Researchers found that pollutants from the Tijuana River brought pristine sewage and industrial waste from Tijuana, which are also emerging in the coastal air near the U.S.-Mexico border.
After collecting samples from air and water along the coast, scientists at San Diego at the University of San Diego determined that fine particles of various pollutants from wastewater were airborne in certain areas of San Diego County. They found that marine sprays contain illicit drugs and drug by-products that occur in human urine, as well as chemicals for tires and personal care products.
The pollutants are carried in wastewater and stormwater runoff and turned into airborne in sprayers, where the river encounters crashed waves near the border and may also enter air from the flowing water of the river itself.
Aerosol samples were collected at Empire Beach Pier.
(Erik Jepsen/UC San Diego)
The findings show that in addition to being polluted by water that forces beach closures and plagues nearby communities, the river is releasing fine air pollution particles beyond what people see or smell. However, the potential health effects of breathing these pollutants are not clear, the researchers said.
“The sewage crisis is often considered a water problem, but we also show it is in the air, too,” said Jonathan Slade, co-author and associate professor of chemistry at San Diego. “This study points out that it is an air quality problem and it requires more focus and more research to understand the effects of exposure to these chemicals.”
The study, published Wednesday in the journal Science Advances, involves air and air water samples collected in 2020, including the U.S.-Mexico border, Empire Beach and the Scripps Institute of Oceanography.
The researchers used a compound called benzylane, a by-product of cocaine use in urine that traces contaminants into wastewater. They also tested cocaine found in wastewater and urban runoff, including methamphetamine, octoxide from sunscreen and dibenzamine from tires.
They found that concentrations were much higher in the air at the estuary of the coastal areas of Scripps Pier in La Jolla and near the Imperial Beach.
“Some of these compounds measure concentrations as high as the level of workers standing directly on the aeration tank,” Slade said. “It is usually recommended that you wear personal protective equipment, such as masks.”
The water from the Tijuana River flows from a pipeline near Saturn Boulevard in San Diego in April.
(Hayne Palmour IV/Times)
The research team includes scientists from the University of California, San Diego and the Scripps Institute of Oceanography, wearing respirators and protective gear while collecting samples near the Tijuana River.
“We see some of these things that may attract attention,” Slade said. “But we don't know people who are long-term exposure, long-term exposure to the South Bay area, breathe in this air for years or decades a day.”
Lead author Adam Cooper said the study is “one of the most comprehensive studies to date that have studied the water flow transfer of these pollutants.”
Other studies are investigating other types of air pollution in the Tijuana River, including bacteria and other pathogens of sewage.
Kimberly Prather, a professor of atmospheric chemistry at the University of California, San Diego, has been studying air pollution in rivers for years.
“This is the first way that water pollution is actually entering the body, even if you're not on the beach,” Prather said. “The beach can be closed, but people are still breathing the air.”
