Glyphosate and Byproducts Still Detected in Orange County Creeks After Spray Halt

Independent testing in May found trace amounts of glyphosate and its breakdown product AMPA in water and soil downstream of Orange County flood-control channels, despite a county-wide pause on herbicide applications that began in early 2025.

After Orange County halted glyphosate applications in flood-control channels in early 2025, independent analysts from the Health Research Institute in Iowa tested downstream sites in May. Water at the Santa Ana River jetties showed no glyphosate but 0.04 ppb of its breakdown product AMPA, while soil there contained 2.59 ng/g AMPA. At Doheny State Beach, water contained a trace of glyphosate and soil held 2.17 ng/g glyphosate, 2.73 ng/g AMPA, and a trace of TCP, a chlorpyrifos by-product.

These levels are far beneath the state’s 700 ppb drinking-water threshold, though the limits are based largely on industry data. The residual chemicals raise questions about long-term exposure, especially since AMPA persists longer in the environment. The testing was prompted by community activism from Creek Team OC, which urged Supervisor Katrina Foley to cease spraying; Foley later confirmed the pause and cited regulatory constraints. Orange County’s public-works contracts for herbicide application, approved between 2018 and 2023, had cost nearly $3 million, but officials have not released further independent testing results since the 2025 pause.