Water Quality after the 2025 Los Angeles Fires: Number of VOCs as a Robust Fire Indicator and Effective Remediation through Multiple System Flushes

The 2025 Palisades and Eaton Fires in Los Angeles caused widespread destruction and public health concerns across diverse environmental matrices, including hazardous levels of volatile organic compounds (VOCs) in drinking water. We investigated postfire drinking water quality at point-of-use in 52 standing homes to evaluate exposure to fire contaminants and the efficacy of district-led remediation efforts. Benzene, a common postfire VOC of concern, was detected in 17% of all samples, with one maximum contaminant level (MCL) exceedance (1.62 ppb). 26 VOCs (out of 52 VOCs tested) were detected at least once. Unregulated VOCs were detected 14% more frequently than expected from a Gaussian distribution and comprised the majority of VOC detections (53%). We found that the number of VOCs detected per sample was a more robust indicator of fire impacts than benzene alone, with the highest numbers of VOCs in zones adjacent but outside of the burned areas. District-led flushing and testing decreased VOC levels below detection, with hydrophobic compounds persisting longer than hydrophilic compounds. Future fire response may benefit from an assessment of exposure limits for currently unregulated fire-related VOCs and from review of emergency response protocols in zones of impacted systems that are outside of burned areas.