KERN COUNTY, CALIFORNIA — California regulators implemented a pesticide regulation in January 2024 to reduce community exposure to 1,3-dichloropropane. Despite this, state records show growers applied one million more pounds of 1,3-dichloropropane in 2025 compared to 2023 and 2024.
Analysis of air monitor data from Delhi, California indicates a 30 percent increase in average 1,3-dichloropropane concentrations during the first three quarters of 2025 compared to the same period in 2024. The California Department of Pesticide Regulation established 2024 rules that restrict 1,3-dichloropropane application near residences by requiring setback distances, deeper soil injection with higher moisture content, specific fumigation methods, and tarp covers. The largest increases in application occurred in Kern County and San Joaquin County, primarily for almond and grape cultivation.
Mark Weller, Campaign Director for Californians for Pesticide Reform, said: "Their new regulations are failures. They put in new regulations and 1,3-D use went up." Adjusted application totals for 1,3-dichloropropane approximately doubled in Kern County and San Joaquin County and increased by nearly 20 percent statewide.
The California Department of Pesticide Regulation maintains separate safety standards for residential bystanders established in 2024 and for occupational bystanders effective at the beginning of 2026. Amy MacPherson, an agency spokesperson for the department, said: "DPR specifically developed methods that could allow for comparable levels of use while reducing overall emissions."
Caroline Cox, a retired pesticide scientist and former research director for the Center for Environmental Health, said: "The whole point of the regulations was not necessarily to reduce 1,3-D use but to reduce emissions. It just doesn't seem like the regulations are really doing what they were designed to do." A legal brief filed by farmworker advocates argued that current 1,3-dichloropropane regulations fail to satisfy mandatory legal obligations or adequately protect public health.
The state of California designated 1,3-dichloropropane as a carcinogen in 1989 after laboratory studies indicated the chemical causes tumors in animal organs. Agricultural growers apply 1,3-dichloropropane to soil before planting strawberries, almonds, grapes, and other crops to eliminate soilborne organisms. Exposure to 1,3-dichloropropane can cause respiratory distress, chest pain, eye irritation, dizziness, nausea, and headaches.
California suspended the use of 1,3-dichloropropane for five years after detecting elevated concentrations at a Merced County junior high school in 1990. A court order kept a township-level cap on 1,3-dichloropropane application in effect until January 2026, despite its exclusion from the 2024 state regulations. State records indicate one township in Kern County exceeded the former annual application cap, and multiple townships in Kern and Merced counties approached the limit during the first quarter of the year. Researchers in China reported in 2023 that a 50-year-old greenhouse worker died of renal failure and brain swelling more than one week after brief exposure to 1,3-dichloropropane in a poorly ventilated workspace.