Los Angeles residents who are already receiving warnings about their tap water could be without tap water for a while, experts told NBC News, amid concerns about damage to local infrastructure and the chemicals released by wildfires.
At least two water departments have told residents not to drink their tap water due to concerns about possible contamination from the ongoing wildfires. And the possibility of chemicals and pathogens entering the water system has raised concerns about potential risks to human health, although it may take some time for testing to determine the extent of the problem, especially as the fires are still active.
On Friday, the Los Angeles Department of Water and Power instructed people in the Pacific Palisades and neighboring communities to use bottled water for cooking, drinking, brushing teeth and washing dishes. The advisory warns that fire-related pollutants such as benzene – a chemical that can cause cancer – may have entered the water system.
The Pasadena Water and Power Department also told many residents last week to switch to bottled water until further notice, citing concerns that debris may have gotten into the system. The Eaton Fire in the area damaged several reservoirs and pump stations, the department said, which could impact water quality.
“There is certainly some level of contamination in these damaged systems. How much, no one knows,” said Jackson Webster, an assistant professor of civil engineering at California State University at Chico.
“Until it is known what level of contamination exists in the system, they should be assumed to be highly contaminated based on previous observations,” he added. “That’s why they’re issuing these ‘don’t drink’ orders.”
Webster said it’s common to see drinking water contamination after wildfires in urban areas — he pointed to the 2023 fires in Maui, Hawaii, the 2018 Camp Fire in Paradise, California, and the 2017 Tubbs fire in Santa Rosa, California.
A telltale sign that drinking water is contaminated, he said, is when a water system loses pressure. Excessive pressure on the system – usually from residents using hoses and sprinklers while firefighters draw water from hydrants – causes water pressure to drop and contaminants to be sucked in like a vacuum.
The Los Angeles Water Department reported last week that water pressure in Pacific Palisades dropped after the system maintained four times its usual demand.
“The pressure loss is concerning and should prompt careful analysis of the water,” said Fernando Rosario-Ortiz, a professor of environmental engineering at the University of Colorado Boulder.
The Pasadena Water Department said Sunday it had begun testing in key areas to determine when the water is safe to drink.
Environmental engineers aren’t particularly concerned that the red flame retardant dropped from airplanes could end up in people’s taps because it consists largely of water and fertilizer. However, a study last year found that this type of fire retardant contains heavy metals.
“You may be disrupting the ecosystem, but from a human health perspective you don’t necessarily have to worry about that,” Young said.
A bigger problem is the ash from household materials. The fires in the Los Angeles area have destroyed more than 12,300 structures. As the property burned, materials such as carpeting, furniture and rubber tires were also burned. Fires can also melt the plastic pipes or water meters on people’s properties.
These processes release gaseous chemicals known as volatile organic compounds, which can enter the water system where they are often difficult to eliminate. People exposed to the chemicals may experience short-term nausea, difficulty breathing or eye irritation. Exposure over time has been linked to certain cancers, birth defects and cognitive impairment.
Two chemicals in particular, benzene and vinyl chloride, pose some of the biggest health risks because they are known carcinogens.
Boiling water doesn’t destroy them, so the Los Angeles Water Department removed a previous “boil water” advisory intended to protect residents from bacteria, viruses or parasites.
Thomas Young, a professor of civil and environmental engineering at the University of California, Davis, said it is common to first test water for the most dangerous chemicals such as benzene and then use that as a general indicator of whether drinking water is safe to consume.
“When we design cleanup measures for these kinds of things, we focus on the components of the most intense health problem. We feel like once we’ve addressed that, the other species will generally come along and be fine because they’re much less potent,” he said.
The testing process can take weeks, months or longer depending on how much contamination is present. Catherine Carpenter, a research data analyst with Tracking California — a program that collects and analyzes water quality data — said testing of people’s homes in Paradise showed persistent contamination long after the Camp Fire subsided.
“It was almost a year later, but we still detected high levels of benzene in the tap water,” she said.
If contamination levels are low, it’s possible to eliminate the danger by flushing water pipes, says Andrew Whelton, a professor of environmental and ecological engineering at Purdue University. But high pollution levels may require replacing the pipes altogether, he added.
Whelton said it’s possible that neighborhoods where homes haven’t burned down could still have contaminated water supplies — though it’s too early to know.
“The greatest potential for contamination in the water distribution system is around destroyed buildings,” he said. “But when firefighters are fighting a fire… they can sometimes suck in contaminated water and drag it through the system.”
This article was originally published on NBCNews.com