On the scat day when the wind blows through the California desert, the Salton Sea regularly emits a rotting foul stench that resembles a rotten egg.
A new study found that shrinking lakes release dirty gas sulfurized gas more frequently and at higher levels than previously measured.
The findings document how odors from the Salton Sea add to air quality issues and health concerns in communities near the lake. There, wind-blown dust drifts out of exposed stretches in the lakebed, causing people to suffer from a rate of asthma and other respiratory diseases.
“Communities around the Salton Sea are at the forefront of a deteriorating environmental health crisis,” says Mara Frelich, co-author of a study at the Department of Global Environmental Sciences at Brown University.
The Salton Sea is California’s largest lake, covering more than 300 square miles in Imperial and riverside counties. Hydrogen sulfide is released as a by-product of lake decayed algae and other organic materials. In lakes, accumulation agents and other nutrients are supplied to algae growth from agricultural runoff and wastewater.
Research has found that hydrogen sulfide, or H2S, is toxic and at certain levels includes dizziness, headache, vomiting, cough, chest tension, and depression. High levels of exposure in the workplace is a widely known health hazard, but little is known about the health effects of chronic gas exposure at low levels.
People living near the Salton Sea, many of them farm workers, have complained for years that the foul odors that tend to appear most strongly in August and September can cause headaches, nausea and nosebleeds.
Frerich and others analyzed existing aviation quality data from three monitoring stations maintained by the South Coast Air Quality Control District of Indio, Mecca, and the Kahiri Indian reservation in the Torres Martinez desert.
They worked with local nonprofit group Alianza Coachella Valley to install additional air quality sensors on wooden piles protruding from shallow waters near the North Shore. Sensors often detected hydrogen sulfide at high levels.
Examining data from different monitoring sites from May 1 to July 25, 2024, we found significant contrast. Torres Martinez’s booking monitors detected hydrogen sulfide at levels above the condition’s air quality standard for only four hours in that time, while the water sensors found 177 hours above the threshold.
Scientists said it shows that a significant portion of the gas released by the Salton Sea has not been measured.
“These findings highlight the need for improved air quality monitoring and more effective environmental management policies to protect local public health,” the researchers wrote that it was published May 31 in the journal GeoHealth.
The Salton Sea is approximately 242 feet below the Salton Trough. It has been cycled for thousands of years while it is filled and dried with the waters of the Colorado River. The lake was recently formed in 1905-2007 when Colorado flooded the area and filled the low-lying basin.
In the 1950s and 1960s, the Salton Sea was a swarm of tourists, fishing, boating and water skiing. Celebrities including Frank Sinatra and Lucille Ball in their heyday.
However, after the floods in the 1970s, the lakeside community deteriorated. Fishing declined as a species-like lake that was introduced, and people stopped boating as water quality deteriorated.
The lake has been maintained for over a century by draining water from farms in Imperial Valley, but has been shrinking since the early 2000s, when Imperial irrigation districts began selling some of the Colorado River water to urban growth under an agreement with San Diego County and Coachella Valley agencies.
Lake levels have fallen by about 13 feet since 2003. The water is now almost twice as salty as the ocean, and continues to have salt due to evaporation. It is found in bird populations.
Hydrogen sulfide below the oxygen-deficient layer of lake water, as decomposes algae and other materials. During the hottest months of the year, warm water layers form. Next, as wind stirs the lake, some of the deep water can rise to the surface and release odorous gases into the air.
California’s ambient air quality standard is 30/billion parts, an average of over an hour. The study found that under certain wind conditions, hydrogen sulfide levels averaged 1.7 billion copies above water with newly installed sensors compared to existing monitors near the coast.
Sometimes the sensor detected levels at about 200 parts per billion.
But people can detect the smell of gas, but at a low level of 1 billion or 2 parts, it’s 1 billion/2 parts.
“Residents exposed to hydrogen sulfide not only experience respiratory irritation, headaches and fatigue, but also impact quality of life,” said Diego Centenno, a doctoral student at UCLA who conducted the research while studying at Brown University.
“If you want to be active outside, run, do something, and smell like rotten eggs, you wouldn’t lean more,” Centeno said. “No one wants to go outside, especially during the summer.”
Centeno grew up right in front of the Salton Sea in a low-income community on the North Shore. He said he is always fascinated by the vast body of waters, unaware of why he has never seen him bathe or boat in the body of waters all the time.
“As the water levels continue to drop, if there’s nothing, this hydrogen sulfide gas can really grow,” says Centeno. “So the more we understand, the more we can learn how to ease and restore the Salton Sea.”
Researchers said their findings underscore the increased air quality monitoring around the Salton Sea and the need for regulators to focus on hydrogen sulfide as a pollutant that affects people’s health.
Freilich said local water controls should prioritize setting water quality standards for the Salton Sea.
“The quality of the oceans affects the quality of the air,” she said. “The caution from multiple agencies is required because it usually connects the water quality and air quality that are treated individually.”
The South Coast Air Quality Control District, or AQMD, regulates air pollution in the Coachella Valley, including the northern part of the Salton Sea. In May, the agency installed a fourth monitor of hydrogen sulfide on the northeastern side of the lake.
“This H2S surveillance network is very comprehensive,” said Rainbow Yeung, a spokesman for AQMD, adding that there are currently few other monitors reporting such data.
Yeung said in an email that the sensors installed by the researchers are of a different type than the agency’s monitors, “the measurements of H2S may be high because the sensor location is likely to be dispersed and therefore do not represent the level experienced by the community.”
AQMD issues alert you whenever the hydrogen sulfide level reaches a condition standard of 33 ppb at any monitoring site. (Residents can sign up to receive these air quality alerts.)
The California Department of Environmental Health Hazards Assessment has established a chronic exposure threshold of 1 billion parts of hydrogen sulfide, at a level where long-term exposures over the years have a health impact.
The highest annual average concentration at any AQMD monitoring site since 2016 was 1.05.5 parts, with annual averages typically below 300 million percent at levels with unpredictable health effects.
Water that is discharged from the Imperial Valley farmland and feeds the ocean comes from the Colorado River. A largely arid quarter century has prompted difficult negotiations among seven states on how water is used from declining rivers.
As these talks are considering water-saving solutions, Frielich said policymakers should “explain the health impacts on the community,” and prioritize steps that will help mitigate the problem.
California officials recently buried shallow pond complexes to control lung-inducing dust from pipes on hundreds of acres of dry lake beds near the South Shore, creating wetland habitat for fish and birds.
It is not clear how these new wetlands will affect hydrogen sulfide emissions. Freirich said she and her team are planning additional research focusing on wetlands and shallow waters.
Consuelo Marquez, a Coachella resident who helped with the research, said she lived on the North Shore for several years as a child.
“I wake up with blood on my pillow,” she said. When she asked her father about it, she recalls what she told him: “This happens because of the lake, for the air.”
She said the findings from the study tested concerns that many people have cultivated over the years.
Aydee Palomino, co-author of the research and environmental justice project manager for the group Alianza Coachella Valley, said the study “breaths pollutants under the radar of traditional surveillance systems.”
“This can have a really far-reaching impact if not addressed,” Palomino said.
Funding for the research came from the Burrows Welcome Fund, Google’s Environmental Justice Data Fund, and NASA. However, Freirich learned in March that the Trump administration had ended its NASA grant under an order targeting diversity, equity and inclusion programs.
Researchers have an ongoing appeal for that decision. Freirich said it was disrupting the ongoing work.
“Who will the community suffer at the end of the day,” Palomino said. “And that’s a shame because now they’re coming back to us to fill in the research gap.”
