Toxic Airborne Microbes

Most of the work done on aerosolized microbes has occurred in the ocean. That research shows that sea spray increases with increasing wind speed and salinity. Raymond Leibensperger, a PhD student at Scripps Institute of Oceanography, studies how aerosols in polluted water—from both sea and river spray—correspond to poor air quality and hydrogen sulfide complaints from communities. More study is needed to determine whether microbes in lake spray are taking a toll on Salton Sea communities, he says, but it could be a significant contributor.

The Salton Sea is fed by agricultural runoff from the Coachella and Imperial Valleys, billion-dollar farming regions that adjoin the sea, which produce the country’s winter salad vegetables like lettuces and broccoli, as well as citrus and dates. Colorado River water supplies, the only source of irrigation in these valleys, is declining sharply as Great Basin states are required to take steps to reduce demand.

The sea’s shrinking footprint mirrors mandatory conservation cuts. And, as the increasingly salty sea recedes, tens of thousands more acres of playa will be exposed—as will decades of pesticides already trapped in the sediments from past farm runoff. These could become airborne too, sickening humans and wildlife alike.

Agricultural Runoff as the Root Cause

“At the root of a lot of the [Salton Sea] difficulties are nutrient inputs that are coming in from agriculture,” said Tim Lyons, a geochemist at U.C. Riverside, at the summit. Due to this agricultural runoff, the Salton Sea is hypereutrophic, a term scientists use to describe water bodies that contain excessive nutrients.

Ammonium sulfate fertilizer inputs are so high in the Salton Sea, Lyons said, that it has 10 times the amount of sulfate measured in seawater. As a result, blooms of gypsum, or sulfate crystals, can occur. The consequence of a gypsum or Harmful Algal Bloom is the same: Blooms cause already low oxygen levels to plummet in the Salton Sea.

Once the water is depleted of oxygen, other microbes, including those that can transform sulfate into hydrogen sulfide or produce additional harmful compounds, can flourish and become airborne. Furthermore, microbial interactions impact the water chemistry, which affects the release of metals, such as arsenic or selenium, from sediments into the water.

At the October summit, the U.C. Riverside scientists made the case that policymakers should account for all of the public health consequences of eutrophic waters when developing plans to stabilize the sea. And that may require more strategic water and air monitoring than is currently being conducted. “This isn’t rocket science,” Lyons said. Eutrophic water bodies have been studied all over the world, he added, but “sadly, they’ve been neglected at the Salton Sea.”

Overlooked Microbes Run Amok

Further investigation identified the dust irritant as a compound called lipopolysaccharide, or LPS, in the Salton Sea sediments. LPS is a key component of the outer cell membrane of bacteria that protects them from threats such as antibiotics. LPS can also elicit an immune response in humans.

Keziyah Yisrael, a biomedical sciences postdoctoral fellow at U.C. Riverside, distinguishes between two types of asthma—an allergic form, most commonly helped by inhalers, and a non-allergic form of lung inflammation. The mice exposed to Salton Sea dust, particularly dust collected from the southern portion of the sea, exhibited the non-allergic form of asthma. No inflammatory response occurred when mice were exposed to dust from a canyon miles away from the sea.

“LPS itself is not toxic to cells,” Yisrael says. Instead, it appears the immune system’s hyper response to LPS is what cause inflammation and tissue damage, she said. “Our current hypothesis is that the microbes are chemically modifying [their] LPS, possibly to better withstand the increasingly extreme conditions—which elicits a stronger immune system response,” Yisrael says. She and colleagues believe that LPS is not the only cause of respiratory inflammation in Salton Sea communities, but “is a large piece of the puzzle” of what’s causing health problems in those living near the lake.

What has gone unnoticed in previous studies is that particles in the air are “not just being generated from the playa, but also from lake spray,” Aronson says. Her team confirmed that LPS in the Salton Sea can survive in aerosols emitted as lake spray, a bigger concern when winds churn the sea’s surface and can carry particles up to 30 miles away.

Additional research from U.C. Riverside suggests that respiratory hospitalizations may be associated with windblown particles originating from the Salton Sea. In a new study, Will Porter, a U.C. Riverside atmospheric scientist, and his colleagues compared observed particles from a range of nearby surfaces—including the Salton Sea—to the number of daily respiratory hospitalizations in Coachella and Imperial counties.

They found the strongest correlation occurred when winds came from the Salton Sea—especially during bloom events there. “I did not expect to see this strong of a signal,” Porter says.

