The rotten egg smell at the Salton Sea isn’t just a nuisance. It can make people sick

Residents around the Salton Sea have long complained of respiratory ailments from particulate pollution that wafts from its shoreline.

Now UCLA researchers have identified another air pollutant that could be sickening people in communities near the inland lake: hydrogen sulfide.

That’s a gas from decaying, organic matter that produces a rotten egg smell and is associated with eye irritation, headaches, nausea and other symptoms. In a pair of reports released last week, the Latino Policy & Politics Institute at UCLA described how algal blooms produce the gas in the water, and how it wafts across nearby neighborhoods.

“Communities that live next to the shore or within a mile of the shore experience exposure to hydrogen sulfide,” said Consuelo A. Márquez, who authored the reports with Alejandra López, and Isabella B. Arzeno-Soltero. “We hear stories: ‘my child faces chronic nosebleeds and have had asthma their whole life.’”

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The Salton Sea crosses Riverside and Imperial Counties, and is California’s largest lake. By many measures it's also the most imperiled. Nearly twice as salty as the ocean, it's polluted by agricultural runoffs and toxic algal blooms. Despite its contamination, the sea is a haven to more than 400 bird species and a key stop on the Pacific Flyway, one of North America’s main bird migration routes.

California recently created a Salton Sea Conservancy to restore habitat for birds and aquatic life. Community advocates say there needs to be greater focus on the lake's effect on public health in neighboring communities.

“They need help getting treatment, getting medication, or care related to possible cardiovascular and respiratory issues,” Márquez said. “It’s happening at such high rates that a lot of them just live with it. I think there should be more attention put on that.”

The UCLA studies aimed to highlight those problems by measuring hydrogen sulfide emissions at the lake. One study focused on how the chemical is produced in the water. High concentrations of nitrates from fertilizer runoff and low oxygen levels in the water column create an environment that generates hydrogen sulfide gases.

The second looked at hydrogen sulfide concentrations in the air. Researchers installed two additional hydrogen sulfide monitors in the area and found that hydrogen sulfide emissions consistently exceed the California Air Resources Board’s state standard of 30 parts per billion. They recorded 243 hours above this threshold between May and September 2024 alone.

At those levels - and even at lower concentrations - the chemical can cause a litany of health problems, according to the U.S. Occupational Health and Safety Administration. Those include nausea, eye irritation, headaches, sleep loss, airway problems, fatigue, irritability, poor memory, dizziness and others.

“As more data highlight connections between water and air-quality, it is crucial to monitor air-quality in all its aspects, not just those related to dust,” the report stated, pointing out that the region is home to primarily Latino, Native American and immigrant residents. “The persistent issue of hydrogen sulfide pollution serves as a clear example of environmental injustice.”

The Salton Sea isn’t the only area with this problem. Hydrogen sulfide emissions also plague areas of San Diego County affected by pollution from the Tijuana River. In parts of South Bay San Diego, researchers with UC San Diego’s Scripps Institution of Oceanography, UC Riverside, San Diego State University and federal agencies found concentrations of hydrogen sulfide about 4,500 times what is typical for an urban area, according to a report released last month.

Márquez said the UCLA researchers are calling for a “holistic systems approach” to improving air quality around the Salton Sea. That could include distributing air purifiers and air quality monitors so residents can play an active role in improving conditions. They also need better access to medical treatment for possible cardiovascular and respiratory issues. Above all, residents want to make sure their concerns are heard and addressed, she said.

“The best people who can create solutions are the people who are affected themselves,” she said.

This article was originally published on CalMatters and was republished under the Creative Commons Attribution-NonCommercial-NoDerivatives license.