The Tijuana River Valley (TRV) faces a severe environmental and public health crisis with over 100 billion gallons of pollutants (untreated sewage, urban runoff, and industrial waste) having been discharged into the Tijuana River over several decades. 1 Recent extreme weather, including Tropical Storm Hilary in August 2023 and an atmospheric river in January 2024, further increased the wastewater accumulation in the TRV. 1 – 3 The deteriorating international wastewater treatment plant on the US-Mexico border has also contributed to untreated wastewater reaching aquifers and natural waterways. 1 , 2 During August 2024, approximately eight months after the impact of the atmospheric river, 1,165 odor complaints were made to the San Diego County Air Pollution Control District (SDAPCD). 4 In 2024, there were 30 shoreline closures resulting from the TRV sewage crisis, with the longest closure lasting more than 365 days. 5 In response, the County of San Diego Health and Human Services Agency (CoSD HHSA) and the Centers for Disease Control and Prevention (CDC) conducted a Community Assessment for Public Health Emergency Response (CASPER) to assess household health, needs, and experiences related to the crisis. Results from the CASPER were used to address community concerns and identify resource needs related to contaminated air and water exposure. This report highlights key CASPER findings, actions taken to address community needs, and the current state of the TRV sewage crisis.
Narrative
During October 17-19, 2024, CoSD HHSA and CDC conducted a CASPER, following standard CDC CASPER cluster sampling methodology. 6 Thirty census blocks (clusters) were selected from the sampling frame with probability proportional to the number of households in the cluster. Within each selected cluster, field teams systematically selected 7 households, consistent with standard CASPER design, yielding a target sample of 210 interviews. This sample size is designed to provide estimates representative of the 40,911 households in the South TRV region when survey weights, accounting for the probability of selection at each sampling stage, are applied. A two-page survey was used to collect household-level data on demographics, water and air exposure concerns, community needs, physical health, and behavioral health related to the crisis. Surveys took about 20 minutes and were administered in English (75.7%; n = 143) and Spanish (24.3%; n = 46). Eligible survey respondents were adults (≥18 years) residing in households within the South TRV region who could speak for the household. This activity was reviewed by CDC, deemed not research, and conducted consistent with applicable federal law and CDC policy.Footnote a
A total of 29 two-person interview teams completed 189 surveys (90% completion rate), representing 56.8% of households where somebody answered the door, and 39.4% of all households approached. Weighted prevalence estimates and projected household counts were calculated using Epi Info™ CASPER analysis procedures that account for the cluster sampling design. 6 Per standard CASPER protocol, all results in this report are weighted to represent households in the sampling frame. Households averaged 3.2 members (range 1-8), most included adults aged 18-64 years (86.8%; n = 37,469), and over half spoke English as the primary language (52.7%; n = 22,748). Many households owned pets (56.0%; n = 24,191), lived in multi-unit homes (e.g., apartments) (53.1%; n = 22,942), and rented (57.9%; n = 24,987) (Table 1).
Household-level survey results (representative of 40,911 households in the South Tijuana River Valley region) for the CASPER assessment of water and air exposure concerns during the Tijuana River Valley sewage crisis—San Diego, October 2024
Table 1. Long description
The table presents survey data across five major sections:
1. Household demographics:
- Age categories: 18 to 64 years is the largest group at 86.8% (37,469 households), followed by 2 to 17 years (35.3%) and 65 or older (33.6%).
- Primary language: English (52.7%) and Spanish (44.8%).
- Structure and Ownership: 53.1% live in multiple-unit structures; 57.9% rent their homes.
2. Household concerns and exposures:
- 72.2% are very concerned about sewage contamination.
- Sewage smells were noticed in the neighborhood by 89.8%, outside the home by 88.6%, and inside the home by 74.1%.
- 16.2% had contact with beach water while closed, and 7.7% had contact with river water.
3. Household disruptions:
- 58.6% changed daily routines, with 42.9% of those reporting many changes.
- 66.6% use bottled water as their usual drinking source; 28.2% changed their water source since the crisis began.
4. Household health and mental health indicators:
- 44.8% experienced symptoms caused by the crisis. Among those, 45.8% reported 4 to 7 symptoms and 34.6% reported 8 or more symptoms.
- Emotional distress: 65.9% reported 1 or more signs. Top signs include headaches, stomachaches, or body pain (49.0%), increased anxiety (37.7%), and lack of energy (33.5%).