The findings challenge the overarching narrative: that dust particles from the playa are the sole health concern. Rather, the sea’s microbes may also be producing airborne compounds that merit greater attention, the scientists say.

However, any direct impacts on health are not yet conclusive. “What we need is causation,” says Ryan Sinclair, an environmental microbiologist at the Loma Linda School of Public Health. “The epidemiological studies necessary to demonstrate causation simply haven’t been done yet,” he adds.

Poor Water Quality, By Design

“In our Clean Water Act terms, [the ag runoff into the Salton Sea] is essentially wastewater and that has a different standard of protection,” said Laurel Firestone, member of the California State Water Resources Control Board, at this year’s October Salton Sea Summit. For example, there are no nutrient discharge limits on the two main rivers or the agricultural drains that deliver agricultural and industrial runoff from Imperial County into the lake.

Nutrient discharge regulation occurs only at individual facilities such as wastewater treatment plants, which must have permits to discharge into the Salton Sea tributaries. The Salton Sea is a glaring example of how the Clean Water Act has failed to address agricultural pollution.

Last year, the Regional Water Quality Control Board began developing a total maximum daily loads (TMDL) in a bid to regulate nutrient pollution flowing into the Salton Sea, but it will likely take years to implement. The board is also taking steps to limit pollutants and promote farming best practices to control the transport of pollutants into the rivers that flow into the Salton Sea. While these are significant changes, it will take time before they have any impact, since the sea is so polluted.

Yet the consequences of the high nutrient loads were clear decades ago, before the vast majority of the Salton Sea’s fish and bird populations plummeted. As far back as 2000, the Salton Sea was characterized by high nutrient concentrations, high algal biomass, low dissolved oxygen, massive fish kills, and noxious odors.

In general, water quality monitoring for nutrients and salinity in the Salton Sea has suffered in recent years. State agencies abandoned water quality measures between 2020 and 2023, citing that existing boat ramps no longer reached the sea. The water board received a $350,000 grant to collect water quality samples for three years, starting in July 2023, but so far sampling has only taken place in one location in the southern portion of the sea that has an accessible boat ramp. The data are not yet publicly available.

And, as playa stabilization and habitat construction projects get underway, some critical data simply aren’t being gathered. “The lack of baseline data being collected on salinity, pollutants, and overall water quality of the newly constructed habitat areas will make it difficult to assess success,” says Michael Cohen, a senior researcher at the Pacific Institute, which provides independent environmental policy analysis.

“It is impossible to get water quality data from public agencies,” says Isabella Arzeno-Soltero, an environmental scientist at UCLA, who has resorted to filing public records requests to access data.

Since 2020, university researchers and citizen scientists have been monitoring water quality and posting it online to fill the gap—including Sinclair, the environmental microbiologist at the Loma Linda School of Public Health, working with Alianza CV.

In 2023, Alianza CV also mounted a hydrogen sulfide monitor on a platform above the sea on the north side to track production of the gas. Based on their results, researchers say the state monitoring isn’t sufficient.

Between January and August 2024, the Alianza hydrogen sulfide (H2S) monitor, mounted directly above the Salton Sea on the northern side, found 214 incidents in which H2S exceeded the 30 ppb threshold set by the California Air Resources Board compared to only 42 such events documented by the South Coast Air Quality Management District monitor on Torres Martinez land to the northwest. (Source: Diego Centeno)

Data from the monitor differs from a hydrogen sulfide monitor run by the South Coast Air Quality Management District (SC AQMD). “Since January, our sensor has detected 200 hydrogen sulfide exceedances; the SC AQMD sensor detected only 40,” says Diego Centeno, a doctoral student working with Arzeno-Soltero at UCLA, who grew up around the Salton Sea.

The California Air Resources Board established the one-hour hydrogen sulfide standard at 30 parts per billion; anything beyond that is deemed an exceedance.  The discrepancy, they believe, is due to the fact that the SC AQMD monitor sits on land northwest of the sea, and the exceedances the Alianza monitor detects typically occur when the winds come from the north.

Arzeno-Soltero says accurate exceedance data is crucial for public health protections. Even chronic hydrogen sulfide exposures below the level authorities consider dangerous have been associated with an increased prevalence of neurological effects, including headaches, mood disorders, and depression, according to a 2023 study.

There’s even less monitoring for HABs, which can produce cyanotoxins that can cause headaches, sore throats, nausea, vomiting, and other symptoms. A pilot study conducted between September 2020 to August 2021 found at least twelve genera of cyanobacteria were detected in the nearshore Salton Sea, and at least one animal was reported dead from ingesting toxins.

