EPA Responds to Siskiyou County’s Illegal Pesticides Crisis Linked to Illicit Cannabis Operations

San Francisco, CA – July 18, 2025 – The U.S. Environmental Protection Agency (EPA) Pacific Southwest Region has launched an immediate investigation into the illegal pesticide crisis in Siskiyou County, California, following a state of emergency declaration by the Siskiyou County Board of Supervisors. Regional Administrator Josh F.W. Cook issued a statement today addressing the escalating public health and environmental threat posed by the illegal importation, distribution, and burning of highly toxic, foreign-manufactured pesticides tied to illicit cannabis cultivation.

EPA’s Response to a Growing Crisis

In his statement, Administrator Cook emphasized the severity of the situation: 

“I have received correspondence from the Siskiyou County Board of Supervisors. They have declared a State of Emergency related to illegal importation, distribution, and burning of foreign-manufactured pesticides and chemicals as part of an international criminal enterprise. I take this very seriously; I have directed Region 9 EPA law enforcement to investigate these issues immediately. We will be working with other County, State, and Federal agencies to ensure Californians are protected and our environmental laws are upheld.”

The EPA’s Region 9 law enforcement team will collaborate with agencies such as the California Environmental Protection Agency (CalEPA), the Drug Enforcement Administration (DEA), and local authorities to address the crisis and enforce environmental regulations under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).

Siskiyou County’s Emergency Proclamation

On July 1, 2025, the Siskiyou County Board of Supervisors unanimously voted to proclaim a local state of emergency, citing the widespread misuse of unregulated, foreign-labeled pesticides in illicit cannabis cultivation and processing operations. According to the county’s resolution (No. 25-109), these pesticides—many banned in the United States—pose severe risks to public health, first responders, waterways, and the environment.

Key findings from county investigations include:

• Identification of 27 Toxic Pesticides: Laboratory analyses revealed the presence of 27 pesticides, including nine classified as nerve agents (acetylcholinesterase inhibitors), three listed as California Toxic Air Contaminants, six identified as groundwater pollutants, and nine recognized as carcinogens under California Proposition 65.
• Illegal Fumigation Practices: Illicit cannabis operators are using highly toxic pesticides as fumigants by burning sawdust-like materials infused with dangerous chemicals, such as organophosphates, carbamates, and chlorinated hydrocarbons, in enclosed grow sites. This practice produces thick, poisonous smoke, endangering nearby residents and first responders.
• Unregulated Imports: Many of these pesticides, often labeled in Chinese, Thai, or Spanish, are imported outside legal regulatory channels, lacking required English-language safety information. Some, like chlorthiophos, diafenthiuron, and hexachlorobenzene, are either unapproved for use in the U.S. or have been banned due to health and safety concerns.
• Environmental and Health Risks: These chemicals threaten soil, air quality, groundwater, surface waters, and wildlife ecosystems. They also pose immediate health risks, including acute poisoning, neurological damage, and long-term genetic abnormalities.

The proclamation highlights the increasing danger to first responders, including firefighters, sheriff’s deputies, and emergency medical personnel, who lack adequate protective equipment and training to handle these hazardous substances safely. Additionally, the county has noted a rise in hazardous materials incidents caused by burning pesticide-laced materials, further endangering communities.

A Call for State and Federal Support

The Siskiyou County Board of Supervisors has requested that California Governor Gavin Newsom proclaim a state of emergency to bolster local mitigation and enforcement efforts. The county has also established a multi-agency emergency response task force, involving the Sheriff’s Office, Environmental Health, Public Health, and the Agriculture Commissioner, to coordinate with state and federal partners.

The task force will focus on identifying and remediating contaminated sites, equipping first responders with proper HAZMAT gear, and launching public education campaigns to raise awareness about the dangers of illegal pesticide use. The county is also seeking emergency funding and technical assistance from state and federal sources to support these efforts.

Environmental and Community Impacts

Under California’s Sustainable Groundwater Management Act (SGMA), the Siskiyou County Flood Control and Water Conservation District manages several groundwater basins, including the Shasta, Scott, and Butte Valley subbasins. The widespread use of illegal pesticides threatens water quality, potentially triggering state intervention by the State Water Resources Control Board if sustainability goals are not met.

Local residents, workers, and landowners face heightened risks from exposure to these toxic substances, which are often found at booby-trapped or structurally unsound grow sites. The county has documented 176 investigations since 2023, uncovering the pervasive use of these dangerous chemicals across Siskiyou County, which leads California in the quantity and variety of illegal pesticides observed.

Next Steps

The EPA’s investigation will prioritize identifying the sources of these illegal pesticides and ensuring compliance with federal environmental laws. The agency will work closely with Siskiyou County’s task force and other partners to mitigate risks and protect public health. Meanwhile, the county’s public education campaign will aim to inform residents about the hazards of illicit cannabis operations and encourage reporting of suspicious activities.

For more information, the full emergency proclamation is available on the Siskiyou County website at: https://www.siskiyoucounty.gov/supervisors/page/siskiyou-county-proclaims-local-state-emergencyresponse-illegal-pesticides.

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