For years, millions of dollars have poured into controlling dust that wafts off the exposed lake shoreline of the Salton Sea, hoping to solve a serious air pollution problem in the Coachella and Imperial valleys.

But a new report finds that the dusty shoreline is only responsible for a small percentage of the pollution, prompting some researchers to emphasize that cleaner air inside people’s homes, workplaces and schools could be more important in addressing the asthma and respiratory disease that plague the area.

“My big takeaway is that there’s so many different sources that what we really need to do is pivot away from source control to start protecting people where they’re exposed,” said Michael Cohen, a senior researcher at the Pacific Institute and lead author of the report.

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Released Thursday, the report draws on data from local, state and federal agencies and finds that dust from the expanding dry shore of the Salton Sea accounts for less than 1% of total small particle pollution in the region.

The Salton Sea Basin, Coachella Valley and Imperial Valley all violate ozone, or smog, limits. When averaged over the year, Imperial Valley and Salton Sea Basin have twice the state limit for larger particles. Recent research also suggests bacteria and hydrogen sulfide as pollutants of concern.

The dust particles are made up of agricultural chemicals from miles of lettuce and spinach fields, manure from livestock operations, diesel exhaust, unpaved roads and fine debris from lithium mining. Previous reports from UC Riverside have called the area one of the most impoverished and environmentally deteriorated regions in California.

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This mix is why state and local agencies have long focused their attention on dust control projects, planting salt-tolerant vegetation and spreading gravel. To date, California has spent some $49 million to put in more than 3,000 acres of dust suppression around the Salton Sea. But pollution is coming from so many places that money may be best spent in other ways, the researchers say.

“It’s just much more effective, more cost-effective to switch to exposure control … because really, at the end of the day, we’re trying to protect public health and improve the lives of people,” Cohen said.

That could mean focusing on distributing filters, weatherizing homes and alerting people when they should stay and avoid exercising outdoors.

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A 2023 survey by the UCR School of Medicine showed more than one in five children in communities near the Salton Sea have asthma — almost twice the state average. Some 29% of parents surveyed said their child has had wheezing or breath whistling in the past, most in the last 12 months.

The Salton Sea’s role in the region’s air quality is amplified by its geography. As a desert basin bordered by mountains, it can trap pollutants. Since 2018, the Salton Sea no longer gets an inflow of fresh water, only agricultural runoff, so it is evaporating and shrinking while the exposed, dry lake bed area is expanding, feeding clouds of particulate.

Wind patterns, including strong gusts that sweep across the lake bed and surrounding farmland, can also kick up fine, toxic particles and carry them into nearby towns — exposing more residents.

Some of the communities have identified pesticides, open burning, road dust and farming operations as among their air priorities.

The region includes Calipatria, Brawley, Riverside, Palm Desert and Indio as well smaller communities, many of them mostly Latino or Indigenous.

It’s not that the Salton Sea is ruled out as a health problem. Dr. David Lo, a UC Riverside professor who has focused for years on air pollution in the region, said certain particles can be especially harmful depending on their chemical or biological makeup.

“A tiny amount of toxic material, even if it’s infinitesimally small, can still have really major health effects,” Lo said.

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If policy emphasis were to shift to indoor air quality, that would leave many people unprotected, said Aydee Rodriguez, environmental justice campaign manager for the nonprofit Alianza Coachella Valley. “We’ve been noticing an uptick … of asthma-related … emergencies, people having nosebleeds, people having migraines, people feeling dizzy, nauseous,” she said.

“My hope is that the people start to get together and start talking to each other,” said study author Cohen. “About what the different agencies are doing, where they’re investing their money and how they can leverage and optimize those investments in public health.”