California paraquat ban moves forward

California has moved a step closer to banning the controversial weed killing chemical paraquat after a key state legislative committee on Thursday allowed the measure to proceed.

The ban would take effect Jan. 1, 2026, outlawing the “use, manufacture, sale, delivery, holding, or offering for sale in commerce” of any pesticide product that contains paraquat. The bill provides for a process that allows state regulators to reevaluate paraquat and potentially reapprove it with or without new restrictions.

A chief concern cited by backers of the bill is research linking chronic paraquat exposure to Parkinson’s disease, an incurable and debilitating brain disease considered a top cause of death in the United States.

Several thousand farmers, agricultural workers and others are suing paraquat maker Syngenta, alleging they developed Parkinson’s because of long-term chronic effects of paraquat.

“California is the breadbasket of the nation. Farm workers put food on our table, and we should do everything we can to make their jobs safer,” California Assemblymember Laura Friedman said. “No one should run the risk of chemical exposure on the job leading to their contracting Parkinson’s disease.”

Friedman, who partnered with the Environmental Working Group (EWG) to introduce the measure, said it passed “not only because banning paraquat is the right thing to do,” but also because there are “readily available, safer, affordable alternatives.”

The movement of the bill out of the appropriations committee this week now sets it up for a vote by the full Assembly next week. A vote has to be completed by Friday, May 24, in order for the measure to be moved to the state Senate for consideration. A majority of 80 Assembly members is needed to keep the bill alive.

Secret Syngenta records  

Paraquat is one of the most widely used weed killing chemicals in the world. Farmers use it both to control weeds before planting their crops and to dry out crops for harvest. In the US, the chemical is used in orchards, wheat fields, pastures where livestock graze, cotton fields and elsewhere.

Syngenta has been making and selling paraquat for more than 50 years, and maintains that scientific evidence does not support a causal link between paraquat and Parkinson’s disease.

Syngenta states on its website that if users follow directions and wear proper protective clothing, including gloves and boots, “there is no risk to human safety.” Paraquat is “not a neurotoxicity hazard,” and “does not cause Parkinson’s disease,” the company states.

In arguing for the bill, Friedman’s office cited internal Syngenta documents uncovered by The New Lede in collaboration with The Guardian showing that Syngenta has long been aware of scientific research showing ties between paraquat and Parkinson’s. Those documents, reported on in a series of articles, revealed years of corporate efforts to cover up evidence that paraquat can cause Parkinson’s disease. 

The documents obtained by The New Lede additionally showed evidence of efforts to manipulate and influence the EPA as well as the publication of scientific literature backing paraquat safety. The documents also show how the company worked to mislead the public about paraquat dangers, among other secret strategies.

Parkinson’s rates climbing

Roughly 60,000 Americans are diagnosed each year with Parkinson’s and in recent years it has been ranked among the top 15 causes of death in the United States, according to the Centers for Disease Control and Prevention. Moreover, the death rate from Parkinson’s has climbed more than 60% in the United States over the past two decades, according to research. 

Despite the company’s safety claims, dozens of countries have banned paraquat, both because of the acute dangers and due to mounting evidence of links to health risks such as Parkinson’s from chronic, long-term exposure. Syngenta currently still sells paraquat products in more than two dozen countries. 

Paraquat was banned in the European Union in 2007 after a court found that regulators erred in dismissing safety concerns, including scientific evidence connecting Parkinson’s to paraquat. It is also banned in the UK, although it is manufactured there. The chemical was banned in Switzerland, Syngenta’s home country, in 1989. And it is banned in China, the home base for ChemChina, which purchased Syngenta several years ago.

Neurology expert Timothy Greenamyre, who directs the Pittsburgh Institute for Neurodegenerative Diseases, said he thinks there is “no doubt” that paraquat causes Parkinson’s, and that paraquat should “absolutely be banned” in the United States.

There is both strong animal study data and strong epidemiological evidence supporting the causal association, as well as the relevant mechanism of action, he said.

“Paraquat causes selective degeneration of precisely those neurons that degenerate in PD [Parkinson’s disease] (out of billions of other neurons); it does not cause random or non-selective neurodegeneration,” Greenamyre said. “Similarly, paraquat exposure causes accumulation and aggregation of the exact protein (out of thousands of others), alpha-synuclein, that defines PD pathology. In this context, the ability of paraquat, at any dose, to model these features of the disease provides compelling support for its role in PD.”

California has a history of moving faster than the US Environmental Protection Agency (EPA) in restricting chemicals that have been associated with serious health concerns in scientific research.

After the EPA failed to follow through on plans to ban the insecticide chlorpyrifos in 2017, for instance, California announced its own ban in 2019. The state cited evidence that chlorpyrifos “is associated with serious health effects in children and other sensitive populations at lower levels of exposure than previously understood, including impaired brain and neurological development.”

The EPA has taken the position that evidence is “insufficient to link paraquat exposure from pesticidal use of US registered paraquat products to PD in humans.”

(Featured image of California Assemblymember Laura Friedman at a press conference. Photo provided by Friedman’s office.)