Coastal environments are extremely dynamic. Pollutants in the land and water can become aerosolized and inhaled by residents of coastal communities. Credit: Adam Cooper / UC San Diego
The 120-mile Tijuana River flows from Baja California into the United States and discharges millions of gallons of wastewater—including sewage, industrial waste and runoff—into the Pacific Ocean every day, making it the dominant source of coastal pollution in the region.
Wastewater pollution has been an ongoing problem for decades and is so severe that the nonprofit environmental group American Rivers recently named the Tijuana River America’s second most endangered river.
A new study from the University of California San Diego examines how pollutants in wastewater travel and are transmitted in the atmosphere through coastal aerosols.
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In the study, researchers found that a mixture of illicit drugs, drug metabolites, and chemicals from tires and personal care products aerosolize from wastewater and are detectable in both air and water. The results appear in Science Advances.
The paper’s lead author, Adam Cooper, collected samples from the air and water at various points along the coast of San Diego County, including the U.S.-Mexico border, Imperial Beach and the Scripps Institution of Oceanography in La Jolla.
Cooper, who graduated last spring with a doctorate in chemistry, was a member of Assistant Professor of Chemistry and Biochemistry Jonathan Slade’s group, and collected the samples as part of a field study with Distinguished Professor of Atmospheric Chemistry Kimberly Prather’s lab.
Prather, who holds a joint appointment at Scripps Oceanography and the Department of Chemistry and Biochemistry at UC San Diego, had been studying the air pollution impacts of the Tijuana River for several years. Cooper was able to join her team’s comprehensive sampling campaign across multiple sites from January to March of 2020.
Even though the samples were taken in 2020, the findings are still relevant because little has changed in how sewage released from the river is processed. In fact, pollution from the river has been an ongoing problem for more than 50 years.
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“The Tijuana River region is a very dynamic environment with implications for public health, environmental policy and international relations between the United States and Mexico,” stated Cooper.
“Ours is one of the most comprehensive studies to date investigating water-to-air transfer of these pollutants.” The study looked at two aspects of wastewater pollution: the source and the concentration of pollutants along the San Diego County coastline.
To determine the origin of the pollutants, Slade’s lab used a compound they knew came from sewage: benzoylecgonine (BZG), a stable metabolite of cocaine, primarily produced when people use cocaine and then excrete it in urine.
They found that after rainfall, BZG levels in Imperial Beach ocean water spiked in correlation with increased Tijuana River flows, while BZG levels in aerosols spiked in correlation with enhanced sea spray aerosol emissions.
Correlating 11 other pollutants to BZG in aerosols allowed the team to determine which ones behaved similarly in the environment and likely originated from the same wastewater source. The results showed a high correlation between BZG; methamphetamine; octinoxate, a UV filter used in sunscreen; and dibenzylamine, a compound used in tire manufacturing.
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The second part of the study measured pollutant concentrations along the coastline in the water and air. Overwhelmingly, they found that these pollutants were higher in the Tijuana River water than in the ocean, and higher in the water and aerosols in the Imperial Beach region than in La Jolla.
Although the amounts of some pollutants, like cocaine, were minuscule, others were more prominent, like octinoxate, which can break down into more toxic components.
In some cases, the octinoxate levels were comparable to measurements made directly above wastewater treatment plant vats, meaning that in some ambient conditions at the coast, the concentrations of pollutants that people are inhaling can be comparable to a worker at a wastewater treatment plant.
“It’s been shown that octinoxate can degrade DNA when exposed to light,” stated Slade. “And if it’s in these tiny aerosols we’re breathing in, it can get deep into our lungs and pass into our bloodstream. That’s very concerning, especially considering the high levels at which we found it in the air.”
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The study shows that the closer you are to the Tijuana River, the more likely you are to be exposed to the pollutants it carries, even though the amounts are still relatively small—on the scale of tens of nanograms per hour. This may not seem like much if your exposure is limited to a few hours, but residents living close to the border are inhaling these chemicals over years, even decades.
Many residents have complained of respiratory illness, insomnia and headaches, and several San Diego beaches have been closed almost continuously for the last three years because of high levels of bacteria from wastewater runoff.
Although the paper doesn’t draw any conclusions about the detrimental effects on the environment or human health, Slade and Cooper emphasize the need for more research, better infrastructure and cross-border collaboration.
“Often the sewage crisis is considered a water issue—and it is—but we show that it’s in the air too. Truthfully, we don’t yet know the acute health effects,” stated Slade. “But the numbers we report can be incorporated into models to help us better understand what we’re breathing in and how much we’re exposed to.”
Cooper was so influenced by his work at UC San Diego that he is now a Science and Policy Technology Fellow with the California Council on Science and Technology, working with State Senator Ben Allen.
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“The solutions to the cross-border sewage crisis aren’t constrained by technical challenges,” stated Cooper. “They’re constrained by political challenges and policy issues. We have to motivate decision-makers to make the right investments.”
In addition to better infrastructure, more public awareness is crucial to improving the region’s water and air quality, including understanding the downstream effects of the products we use, such as sunscreens and tires.
“Although our study focuses on the Tijuana River, there are other notable sources of wastewater and pollution run-off in Southern California, including wastewater treatment outfalls, the San Diego River and the Los Angeles River,” said Slade, who also noted that “turbulence in rivers and streams may aerosolize wastewater, requiring further study.”
Coastal port environments are extremely dynamic and complex, but these pollution issues are not relegated just to the San Diego-Tijuana region. They pose a global hazard.
