Exposure to Toxic Herbicide Paraquat May Increase Risk of Parkinson’s Disease, Study Finds

The findings of a new study add to a growing body of evidence connecting exposure to a highly toxic herbicide called paraquat to an elevated risk of neurodegenerative diseases like Parkinson’s disease. Previous research has established a strong correlation between the development of Parkinson’s disease and exposure to paraquat, which is sprayed on nearly 15 million acres of corn, cotton, soybean, and other crops in the United States every year. According to this latest study, inhaling even small amounts of the herbicide can affect the brain and lead to symptoms indicative of Parkinson’s disease. If you or someone you know was diagnosed with Parkinson’s disease following occupational or environmental exposure to paraquat, contact us as soon as you can to discuss whether you are eligible to file a claim against the makers of paraquat.

Toxic Paraquat Widely Used in U.S. Agriculture

Paraquat dichloride (“paraquat”) is the active ingredient in a number of different brand-name herbicide products commonly used in commercial crop operations to control invasive grasses and weeds, including Gramoxone, Helmquat, Blanco, Firestorm, Quik-Quat and Para-Shot. Paraquat has been on the market since the early 1960s and its high toxicity is well documented. Concerns about paraquat’s toxicity has led to paraquat bans in 32 countries, yet the herbicide’s ubiquitous use in the U.S. continues, albeit under restrictions established by the U.S. Environmental Protection Agency (EPA). These restrictions limit the mixing, loading, handling, and application of paraquat to certified commercial or private applicators who have completed an EPA-approved paraquat training program. Unfortunately, these restrictions may not be enough to prevent paraquat-related health effects among farmers, agricultural workers, and others who mix, load, spray, or otherwise handle paraquat, nor among people who live nearby farms and other areas where paraquat is sprayed.

Link Between Paraquat Exposure and Parkinson’s Disease

Even as other countries move away from paraquat due to concerns about the herbicide’s toxicity, its use is picking up in the U.S., where thousands of lawsuits are currently pending against the makers of Roundup, a glyphosate-based weed killer that has been widely associated with an increased risk of non-Hodgkin’s lymphoma, a cancer originating in the lymphatic system. Of the 400 pesticides used on agriculture crops in the U.S., Roundup’s active ingredient, glyphosate, is used at least three times more than any others. However, as weeds become resistant to Roundup, more and more farmers are turning to paraquat as an alternative. This poses a significant concern, considering several decades’ worth of research has established a link between paraquat exposure and Parkinson’s disease, a progressive disorder of the central nervous system that affects predominantly dopamine-producing neurons in a section of the brain called the substantia nigra.

In one paraquat study published in 2017, researchers reported that “Paraquat, a herbicide linked to Parkinson’s disease, generates reactive oxygen species (ROS), which causes cell death.” According to the study findings, the herbicide can destroy dopamine-producing cells in the brain via a mechanism called oxidative stress, which occurs when there is an imbalance between the production of ROS and the body’s ability to counteract their harmful effects. An earlier study published in 2011 found a 2.5-times increased risk of Parkinson’s disease among people who used paraquat, compared to non-users. “Paraquat increases production of certain oxygen derivatives that may harm cellular structures,” the researchers concluded, noting that “People who used these pesticides or others with a similar mechanism of action were more likely to develop Parkinson’s disease.”

In this latest paraquat study, published in the journal Toxicological Sciences in December 2020, researchers from the University of Rochester School of Medicine linked prolonged low-dose inhalation exposure to paraquat among mice to olfactory impairment, which is an early symptom of Parkinson’s disease. According to the study authors, inhaling paraquat in the air can allow the herbicide to travel into the brain, where it can wreak havoc on the neurons responsible for a person’s sense of smell. “Taken together,” the researchers reported, “these data suggest that prolonged low-level inhalation exposure to [paraquat] aerosols leads to translocation of [paraquat] to the brain, as well as persistent male-specific olfactory deficits consistent with the prodromal trajectory of [Parkinson’s disease].”

Paraquat Maker Denies Parkinson’s Risk

Syngenta, the agrochemical company that manufactures paraquat, has long denied the alleged link between the herbicide and Parkinson’s disease, claiming that the company “would never market or continue to market any chemical which we genuinely felt posed a health risk or an environmental risk.” Nevertheless, the EPA has indicated that “there is a large body of epidemiology data on paraquat dichloride use and Parkinson’s disease.” This declaration came in a 2016 regulatory filing in which the agency indicated that it would conduct an in-depth statistical analysis of paraquat and its human health effects in response to “a combination of public health concerns and the EPA’s evaluation of incident data.” Despite claims by Syngenta that paraquat does not cause Parkinson’s disease, there is a great deal of research indicating otherwise, the scope of which a scientist with the National Institutes of Health who has studied the Parkinson’s link says is “about as persuasive as things can get.”

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