Coastal aerosols contain wastewater pollutants

For decades, locals have known that the Tijuana River at the US-Mexico border is polluted with unhealthy levels of sewage, industrial waste, and runoff. Millions of gallons of contaminated water flow into the Pacific Ocean daily between Tijuana and San Diego. Now, researchers from the University of California San Diego (UCSD) have shown that the pollution not only poses a serious health risk in the water but also contributes to poor air quality in the surrounding area (Sci. Adv. 2025, DOI: 10.1126/sciadv.ads9476). The scientists spoke about their work at a media briefing hosted by UCSD.When the polluted water of the Tijuana River flows into the ocean, it gets stirred up by waves crashing in the surf zone. When waves break, they create bubbles. “When those bubbles pop, they release aerosols,” says Kimberly Prather, an atmospheric scientist at UCSD Scripps Institution of Oceanography and co-corresponding author of the study.Aerosols can contain whatever was in the body of water where they originated. In other words, pollutants can hitch a ride on aerosols from the water into the air. The tiny particles can travel for miles. If a person inhales aerosols, the smallest particles can make it into their bloodstream.“This is the number one way that this pollution from the water is actually making its way into your body, even if you're not at the beach,” Prather says. Past work by Prather and others has found bacteria and microplastics in aerosols. This new work focuses on chemical pollutants, she says.The scientists’ analysis focused