Researchers have found that pollutants from the Tijuana River, which carry raw sewage and industrial waste from Tijuana, have also appeared in the air along the coast near the US-Mexico border.
After collecting samples from coastal air and water, scientists in San Diego, California determined that fine particles of various contaminants from the wastewater are found in air in parts of San Diego County. They discovered that shea spray aerosols contain illicit drugs and drug byproducts that occur in human urine, as well as chemicals from tires and personal care products.
Researchers said the pollutants are transported by wastewater and stormwater runoff, and are likely to be airborne by sprays where the river encounters crashed waves near the border, and also enter the air from the ocean waves of the river itself.
Aerosol samples will be collected at Imperial Beach Pier.
(Erik Jepsen/UC San Diego)
Findings show that rivers release fine particles of air pollution beyond what people see and smell, in addition to carrying beach closures and odor-forced water pollution that have plagued nearby communities. However, the researchers said the potential health effects of respiration of these contaminants are not yet known.
“In many cases, the sewage crisis is considered a water issue, and that is true, but it also indicates it is in the air,” said Jonathan Slade, co-author and associate professor of chemistry at UC San Diego. “This study points to an air quality issue, which requires a future focus and more research to understand the impact of exposure to these chemicals.”
The study was published in the journal Science Advances on Wednesday and involved testing air and air force samples collected in 2020 at locations such as the US-Mexico border, Imperial Beach and the Oceanographic Institute in La Jolla.
Researchers used a compound called benzoylukgonine, a by-product of cocaine use found in urine, to track contaminants into wastewater. They also tested about 12 chemicals found in cocaine and wastewater and urban spills, including methamphetamine, octino acid salts from sunscreens and dibenzylamine from tires.
They found significantly higher concentrations in the air near the river mouth of the border and Imperial Beach, along further north along the coast of the Scripps Pier in La Jolla.
“Some of these compounds measured concentrations as high as those exposed to wastewater treatment plants when standing directly above the aeration tank,” Slade said.
Water from the Tijuana River flows from a pipe near Saturn Boulevard in San Diego in April.
(Hayne Palmour IV / for the Times)
Researchers, including UC San Diego scientists and the Scripps Oceanographic Institute, were wearing respiratory and protective equipment while collecting samples near the Tijuana River.
“We’re seeing some of these things come out at a level that could be of concern,” Slade said. “But I don’t know the effects of chronic exposure, long-term exposures from people living in the South Bay area, and the daily inhalation of this air for years or decades.”
Lead author Adam Cooper said the study was “one of the most comprehensive studies that have investigated the movement of these contaminants into water supply.”
Other studies have examined other types of air pollution from the Tijuana River.
Kimberly Plazer, a professor of air chemistry in San Diego, California, has been studying air pollution from rivers for many years.
“This is the number one way that even if you’re not on the beach, this contamination from the water is actually going that path to your body,” Plazer said. “The beaches can be closed, but people are still breathing that air.”
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