Feds find ‘no threat from hydrogen cyanide’ with sewage flows along border

SAN DIEGO (FOX 5/KUSI) — The Environmental Protection Agency and state health officials are contesting a recent discovery of hydrogen cyanide in the Tijuana River Valley by local researchers that stoked panic among South Bay residents about the sewage crisis’ health impacts.

The federal and state officials, who were enlisted to investigate concerns about worsening air quality due to the sewage and a recent heat wave, echoed statements made by county leaders last week to ease fears that the conditions the pose an imminent danger to residents in the area.

In a statement on Friday, EPA press officer Julia Giarmoleo described the monitoring methods that caught the spike in toxic gases, like hydrogen cyanide, as “flawed” and added that their assessment indicated “no imminent danger or threat from hydrogen cyanide.”

Dr. Tomás J. Aragón, director of the California Department of Public Health, took this determination a step further calling the reports of hydrogen cyanide in the air “inaccurate.”

On Monday, Dr. Kimberly Prather, a researcher at Scripps Institution of Oceanography who leads the team studying the Tijuana River Valley that reported observing hydrogen cyanide, said the compound was no longer showing up on their monitors.

Nonetheless, Giarmoleo added that the EPA will be conducting further analysis related to the gases emanating from the sewage in coordination with county officials to determine if there is any possibility, “however remote, of hydrogen cyanide presence in the area.”

The other toxic gas from the raw sewage, hydrogen sulfide, that Prather and her team identified last week remained within levels considered safe for the health of the general public, although both state and federal officials noted its stench likely still contributed to short-term illness.

According to Aragón, this includes headaches, throat and lung irritation, and gastrointestinal issues in those especially sensitive to the odor.

Investigations by the Centers for Disease Control and Prevention and CDPH into the risks with continued exposure remain ongoing. The EPA added they are also supporting county health partners to “implement enhanced monitoring protocols” for pollutants tied to the sewage.

The statements from both the state and federal officials on Friday come after days of back and forth between county leaders and local researchers sounding alarms about the sewage crisis’ apparent health impacts.

Prather has been one of the predominant voices pushing against health officials’ assessments in a number of posts on social media.

In one post on X , formerly Twitter, on Friday, Prather took issue with the description of hydrogen sulfide as within safe levels, pointing to reports from residents dealing with health impacts from the sewage’s odor.

“These people have nonstop headaches, mental health issues, and the potential for long term neurological and other serious health issues,” she said.

“Just because [hydrogen sulfide] levels in South Bay are below the threshold for causing instant fatalities of all residents doesn’t mean the air is safe,” Prather continued in another post.

Sewage flows temporarily slowed through the Tijuana River Valley towards the end of the week after Mexico brought a third pump at a treatment plant on its side of the border online, easing some of these impacts.

The atmospheric chemist told FOX 5/KUSI that the reduced flows were a good step, but noted there is still a long way to go to fully address the pollution and associated health concerns.

“We had a hypothesis that if they stopped the flow, if they could lower the flow at that point, levels of hydrogen sulfide would go down,” Prather said. “Clearly, we’re not done.”

South Bay leaders are continuing to lobby Gov. Gavin Newsom and President Joe Biden to declare an emergency over the sewage crisis, which has been ongoing for decades but worsened in the last few years due to failing treatment infrastructure along both sides of the border.

Last month, closures in Imperial Beach due to unsafe bacteria levels reached a landmark 1,000 consecutive days — or over two-and-a-half years.

“We don’t know what’s in that water and what people are being exposed to when they breathe in that air,” Dr. Matt Dickson with South Bay Urgent Care told FOX 5/KUSI last week. “My honest concern is this going to be the next Flint, Michigan?”

FOX 5/KUSI’s Elizabeth Alvarez and Tony Shin contributed to this report.

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