California Air Resources Board

The California Air Resources Board (CARB) closely monitors environmental concerns in the Tjuana River Valley as part of our mission to improve air quality, though we are not the lead oversight authority. CARB works closely with the California Environmental Protection Agency (CalEPA), the San Diego County Air Pollution Control District (SDAPCD), County of San Diego Public Health, and other relevant agencies to ensure a coordinated response.

More Information

Historically, a combination of several factors has led to cross-border flows, resulting in untreated sewage, urban runoff, and industrial contamination entering the Tijuana River and ocean on both the Mexico and United States sides of the border. This has been a continued concern for communities.

Through its ongoing engagement under the Assembly Bill (AB) 617 Community Air Protection Program (CAPP), CARB coordinated closely with SDAPCD and local leaders to respond to community concerns. CARB provided active and targeted support by sharing technical expertise, participating in interagency coordination efforts, and supporting local actions to address air quality impacts associated with the Tijuana River crisis.

CARB engaged with SDAPCD and County leaders to identify and monitor hydrogen sulfide, a colorless gas with a strong “rotten egg” odor, and to support the use of earned interest from existing CAPP Incentives for home air purifiers, appropriate for trapping gasses, to take immediate actions to mitigate exposure to hydrogen sulfide and potentially other chemicals.

SDAPCD developed a Supplemental Environmental Project (SEP) (see CARB’s SEP program page) proposal to fund indoor air filtration in San Diego County. In April 2025, SDAPCD’s SEP addressing odors from the Tijuana River Valley was partially funded for $133,335.50, supporting distribution of air filters to residents directly affected. The SEP will remain on the Available SEPs List until fully funded (see SEP Active List).

CARB continues to provide technical support for monitoring activities and participates in multi-agency efforts to curb the contaminated flows into the river and reduce community exposure to hydrogen sulfide and potentially other emissions.

Air Purifiers

Air purifiers are an important tool for preserving indoor air quality, particularly in an air pollution crisis such as the Tijuana River Valley Wastewater. Air purifiers using filter media with potassium permanganate and activated carbon are ideal. Correct installation and maintenance are crucial for best results. CARB is committed to helping residents reduce their exposure to pollutants.

Indoor Air Quality

Please refer to CARB’s webpage here for more information on the use of indoor air cleaners for removal of odors and gases.

Air Improvement Relief Effort Program (AIRE)

As part of a coordinated response to environmental concerns in the Tijuana River Valley, SDAPCD launched the Air Improvement Relief Effort Program (AIRE) in February 2025. This program provides immediate, practical relief to affected residents. Through AIRE, SDAPCD is distributing free air purifiers and replacement filters to households in eligible communities within the Cities of San Diego and Imperial Beach that are most directly impacted by odors from transboundary wastewater and sewage flows near the Tijuana River Valley. These air filtration devices help improve indoor air quality by reducing contaminants and pollutants within a room, offering short-term protection while longer-term infrastructure and mitigation solutions are implemented. 

Eligibility for AIRE

Most households in the City of San Diego communities of Otay Mesa West, San Ysidro, Egger Highlands, Nestor, and Tijuana River Valley, and the City of Imperial Beach are eligible to participate in the program.

Visit the SDAPCD AIRE Program webpage for further information and to learn how to apply.

Questions or Concerns

Please refer to the SDAPCD page here to submit air quality questions and/or complaints.

Please refer to the San Diego County page to learn more about the topic and efforts led by the County and others: Tijuana River Valley & Beach Water Sewage Crisis Public Health Response.