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4h ago

Peer-Reviewed Study Ties Tijuana River to Toxic Air in San Diego’s South Bay

Researchers pinpoint a turbulent hotspot releasing sewer gas at levels far above health standards.

Sewage and drain pipes are seen at Playas de Tijuana, Baja California state, Mexico, on March 21, 2024.
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Ryan Duffy, a San Diego State University graduate student, collects water samples from the Tijuana River on Tuesday, Sept. 10, 2024. (Ana Ramirez / The San Diego Union-Tribune)
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Overview

  • Monitors near Nestor recorded hourly hydrogen sulfide around 2,100 ppb with short peaks up to 4,500 ppb, exceeding California’s 30 ppb one-hour limit for five to 14 hours per day.
  • The foamy Saturn Boulevard section was identified as a primary aerosolization source, and levels dropped sharply after a Sept. 10, 2024 wastewater diversion in Mexico, reinforcing causation.
  • Beyond hydrogen sulfide, instruments detected hundreds to more than 1,000 additional airborne compounds from sewage and industrial waste, broadening potential toxic exposures.
  • The study validates years of community odor complaints and reported symptoms, though the long-term health impacts of chronic exposure to this gas mixture remain uncertain.
  • Policy steps include a new U.S.–Mexico memorandum and an EPA-announced expansion of the South Bay treatment plant, alongside local air-purifier programs and warning signs; an earlier hydrogen cyanide claim was retracted as a false positive.