Parkinson’s disease (PD) is a neurodegenerative disease that affects approximately 1 million people in the United States. It is thought to be caused by a combination of genetic and environmental risk factors. Research has found a consistent relationship between Parkinson’s disease and environmental exposure to pesticides.

The most commonly linked pesticides are:

• Rotenone
• Paraquat
• Organophosphorus chemicals
• Agent Orange, a mix of chemicals used to destroy crops from 1961 to 1971 in the Vietnam and Korea wars

However, pesticide exposure alone likely does not lead a person to develop PD and the increased risk is small. Rather, it’s thought that people with Parkinson’s have a genetic susceptibility (or likelihood) of developing the condition, and environmental factors like pesticides may trigger disease development in them. The risk of Parkinson’s disease due to pesticides may depend on factors such as how much, how often, and how long you have been exposed to different kinds of the chemicals.

Here’s what to know about pesticide exposure and Parkinson’s disease, as well as how to reduce your risk.

What Is Parkinson’s Disease?

Parkinson’s disease is a movement disorder in which the nerve cells that transmit messages from your brain and spinal cord to your muscles become damaged. That damage results in progressively worsening motor function and symptoms such as:

• Tremors (shaking) in your arms, legs, hands, and face
• Slowed bodily movements
• Difficulties with balance, coordination, and speaking
• Stiffness in your arms and legs
• Nonmotor symptoms like depression, fatigue, and cognitive impairment

These symptoms are caused by damage and destruction to dopamine neurons (nerve cells) in a person’s brain and spinal cord — a process called neurodegeneration. However, it’s unclear exactly why this cell damage happens in people with PD.

What Are Pesticides?

Pesticides are substances used to control pests. Pesticides can include:

• Insecticides to control insects
• Fungicides to prevent molds
• Disinfectants to kill bacteria
• Herbicides to destroy weeds

While pesticides can help agricultural and farming practices, pesticides often contain chemicals that can be harmful to human health. People may be exposed to pesticides by drinking well water, eating food grown with pesticides, and using household products that contain pesticides.

How Can Pesticides Increase Parkinson’s Disease Risk?

Pesticides can enter the body through oral exposure via food and water, skin exposure by direct touch, and respiratory exposure by breathing pesticides in through the air. Once pesticides are in your body, the chemicals can have a variety of effects. In particular, there are several different biological mechanisms through which pesticides may contribute to Parkinson’s, such as by:

• Damaging brain cells and causing inflammation in your brain and spinal cord
• Impairing your mitochondria (the structure within cells responsible for producing energy) in brain cells, triggering the process of cell aging and neurodegeneration
• Triggering the accumulation of a protein called alpha-synuclein, which kills nerve cells and is a common feature of Parkinson’s

Most of the research on pesticides and the risk of PD focuses on people who live in rural areas and those who work directly with pesticides for their occupation, such as farmers. There is not as much evidence about the relationships between pesticides and PD risk in people who live in urban areas and do not work directly with pesticides every day.

Household Exposure

In the U.S., up to 90 percent of people use products that contain pesticides in the home or garden. However, there is not a wealth of research studies on household pesticide use. That may be because measuring the amount of pesticide exposure in the home depends on a person’s memories of what products and chemicals they bought and used over a period of time.

A study published in the International Journal of Epidemiology in 2013 found that people who used pesticides that contained organophosphorus chemicals had a nearly 47 percent increased likelihood of developing PD.

Organophosphorus chemicals include:

• Chlorpyrifos
• Glyphosate
• Dichlorvos
• Bensulide
• Diazinon
• Malathion
• Tetrachlorvinphos
• Oxydemeton-methyl
• Parathion
• Demeton
• Glufosinate-ammonium
• Disulfoton
• Methidathion

This study also found that the risk of developing PD was higher in people who had an underlying genetic susceptibility to PD.

Other studies have had contradictory findings. A 2005 study, for example, compared people who had already developed Parkinson’s to similar people who did not have Parkinson’s. The scientists found no evidence of an increased risk of PD from a person’s household exposure to pesticides (like organophosphorus chemicals).

Rotenone, used commonly in home gardening, is an example of a chemical that has been linked to an increased risk of PD. Because rotenone is extracted from plants, it is often considered a safe pesticide — but it can interrupt the proper functioning of a person’s mitochondria. And, in studies, its exposure has been shown to induce a Parkinson’s-like state in mice. The use of rotenone was stopped in the U.S. in 2007, but trace levels of the chemical may still linger in the soil and water where rotenone was previously used.

Occupational Exposure

Another way in which a person may be exposed to pesticides is through their occupation — if they work with pesticides. One 2005 research study found that people who had been exposed to the pesticides rotenone or paraquat through their occupations had a 2.5 times higher risk of developing PD.

Exposure to paraquat poses health risks by increasing the production of free radicals in your body, a process that contributes to oxidative stress, aging, and the development of degenerative diseases, like PD. In 2020, the U.S. Environmental Protection Agency (EPA) reapproved the use of paraquat as a pesticide, despite some evidence linking it to PD.

Duration of Exposure

The amount of time a person is exposed to pesticides can influence their risk of diseases like PD. One study claimed that pesticides were a risk factor for PD only in people who were exposed to the chemicals for at least 10 to 20 years.

Reducing Exposure to Pesticides

Because evidence suggests that organophosphorus chemicals, rotenone, and paraquat may play a role in increasing your risk of PD, it may be important to reduce your exposure to these pesticides for better health.

To reduce your exposure to pesticides:

• Wear chemical-resistant gloves, goggles, and long sleeves when working with chemicals anywhere at home, including outdoors.
• Wash your hands throughout the day, especially after using any chemicals (even if you wear gloves).
• Pay attention to the labels on cleaning products and other chemical products. If possible, choose products that don’t contain organophosphorus chemicals or other pesticides.
• If you work in a profession where pesticide exposure is likely or known, take extra safety precautions, like wearing personal protective equipment (such as suits, goggles, and masks) to prevent exposure to chemicals, and wash your hands and change clothes after working with chemicals.

Talk With Others Who Understand

On MyParkinsonsTeam, the social network for people with Parkinson’s and their loved ones, more than 81,000 members come together to ask questions, give advice, and share their stories with others who understand life with Parkinson’s.

Are you living with Parkinson’s disease and have you had high exposure to pesticides in the past? Share your experience in the comments below, or start a conversation by posting on your Activities page.