As wildfires rage across Los Angeles, several utility companies have reported that their drinking water is unsafe until thorough testing can confirm its safety. The increasing severity of wildfires, influenced by a warming and drier climate, is encroaching further into urban areas, causing significant consequences. When these fires occur, toxic chemicals can infiltrate damaged water systems, and experts indicate that conventional methods like filtering or boiling will not mitigate these risks.
Pasadena Water and Power recently issued its first-ever “Do Not Drink” advisory to nearly a third of its customers since it began providing water over a century ago. Following significant damage to at least one pump, multiple storage tanks, and nearby homes from the flames, officials recognized the potential for hazardous substances to have entered the water supply. “Out of an abundance of caution, you have to assume the worst,” stated Stacie Takeguchi, the chief assistant general manager for the utility. Fortunately, most of the area received clearance after subsequent testing was completed.
The risk posed by urban wildfires to drinking water supplies stems from the destruction of infrastructure. In the event of substantial fires within populated areas, water distribution systems can sustain significant harm. According to Andrew Whelton, an engineering professor at Purdue University with a focus on water contamination post-fire, when such infrastructure is compromised, elements like ash, smoke, soot, and additional debris can infiltrate the water piping networks. The toxic nature of these elements is exacerbated when chemically engineered materials found in buildings and homes ignite, releasing harmful particles and gases. Many of these chemicals can be detrimental, even in minimal concentrations.
Water systems typically maintain internal pressure strong enough to keep pollutants at bay. However, this vital pressure can diminish in various ways during a fire, allowing toxins to seep in. There’s a standard demand on water systems from residents who remained during evacuation orders, while firefighters utilize substantial amounts of water. Damage to pipes in burned structures can also lead to water leaks. Power outages that disrupt pump operations contribute further to this pressure loss, as noted by Greg Pierce, an urban environmental policy professor at the University of California. This situation was evident during the wildfires in Maui earlier this year.
“It’s incredibly challenging, if not impossible, to maintain a consistent power supply to the entire water system amidst a fire. Utility companies may need to shut off power, as it can contribute to the fire’s spread, or the power can simply fail,” Pierce stated. “Under such conditions, you may have to rely on generators where available.” Decreased water pressure not only endangers water quality but also diminishes the availability of water for firefighting. In Pacific Palisades, some hydrants ran dry while surrounding buildings were consumed by flames. Although the utility claimed that high water demand and operational pumps caused the issue, California Governor Gavin Newsom announced plans to investigate the matter.
The presence of toxic chemicals in post-fire drinking water is linked to numerous health risks, ranging from temporary nausea to more severe conditions like cancer. Dr. Lynn Goldman, dean of the Milken Institute School of Public Health at George Washington University, mentioned high benzene levels that could have led to blood disorders in children following the destructive Camp Fire in Paradise, California, in 2018. Even trace amounts of certain chemicals can raise alarms; California officials maintain that only one part per billion of benzene, a recognized carcinogen, is deemed acceptable in drinking water over a lifetime of exposure, while the national guideline sets the threshold at five parts per billion. “When assessing cancer risks, we’re particularly focused on the cumulative exposure throughout a person’s life,” said Goldman. “Short-term exposures that significantly increase this cumulative amount pose genuine risks.”
Benzene and similar chemical compounds are known for their tendency to become gaseous; a behavior similar to how gasoline vaporizes when spilled. Following the 2021 Marshall Fire in Louisville, Colorado, semi-volatile organic compounds (SVOCs) were detected in water pipes, even in instances where benzene and other well-known chemicals were absent. Whelton stressed the importance of testing for both classes of compounds.
Los Angeles County contains over 200 water service providers, yet only a limited number have suspected that infrastructure damage or pressure loss has led to chemical contamination and have accordingly issued “Do Not Drink” advisories. Utilities are primarily focused on ensuring there is enough water available to combat fires, although some are beginning to conduct contaminant tests. The process of declaring water safe for consumption in areas with minimal damage can take weeks or even months.
In some scenarios, such as the aftermath of the Paradise Fire, where nearly all structures burned, the situation is particularly grave. The city is currently engaged in a massive effort to rebuild a reservoir, replace around 10,000 service lines, and expects to take a decade and forfeit roughly $50 million to remediate approximately 17 out of 172 miles of main lines that were contaminated. Whelton advises against homeowners investing in expensive water testing until their utility confirms the safety of the public water system. Many available water quality tests might not detect contaminants related to fire damage, according to Whelton. He suggests professional testing for water quality after the utility has deemed the water safe would be the best course of action. As residents wait for clearances, they should adhere to guidelines issued by their utility or local health department.
