California regulators sound alarm: Herbicide paraquat linked to birth defects, thyroid disease and wildlife risks

• California’s pesticide regulators have linked the herbicide paraquat to severe human health risks, including thyroid disease, birth defects and reproductive harm, as well as significant threats to wildlife, such as endangered species like the San Joaquin kit fox and Swainson’s hawk.
• Paraquat is highly toxic, with even small amounts causing severe health complications like cancer, organ failure and lung scarring. The EPA warns that ingestion can be fatal, and its persistence in the environment exacerbates its impact.
• Despite its well-documented risks, California used over 350,000 pounds of paraquat in 2023, primarily in the San Joaquin Valley, where farmworkers and nearby communities face heightened exposure through volatilization and dust drift.
• Environmental and public health advocates are urging California to ban paraquat, citing its dangers and the availability of safer alternatives. A 2023 study showed that farmers in other countries successfully transitioned away from paraquat without reducing agricultural productivity.
• A 2021 lawsuit challenges the EPA’s reapproval of paraquat, while California’s 2024 passage of A.B. 1963 requires a reevaluation of its use, potentially paving the way for a statewide ban. Mounting evidence, including links to Parkinson’s disease, underscores the urgency for decisive action.

California’s pesticide regulators have released preliminary findings that underscore the grave risks posed by the herbicide paraquat, linking it to serious human health harms, including thyroid disease and birth defects, as well as significant threats to wildlife. The findings have reignited calls for a statewide ban on the toxic chemical, which is already prohibited in more than 70 countries.

Paraquat, one of the most lethal herbicides still approved for use in the United States, has long been associated with a range of devastating health effects. Ingesting or inhaling even small amounts of the chemical—or exposing it to the skin—can lead to severe health complications, including cancer, heart failure, kidney failure, liver failure and lung scarring. The U.S. Environmental Protection Agency (EPA) warns that “one sip can kill,” highlighting the herbicide’s extreme toxicity.

The preliminary assessment by the California Department of Pesticide Regulation (DPR) found that paraquat poses significant risks to birds and mammals, including some of California’s most endangered species, such as the San Joaquin kit fox and Swainson’s hawk. The herbicide’s persistence in the environment makes it particularly difficult to mitigate its impact on wildlife, even with restrictions on its use.

For humans, the risks are equally alarming. The DPR’s findings confirm a strong association between paraquat exposure and thyroid disease, as well as reproductive harms and birth defects. Farmworkers and agricultural communities in the San Joaquin Valley, where paraquat use is heavily concentrated, are at heightened risk due to the herbicide’s ability to volatilize and spread through dust, which can drift into nearby neighborhoods.

“The evidence continues to mount that paraquat is just too dangerous,” said Jonathan Evans, environmental health legal director at the Center for Biological Diversity. “The most effective way to avoid paraquat’s risks is for California to join nations throughout the world and ban its use. The state can’t keep letting Big Ag use hundreds of thousands of pounds a year of this incredibly harmful herbicide.”

Despite its well-documented dangers, California used more than 350,000 pounds of paraquat in 2023 alone. This widespread use has drawn sharp criticism from conservation and public health groups, which have long called for a reevaluation of the herbicide’s approval. In 2024, California took a step toward addressing these concerns with the passage of A.B. 1963, a bill authored by former state legislator Laura Friedman, now a member of Congress. The legislation requires the DPR to reevaluate paraquat’s use, potentially paving the way for a ban.

It’s just too dangerous

The push to phase out paraquat is not without precedent. Research shows that banning the herbicide does not negatively impact agricultural productivity, as a wide range of safer alternatives are available. A 2023 study published in PMC highlighted the success of over 1.25 million farmers in low- and middle-income countries who have transitioned away from paraquat without sacrificing yields. These farmers have adopted alternative weed management practices, many of which do not rely on herbicides at all.

The study’s authors emphasized that eliminating paraquat would save lives without reducing agricultural output. “Less hazardous and more sustainable alternatives exist,” they wrote. “To enhance successful adoption and uptake of these methods on a wide scale, farmers require training and support within an enabling policy environment.”

Paraquat’s dangers extend beyond acute poisoning. The herbicide has also been linked to Parkinson’s disease, a devastating neurological condition with no known cure. Researchers have found that paraquat exposure in California’s agricultural communities increases the risk of Parkinson’s and thyroid cancer, further underscoring the urgent need for action.

In 2021, a coalition of farmworker groups, environmentalists and health organizations represented by Earthjustice filed a lawsuit challenging the EPA’s reapproval of paraquat. The legal challenge is ongoing as the agency continues to review the herbicide’s risks.

As California grapples with the findings, the question remains: Will the state take decisive action to protect its residents and wildlife from this toxic chemical? With mounting evidence of paraquat’s dangers and viable alternatives readily available, the case for a ban has never been stronger.

For now, the preliminary findings serve as a stark reminder of the human and environmental costs of relying on hazardous chemicals in agriculture. As Evans aptly put it, “The state can’t keep letting Big Ag use hundreds of thousands of pounds a year of this incredibly harmful herbicide.” The time for change is now.

Sources include:

ChildrensHealthDefense.org

PubMed.gov

BiologicalDiversity.org