective enclosed cab or air filters.

Instead, Steve wore a Dodger baseball cap and a red bandana—a gift from his brother to keep the dust out of his nose. He rode the open tractor around one-mile-square tracts enclosed by barbed wire fences. As he drove, he sprayed the cotton plants, and depending on the wind, the weed killer would blow back onto him.

Steve sprayed every weekday for the entire summer. When his fifty-five-gallon tank ran dry, a refueling truck would replenish it. Each day, he would finish a square mile, but even with five to six tractors running, it took weeks to spray all the fields. As soon as they finished, the spraying cycle would begin again.

When the season ended, Steve returned to California with a decent paycheck, putting the long days in the fields out of mind. He went on to college, studied organization management, and built a successful career as a leadership consultant.

He was looking forward to a productive retirement until 2008, when, while hosting a dinner for executives in Saint Thomas in the Caribbean, the fifty-seven-year-old could not make his left hand work.

Steve looked for explanations, including stress, fatigue, or the couple of drinks he had while sailing earlier in the day. However, he soon noticed that his left foot would occasionally stick to the floor and that his left arm did not swing much when he was walking.

A neurologist confirmed the diagnosis: Parkinson’s disease.

He was completely unaware that the disease might be related to his activities in the summer of 1969. That changed, however, in 2015 when he started reading the emerging research linking paraquat to the disease.

The Paraquat Connection to Parkinson’s

Four years earlier, Caroline Tanner, MD, PhD, a neurologist and an epidemiologist, had conducted a study that highlighted the risks. Tanner was interested in determining whether farmworkers, like Steve, who worked with pesticides known to damage mitochondria, were more likely to develop Parkinson’s.

Tanner compared more than 100 farmers and spouses with Parkinson’s to agricultural workers without the disease. She found that those exposed to paraquat were 150 percent more likely to have Parkinson’s.

Learning this, Steve was furious—and determined to act. Today, he is an active member of the PD Avengers—a global grassroots organization aimed at ending the disease (learn more at www.PDavengers.com).

He previously led its pesticide action committee and is urging the United States to ban paraquat and protect others from developing his debilitating disease. Steve says, “There is continuing and mounting evidence that [chemicals in] our food, water, and air are the true causal elements of Parkinson’s disease and that Parkinson’s disease is entirely avoidable.”

Manufactured Ignorance

In addition to cotton, paraquat is sprayed on fields of corn, soybeans, and grapes throughout the United States. Over the last five years, use of paraquat has doubled. In 2018, a record fifteen million pounds of the weed killer were used in the United States alone!

Globally, the story is different: more than fifty countries—including China and the UK—have banned paraquat. Ironically, while the UK prohibits domestic use, it continues to manufacture and export it to countries like the United States, Mexico, and Brazil.

The global bans are hardly surprising given the consistent body of research showing that laboratory animals exposed to paraquat develop reduced mobility and exhibit Parkinson’s-like changes in their brains.

The chemical damages mitochondria, which are known to be impaired in the disease. In fruit flies, paraquat can induce misfolding of the alpha-synuclein protein—a key pathological hallmark of Parkinson’s. These findings have been replicated by multiple researchers worldwide.

Yet perhaps the most damning evidence comes not from independent scientists, but from the company’s own files.

Countless farmers have filed lawsuits against the weed killer manufacturer. As part of those lawsuits, the company has had to disclose internal documents dating back to the 1950s regarding its “blockbuster” product.

According to documents reviewed in investigative reports from The Guardian and The New Lede, the company’s very own research has implicated paraquat as causing features of Parkinson’s (eg, stiff gait and tremors) in laboratory animals.

The “extraordinarily high correlation” was concerning and an internal company memo warned that paraquat could, like asbestos, become a huge legal liability. Yet instead of pulling the product, the company doubled down, launching a “freedom to sell” campaign, downplaying risks, and discrediting independent researchers.

To this day the manufacturer still publicly maintains, “There is no causative link, at all, between paraquat exposure and Parkinson’s disease.” In fact, the principal science advisor says, “No scientist or doctor has ever concluded in a peer-reviewed scientific analysis that paraquat causes Parkinson’s.”

In 2021, the EPA reapproved the continued use of paraquat, even though its own website states, “One sip can kill.” With support from the Michael J Fox Foundation, a variety of farmworker groups, environmentalists, and health organizations sued the EPA over its reauthorization.

As a result, the US Department of Justice instructed the EPA to review its decision, again to no avail. In 2024, the EPA reauthorized the continued use of paraquat.