5. Household greatest need:
- 64.3% requested specific actions (air purifiers, cleanup, fixing treatment plants).
- 38.2% cited improving air quality and 27.1% cited improving water quality as primary needs.
CI, confidence interval.
a Other includes Tagalog, Swedish, and Persian.
b Weighted analysis and CIs were only calculated for cells with ≥5 observations.
c Households could choose more than one response.
d Other includes entire house filtration systems, filtered water, water fill locations, spring water, and wells.
e Actions requested include air purifiers, filters, cleanup, general fixing the problem, fixing the treatment plant and pump station, etc.
f Improve air quality includes quality of air, addressing odor/smell concerns, etc.
g Improve water quality includes quality of river and beach water, beaches, drinking water concerns, etc.
h Quality of life includes needing to adjust normal activities/routines, moving away, housing rates, etc.
i Nothing includes refused to answer, nothing.
j Communication needs includes request more information, etc.
k Health and safety includes health, health symptoms, dangers to health, breathing needs, safety, health effect concerns, mental health, etc.
Virtually all households reported that they were aware of (96.4%; n = 41,728) or concerned about (96.4%; n = 41,615) the sewage contamination. Nearly all households (93.6%; n = 40,412) reported a sewage smell in the past month, most commonly in their neighborhood (89.8%), outside the home (88.6%), and inside the home (74.1%), with 71.6% reporting exposure in all three locations. Many households noticed the smell during the evening/night (69.2%; n = 27,980), followed by the morning (19.0%; n = 7,670), and afternoon (11.8%; n = 4,762). Roughly 89% (n = 38,406) of households tried at least one solution to reduce the smell (e.g., closing windows, using candles, incense, oil), and most (66.0%; n = 25,360) said their actions did not help (23.2%; n = 8,906) or only helped sometimes (42.8%; n = 16,454). Few households reported exposure to river water (7.7%; n = 3,303) and beach water while the beaches were closed (16.2%; n = 6,986), but most households reported sometimes or frequently taking steps to avoid certain areas (65.4%; n = 28,215). For example, many households reported decreased beach visit frequency (65.9%; n = 28,431) and time spent outdoors (60.6%; n = 26,173). Overall, 75.9% (n = 32,775) of households reported decreased participation in one or more outdoor activities in the past month.
The biggest reported concern about the sewage contamination was the health of household members (81.0%; n = 34,971). This was reflected by 44.8% (n = 19,337) of households reporting sewage-related health symptoms (e.g., headache, nausea/upset stomach, cough, dry/irritated throat), of which 80.4% (n = 15,539) reported four or more symptoms experienced by household members in the past month. Approximately 73% (n = 31,334) of households reported the sewage crisis negatively affected their peace of mind, and 65.9% (n = 28,443) reported at least one member experienced one or more signs of emotional distress (e.g., increased anxiety or worry, sadness or depression) because of the sewage crisis.
The top three greatest needs included action requests (e.g., resource provision) (64.3%; n = 27,778) and broader requests for air quality (38.2%; n = 16,509) and water quality improvement (27.1%; n = 11,709). Additionally, safety concerns were prevalent, with 32.2% (n = 13,879) of households reporting that they felt unsafe in their homes due to exposures related to the sewage crisis. These concerns were reflected in high proportions of households reporting perceived concerns about tap water safety (71.2%; n = 30,753), as well as the quality of the Tijuana River water (92.7%; n = 40,004), nearby ocean water (90.5%; n = 39,079), and air (77.0%; n = 33,241). Correspondingly, more than a quarter of households reported changing their drinking water source since the crisis began (28.2%; n = 12,108), and approximately 67% (n = 28,605) reported bottled water as their primary source of drinking water despite routine water quality monitoring. 7
Overall, the survey revealed several shared beliefs and experiences among households impacted by the sewage crisis, including perceptions that the sewage caused air and water pollution (98.1%; n = 41,534), that the crisis was worsening (89.3%; n = 38,553), that it negatively affected quality of life (80.4%; n = 34,418), and that it worsened the health of household members (67.3%; n = 27,656) (Table 1).
Limitations
While the TRV sewage crisis has continued over several decades, the CASPER results represent household health, needs, and experiences related to the crisis at a point in time. Survey respondents were limited to those residing in households within the South TRV region; therefore, the results do not represent individual-level responses or those visiting the region for work, school, or recreation.
