According to the paraquat lawsuits filed in St. Clair County Illinois, and across the nation, the herbicide paraquat can cause Parkinson’s disease.

An experiment in Southern California in the 1980s showed that MPTP, a heroin contaminant, caused users to experience symptoms similar to those associated with Parkinson’s disease. The experiment demonstrated that the heroin contaminant killed dopamine neurons, the same neurons that are damaged in Parkinson’s disease patients. MPTP and paraquat have chemical structures that are very similar.

The Environmental Protection Agency (EPA) declared in 1997 that the primary route of exposure to paraquat was during the mixing, loading, and application of the herbicide, as well as during the post-application period. The agency also stated that, despite the fact that the herbicide is not licensed for residential use, such exposure is possible for people who live near farms where the herbicide is used.

Over the last two decades, scientists have increased their research into the effects of paraquat toxicity on humans, especially the risk of Parkinson’s disease.

According to a 2009 study published in the American Journal of Epidemiology, any exposure to paraquat within 1,600 feet of a home increased the risk of Parkinson’s disease by 75%.

Environmental Health Perspectives, in collaboration with the National Institute of Environmental Health Sciences, released findings from a comprehensive review of Parkinson’s disease cases and pesticides in 2011. Paraquat emerged as a major concern in this report.

Pesticides that block mitochondrial complexes and those that induce oxidative stress have been linked to Parkinson’s disease. Paraquat works by producing intracellular molecules that cause oxidative stress in cells. According to the report, “Parkinson’s disease was closely correlated with” paraquat. The authors also stressed that the risk of paraquat exposure extends beyond the occupational/agricultural climate, and that many people may be exposed to the pesticide without even being aware of its presence in their surroundings.

The study also found a significantly increased risk of Parkinson’s disease in people who had been exposed to both paraquat and a form of fungicide known as fungicide maneb. Finally, participants in the study who lacked an active copy of a particular gene (missing in 20% of Caucasians and 40% of Asians) were at a higher risk of paraquat toxicity.

The EPA announced in 2016 that it would re-evaluate paraquat, including the possible correlation to Parkinson’s disease.

The Unified Parkinson’s Advocacy Council sent a letter to the EPA on July 24, 2017, in anticipation of the agency’s paraquat registration review. The petition, signed by all council members, listed a laundry list of evidence linking paraquat to the development of Parkinson’s disease symptoms and pathology and concluded by urging the EPA to refuse paraquat’s reregistration.

The letter went on to emphasize the financial costs of Parkinson’s disease, including:

Individual treatment for a person with Parkinson’s disease costs $26,400 per year.

Annual economic burden in the United States between $19.8 to $26.4 billion. Costs associated with dependence on services such as Medicaid, Medicare, and Social Security.

Syngenta and Growmark, the manufacturers of paraquat, were sued on October 6, 2017. The lawsuit was lodged on behalf of farmers and agricultural workers who were exposed to paraquat and developed Parkinson’s disease. Chevron Chemical has been added as a defendant in the case since the initial charge was filed.

The National Toxicology Program (NTP) of the U.S. Department of Health and Human Services released its protocol for a study of paraquat dichloride toxicity and Parkinson’s disease in 2018. Recognizing that hundreds of studies have been conducted to examine the correlation between paraquat exposure and Parkinson’s disease, the analysis will attempt to map evidence that links the two.

How does paraquat work?

Paraquat is sprayed directly onto plants, where it destroys the leaves on contact. When the compound comes into contact with soil, it becomes inactive.

The chemical is sprayed to clear fields before crops are cultivated, as well as to eradicate marijuana crops in Mexico and the United States.

Paraquat is often used as a herbicide for weeds that have gained resistance to Roundup and other glyphosate-based herbicides, according to the Unified Parkinson’s Advisory Council.

What Do We Know About Parkinson’s?

Parkinson’s disease is a debilitating neurodegenerative condition that manifests itself in humans in their middle to late years of existence. Tremors in the arms and legs, weakened coordination and balance, sluggish movements, and rigidity of the body and limbs are some of the effects on the motor system. Such symptoms are due to the brain’s gradual degeneration of dopaminergic neurons.

Parkinson’s disease is the second most common neurodegenerative disease in the world. The disorder is chronic and progressive, with current medical treatments only providing partial relief of symptoms. 

While genetic factors play a role in a small percentage of Parkinson’s disease cases, the primary cause of Parkinson’s disease has remained unknown for many years. A growing number of scientific studies in recent years have linked Parkinson’s disease to environmental exposures such as pesticides.