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How Do Chemicals from Wildfires End Up in Water Supplies?

The relatively new and potentially dangerous phenomenon of chemicals from wildfire smoke finding their way into water systems is occurring after ‘high severity’ fires, and scientists are just now learning about it.

High-severity wildfires produce smoke with dangerous chemicals that somehow get into water systems.
When we see smoke from a wildfire, most of us can deduce that it’s probably not very healthy to be breathing in. But it turns out it could be far worse than that — contaminants from wildfires can be found not only in the smoke, but they can also find their way into the local water supply.

Chemicals were first discovered in a local water supply in 2017 after the Tubbs Fire in Northern California. The next year, chemicals were again detected in the water supply after the Camp Fire in California, but this time to a much greater degree. Both of those fires were noted to be “high severity” fires, which may explain why these contaminated the supplies and others haven’t.

“It’s kind of complex because this type of contamination doesn’t happen every single time there’s a wildfire and the community experiences some kind of destruction,” said Yvonne Heaney of the California State Water Resource Control Board.

“We’ve gone out and tested after a number of fires, and in the majority of them we don’t actually find benzene or other types of organics in the water,” Heaney said. “It first happened in 2017 in Santa Rosa after the Tubbs Fire and the following year when the Camp Fire happened, we saw it on a very large scale,” Heaney said. “But again, it doesn’t happen after every single fire and that’s why it’s difficult to know when it’s going to occur.”

She said officials are still trying to determine exactly how the chemicals are formed and how they get into the water supply. Heaney said scientists have theories on how it’s happening but it’s like a case of “having to wait for the science to catch up and prove or disprove some of these theories.”

In New Mexico, after the Calf Canyon/Hermits Peak Fire and subsequent rains, toxic chemicals were found to have leaked into the Las Vegas, N.M., water supply. This was a case of a massive fire followed very soon after by heavy rains that pulled ash with it into the ground, contaminating a water supply.

Matt Campen, director of the Center for Metals in Biology and Medicine at the University of New Mexico, said it’s complicated and hard to “disentangle all the components” of how the chemicals end up in the water and their potential harm to humans.

“Not a lot of people have looked at this yet and the data we’re generating in our lab is really concerning,” Campen said. “We’re trying to drum up enthusiasm from the population of health researchers to try to look at the entire country for behavioral mood issues related to wildfire smoke.”

Studies on mice have shown that those exposed to chemicals generated by wildfire smoke have reduced serotonin levels not just immediately after exposure, but more than 10 weeks later as well.

“So for the people fighting these fires, we know that post-traumatic stress is an issue for a lot of firefighters, but maybe we don’t appreciate how much of that is biochemical in nature and that it may be long-lasting,” Campen said. He added that there is potentially a huge impact on the millions of people in the Mountain West states who have been exposed.

Most concerning to New Mexico scientists are the potential long-term effects from the exposure to these chemicals, starting with the reductions in serotonin, which has a direct impact on mood and then what the brain must do to correct the issue.

The brain will undergo an inflammatory process because the blood/brain barrier is damaged and that is temporary, but the healing process may take weeks or months. “So how is that going to impact people who already have other issues like psychiatric issues or risk of neurodegenerative diseases like dementia and things of that nature?” Campen said.

Scientists in California are studying how a whole bunch of toxic smoke moving around during a wildfire can end up in the water supply. They are looking at plastics and other synthetic materials and what happens when they are heated, along with the potential avenue into the water supply.

One question is whether the smoke can be sucked into the water system during a deep-pressure inversion event, Heaney said. “So, like moving the pressure and the waterlines can create a vacuum in some circumstances and cause air from the outside to be pulled in.”

Denver's wake-up call came in 1996 after the Buffalo Creek Fire and subsequent flood-inducing downpours. The fire was located upstream of Strontia Springs Reservoir, and the subsequent heavy rains carried all manner of debris and sediment into the reservoir.

It happened again in Colorado in 2002 with the Hayman Fire, but on a larger scale. Denver Water spent $29 million on recovery after those two fires. Most of the cost was from a dredging operation to remove the sediment and debris from Strontia Springs.

The impact of wildfires on water supply is the result of several factors, said Christina Burri, who manages Denver Water’s watershed health group. “So when a fire burns really hot they call it high-severity fire, and it can actually change the soil structure,” she said.

“So you’ll get different impacts in terms of water chemistry, [and] also the movement of the sediment and debris,” Burri said.

Those impacts depend on several factors, including where the fire is located relative to critical infrastructure like reservoirs or diversions for water utilities. Also, when a fire burns especially hot it changes the soil, making it more hydrophobic, which means it’s more prone to run off.

That runoff can travel far, up to 11 miles in some cases through stream channels, causing great concern for water utilities.

Since those two wildfires in Colorado, the state has adopted proactive investment in watershed and forest health to try to reduce the risk of the catastrophic wildfires. In 2010, Denver Water partnered with the U.S. Forest Service to form the Forest to Faucets partnership to help reduce the risk to the watershed from wildfires.

Denver Water committed $16.5 million and that was matched by the Forest Service for proactive investments in forest and watershed health. That entails to a large degree removing fuels — unhealthy trees, slash — from the forest to reduce the risk of high-severity fires.

Burri said about $96 million has been spent since the partnership on forest health and that has yielded a return on investment of around $247 million.