San Diego County, schools and air pollution officials respond to reports of “unhealthy levels” of toxic gases near the Tijuana River

The discovery of a second, potentially deadly gas in the Tijuana River Valley, where sewage from Mexico regularly crosses the border into communities south of San Diego, prompted school districts in the county's south to cancel outdoor activities on Monday and again ask authorities for emergency assistance.

Preliminary results continued to show high levels of hydrogen sulfide and the presence of an even more deadly gas, hydrogen cyanide, prompting the San Diego County Air Pollution Control Agency to issue its first warning about the noxious odors caused by the cross-border crisis.

“Residents near the affected areas who notice strong odors are advised to limit outdoor physical activity,” the statement said. “Stay indoors if possible, especially if you have respiratory or heart conditions, are elderly, or have small children in your household.”

When county officials learned of the new readings, they announced they would send the Hazardous Incident Response Team to the same area of ​​the Tijuana River Valley to conduct their own readings. These teams are typically dispatched to ensure an area or building is safe for firefighters and other first responders to access.

The Sweetwater Union High and South Bay Union school districts ordered physical education classes, recess and after-school programs to be moved indoors and canceled sporting events on their school campuses near the Tijuana River Valley because of “high levels of toxic air” caused by cross-border sewage pollution.

“If the heat and toxic levels continue to be this high, we will maintain these orders throughout the week,” said a warning from Berry Elementary School, which is less than a mile, or about a two-minute drive, from where researchers measured some of the highest levels of hydrogen cyanide in the early hours of Monday.

According to the U.S. Centers for Disease Control and Prevention, hydrogen cyanide (HCN) is a colorless, toxic gas or liquid with a faint, bitter almond odor that is detectable at concentrations of 2 to 10 parts per million (ppm). It is used commercially in electroplating, fumigation, mining, and the manufacture of plastics and dyes. Exposure can cause symptoms such as headaches, nausea, vomiting, and even death. Exposure limits exist only for work environments. For example, the Occupational Safety and Health Administration sets a “permissible exposure limit” of 10 ppm during an eight-hour work shift.

A special team of firefighters from Austin, Texas, detected 50 parts per million of hydrogen cyanide levels on Saturn Boulevard near Sunset Avenue in the Tijuana River Valley, an area about a mile from several elementary, middle and high schools.

The first responders, called the Robotics Emergency Deployment Team, or RED Team, flew in on Sunday at the request of Paula Stigler Granados, a professor of environmental health at SDSU. She and other UC San Diego researchers studying the health and environmental impacts of the wastewater crisis temporarily pulled their teams out of the area on Friday after detecting high levels of hydrogen sulfide, a toxic gas with a strong rotten egg smell.

RED team members were asked to collect data because they have experience using technology such as drones for hazard mitigation and other emergencies. The team focused on gathering information on hydrogen sulfide and did not anticipate hydrogen cyanide meters to fail, Granados said. Levels ranging from 1.5 ppm to 50 ppm were detected in various communities in the South Bay, particularly Imperial Beach, Nestor and the Tijuana River Valley, she added.

Researchers and other members of a working group studying the impact of the wastewater crisis said they felt it was necessary to inform state and county authorities and local school districts of the preliminary findings.

A county spokesman said the data still needs to be reviewed by public health experts.

The San Diego Air Pollution Control District will be tasked with evaluating data collected by the county's Hazardous Incident Response Team.

Also on Monday, the South Bay Task Force called on the county to distribute appropriate air filters to all affected households, post signs throughout the Tijuana River Valley warning recreationists about exposure to toxic gases, and encourage the aviation district to install fully calibrated air pollution monitoring infrastructure.

County officials said they and the air district will likely distribute a second round of air purifiers thanks to $160,000 in federal funding. Over 400 units have already been deployed in the past month.

Initial findings of toxic gases also caught the attention of members of Congress.

On Monday, San Diego's congressional delegation reiterated its call to Governor Gavin Newsom and President Joe Biden to declare a state of emergency in a letter, specifically mentioning “unhealthy levels of hydrogen sulfide and hydrogen cyanide.”

“Immediate action must be taken to respond to this immediate and serious threat to our communities posed by regular exposure to air and water toxics,” their letter said. “A federal emergency declaration would help South San Diego residents gain access to the air purifiers and testing equipment they need to protect themselves from this immediate threat.”

The calls come as the U.S. Centers for Disease Control and Prevention (CDC) and San Diego County prepare their own door-to-door survey, officially known as the Community Assessment for Public Health Emergency Response. The survey's goal is to measure the public health impact of transboundary pollution.

Years of neglect and underinvestment in wastewater treatment plants in both countries have resulted in unprecedented levels of sewage and garbage that are impacting people's health and local economies. Major repairs are currently underway on both sides of the U.S.-Mexico border, but substantial relief will be years away.

Residents and local politicians have criticized the government for not declaring emergency declarations, which they say could speed up solutions. But state and federal governments have said the binational crisis is not grounds for an emergency declaration.

Originally published: September 9, 2024 at 19:43