A foul threat from Tijuana River

Study finds high levels of toxic gas near sewage-filled waterway in San Diego County

- BY IAN JAMES

Photographs by LUKE JOHNSON Los Angeles Times
UC SAN DIEGO researchers prepare to check the water quality at the Saturn Boulevard river crossing in Imperial Beach in July.

New research backs up the concerns of people who live near the Tijuana River and have long complained that foul air wafting from the polluted waterway is making them sick — irritating their eyes and noses, making breathing difficult and causing headaches. The study indicates they're being exposed to high levels of the toxic gas hydrogen sulfide.

As the river flows through Baja California, it takes in untreated sewage and industrial waste from Tijuana, then crosses the U.S.-Mexico border into San Diego County, where beaches are regularly closed because the surf is filled with bacteria from the river. Researchers have now gained new insights into how that water pollution is creating air pollution that besets nearby communities.

Using an air-quality monitor nearly half a mile from the river in the community of Nestor, scientists found extremely high levels of hydrogen sulfide, a gas linked to sewage that smells like rotten eggs.

"It validates what the community has been saying for so long," said Benjamin Rico, a doctoral researcher at UC San Diego and coauthor of the study.

BEN RICO and others have gained insights into how polluted river water is creating air pollution.

The findings show "their complaints are real and valid, and need to be listened to," he said.

The study, published Thursday in the journal Science, tracked air pollution emanating from a foamy, churning section of the river where water falls from culverts. Rico said it's a hot spot where the falling water forms bubbles that burst and send fine particles of pollutants into the air.