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South Bay residents have been breathing chemicals emanating from the Tijuana River including one that has been known to damage DNA, another that is used in tire manufacturing and traces of methamphetamine, according to a new study.
The research comes from a team of scientists from UC San Diego and the Scripps Institution of Oceanography that says it's the first study of its kind to track a wide range of chemical pollutants being transmitted from polluted water into the air.
Researchers say that when rainfall causes sewage overflows, southern San Diego air can carry toxic chemicals from the Tijuana River at levels similar to those faced by workers at a wastewater treatment plant. But while wastewater workers may be exposed for a limited amount of hours and with protective gear, residents have likely been exposed to the chemicals for decades.
"It's not just one compound at a time you're breathing in, it's this complicated soup of thousands of chemical compounds, bacteria, viruses, all at the same time," said Adam Cooper, the researcher who authored the study.
"If you live in the region for decades at a time, we simply don't have the information to know the long term health effects of that."
UCSD scientists have been researching air in the Tijuana River Valley for several years. Some of that research made national headlines last year when Scripps scientist Kim Prather announced concerns about high levels of hydrogen sulfide in the air at hotspots in the river.
This study, co-authored by Prather, sampled air at several locations near the river and as far north as La Jolla and determined that chemical pollution from the river is becoming airborne.
Researchers found high levels of octinoxate, a UV filter used in sunscreen that can break down into more toxic components. They also found dibenzylamine, a substance used in tire manufacturing, as well as a mixture of illicit drugs.
Some of the chemicals, like those linked with tire particles, may also have local sources. But the researchers say the majority of aerosolized chemicals come from polluted water in the Tijuana River which feeds into the Pacific Ocean and are transferred to the air through sea spray.
UCSD researcher Jonathan Slade says that octinoxate can degrade DNA under certain conditions. He said when one applies sunscreen, it doesn't penetrate the skin.
"But when it's in aerosols... you're breathing them in, inhaling them, and they're depositing deep into our lungs, where they're more likely to transfer into our bloodstream, and that's something that's important," he said.
Residents in southern San Diego have been complaining about respiratory and gastrointestinal problems they associate with pollution from the river. The researchers say their results suggest more studies are needed to determine the public health impacts of inhaling polluted air in the Tijuana River Valley.
The study says that air quality worsens as you near the river. Although the study does not draw conclusions on health impacts, the scientists are concerned about long-term effects of breathing in the pollutants, even at lower levels, especially for those who live near the border and have been breathing the air for decades.
"Often the sewage crisis is considered a water issue -- and it is -- but we show that it's in the air, too. Truthfully, we don't yet know the acute health effects," Slade said.
Prather says air pollution from aerosolized wastewater is a growing global health threat. An estimated 80% of the world's wastewater goes untreated.
"Aerosolization of this polluted water exposes billions of people through airborne transmission, reaching far beyond those in direct contact and impacting countless others who inhale contaminated air that can travel for many miles," Prather said.
Prather says that studies such as this one are shining a light on the health impacts of what is a "newly identified source of pollution."