The Hidden Air Quality Crisis Linked to Border Sewage: Why Your Lungs May Be at Risk

A groundbreaking study has revealed that the chronic sewage pollution plaguing the Tijuana River and New River isn't just a water problem; it's also poisoning the air that border communities breathe. Researchers from UC San Diego and San Diego State University (SDSU) established for the first time that poor water quality can profoundly degrade air quality, exposing entire communities to toxic gases that trigger respiratory symptoms, cognitive problems, and behavioral changes.

What's Actually Happening at the Border?

The Tijuana River was named the second most polluted river in America in 2025, carrying hazardous industrial waste and raw sewage that has crossed into the United States at alarming volumes. Since the North American Free Trade Agreement (NAFTA) took effect in 1994, trade between California and Mexico surged, fueling rapid growth of manufacturing facilities in northern Mexico. However, this industrial expansion outpaced the capacity of existing wastewater and stormwater infrastructure, creating a chronic pollution crisis that now affects millions of people on both sides of the border.

The numbers are staggering. More than 100 billion gallons of toxic effluent have crossed into the United States since the United States-Mexico-Canada Agreement (USMCA) took effect in 2020, despite more than 650 million dollars in federal investments to upgrade the South Bay International Wastewater Treatment Plant (SBIWTP). The New River, which originates in Mexicali, Baja California, and flows through Calexico and Imperial County into the Salton Sea, carries untreated sewage, industrial waste, agricultural runoff, and toxic contaminants, with fecal coliform levels nearly 800 times the federal legal limit.

How Is Sewage Pollution Creating an Air Quality Crisis?

Until recently, the crisis at the Tijuana River Valley was thought to be mainly a water contamination issue. But the UC San Diego/SDSU research changed that understanding entirely. When sewage and industrial waste decompose in water, they release hydrogen sulfide and other volatile organic compounds (VOCs) into the air. These toxic gases drift across neighborhoods, exposing residents to respiratory hazards that rival outdoor air pollution from traffic and industrial sources.

Community surveys conducted in the affected areas paint a troubling picture of the health impact. The research found that 76% of respondents reported respiratory issues, including coughing, wheezing, and shortness of breath. Beyond lung problems, 51% of respondents experienced cognitive symptoms like difficulty concentrating, and over 90% reported poor air and water quality. Doctors working in the area have testified they're seeing children with headaches, nausea, and wheezing symptoms when sewage odors are present in the air, suggesting that exposure is affecting the youngest and most vulnerable members of these communities.

The impact on daily life is profound. About three-quarters of survey respondents reported reducing outdoor activity due to pollution, meaning families are essentially confined indoors to avoid toxic air exposure. This isn't just an environmental health issue; it's a quality-of-life crisis that's reshaping how border communities function.

Steps to Protect Your Family From Transboundary Pollution Exposure

• Monitor Air Quality Alerts: If you live in San Diego County, Imperial County, or other border communities, check the EPA's AirNow website daily for air quality index (AQI) readings. When AQI levels spike above 100, limit outdoor activities, especially for children, elderly people, and those with respiratory conditions.
• Use HEPA Filtration Indoors: Install high-efficiency particulate air (HEPA) filters in your home's HVAC system or use standalone HEPA air purifiers in bedrooms and living spaces. These filters can capture hydrogen sulfide and other volatile organic compounds (VOCs) released from sewage decomposition.
• Avoid Waterway Contact: Do not swim, fish, or allow children to play in the Tijuana River, New River, or beaches near sewage discharge points. Fecal coliform levels in these waterways exceed federal safety limits by hundreds of times, creating serious infection risks.
• Advocate for Infrastructure Investment: Support local organizations and elected officials pushing for enforceable environmental commitments in trade agreements. Contact your representatives to demand measurable progress on wastewater treatment upgrades and pollution reduction timelines.

Why Trade Agreements Matter to Your Air Quality

Senator Steve Padilla (D-San Diego) introduced Senate Joint Resolution 13 (SJR 13) this year, which urges the United States to halt the extension of the USMCA unless Mexico secures enforceable and measurable commitments to eliminate chronic transboundary sewage discharges. The USMCA is structured to remain in force for 16 years, expiring on July 1, 2036, unless the parties agree to extend it. This year's six-year joint review presents a critical opportunity to tie trade benefits to real environmental progress.

"Trade agreements must not ignore environmental harm and the real public threat increased economic activity has on our border communities. Ensuring renewal of the USMCA must depend on measurable progress. Our federal government must secure real and meaningful protections for our community," said Senator Steve Padilla.

The resolution calls on the United States to use the renewal process to secure measurable, enforceable progress in eliminating transboundary sewage pollution and to make clear that continuation of the USMCA is contingent upon full and sustained compliance with agreed-upon environmental benchmarks, timelines, and accountability measures. This approach recognizes that border communities, who are overwhelmingly working-class families and communities of color, have borne the heaviest impacts of this pollution crisis, raising serious environmental justice concerns.

The pollution has led to prolonged beach closures in San Diego County, harmed tourism and local businesses, threatened public health in border communities, and disrupted United States Navy training operations. These aren't abstract environmental statistics; they're real consequences affecting real people's health, livelihoods, and access to public spaces.

What Local Leaders Are Demanding

Support for SJR 13 comes from local leaders and advocacy groups across communities impacted by cross-border sewage. San Diego County Supervisor Paloma Aguirre emphasized that the upcoming six-year review of the USMCA is a critical moment for change. The Tijuana River Coalition, which includes the YMCA of San Diego County, has proposed common-sense policy solutions to fix the sewage, industrial waste, trash, hydrogen sulfide, and other toxins, prevent future impacts, and heal communities.

"For decades, the 'cost of doing business' under our trade agreements has been paid for with the lives of our border communities. While billions in goods flow north, billions of gallons of toxic sewage and industrial waste flow into our backyards, our air, and our oceans," stated San Diego County Supervisor Paloma Aguirre.

The key takeaway is clear: environmental protections and infrastructure investment are not negotiable add-ons to trade agreements; they are prerequisites for economic integration. The science now confirms that sewage pollution affects both water and air quality, creating a dual health crisis that demands immediate, measurable action from policymakers on both sides of the border.