Despite the report’s conclusion that the algal blooms presented “a significant health risk” from toxins, there is minimal monitoring at the state level. “Due to funding, recent Harmful Algal Bloom monitoring has only occurred before holidays when people may be recreating on the sea,” the Regional Water Quality Control Board responded in an email.

“Currently, there are no federal or state regulatory standards for cyanotoxins in recreational waters,” the board said. Participating state agencies have developed voluntary guidance for responding to HABs in recreational waters. The guidance suggests that if field screening determines cyanobacteria or cyanotoxins are present, responding organizations should collect water, scum or algal mat samples for laboratory analysis; if HABs or toxins meet or exceed trigger levels, the responding organization should report to the HABs hotline and post an advisory sign.

UCLA graduate student Cruz Marquez checks the mooring for the Alianza water quality monitor in the Salton Sea. (Photo credit: Alejandra Lopez)

Roxana Chavez, a regional organizer for a women’s farmworker leadership organization, Alianza Nacional de Campesinas, Inc, says the Imperial County Division of Public Health put up a billboard in early October near her home in Desert Shores, a community on the northwest shore of the Salton Sea. The billboard explains: “In certain conditions, the water may produce toxic Harmful Algal Blooms (HABs), in which children and pets are most susceptible to illness from water contact and/or ingestion.”

It also offers a QR code that it says will be updated to reflect current water quality as yellow, orange, or red, corresponding to caution, warming, or danger, respectively. But they’ve done little else to inform the community about HABs. “We notice the smell but also the color when the water changes—it becomes more greenish,” Chavez says.

Jasmyn Phillips lives in Calipatria, on the sea’s southern end. Beyond billboards, she wants to see more effort to educate Salton Sea communities about HABs—and more consistent water quality monitoring, since the Salton Sea is such a dynamic ecosystem. “Just because there are algal blooms doesn’t necessarily mean they are producing toxins,” she says.

Looking to Nature-Based Solutions

The “LPS in sea spray” hypothesis is an intriguing one that needs further research—but it’s not clear how the story ends, says Cohen. “Even if you stopped nutrient inputs immediately,” he says, “you would not see immediate benefits, and you might not see benefits for decades, because there’s too much nutrient cycling within the Salton Sea.”

Community members, including Eric Reyes, executive director of Los Amigos de la Comunidad, a nonprofit organization that aids underserved communities facing environmental injustices in Imperial County, say the lack of engagement from policymakers as well as the agricultural community is wearisome. “We have a sense of urgency that we don’t see anyone else expressing,” says Reyes.

Palomino rejects the notion that nothing can be done to soak up nutrients. “How do we preserve wetlands or construct more, so they are a nature-based solution?” she asks.

The biggest challenge: Constructing wetland habitat is expensive. Tamping down windblown dust has been a key goal of the ten-year Salton Sea Management Plan so far. Over the last two years, roughly one-third of the $750 million state and federal dollars for restoration were used to develop the first large-scale project, called the Species Conservation Habitat (SCH), to suppress dust and create ponds of less salty water to support fish and fish-eating birds, as well as wetland habitat on 4,100 acres of exposed playa. While projects like these are valid, the surrounding community is frustrated that water quality is not also on the agenda, says Palomino.

The shrinking Salton Sea is also proving to be more dynamic than the conservation projects it has taken over a decade to design and construct. At the SCH, for example, nature’s attempts to restore itself have been thwarted by slower-moving conservation measures. Wetlands have been naturally forming on exposed playa where agricultural drains no longer reach the lake. The water that now spills on the playa allows vegetation to thrive, preventing dust. But in a twist, 153 acres of those emergent wetlands were destroyed during the creation of the SCH, according to Keilani Bonis-Ericksen, a geospatial scientist at Audubon California.

This year, the SCH project got a one-time $70 million boost from the Inflation Reduction Act to expand the wetland habitat by another 750 acres. Yet Cohen anticipates the incoming federal administration could further hamper both state and federal funding levels, which will stymie progress at Salton Sea.

Two years ago, an international team of researchers explored “algae turf” farming, purposefully growing algae to soak up contaminants in the Alamo River wetlands, one of the tributaries to the Salton Sea. The algae harvest effectively removed nitrogen, phosphorus, selenium, and other metal contaminants, but it’s not clear whether similar projects will continue.

“We need to be more ambitious,” says Palomino. “I’m tired of going back to community and saying, ‘I don’t know what we can do about the water.’”

Reporting for this piece was supported by the Nova Institute for Health.

This article was updated with the name of the water quality board and the current depth of the Salton Sea.