Farmers, agricultural workers, and those who have lived near an industrial farm, and have been diagnosed with Parkinson’s disease, may have a claim against the manufacturers of paraquat, a toxic weed killer that has been linked to the degenerative neurological condition. Paraquat has grown in use in the past decade, doubling between 2006 and 2016. Paraquat’s popularity has resulted in increased exposure and greater potential for certain individuals to be harmed by its toxic effects. Currently, hundreds of lawsuits have been filed against paraquat manufacturers Syngenta and Chevron USA by agricultural laborers who have been diagnosed with Parkinson’s disease.

What is Parkinson’s Disease?

Parkinson’s disease is a disorder of the nervous system that results in progressive deterioration. Nerve cells in the brain may weaken or die, leading to neuron loss. Neurons produce a chemical called dopamine, which is responsible for transmitting messages between nerve cells. The reduction in dopamine in Parkinson’s patients causes a range of physical symptoms.

The most common symptoms of Parkinson’s are tremors, stiffness, and impaired movement. The characteristic stiffness found in Parkinson’s patients can significantly limit muscle control. A patients’ speech, balance, and automatic movements (such as blinking or smiling) may also be impaired. Factors that appear to play a role in developing Parkinson’s disease include genetic history and environmental triggers.

Scientific Literature Supports a Link Between Paraquat and Parkinson’s Disease

Several well-known publications have demonstrated that pesticides can have harmful effects on the brain. The American Journal of Epidemiology found that pesticides may increase the risk of Parkinson’s disease after concluding that exposure to maneb and paraquat within 500 miles of a subject’s home (between 1974 and 1999) elevated the risk of Parkinson’s by 75%. Both younger subjects and those over 60 years old who were exposed to these pesticides had the highest risk of developing Parkinson’s.

The journal Jama Neurology also reported that pesticide use caused an increase in the risk of Parkinson’s. Specifically, occupation-based exposure to pesticides was linked to a nearly 80% higher incidence of the disease. Several pesticides were studied and paraquat demonstrated a 3-fold elevated risk of Parkinson’s. According to the study, “occupational pesticide exposure emerges as the most consistent etiologic association with parkinsonism.” Moreover, paraquat, along with two other specific insecticides, had effects on “dopaminergic neurons in experimental settings.”

In a joint study between the National Institute of Environmental Health Sciences and the Parkinson’s Institute and Clinical Center in California, researchers concluded that people who were exposed to either rotenone or paraquat developed Parkinson’s disease 2.5 times more often than those who did not come into contact with these pesticides. The study observed 110 subjects with Parkinson’s disease and 358 control subjects from the Farming and Movement Evaluation Study, a case-control study that is associated with the Agricultural Health Study.

According to researchers, paraquat leads to an increase in oxygen derivatives that can impair certain cell structures and increase the risk of Parkinson’s disease.

EPA Issues Safety Measures for Paraquat

Although paraquat has been outlawed in dozens of countries, it is still widely available for commercial use in the United States. Classified as a “restricted use” pesticide, only licensed applicators may purchase and use it. The United Parkinson’s Advocacy Council requested that the Environmental Protection Agency (EPA) ban the use of paraquat due to research linking paraquat to the development of Parkinson’s disease. In August 2021, the EPA issued an interim decision permitting the continued use of paraquat, but required additional safety measures, such as no-spray buffers in residential areas. Despite acknowledging the pesticide’s toxicity, the agency dismissed scientific reports linking paraquat to Parkinson’s disease.