Tijuana river pollution crisis: health symptoms and environmental perceptions from the Healthy Water Healthy Air Study

Untreated sewage, industrial waste, and urban runoff carried by the Tijuana River from Mexico into the U.S. has created a longstanding transboundary environmental crisis. This pollution significantly intensified in July 2024, with border community members reporting noxious odors and major health symptoms. In response to these escalating concerns, we launched the Healthy Water Healthy Air Study.

A bilingual (Spanish/English) online survey was conducted to establish a comprehensive community profile characterizing members' environmental perceptions, health burdens, and resilience. Individuals living and/or working within the border communities in southern San Diego County, CA were recruited through a multipronged approach grounded in deep-seated community partnerships. We performed descriptive analyses to summarize the participants' sociodemographic characteristics, major health symptoms, air and water quality perceptions, and precautionary and high-risk behaviors at baseline. We fitted Poisson regressions to estimate the associations of environmental perceptions with health symptoms and precautionary behaviors, controlling for sociodemographic characteristics.

Among 409 adult community members who had completed the baseline survey through October 31st, 2025, most self-identified as women, White, and of relatively high socioeconomic status. The majority expressed high levels of concern regarding local ambient air and the water quality of the Tijuana River and its adjacent water bodies. Frequent exposure to strong malodors was common. Community members reported a wide range of health symptoms, most notably upper respiratory symptoms (74%), certain gastrointestinal symptoms such as nausea (50%) and bloating (52%), and several symptoms of psychological distress. Compared to those reporting good or moderate air quality, poorer air quality perceptions were associated with a 35-80% higher prevalence of any upper respiratory symptoms, a 2.02-3.51-fold increase in counts of gastrointestinal symptom scores, a 1.72-2.19-fold increase in psychological distress symptoms and high-risk behaviors, and a 3.39-4.16-fold increase in precautionary behaviors. Similar associations were derived from participants reporting more frequent malodor exposure and experiences with boil water notices.

This study is among very few to understand health symptoms and behavioral changes of border communities during the Tijuana River pollution crisis. These findings provide support for immediate public health interventions and binational policy actions aimed at mitigating transboundary sewage pollution.