Beyond Paraquat

Despite the best efforts of some pesticide producers to conceal risks, a few farmers are getting the message.

After twenty-five years of growing millions of onions in upstate New York, Matt Mortellaro, a second-generation farmer, called it quits. The main reason—pesticides.

Every onion season since he was in his twenties, Matt had loaded a sprayer with nerve toxicants designed to kill tiny insects that wreak havoc on onion fields. He sprayed his onion crops every seven to ten days, about twenty times during a growing season.

For many years, the pesticide of choice for onion farmers was chlorpyrifos, a chemical that has been used worldwide since 1965. In addition to farms, it is found on utility poles, wood fences, and golf courses. The chemical has cost twenty-six million American children an estimated seventeen million IQ points.

Like paraquat, chlorpyrifos can produce the pathology of Parkinson’s in laboratory animals and is associated with an increased risk of Parkinson’s in humans. Because of pesticides like chlorpyrifos, farmers are at a higher risk for Parkinson’s and cancer.

For Mortellaro, that was too much. He says, “Not handling pesticides is the most significant reason why I left farming.”

Today, three years after selling his Cry Baby onion business, Matt misses farming. He and his wife, Stephanie, have just purchased a small farm where they can grow fruits and vegetables and raise some livestock. But this time, the farm will be different. It will be organic.

Multiple countries have long banned chlorpyrifos and it’s time for the United States to do the same. The Environmental Protection Agency (EPA) issued a rule effectively banning the pesticide in 2021; however, two years later, a court of appeals set aside its rule and allowed for the continued use of chlorpyrifos on foods we eat.

Take Action

While pesticides remain a fixture in modern agriculture, there is much we can do to limit our exposure—and in turn, lower our risk of Parkinson’s. Here we outline ten practical steps for reducing contact with harmful chemicals.

These recommendations may be especially important for those at genetic risk for Parkinson’s or even those who already are affected. By the time Parkinson’s is diagnosed, about sixty percent of the nerve cells that produce dopamine in the substantia nigra—a region of the brain that helps control movement—are already lost. We need to protect the remaining forty percent.

It is also never too late to get started. We take a lesson from smoking. For smokers, cessation helps all regardless of age, and the benefits accrue fast. Twenty minutes after the last cigarette smoked, an individual’s heart rate returns to normal.

A day later, the risk of heart attack lowers. By nine months, coughing is reduced, and a decade later, the risk of lung cancer is halved. The same could be true for environmental toxicants and Parkinson’s.

1. Choose your grocery store wisely. Perchloroethylene (PCE), a common dry-cleaning chemical, can readily spread beyond the cleaner’s walls In Germany, PCE was found in dairy products at supermarkets near dry cleaners at two to twenty times the levels found in stores farther away. Germany now prohibits supermarkets from being located close to dry cleaners. Next time, before you shop at your local market, look around to see what is located nearby.
   
   The same precaution applies to your child’s day care. Dry cleaners can contaminate soil and groundwater, and their chemical vapors can infiltrate nearby homes, schools, workplaces, and child-care centers. Early exposure to such toxins may lay the groundwork for future cases of Parkinson’s, so choose a day care well away from any current or former dry-cleaning facility.

2. Test your well water. About 40 million Americans get their drinking water from private wells, which are not regulated under the Safe Drinking Water Act. These wells are rarely tested and are prone to be contaminated with pesticides and industrial chemicals. If you have a private well, test it regularly (eg, annually) and ensure that you test it for pesticides and chemicals like trichloroethylene (TCE).
   
   The EPA provides a list of laboratories that are certified to test water, and mail-in options are available. Additionally, a simple carbon filter, widely available in supermarkets, can reduce exposure to pesticides, TCE, and other chemicals. These carbon filters can be installed for the whole house at the “point of entry” or at the point of use, such as faucets or even water pitchers.

3. Avoid poisoning yourself at home. Insects, including fleas, ants, and moths, can be unwanted guests. Unfortunately, some commonly used pesticides can increase the risk of Parkinson’s. A synthetic class of pesticides called pyrethroids are widely used to kill insects. Among these is the pesticide permethrin.
   
   Research has tied permethrin exposure to loss of dopamine-producing nerve cells in laboratory animals, and early-life exposure may set the stage for the later development of Parkinson’s. The pesticide is found in flea collars, ant sprays, moth balls, and outdoor apparel. Some of the products containing this and related pesticides are household names that are commonly sold in stores and are likely in millions of homes and garages, including possibly yours.

