Every company that sells paraquat in California has pulled its product registrations rather than handing state regulators the health and safety data they were ordered to produce, triggering a phase-out of one of the most widely used herbicides in the United States.
The California Department of Pesticide Regulation announced the development on Aug. 10, after the last remaining registrant canceled on Aug. 6. The cancellations were voluntary. They were also, in the department's own description, a choice made in lieu of compliance: the agency had set a June 5 deadline for companies to submit scientific data addressing newly identified gaps in its human health toxicology database, and the companies withdrew instead.
For agricultural workers and families living near treated fields, the phase-out does not take effect immediately. Under state law, licensed dealers may continue to possess and sell canceled products for up to two years from each product's cancellation date, meaning paraquat can remain in California commerce until 2028.
The Regulatory Sequence Behind the Withdrawal
California opened its reevaluation of paraquat in November 2024, in accordance with Food and Agricultural Code section 14086, a provision added by Assembly Bill 1963. The department released two preliminary scientific assessments the following month.
Those preliminary reports identified a potential association between paraquat exposure and thyroid impacts and birth defects, and indicated the herbicide may adversely affect other organisms, with the most significant risks to birds. Reevaluation gave the department authority to compel registrants to develop and submit new studies addressing questions that were unknown at the time of registration.
The first cancellation took effect on April 1, when Syngenta withdrew registration of Gramoxone SL 3.0. Others followed through the spring and summer.
"For years, communities have fought to end the use of paraquat," said California Secretary for Environmental Protection Yana Garcia, describing the herbicide as associated with negative impacts on human health and wildlife. Department Director Karen Morrison framed the underlying issue as an evidentiary one, saying the agency needs the right data to identify where risks to people and the environment exist.
The reevaluation had been scheduled for completion by January 2029. The withdrawals resolve the products' status more than two years early, without the department having issued a final risk determination. Other pesticides remain under the department's continuous evaluation process.
The Parkinson's Question the State Assessment Did Not Address
The health concern that has driven most public attention to paraquat is Parkinson's disease, and it is important to be precise about what has and has not been established.
California's preliminary assessments flagged thyroid effects, birth defects, and wildlife harm. They did not identify Parkinson's disease as the basis for the reevaluation.
The federal picture is one of unresolved and conflicting evidence rather than a settled association. The U.S. Environmental Protection Agency says it evaluated hundreds of studies, including epidemiological studies on Parkinson's, and found that they vary in quality and produce conflicting results. An updated analysis of the Agricultural Health Study cohort published in 2020 reported no association between paraquat exposure and Parkinson's disease, and did not replicate earlier findings from the same cohort that had suggested a possible link. EPA states that it has not found a clear link between paraquat exposure from labeled uses and outcomes such as Parkinson's disease or cancer.
That is not the same as an exoneration, and the agency's own review is still moving. After Syngenta submitted a new vapor pressure study in 2024, EPA concluded in November 2025 that there is greater uncertainty than previously assumed about how much paraquat can convert into airborne vapor, a question that bears directly on exposure for workers and people living near treated fields. The agency said it will issue a data call-in to manufacturers to resolve it.
Thousands of personal injury lawsuits have been filed on the theory that paraquat exposure causes Parkinson's disease. Those claims have not been resolved by either regulator.
Who Actually Comes into Contact with It
Paraquat is not a consumer product. There are no homeowner uses and no products registered for application in residential areas. All paraquat products in the United States are restricted-use pesticides that may be used only by certified applicators, and unlike most restricted-use products, paraquat may not be applied by workers operating under a certified applicator's supervision.
Exposure risk therefore concentrates among certified applicators, farmworkers entering treated fields, and people living close to agricultural operations where spray drift can occur. EPA's draft risk assessment identified potential risks to workers who mix, load, and apply the herbicide, as well as potential drift risks to bystanders at field edges. The herbicide is used for weed control in many agricultural settings and for desiccation of crops such as cotton before harvest.
Acute paraquat poisoning is severe, and there is no antidote. EPA states that one small sip can be fatal, which is why the herbicide carries some of the strictest handling requirements of any registered pesticide, including closed-system packaging and a prohibition on transferring it to any other container. The agency distributes a dedicated safety message to applicator training programs on that basis.
Residents in agricultural counties with questions about applications near their homes can contact their county agricultural commissioner, who administers pesticide use enforcement locally in California.
The Transition Period and What Comes Next
The two-year sell-through window is the part of this announcement most likely to be misread. Cancellation of a registration does not pull existing product off shelves or out of storage sheds. Growers may continue to use remaining stock in accordance with all label directions and applicable state and federal requirements.
The department has said it will support growers transitioning away from paraquat and is directing research funding toward alternatives. Its Sustainable Pest Management grants program has named projects likely to decrease pesticide use, including paraquat, and projects offering weed management alternatives as 2027 priority areas, with the current application period open through Sept. 1.
Paraquat remains registered federally and in other states. This action applies only to California, meaning the same product will continue to be subject to EPA's existing mitigation requirements elsewhere, including restricted entry intervals, personal protective equipment rules, and spray drift management labeling. Whether other states follow California's reevaluation path is unresolved.
Workers with occupational exposure who develop neurological symptoms should raise their exposure history with a clinician rather than waiting for regulatory conclusions. Agricultural employers remain subject to worker protection standards for as long as the product is in use.
The practical near-term change for California households is limited. The longer-term change is that a widely used agricultural chemical is leaving the state's market without any agency having formally concluded it was unsafe, because the companies selling it declined to produce the evidence that would have informed such a conclusion.
Key Questions Answered
What exactly did California announce? The Department of Pesticide Regulation said all manufacturers of paraquat products have voluntarily canceled their California registrations, marking the beginning of a phase-out. The last registrant canceled on Aug. 6.
Does this mean paraquat is banned in California now? Not immediately. Licensed dealers may continue to possess and sell canceled products for up to two years after each product's cancellation date, and growers may use any remaining stock in accordance with label requirements.
Why did the companies withdraw? The department required registrants to submit scientific data by June 5 to address newly identified gaps in its human health toxicology database. Companies canceled registrations in lieu of providing that data.
Did the state find that paraquat causes disease? No. Preliminary assessments identified potential associations with thyroid impacts, birth defects, and possible harm to wildlife. The reevaluation was not completed, so no final risk determination was issued.
Could I have paraquat at home? Very unlikely. Paraquat is a restricted-use pesticide with no homeowner use and no products registered for residential areas. Only certified applicators may use it.
Who faces the most exposure? Certified applicators, farmworkers entering treated fields, and people living near agricultural operations where spray drift can occur.
Is paraquat still legal in other states? Yes. This action applies only to California. Paraquat remains federally registered and subject to EPA mitigation requirements elsewhere in the country.
