Salton Sea Study Links Toxic Dust, Lung Disease, Injustice

Though it may not always feel like it, we are a part of nature, and our health depends on the quality of our environmental surroundings. A new study published in Nature Scientific Reports explores a surprising new connection between climate change, pollution, and the negative health impacts marginalized communities disproportionately face.

The researchers, including UConn researcher co-first author of the study Mia Maltz and University of California Riverside researchers including co-first author Talyssa Topacio and senior co-author Emma Aronson detail how dust from a rapidly drying, heavily polluted body of water is contributing to widespread lung disease in communities living nearest to the shore. The researchers also demonstrate how chronic inhalation of the toxic dust causes changes in the gut microbiomes of mice.

California's largest inland lake, the Salton Sea has a fascinating history. The sea originally formed when an irrigation canal from the Colorado River overflowed in the early 20^th century and the resulting body of water became a popular resort.

This has changed drastically over the years, Maltz explains. Water from the Colorado River has been diverted and the sea is now largely fed by agricultural runoff where excessive salts and nutrients contribute to increasing salinity and poor water quality. Now, the sea is highly polluted, resulting in frequent fish and bird die offs and the area's characteristic sulfurous odor.

"It was a thriving destination for recreation and then in the last several decades it has turned into a barren wasteland," says Maltz. "People who live near it are those who can't afford to live elsewhere. It feels like a sacrifice zone."

Besides poor water quality, as the climate warms the lake is drying fast and shrinking, the playa or muddy shoreline which Maltz describes as being almost like quicksand, is a source of easily aerosolized dust. Despite the community's attempts to avoid the dust, rates of lung disease for those living around the sea are extremely high. Aronson adds that there may also be harmful compounds in the sea spray that is released as seasonal winds whip up the top of the Sea.

This project seeks to dig deeper into the drivers behind these high lung disease rates and builds on previous research where Maltz and her collaborators demonstrated that the microbial community within our lungs is shaped by what we are exposed to in the environment.

For this work, the researchers collected dust from three sites around the Salton Sea, at varying distances from the shore, in the fall months for the years of 2020, 2021, and 2022. The samples were analyzed for the amounts of toxins, organic matter, and microbial composition they contained, and using an environmental chamber that Maltz and colleagues designed, mice were exposed to the samples. The researchers then studied the lung and fecal microbiomes of the mice, where they found a surprising connection.

"The dust closest to the sea caused inflammatory responses in the lung and since there is a gut-lung axis it caused opposing effects in the gut microbiome," says Maltz. "The dust closest to the Sea decreased the microbial diversity in the gut, and increased diversity in the lung. Along with the increased lung microbial diversity, there were also enrichments in the relative abundance of certain microbes in the sea. The dust collected from close to the Sea yielded systemic responses which impacted mouse gut microbiomes by reducing microbial diversity."

Topacio adds that these findings are unique in that they position the gut-lung axis as a potential driver of systemic consequences to environmental exposures.

"Here, we showed first how much the lung microbiome is impacted by toxic dust exposure, then subsequently, how fecal microbiome diversity is also significantly reflective of systemic dysbiosis," says Topacio.

The observed increase in microbial diversity in the lungs was in gram negative bacteria containing an endotoxin called lipopolysaccharide (LPS), which elicited an inflammatory immune response and non-allergic asthma in the mice.

In allergic responses, Maltz explains they would see an uptick in immune cells called eosinophils, but instead they see an inflammatory response with an increase in another class of immune cells called neutrophils. This type of response can be more severe and does not really respond to common asthma treatments like corticosteroid inhalers.

These experimental results reflect observations in the community and Maltz explains that asthma rates in children close to the Salton Sea are high, while the rates decrease for those living further from the sea. The team recently submitted a proposal for a National Institutes of Environmental Health Sciences (NIH's NIEHS) grant to study the asthma phenotype in children living in the area which has high rates of misdiagnoses of allergic asthma. The grant is led by Ann Cheney '10 Ph.D., now a professor at the University of California, Riverside.

"This is all happening because this polluted sea is eliciting a different type of non-allergic, neutrophilic asthma. It is leading to systemic responses, most profound in the dust closest to the sea," says Maltz.

Since medical treatments are limited for non-allergic asthma, the researchers are collaborating with medical doctors and community health practitioners to create bilingual fact sheets to inform the Salton Sea-area residents of things they can do, such as support different lifestyle changes, breathing exercises, and use air purifiers. The team is also working to collect household dust samples, and Maltz is testing the samples to see if it is similarly enriched with the neutrophil-recruiting LPS as the dust found outdoors around the sea.

"A lot of these homes are manufactured and not shored up against the dust and weather. Many of these families are immigrant and migrant farmworkers, some speak in indigenous dialects like Purépecha, or speak solely Spanish," says Maltz.

The Salton Sea presents a clear example of marginalized communities and the need for environmental justice, but this is further complicated by the fact that it is also home to one of the largest lithium deposits known, earmarked for California's Lithium Valley Vision.

"There is potential for mitigation but instead there is a push for more mining and more environmental disturbance at the sea due to critical minerals," says Maltz. "We want to empower the people in the area with the social and political capital to enact change, but we are talking about a sea that is drying due to water diversion decisions that were made outside of the community members hands, and then we have climate change impacts. It all leads to the snowball effect as the sea continues to shrink."

This research shows the interconnections and importance of considering environmental, social, and health impacts on a community, but also demonstrates ways to work with a community to collaboratively seek solutions.

"When you're there, you see the families and feel the love. These people live there. They're exposed and air pollution is one of the hardest things to control," says Maltz. "I am excited to work with the families to teach them about what is in the dust and translate the science into useful facts and interpretations that they can understand to enact positive change."