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Potential threat to water safety from wildfires

In a research letter in the journal Science, researchers from the UTS Center for Technology in Water and Wastewater write that wildfires can contaminate drinking water distribution systems, posing substantial and escalating public health risks, with nearly half a billion people globally having experienced wildfires within 1 kilometer of their homes over the past two decades.

They write, "Authorities in areas of recent wildfires, such as the 2025 Los Angeles fires, should ensure that drinking water is safe by monitoring and mitigating contamination in water distribution systems.

"Distribution systems transport drinking water from treatment plants to consumers. Water must meet safety standards before leaving a treatment plant, but contamination can occur during transport.

"Over the past decade, more than 50 volatile organic compounds (VOCs), including carcinogens such as benzene, have been detected in water distribution systems after wildfires.

"These VOCs likely enter the distribution systems through plastic pipes that have suffered thermal degradation or the infiltration of smoke into depressurized pipes.

"Once inside, VOCs can spread through connected pipes, infiltrate water distribution materials and persist for months, contaminating water supplied to consumers."

Letter first author, Chancellor's Research Fellow Dr. Xuan Li, said such contaminants posed carcinogenic risks to consumers.

"For example, 11 months after the 2017 Santa Rosa wildfire in northern California, 40,000 micrograms per liter of benzene remained in drinking water from distribution systems.

"Even short-term exposure to 26 micrograms per liter of benzene harms children, and long-term exposure increases leukemia risk.

"These contaminants are rarely monitored in water distribution systems, particularly at the consumer end, and communities often remain unaware of these risks."

The letter's corresponding author, Professor Qilin Wang, also warned that climate change and urbanization are intensifying wildfire risks, exacerbating the threat of drinking water system contamination.

"Wildfire-related VOC levels often correlate with the scale of building destruction, underscoring the growing threat that future wildfires pose to water safety, especially in areas such as Los Angeles.

"To address wildfire-driven drinking water contamination, governments must establish clear guidelines, identify wildfire-related VOCs in drinking water distribution systems, set safety limits and enforce robust monitoring and testing protocols."