4. Roll up your windows in traffic. Traffic-related air pollution, especially in tunnels or on congested highways, is linked to a higher risk of both Parkinson’s and Alzheimer’s. When stuck in traffic, close your windows and set your car’s ventilation to recirculate the cabin air to avoid drawing in exhaust fumes.

5. Look around your children’s school. One of the most common sports-field herbicides, 2,4-D, was developed in 1941 and is associated with a 150 percent increase in Parkinson’s symptoms. Millions of children encounter it during school or recreational play. Parents can ask school officials what pesticides, if any, are used on playgrounds and soccer fields and advocate for safer or reduced use.

6. Rethink government subsidies. The US federal government spends about $15 billion a year on farm subsidies. Most of that goes to conventional farming, which uses pesticides. In the United States, the two most subsidized crops are corn and soybeans, and according to the US Geological Survey, paraquat is sprayed the most on those fields. In essence, billions of taxpayer dollars are subsidizing the production of crops on fields that are sprayed with millions of pounds of paraquat.
   
   The Department of Agriculture does have a few programs to incentivize organic farming. However, the size of these programs is approximately one percent the size of the subsidies for farms using pesticides. If we are going to subsidize farming, we should support programs that improve, rather than harm, the health of farmers, rural communities, and consumers.

7. Opt for organic wine. Like produce, organic wines are not immune to pesticide contamination, but they have lower levels and thus reduced health risks. In addition, organic vineyards are likely safer for those who work there and for those who live nearby. Currently, organic wines represent only a small slice—approximately three percent—of global sales, but their share is rising. Organic choices in what we eat and drink could improve the health of consumers, farmers, and communities.

8. Push for organic golf courses. Like most exercises, golf can be beneficial for individuals with Parkinson’s. One small study even found that golf improved performance on a walking test and was more likely to be continued by those with the disease. A 2021 review concluded that “regularly playing golf can lower the risk of falls in older adults with Parkinson’s disease and demonstrates the potential to improve quality of life.”
   
   However, we’ve recently had to ask a more ominous question: Could living near a golf course increase the risk of Parkinson’s? In 2013, two neurologists thought that question was worthy of investigation after they found that nineteen of twenty-six patients in their cohort with Parkinson’s lived within two miles of a golf course. And sixteen of the nineteen lived downwind.
   
   In the 1990s, the New York State Attorney General produced a report titled Toxic Fairways. The report examined the use of pesticides on golf courses on Long Island and found that, in a single year, fifty-two golf courses used 200,000 pounds of dry pesticide products and 9,000 gallons of liquid pesticide formulations—amounting to roughly two tons of pesticides per course annually. One weed killer used was also one of the two main ingredients in Agent Orange.
   
   These pesticides, used on some of the country’s top golf courses, can contaminate underground water systems, and some can linger in the air where they can be inhaled.
   
   Ask your favorite course or neighborhood club—whether you play there or simply live nearby—what pesticides they use and when applications occur. Encourage management to reduce usage and explore safer alternatives. In the meantime, avoid the course immediately after they have been sprayed.

Ultimately, our risk of Parkinson’s—and our overall health—reflects the environments we have lived in. Those environments are shaped by the choices we make as individuals, the standards we set as communities, and the policies we enact as societies. If we want to bring about the end of Parkinson’s for us, for our children, and for all time, we can. It just requires the courage to act.

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Ray Dorsey is the director of the Center for the Brain & the Environment at the Atria Health and Research Institute. The center’s mission is to identify the root causes of brain diseases from autism to Alzheimer’s so that we can prevent them. Ray is also a professor of neurology (part-time) at the University of Rochester where he previously directed the Center for Health + Technology. He also chaired the international Huntington Study Group, led the movement disorders division at Johns Hopkins, and consulted for McKinsey & Company.

Michael S Okun is an internationally renowned neurologist, translational scientist, and thought leader in movement disorders and neuromodulation. He is the cofounder and Director of Centering Cereal the Norman Fixel Institute for Neurological Diseases and has led numerous NIH- and foundation- funded studies advancing brain circuit therapeutics. The author of more than 600 peer-reviewed publications, Dr. Okun’s research has shaped clinical practice guidelines and expanded the understanding of Parkinson’s disease pathophysiology and treatment. He is widely recognized for integrating patient-centered care with cutting-edge neuroscience to drive global innovation in the field.

Well Being Journal adapted the above excerpt from The Parkinson’s Plan: A New Path to Prevention and Treatment Copyright © 2025 by Ray Dorsey, MD and Michael S Okun, MD. Available from PublicAffairs, an imprint of Hachette Book Group, Inc.