US-Mexico border: 100 billion gallons of toxic sewage creating a 'public health crisis'

The U.S.-Mexico border region faces a public health crisis as billions of gallons of contaminated sewage flow from Mexico into San Diego, California, according to a newly released report.

"South San Diego County is in a total state of emergency related to transboundary pollution, and this is a public health ticking time bomb," Imperial Beach Mayor Paloma Aguirre told ABC News. "We are living in conditions that nobody in this great nation should be living in."

The Tijuana River – which has been classified as an impaired water body, according to the U.S. Clean Water Act -- flows north for 120 miles from Mexico to California before reaching the Pacific Ocean on the U.S. side of the border in the Imperial Beach, San Ysidro and Coronado coastal areas.

Over the last five years, 100 billion gallons of untreated sewage, industrial waste and urban runoff have been dumped into the Tijuana River, according to the International Boundary and Water Commission.

Tuesday marks the 805th day Imperial Beach has been closed due to the ongoing sewage issue, according to Aguirre, but the health risks are affecting residents far from the shore.

San Diego State University's (SDSU) School of Public Health deemed the cross-border contamination a "public health crisis" and warned that "current regulation and monitoring measures are inadequate," according to the new report, released on Feb. 13.

Untreated sewage pollutants originating in Mexico and not properly treated at the International Wastewater Treatment Plant include human and livestock diseases, pathogens carrying antibiotic-resistant genes, and industrial chemicals not permitted to be discharged in California, according to the report.

Studying soil samples from South San Diego, researchers found levels of the poisonous elements arsenic and cadmium that exceeded Environmental Protection Agency (EPA) thresholds for safety.

Water samples taken from the Tijuana River and Estuary, located on the U.S.-Mexico border, showed a range of dangerous viruses and bacteria, including HIV, hepatitis B and C, Salmonella, Vibrio, Streptococcus, Listeria, and Mycobacterium tuberculosis, according to the report.

The report also cites levels of antibiotic-resistant strains of E. coli and Legionella bacteria found in the contaminated water, "which are of considerable public health concern."

Exposure to the contaminants, viruses and bacteria can impact the health of people who live and work nearby, which include children, seniors, lifeguards, military personnel, border patrol officers and at-risk populations, according to the study.

"Urgent interventions are needed to help reduce and address both the immediate and long-term potential health repercussions to those living near this hazardous environment," Paula Stigler Granados, associate professor in SDSU's School of Public Health and the paper's lead author, told ABC News in a statement.

"The longer we take to stop the contamination, the greater the risk of exposures," Granados noted. "Investment in our infrastructure to stop the pollution is critical."

Toxic chemicals and bacteria – which were once believed to be isolated in the sewage alone – can be dispersed in water and air, especially during weather events, the report reveals.

For example, the California-Mexico border region has been hit recently with heavy rain and flooding caused by back-to-back atmospheric river storms. The resulting greater than usual influx of water can overwhelm California's and Tijuana's sewage treatment plants, researchers say.

Doctors Kimberly and Matt Dickson, a married couple who run South Bay Urgent Care in Imperial Beach, told ABC News that amid the February storms they have seen a 200 to 300 percent increase in patients with gastrointestinal illness, with symptoms including vomiting and diarrhea.

"These were people that were in the streets, going to school, but not swimming in the ocean. So, where was the transfer of bacteria and viruses going?" Matt Dickson asked. "How was it getting to these people if they weren't swimming in the ocean?"

The couple says they began to realize that the heavy rains were causing the sewage to spill into the city's streets, spreading illnesses across the community.

"If you're driving down the street that's flooded with sewage water, then you're tracking bacteria back to your home or to the store. Or if kids are walking to school through a flooded street that's got sewage water in it, then they go to class and they touch their shoes, and then they eat their lunch. People are getting sick," Matt Dickson said.

"You don't have to have a medical degree and to understand if there's sewage on the street, people are going to get sick," he noted.

The repeating cycle of rainstorms and illnesses in the community is "flabbergasting" to Kimberly Dickson, who says the cycle can be broken with better infrastructure to help reduce or eliminate the sewage overflow.

When it comes to the long-term health effects of the sewage problem, Kimberly worries, "It's just the tip of the iceberg. We're missing a lot of it. We don't know the long-term consequences."

In 2020, Congress approved a $300 million fund to expand the International Wastewater Treatment Plant San Ysidro. However, after the devastating infrastructure effects of Hurricane Hilary in August 2023, and the ongoing storms in the area, half of those funds were allocated to deferred maintenance before any type of expansion could happen, according memos obtained by The San Diego Union-Tribune.

Mayor Aguirre and other state politicians, including Gov. Gavin Newsom, have asked Congress for an additional $310 million in federal funds to address the issue, but it has yet to be approved.

"It's challenging to maintain the attention and focus that this emergency needs when we're located 3,000 miles away," Aguirre said of requesting federal intervention from Washington, D.C.

"We also need additional intervention from our state administration. Our governor has advocated for that supplemental funding request, but he has fallen short of declaring a state of emergency," Aguirre added.

In Dec. 2023, the International Boundary and Water Commission announced the Rehabilitation and Expansion Progressive Design-Build project for the International Wastewater Treatment Plant. The project includes essential rehabilitation of existing infrastructure and expansion of the plant, according to the press release.

"We have participated in many public meetings in the affected areas and want to assure residents our priority is improving the health and welfare of communities on both sides of the border," Frank Fisher, Public Affairs Chief for the International Boundary and Water Commission, told ABC News in a statement.