Hydrogen sulfide (H₂S) is a gas associated with wastewater-related odors. It is measured as part of ongoing scientific research, and the data are shared here to support transparency and community awareness.
This plot shows near-real-time hydrogen sulfide (H₂S) concentrations, reported as 1-minute averages, measured by an instrument located in the Nestor neighborhood (Leon Avenue), approximately 0.5 miles from the Tijuana River hotspot. The figure updates automatically every five minutes (you might need to refresh the page).
What does this mean?
Because these data are displayed in near real time, they have not yet undergone the full review, validation, and calibration procedures used in peer-reviewed scientific studies. Short-term spikes or drops may occur, especially during instrument startup, power outages, maintenance, or data transmission interruptions. These temporary effects are expected and do not necessarily represent actual environmental conditions.
Measurements reflect air quality at a single monitoring location and may not represent conditions across the broader community. H₂S levels can change rapidly depending on wind direction, weather conditions, temperature, and distance from emission sources, including the Tijuana River.
These data are provided to support community awareness, communication, and precautionary actions (for example, turning on indoor air filters or closing windows during odor events). They should not be used as the sole basis for medical, health, regulatory, or legal decisions.
Low or non-detectable H₂S levels do not necessarily mean the air is free of pollution. Hydrogen sulfide is only one of many gases released during sewage-related pollution events. As shown in Rico et al. (Science), contaminated waterways can emit hundreds to thousands of other airborne chemicals, many of which are not measured by this instrument and may also contribute to odors, irritation, or health symptoms. Therefore, the values shown here represent partial and preliminary information, not a complete picture of air quality or exposure.
How can I get involved?
To complement environmental monitoring, we are collecting community feedback through a short sleep quality and well-being survey. This helps researchers understand how environmental conditions may relate to sleep and daily health. Participation is optional, anonymous and voluntary.
Please continue reporting odors and air quality concerns to SDAPCD.