San Diego County
Air Pollution
Control District
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Air Quality Forecast -
AQ Forecast by Site -
About
H₂S Air Quality Advisory
The San Diego County Air Pollution Control District (SDAPCD) issues H₂S air quality advisories to notify the public when elevated levels of hydrogen sulfide (H₂S) are detected for the communities that may potentially be affected by H₂S odors produced by the transboundary wastewater and sewage flows near the Tijuana River Valley.
SDAPCD has placed community monitoring sites to measure H₂S levels and the current information captured is below:
Locations |
Date |
Time |
H₂S Levels(ppB [1]) |
|---|---|---|---|
| Berry Elementary School | 6/2/26 | 10 PM - 11 PM | 31 |
| San Ysidro Fire Station #29 | 6/2/26 6/3/26 6/3/26 6/3/26 6/3/26 | 11 PM - 12 AM 1 AM - 2 AM 2 AM - 3 AM 3 AM - 4 AM 4 AM - 5 AM | 56 66 47 57 35 |
| [1] "parts per billion" or ppB is a unit of measurement used to describe the concentration of a substance in the air, water, or soil. Specifically, one part per billion means one part of a substance per one billion parts of the medium (such as air). | |||
The California Office of Health Hazard Assessment has established a threshold of 30 parts per Billion of hydrogen sulfide (H₂S) emissions to protect sensitive groups, including children, older adults, and people with certain health conditions.
H₂S is a gas that can cause a “rotten egg” smell and some individuals may experience odor-related symptoms such as headaches and nausea. H₂S can cause strong odors even at low concentrations.
This H₂S Air Quality Advisory is in effect until 5 PM due to possible changes in weather and wind patterns that can cause H₂S levels to fluctuate throughout the day. If any additional information is available, an update will be issued.
For current H₂S levels, visit Air Quality Monitoring.
Precautions if odors persist:
- Limit outdoor activities.
- Create a Cleaner Air Space inside your home by closing windows and doors and use air conditioning if available and/or indoor air purifiers.
- People with asthma, chronic obstructive pulmonary disease (COPD), or other chronic lung conditions should have their rescue medication(s) readily available.
- If symptoms from strong odor persists, are worrisome, or worsen, seek medical care.
- If possible, it’s recommended businesses run the HVAC system for 1-2 hours before business hours.
A full guidance of these precautions is available in the Community Hydrogen Sulfide Guidance, a document developed in partnership with multiple agencies to help interpret hydrogen sulfide (H₂S) threshold levels, about what to expect and recommended actions for each level range.
For more information, please visit www.sdapcd.org/TJRiver.
Last Updated: June 3, 2026 at 10:09 AM
There are no current active H2S Air
Quality Advisories or Updates at this time.
For more information, please visit www.sdapcd.org/TJRiver .
Last Updated: June 5, 2026 at 2:40 PM