A toxic agricultural weedkiller associated with Parkinson’s disease and other health concerns is leaving California’s registered pesticide market. Here’s what the change means for farmworkers and families in communities where paraquat use has been concentrated.
California is beginning the phaseout of paraquat, a highly toxic agricultural herbicide that has been used for decades to control weeds.
On Aug. 10, 2026, the California Department of Pesticide Regulation (DPR) announced that all manufacturers of pesticide products containing paraquat-dichloride had voluntarily canceled their California registrations. The final registrant canceled its registration Aug. 6, following a state demand for additional scientific data.
The decision matters far beyond California’s pesticide industry.
Paraquat has been used heavily in parts of the Central Valley, including counties with large Latino populations and agricultural workforces. Research conducted in California has also found an association between paraquat exposure and Parkinson’s disease.
But there is an important distinction:
California’s announcement begins a phaseout. It does not mean every existing paraquat product disappears immediately.
Here’s what California families and farmworkers should know.
Why is California phasing out paraquat?
California began a formal reevaluation of paraquat in November 2024. The process was designed to examine newer scientific evidence and determine whether additional regulatory action was necessary.
DPR’s preliminary scientific assessments identified potential concerns involving human health and the environment, including potential associations between paraquat exposure and thyroid impacts and birth defects. The environmental assessment also identified potential risks to birds, mammals and aquatic organisms, with the greatest risks identified for birds. New Study Links Herbicide Exposure to Early Colon Cancer Risk. What Latino Workers Need to Know Now
The state subsequently required paraquat manufacturers to provide additional scientific information by June 5, 2026.
Instead of submitting the required data, manufacturers began voluntarily canceling their California registrations. The final registration was canceled Aug. 6.
The result is the beginning of California’s transition away from registered paraquat products.
What does paraquat have to do with Parkinson’s disease?
Researchers studying agricultural communities in California’s Central Valley have investigated whether pesticide exposure is associated with Parkinson’s disease.
A 2024 study examined 829 people with Parkinson’s disease and 824 community controls and used California pesticide-use records to estimate exposure around participants’ homes and workplaces.
The researchers found that people with repeated occupational exposure to paraquat had substantially higher odds of Parkinson’s disease. They also found an association between residential exposure and Parkinson’s disease. The study examined pesticide applications within 500 meters, or roughly one-third of a mile, of homes and workplaces.
The study does not mean that everyone exposed to paraquat will develop Parkinson’s disease. It identifies an association at the population level.
That distinction matters.
California regulators have also been cautious about the evidence. DPR’s preliminary assessment did not establish a causal relationship between paraquat and Parkinson’s disease, while identifying other health concerns that warranted additional investigation.
So the most accurate takeaway is:
Research—including research conducted in California—has found an association between paraquat exposure and Parkinson’s disease, but association is not the same as proving that exposure caused an individual’s illness.
Why this matters particularly to Latino communities
The geography of paraquat use gives this story an important environmental-justice dimension.
An Environmental Working Group analysis of California pesticide-use records found that 5.3 million pounds of paraquat were applied in California between 2017 and 2021.
Five counties—Kern, Kings, Fresno, Tulare and Merced—accounted for 66% of the state’s paraquat use during that period. Those counties also have majority-Latino populations.
EWG identified particularly high-use communities including Shafter, Wasco, Delano, McFarland and Corcoran.
Its analysis found that nearly 80% of California’s paraquat use occurred in areas where the Latino share of the population was greater than California’s statewide Latino share.
That does not mean that every Latino resident of those communities was exposed to paraquat.
It does show why California’s decision has particular significance for Latino agricultural communities.
For many farmworkers, agricultural fields are both a workplace and part of the environment surrounding their homes.
Exposure isn’t limited to the person applying the pesticide
Paraquat is a restricted pesticide in California, meaning its use is subject to licensing and other requirements.
But researchers have examined more than direct occupational exposure.
The California Central Valley Parkinson’s research looked at pesticide applications near both workplaces and residences. That matters in communities where homes and agricultural fields can be relatively close together.
The question is therefore broader than:
“Did you personally spray paraquat?”
Researchers also want to understand potential exposure associated with agricultural activity around where people live and work.
That does not mean that living near farmland automatically results in harmful exposure. Actual exposure depends on factors such as pesticide use, application practices, distance, environmental conditions and other variables.