Discussion
The CASPER highlighted widespread concern and significant impacts on water usage, air quality, daily activities, physical health, and behavioral health among households impacted by the sewage crisis. CDC provided data-driven considerations for action to CoSD HHSA. These considerations included providing multilingual educational resources focused on air and water exposure concerns; collaborating with SDAPCD on supplying air purifiers that contain filter media (e.g., activated carbon impregnated with potassium permanganate) to reduce in-home hydrogen sulfide exposure; promoting available hotlines (e.g., 211 and 988) to connect households to needed services; and conducting a follow-up assessment on crisis-related needs to identify and characterize ongoing and long-term health and behavioral health effects.
On October 21, 2024, shortly after the CASPER, CoSD HHSA, CDC, and the Agency for Toxic Substances and Disease Registry (ATSDR) conducted an Assessment of Chemical Exposure (ACE) to collect individual-level responses about the sewage crisis impact, highlighting the importance of multi-agency collaboration. The ACE sample population included adults and children who resided in or visited the TRV for work, school, or recreation. The ACE revealed similar findings to the CASPER in reports of physical and mental health symptoms due to the sewage crisis, concern about air and water quality, bottled water usage due to tap water concerns, and reports of needs for clean air and water, health care, and action. 8 , 9
After conducting the CASPER and ACE, CoSD HHSA collaborated with CDC and ATSDR to create an educational resource—an interactive, bilingual dashboard—for the public. CoSD HHSA released CASPER results on January 16, 2025, and ACE results on July 8, 2025. As of September 10, 2025, the dashboard webpages have garnered 4,787 combined views, suggesting it is a valuable resource aiding in the transparency, availability, and accessibility of data related to the impact of the sewage crisis.
On May 20, 2025, shortly after the results of the CASPER were made publicly available, the TRV-located wastewater treatment plant addressed public concern about the water pollution by announcing an accelerated timeline for capacity expansion to reduce pollutants discharged into the Tijuana River. 10 Additionally, on August 20, 2025, warning signs for hydrogen sulfide gas were posted in areas of the TRV, making residents and visitors aware of this potential exposure.Reference Lightfoot 11 To address the presence of hydrogen sulfide and community concerns about air quality, CoSD HHSA collaborated with SDAPCD to distribute 6,800 air purifiers to households affected by the hydrogen sulfide (i.e., sewage) odors, as of September 5, 2025. These air filters trap particles of contaminants and pollutants, improving air quality in the homes of impacted persons. 12
The CASPER results provide valuable data on the environmental and public health crisis in the TRV, informing the following response activities: distribution of air purifiers to reduce indoor pollution, improved public health messaging about the crisis, and promotion of available hotlines to connect households to needed services (e.g., health care providers, resources). Ongoing communication, availability of educational materials, and improvements in the wastewater treatment center capacity may alleviate public concern. The impact of these interventions may be assessed through future follow-ups.
Acknowledgments
All community members and associates from the CDC Public Health Associate Program who participated in field interviews; County of San Diego Health and Human Services Agency Epidemiology and Immunization Services Branch; County of San Diego Health and Human Services Agency Public Health Preparedness and Response Branch.
Author contribution
Audrey E. Kennar and Jelonia Tasha Rumph contributed equally.
Audrey E. Kennar and Jelonia Tasha Rumph: Wrote and edited the final drafts of the manuscript. Created table. Developed survey questions. Conducted analyses and household-level surveys.
Brooke S. Staley: Edited drafts of the manuscript. Conducted analyses and household-level surveys.
Andrea Danielle Brown: Edited drafts of the manuscript. Conducted analyses and household-level surveys.
DaJuandra Eugene: Edited drafts of the manuscript. Conducted analyses and household-level surveys.
Nadia T. Saif: Edited drafts of the manuscript. Conducted analyses and household-level surveys.
Fhallon Ware-Gilmore: Edited drafts of the manuscript. Conducted analyses and household-level surveys.
Fuyuen Yip: Edited drafts of the manuscript. Developed survey questions.
Amy Helene Schnall: Edited drafts of the manuscript. Developed survey questions. Conducted analyses and household-level surveys.
Mark E. Beatty: Edited drafts of the manuscript. Developed survey questions.
Ankita Kadakia: Edited drafts of the manuscript. Developed survey questions.
Seema Shah: Edited drafts of the manuscript. Developed survey questions.
Competing interests
None.
