Toxic Dust Reshapes Lung Microbiome

The Salton Sea, located in Southern California, is a bit of a misnomer.

The "Sea" is actually a highly polluted, rapidly shrinking lake. Agricultural runoff into the lake in the 20^th century caused massive bird and fish die-offs. When the lake began shrinking in 1999, the contaminated lakebed was exposed and began producing clouds of toxic dust.

A study led by UConn mycologist Mia Maltz demonstrated that breathing in the dust from the lake can reshape the microscopic world inside our lungs.

Maltz is an assistant professor of microbial ecology and soil health in the Department of Plant Science and Landscape Architecture in the College of Agriculture, Health and Natural Resources (CAHNR). She conducted this work while at the University of California, Riverside. Maltz collaborated with UC Riverside researchers David Lo, Emma Aronson, Talyssa Topacio, and undergraduate student Marina Zaza.

At one point, scientists thought healthy lungs were a sterile environment. We now know that, much like the stomach and other parts of the body, there are beneficial bacteria in healthy lungs and they can be disturbed by inhaled substances.

Scientists had previously discovered that genetic or bacterial diseases can influence lung microbes. This discovery marks the first time scientists have observed such changes from environmental exposure rather than a disease.

Published in the journal mSphere, the study shows that inhalation of airborne dust collected close to the shallow, landlocked lake alters both the microbial landscape and immune responses in mice that were otherwise healthy.

"Even Salton Sea dust filtered to remove live bacteria or fungi is altering what microbes survive in the lungs," Maltz says. "It is causing deep changes to our internal environment."

The researchers collaborated on the design of an exposure chamber that mimicked real-world air conditions. The team collected dust samples both closer to and farther from the Salton Sea, then exposed mice to the aerosolized particles during a series of one-week trials.

This study relied on a method Maltz developed over four years to isolate microbial DNA from host tissue, enabling a more detailed look at the lung microbiome than ever before.

Among the bacterial species that proliferated amongst mice exposed to the sea dust were Pseudomonas and Staphylococcus, both linked to respiratory inflammation. The most affected samples were rich in bacteria that produce LPS, a molecular residue on their outer membranes known to trigger immune responses.

"We think microbial products like LPS are part of what's causing the inflammation," Maltz says. "It's like breathing in a chemical fingerprint of dead bacteria."

Some dust samples were especially potent. In one case, up to 60% of lung immune cells contained markers of neutrophil activation, showing aggressive inflammation. In mice breathing filtered air, levels of neutrophils were only 10% to 15%.

As the Salton Sea lakebed continues to dry, more of its toxic sediment becomes airborne. The research group is examining whether similar microbial shifts or asthmatic inflammatory responses occur in local children.

The research also raises broader questions. If dust can alter lung microbes, what about smoke, exhaust, or vaping aerosols? The researchers plan to test whether other exposures cause similar disruptions.

Maltz received a UConn InCHIP Seed Grant to continue this research. Working with Zaza, UConn graduate student Paulette Goyes, and UC Riverside researcher Ann Cheney '10, they visited communities around the Salton Sea and taught community health practitioners (promotoras) affiliated with Unidas por Salud how to collect dust inside the homes of community members that have children suffering from asthma.

The next step is to determine whether protective bacteria species are being lost, and how long any noticeable changes to the microbiome persist. Maltz is also investigating which medically relevant microbes are found in the dust that may be responsible for the inflammation and neutrophil recruitment they observed.

"We've only just begun to understand how dust exposure changes the lung microbiome," Maltz says. "We don't yet know how long the changes last, or whether they're reversible. That's another big question."

This work relates to CAHNR's Strategic Vision area focused on Enhancing Health and Well-Being Locally, Nationally, and Globally and Advancing Adaptation and Resilience in a Changing Climate.