But the geography helps explain why paraquat became an environmental-health issue for some Central Valley communities.
What about thyroid problems and birth defects?
This part of the science requires especially careful language.
DPR’s preliminary human-health assessment identified potential associations involving thyroid effects and birth defects. Those findings became part of the state’s reevaluation process and the demand for additional scientific information.
That is different from saying California has established that paraquat causes birth defects.
For readers, the distinction is important:
- Parkinson’s: California research has found an association between paraquat exposure and Parkinson’s disease.
- Thyroid and developmental effects: California regulators identified potential concerns that warranted additional evaluation.
- Individual health: Population-level research cannot determine the cause of a particular person’s illness.
Anyone concerned about a possible pesticide exposure or health symptoms should discuss the situation with a qualified medical professional rather than trying to determine causation from pesticide-use data alone.
California also found environmental risks
The health concerns are only part of the state’s decision.
DPR’s review found that paraquat may adversely affect birds, mammals and aquatic organisms, with birds facing some of the most significant identified risks.
That makes the phaseout both a public-health and environmental story.
California is also trying to reduce reliance on pesticides through its broader Sustainable Pest Management strategy. DPR says its 2027 grant priorities include research designed to reduce use of pesticides targeted for mitigation or evaluation, including paraquat, as well as developing alternatives for weed management.
Does this mean paraquat is banned immediately?
No.
This is the most important practical detail for growers, workers and communities.
Although all manufacturers have now canceled their California registrations, DPR says licensed dealers can continue to possess and sell voluntarily canceled pesticide products for up to two years after the applicable cancellation date.
Growers who continue using existing products must follow the applicable product labels as well as state and federal requirements.
In other words:
The Aug. 10 announcement starts the phaseout. It does not mean all existing paraquat supplies become illegal overnight.
What happens next?
California’s action follows Assembly Bill 1963, which established the state’s paraquat reevaluation process.
The manufacturers’ voluntary cancellations mean the state will now move through the transition away from registered paraquat products rather than completing a conventional regulatory decision on continued registration.
DPR says it will support research into safer and more sustainable alternatives as growers transition away from paraquat.
For communities that have lived alongside intensive agricultural pesticide use, the longer-term question will be whether alternatives can protect crops while reducing potential risks to workers, families and ecosystems.
What should farmworkers and families do?
The phaseout does not mean that someone who has worked around paraquat should assume they have been harmed.
But people concerned about pesticide exposure can take practical steps.
Farmworkers: Follow required pesticide-safety instructions and protective measures at work. If you believe you were exposed to pesticides or witnessed unsafe pesticide handling, California DPR provides a process for reporting pesticide incidents.
Families near agricultural areas: DPR maintains information about pesticide use and community health resources.
People with health concerns: Talk with a healthcare professional about symptoms or possible exposure. Do not assume that a particular pesticide caused an illness based solely on proximity to agricultural fields.
For readers who want to understand the broader health issues affecting California’s Latino communities, Parriva’s Health coverage provides additional reporting on health risks, prevention and access to care.
The bigger California story
California’s paraquat decision is bigger than one weedkiller.
It is a test of how the state balances agricultural productivity with the health of workers, nearby residents and ecosystems—and whether safer pest-management alternatives can replace a chemical that has been the subject of decades of scientific and regulatory concern.
The Latino connection is not simply demographic.
The pesticide was heavily used in agricultural counties with large Latino populations, while many California farmworkers are Latino. EWG’s analysis documents the geographic overlap between paraquat use and Latino communities.
That makes California’s phaseout especially relevant to the people who live and work in the state’s agricultural heartland.
California is beginning the phaseout of paraquat after every manufacturer voluntarily canceled its California registration.
The strongest California-specific health evidence concerns the association between paraquat exposure and Parkinson’s disease. State regulators have separately identified potential thyroid and developmental concerns and significant ecological risks.
But the phaseout will not happen overnight. Existing canceled products can remain in the distribution system for a limited transition period, and growers using existing supplies must continue following applicable requirements.
For Latino farmworker communities in places such as Kern, Fresno, Tulare, Kings and Merced counties, the significance is clear: California is moving away from a pesticide that was heavily used in the communities where many Latino families live and work.
The next question is whether the state can make that transition while protecting both agricultural workers and the future of California farming.
This article is for public-information purposes and is not medical advice. Population-level research cannot determine the cause of an individual’s illness.
