LA wildfires: How contaminated drinking water is the latest worry for residents

The warning couldn’t be clearer: “Do not drink or cook with the tap water … Do not treat the tap water yourself,” warned the Los Angeles Department of Water and Power. Issued in bold, all caps, the alert targeted residents of Pacific Palisades and nearby neighbourhoods, who continue to grapple with the devastation of relentless wildfires.

Experts caution that toxic chemicals from the fires can infiltrate damaged water systems, and neither filtering nor boiling the water can remove these harmful substances.

Pasadena Water and Power, a utility with over a century of history, issued a similar notice recently. They reported damage to at least one pump, several storage tanks, and residential areas, raising fears that toxic chemicals might have entered the water pipes.

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“Out of the abundance of caution, you kind of have to assume the worst," Stacie Takeguchi, chief assistant general manager for the utility told AP. After extensive testing, the utility has since lifted the notice for most of the affected areas.

But how do wildfires lead to water contamination? And what health risks does this pose? Here’s a closer look.

How urban fires comprise drinking water

When fires ravage towns and cities instead of forests or grasslands, they can severely damage critical infrastructure, including drinking water systems.

When drinking water systems are damaged in a fire, “we can have ash, smoke, soot, other debris and gases get sucked into the water piping network,” Andrew Whelton, a Purdue University engineering professor who researches water contamination in communities hit by fire told AP.

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These elements can be especially dangerous because building materials and household items, often made of chemically engineered synthetics, burn and release harmful particles and gases. Some of these chemicals are toxic even at low concentrations, experts warn.

How do chemicals penetrate the pipes?

Water systems typically are under enough internal pressure to keep harmful elements out. But that critical pressure can be lost in many ways during a fire, which means toxins can get in.

There is normal water demand from residents who have not evacuated, and firefighters also use large amounts of water. Additionally, pipes in burned buildings can be damaged, causing water to leak.

Power outages can further exacerbate the issue by causing pressure loss when pumps stop working, explained Greg Pierce, a professor of urban environmental policy at the University of California. This was the case during the 2023 Maui fires.

“It’s really hard, if not impossible, to keep up the power supply to the whole water system in the event of a fire, because you’re either shutting off the power, because power can contribute to the fire, or it just goes out,” Pierce said. “And then you’re relying on generators at best in spots.”

The loss of pressure not only compromises water quality but also limits water availability for firefighting. In the Pacific Palisades neighbourhood, hydrants ran dry as nearby homes burned. The utility attributed this to high demand, stating that pumps were still functioning. However, California Governor Gavin Newsom announced that the state would investigate the incident.

Also read: LA wildfires: Eaton blaze 45% contained, Palisades fire 19% as another breaks out in San Bernardino

What are the health risks?

Toxic chemicals in drinking water following a fire can pose serious health risks, ranging from temporary nausea to long-term conditions like cancer, experts warn.

“In Paradise (California), there were benzene levels high enough to acutely give a child a blood disorder,” said Dr. Lynn Goldman, dean of the Milken Institute School of Public Health at George Washington University, referencing the 2018 Camp Fire that destroyed much of the city.

Even low concentrations of certain chemicals can be concerning. In California, state regulators consider a limit of one part per billion of benzene — a known carcinogen — as the safe level for drinking water over 70 years of exposure. The national guideline is no more than five parts per billion.

“In terms of cancer risk, what we’re really interested in is the cumulative amount that you’re exposed to over your entire lifetime," Goldman explained. “And if a short-term exposure adds a lot to that, that is a real risk.”

Benzene and similar compounds are volatile, meaning they can easily become airborne, much like gasoline turning to vapour when spilled. Additionally, a group of heavier chemicals, called semi-volatile organic compounds (SVOCs), was found in water pipes in Louisville, Colorado, after the 2021 Marshall Fire, even when benzene and other more commonly known chemicals were not present. Whelton stresses the importance of testing for both types of compounds.

The long road to recovery

Vast Los Angeles County has more than 200 water service providers, but so far only a handful believe that damage or loss of pressure may have resulted in chemical contamination and have issued “Do Not Drink” notices. Utilities are focused on ensuring there’s enough water for fighting fires, though some are beginning to test for contaminants. It can take weeks to months of testing before water can be declared safe for drinking in areas with minimal damage.

That is sometimes a best-case scenario.

In the Paradise Fire, most buildings burned. The city rebuilt a reservoir and is working to replace 10,000 service lines. It expects to spend the next decade and $50 million to replace roughly 17 of 172 miles of main lines that were contaminated.

Whelton doesn’t recommend people pay for expensive water testing in their homes until their utility has declared the public water system safe.

Many publicly available water quality tests are “not capable of finding fire-related drinking water contamination,” Whelton wrote on X this week.

Precautionary steps for residents

 Utilities and health departments recommend residents follow official guidance on water use until the supply is declared safe. Professional testing of household pipes is best conducted after the public system is cleared of contaminants.

As Los Angeles continues to battle fires and their aftermath, the focus remains on ensuring water availability for firefighting efforts while addressing long-term contamination risks.

With input from AP