CALIFORNIA — The California Department of Pesticide Regulation canceled the state’s last remaining paraquat pesticide registration. Paraquat use will be phased out in California over two years.

Pesticide makers voluntarily decided to stop using paraquat in California instead of sharing updated health and environmental risk data requested by regulators. Syngenta withdrew its paraquat use permit in April and announced it would stop producing the substance altogether.

The cancellation follows a legislative mandate. The California legislature passed A.B. 1963 in 2024, requiring the pesticide division to re-evaluate paraquat’s health risks. Regulators conducted a preliminary review that confirmed associations between paraquat exposure and thyroid disease, reproductive harms, and birth defects.

"We need the right data to identify where there are risks to people and the environment," said Karen Morrison, director of the California Department of Pesticide Regulation. The agency also found potential risks to birds and mammals, including the San Joaquin kit fox and the Swainson’s hawk.

Environmental concerns extend beyond immediate toxicity. The California Department of Pesticide Regulation stated that restrictions designed to reduce environmental exposure might not be effective because paraquat remains in the soil potentially for decades. Exposure to paraquat via skin or inhalation is linked to death, cancer, heart failure, kidney failure, liver failure, and scarring of the lungs.

There is no antidote for paraquat poisoning. Research shows paraquat interferes with dopamine production and regulation. An epidemiological study of central California farming communities showed an increased level of Parkinson’s disease among those exposed to paraquat.

California is the largest user of paraquat in the United States. More than three-quarters of California's paraquat use is concentrated in eight San Joaquin Valley counties. Approximately 14 million pounds of paraquat are sprayed annually on U.S. crops including wine grapes, pistachios, almonds, walnuts, pears, citrus, soya beans, and cotton.

Paraquat use in the U.S. tripled between 2008 and 2018. Despite these trends, the U.S. Environmental Protection Agency reapproved paraquat for use in 2021 and 2024. Public health groups led by Earthjustice sued the EPA in 2021 over its reapproval of paraquat. The legal challenge against the EPA’s reapproval of paraquat remains ongoing.

Paraquat is outlawed in more than 70 countries, including China, the U.K. and the E.U. California is the second U.S. state to prohibit paraquat, following Vermont. Under California law, licensed dealers can possess and sell paraquat for up to two years following the date of the product’s cancellation.

"Paraquat is the most acutely lethal pesticide ever made," said Nathan Donley, environmental health science director with the Center for Biological Diversity. "I don’t think anyone thought this was going to happen this quickly, but it’s very welcome news."

Why It Matters

The cancellation marks a shift in pesticide regulation within the nation's largest agricultural state. By removing the registration, California authorities addressed documented links between the herbicide and serious health conditions, including Parkinson’s disease and reproductive harms. The decision affects the supply chain for multiple major crops, as millions of pounds of the chemical are used annually across the country.

The move places pressure on federal regulators who have continued to approve the substance. With legal challenges pending against the EPA and international bans already in place in dozens of countries, the state action shows a divergence between local health protections and federal pesticide policy. The two-year phase-out period allows for an orderly transition while removing the chemical from future use.

Timeline

Public health groups led by Earthjustice sued the EPA in 2021 over its reapproval of paraquat. The California legislature passed A.B. 1963 in 2024, requiring the pesticide division to re-evaluate paraquat’s health risks. Lily Dalton, 23, died in January 2026 after battling Ewing sarcoma following her college graduation.

Brody Matteson, 17, died in March 2026 after battling Ewing sarcoma for nearly two years. Effective April 1, 2026, pesticide registrant Syngenta has voluntarily canceled registration of the pesticide Gramoxone® SL 3.0 in California, a product that contains the active ingredient paraquat-dichloride (paraquat).

What's New

Health officials have stated that no environmental cause has been identified for the cluster of Ewing sarcoma cases in the Southern California community. Under California law, licensed dealers can possess and sell paraquat for up to two years following the date of the product’s cancellation. A large container of paraquat fell off a truck in Dorris in March, spilling about 60 gallons of the chemical and causing officials to put 600 homes and a local elementary school under lock down.

More than three-quarters of California's paraquat use is concentrated in eight San Joaquin Valley counties. Since 2007, about nine children in a Southern California community have been diagnosed with Ewing sarcoma.