San Diego, CA – Residents in the South Bay are being urged to take precautions after high levels of hydrogen sulfide (H₂S) were detected in the air near Nestor – Berry Elementary School on the night of February 23, 2025, and early February 24, 2025.
According to the San Diego County Air Pollution Control District (SDAPCD), air monitors recorded H₂S levels exceeding the 30 parts per billion (ppB) safety threshold set by California health officials. Exposure to H₂S—a distinctive “rotten egg” odor—can cause headaches, nausea, and respiratory irritation, particularly in children, older adults, and individuals with pre-existing respiratory conditions.
Background on Hydrogen Sulfide and the Tijuana River Area
Hydrogen sulfide is a colorless, flammable gas often associated with natural processes (such as decomposing organic matter) and industrial activities (like sewage treatment and petroleum refineries). In coastal areas near the U.S.–Mexico border, H₂S can be generated by sewage flows, stormwater runoff, and other organic waste from the Tijuana River.
The Tijuana River flows northward from Mexico into southern San Diego County, passing through the Tijuana River Valley and into the Tijuana River Estuary. This region has historically faced water and air quality challenges due to cross-border sewage flows and industrial pollutants. Local, state, and federal agencies—including the Environmental Protection Agency (EPA) and the International Boundary and Water Commission (IBWC)—have partnered on ongoing efforts to monitor and mitigate these issues.
Health Precautions and How to Protect Yourself
In response to elevated H₂S levels, health officials recommend the following measures if strong odors persist:
- Limit outdoor activities when strong odors are present, especially for children, older adults, and those with respiratory conditions.
- Keep doors and windows closed to prevent odors from entering your home, and ventilate when the smell dissipates.
- Air purifiers and HVAC systems with HEPA and activated charcoal filters should be used to improve indoor air quality.
- Businesses should run HVAC systems for 1–2 hours before opening to clear indoor air.
- Individuals with respiratory conditions should have their rescue medications readily available.
- Seek medical attention if symptoms such as headaches, nausea, or throat irritation worsen or persist.
For real-time air quality updates and H₂S monitoring data, visit the Air Quality Monitoring page.
Free Air Purifier Program Available
SDAPCD is offering eligible South Bay households a free air purifier and up to two replacement filters through the AIRE program to help reduce exposure to harmful pollutants. These devices can be especially beneficial for individuals with respiratory sensitivities, as they help filter out common indoor pollutants, including hydrogen sulfide.
For more details and eligibility requirements, visit the AIRE program website.
Community and Agency Response
- County of San Diego: Officials continue to monitor air quality conditions in affected neighborhoods and provide health advisories as needed.
- Local Environmental Groups: Organizations in the Tijuana River Valley are working with residents to document and report odor events, emphasizing the need for long-term infrastructure solutions.
- Federal Partners: Agencies like the EPA and IBWC have ongoing projects to mitigate sewage flows in the Tijuana River watershed and improve cross-border water quality.
Stay Informed
For more information on air quality and health precautions, visit www.sdapcd.org/TJRiver. Residents can also sign up for email alerts from the Air Pollution Control District at https://public.govdelivery.com/accounts/CASDCAPCD/subscriber/new to receive real-time notices and updates on local environmental conditions.