Toxic saline sea dust induces changes in the lung microbiome after just one week

Dust from California’s drying Salton Sea doesn’t just stink. UC Riverside scientists found that breathing dust can rapidly shape the microscopic world inside the lungs.

Genetic or bacterial diseases first affect the microbes in the lungs. However, this discovery is the first time scientists have observed such changes from an environmental exposure rather than a disease.

Published in the Journal Mapthe study showed that inhalation of airborne dust deposited near a shallow, landlocked lake altered both the microbial landscape and immune response in mice that were otherwise healthy.

“Even salty sea dust is directly filtered to remove bacteria or fungi that may alter the survival of microbes in the lungs,” said UCR mycologist and lead study author Mia Maltz. “It’s causing profound changes in our internal environment.”

Scientists have studied the gut microbiome extensively, linking it to digestion, immunity and even mental state. In contrast, the lung microbiome is less well understood, although it is increasingly important to overall health.

“Studies from our lab have shown that dust generated in the Salton Sea can have significant health effects, particularly in the lungs, and is likely a major factor in the high incidence of asthma in nearby communities.”

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

Even before deeper analysis there were some indications of ill effects.

“Residents of the Salton Sea have ongoing suspicions that the environment is linked to respiratory illness, and our lab has certainly noticed the effects of heat, dust, and high winds during field work.”

“Dust doesn’t smell good either,” said Emma Aronson, UCR environmental microbiologist and study author. “When we were processing it in the lab, it could be smelly.”

Bacterial species that spread among mice exposed to sea dust included Pseudomonas and Staphylococcus, both linked to respiratory inflammation. The most infected samples were rich in bacteria that produce LPS, a molecular residue on their outer membranes known to stimulate immune responses.

“We think microbial products like LPS are part of what causes inflammation,” Maltz said. “It’s like breathing in the chemical fingerprint of dead bacteria.”

Some dust samples were particularly potent. In one case, up to 60 percent of lung immune cells contained markers of neutrophil activation, indicating aggressive inflammation. In the filtered air inhaled by mice, neutrophil levels were only 10% to 15%.

These findings challenge long-held assumptions in pulmonary science, Aronson said. “We’ve seen these kinds of microbial shifts in people with cystic fibrosis or infections,” he said. “But these mice didn’t have pre-existing conditions. It was a clean slate, and it still happened.”

As the Salton Sea continues to dry up, more and more of its toxic sediments become airborne. The research group is examining whether similar microbial shifts occur in local children.

“Inhaling dust over time can have chronic effects in the lungs, and these studies of the potential to alter the lung microbiome are an important first step in identifying factors that can lead to asthma and other chronic diseases,” Lowe said.

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 produce similar inhibition.

The study relied on a method Maltz developed over four years to isolate microbial DNA from host tissues, providing a more detailed look at the lung microbiome than ever before. The next step is to determine whether protective species are being lost, and how long any significant changes in the microbiome persist.

“We’re only just beginning to understand how dust exposure changes the lung microbiome,” Maltz said. “We don’t yet know how long the changes last, or whether they’re reversible. That’s another big question.”