An estimated 80% of all global wastewater is untreated. Of the portion that is treated, many plants remove bacteria, but not chemical pollutants. These chemicals remain in the water, which is released into rivers, lakes and oceans, traveling around the world through waterways and in the atmosphere.
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“The global surge of untreated wastewater entering lakes, rivers and oceans poses a growing health threat. Aerosolization of this polluted water exposes billions of people through airborne transmission, reaching far beyond those in direct contact and impacting countless others who inhale contaminated air that can travel for many miles,” stated Prather.
“We are continuing our studies in this region to better understand the short and long-term health impacts of inhaling this newly identified source of airborne pollution.”
More information:
Adam Cooper et al, Identifying Wastewater Chemicals in Coastal Aerosols, Science Advances (2025). DOI: 10.1126/sciadv.ads9476. www.science.org/doi/10.1126/sciadv.ads9476
Provided by
University of California – San Diego
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Pollution from the Tijuana river affects air quality in San Diego, finds study (2025, May 28)
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SAN DIEGO (FOX 5/KUSI) — San Diego Police responded to a barricaded individual in the Mission Valley area Thursday afternoon, prompting a heavy law enforcement presence.
The Nexstar Media video above details resources for crime victims
The department confirmed around 1 p.m. that officers were on scene in the 1400 block of Hotel Circle North, and are working to safely resolve the situation. Authorities asked the public to avoid the area and allow officers the space needed to conduct their operations.
Police described the incident as a domestic violence restraining order violation. At this time, it’s unknown if the person is armed.
No injuries have been reported.
The suspect was taken into custody within an hour.
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Further details about the barricaded person were not immediately released. Police say updates will be shared as more information becomes available.
This is a developing story. Check back for updates.
1 — The number of plate appearances for Campusano while in the majors between June 1 and June 13 and the one at-bat resulted in a weak, pinch-hit groundout against a position player (Kike Hernandez) on the mound in mop-up duty. Campusano was recalled to the majors four times in 2025 but did not get a real opportunity get settled after he went 0-for-6 with four walks and a strikeout in three straight starts as a DH in early May. Of course, hitting .227/.281/.361 with eight homers over 299 plate appearances after getting the first real chance to start in 2024 likely informed how the Padres viewed his opportunity in 2025.
TRENDING
Down — Called up a final time on the last day of the regular season, Campusano balked at the idea that the season did not go the way he wanted. “I had a great season,” he said as he and his teammates packed for the NL Wild Card Series in Chicago. And he did … for Triple-A El Paso. He hit more home runs than ever (25), drove in more runs (95) and finished with a career-high 1.036 OPS, tops among all qualifying Triple-A hitters. The disappointment inferred in the question posed to Campusano was that he was not able to impact the big-league team in any way in 2025, which began with the team choosing to bring in a 40-year-old Yuli Gurriel a chance on the opening day roster over a homegrown product. Once billed as the catcher of the future, Campusno did not catch a single game in the majors, nor did he get any hits, although the opportunity to play was sporadic after getting three straight starts as a DH in early May (see stat to note). The Padres even lost back-up catcher Elias Díaz to an oblique injury over the final weekend of the regular season, but Campusano — who played out the string for a Triple-A El Paso team that did not make the playoffs rather than participate in the majors as a September call-up — was added to the postseason roster more as a right-handed bat than a third catcher (Martín Maldonado was also re-added to the team for the playoffs as the defensive back-up to Freddy Fermin). Campusano, of course, was not asked to help the team in either capacity before the Padres were eliminated in three games.
2026 OUTLOOK
Campusano is finally out of minor league options this year, so the Padres will either have to carry him on the roster, trade him or expose him to waivers. He has fans in the organization, but two big-league staffs headed by Bob Melvin and Mike Shildt seemingly lost faith in his ability to catch a game and all the responsibilities that come with that. It remains to be seen what impact the arrival of robo umps will have on how new manager Craig Stammen views Campusano’s ability behind the plate, but he’s been a potent minor league hitter who has yet to truly get on track in the majors beyond the second half of 2023 (.875 OPS, 6 HRs). Campusano has dabbled at first base in recent years in the minors (12 starts total), so perhaps he settles into a role as a second catcher/right-handed DH/first base option to start 2026.
Luis Campusano #15 of the San Diego Padres and Nick Pivetta #27 walk to the dugout during a practice before the Wildcard series against the Chicago Cubs at Wrigley Field on Sept. 29, 2025 in Chicago, Illinois. (Photo by K.C. Alfred / The San Diego Union-Tribune)
SAN DIEGO, CA — Two San Diego County eateries were named among the most beautiful restaurants that opened last year in the country.
Carlsbad-based Lilo was ranked No. 4 and La Jolla-based Lucien was ranked No. 9 on Robb Report’s list of the most beautiful new restaurants in the U.S. for 2025.
Lilo, which opened in April, features a multi-course tasting menu served around a 24-seat chef’s counter.
The restaurant, co-owned by Chef Eric Bost and John Resnick, earned a Michelin star just months after opening its doors. The eatery was also the only one in San Diego to land on The New York Times list of the 50 best restaurants in America.
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Lucien, which opened in July, also offers a chef’s tasting menu, with more than a dozen courses. The 30-seat restaurant, is owned and helmed by Northern California native Chef Elijah Arizmendi, along with partners Brian Hung and Melissa Lang.
“I’m very grateful for the recognition from Robb Report,” Arizmendi told Patch. “Lucien is deeply personal to me, and the space was designed as an extension of my philosophy — one centered on intention, hospitality and the joy of sharing something meaningful to others.”
The list spotlights 21 restaurants in Chicago, Los Angeles, New York City and other cities across the country. View the full report here.
