Study shows Tijuana River water pollutes the air
Researchers identify hundreds of different gases emitted into the atmosphere
Sep 2, 2025 - by Audrey Merket
University of California, San Diego Research and Development Engineer Greg Sandstrom takes measurements with a Coriolis air sampler at the river hotspot. Credit: Beatriz Klimeck/UC San Diego.
Newly published research indicates that poor water quality can drastically affect air quality—an observation with important implications for global waterways.
The paper, published last week in Science, showed a link between poor water quality in the Tijuana River with reduced local air quality. The authors are a team of researchers from University of California, San Diego; University of California, Riverside; San Diego State University; and the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR). The research was funded by NSF, NOAA, and the Balvi Philanthropic Foundation.
During the study, the research team measured peak concentrations of the toxic gas hydrogen sulfide – commonly known as “sewer gas” because of its association with sewage and rotten egg smell – that were 4,500 times more than what is typical for an urban area. In addition, they identified hundreds of other gases released into the air by the river and its ocean outflow.
“The research shows that while hydrogen sulfide is an excellent marker of the sewage impacting area residents, there are multiple sources of waste entering the Tijuana River and a multitude of other hazardous gases that area residents are potentially inhaling,” said NSF NCAR scientist Kelley Barsanti, who led the analysis of additional gases detected at the site.
Barsanti worked with Karolina Cysneiros de Carvalho, a postdoctoral student at the University of California, Riverside, to identify additional gases emitted into the atmosphere by the polluted river. They measured the concentrations of various air pollutants for roughly three weeks and combined these measurements with river flow data and atmospheric modeling to track how far the air pollutants spread through nearby communities.
“We were able to demonstrate the impact of this water pollution crisis on air quality, not only at the identified hotspot, but across the region," said Cysneiros de Carvalho. “Sustained monitoring along with further research is still needed to fully understand the combined health risks that arise from simultaneous exposure to multiple air pollutants.”
For more about the research, see the University of California, San Diego news release.