Sea spray releases water pollution into the air

Water pollution is released into the atmosphere through aerosol droplets from sea spray, according to a new study led by Scripps Institution of Oceanography at UC San Diego. The experts report that these airborne pollutants can potentially reach people on land, hundreds of kilometers from the beach. 

“Coastal water pollution (CWP) is an ever-growing global environmental problem and public health threat,” wrote the study authors. “Over one hundred thousand cases of illness and tens of thousands of deaths occur annually worldwide due to people entering contaminated waters or eating tainted seafood.”

The researchers noted that coastal water pollution at the Mexico-US border between Tijuana and Imperial Beach has persisted for decades and has been officially declared a state of emergency. Rainfall in this region causes untreated sewage to spill over into the Tijuana River, where it flows into the ocean in south Imperial Beach.

The study reveals that the sewage pollution is transferred into the atmosphere in sea spray aerosol that is formed by breaking waves and bursting bubbles. The experts found that the sea spray aerosol contains bacteria, viruses, and chemical compounds.

Lead researcher Professor Kim Prather said the study appears in the midst of a winter in which an estimated 13 billion gallons of sewage-polluted waters have entered the ocean via the Tijuana River.

“We’ve shown that up to three-quarters of the bacteria that you breathe in at Imperial Beach are coming from aerosolization of raw sewage in the surf zone,” said Professor Prather. 

“Coastal water pollution has been traditionally considered just a waterborne problem. People worry about swimming and surfing in it but not about breathing it in, even though the aerosols can travel long distances and expose many more people than those just at the beach or in the water.”

The experts used DNA sequencing and mass spectrometry to analyze bacteria and chemical compounds found in coastal aerosol samples from Imperial Beach. They confirmed that these aerosol samples contained bacteria and compounds that originated in the Tijuana River.

The researchers emphasize that people are not necessarily getting sick from sewage pollution in sea spray aerosol. They noted that most bacteria are harmless, and that further investigation is needed to determine exposure levels and infection risks. 

“This research demonstrates that coastal communities are exposed to coastal water pollution even without entering polluted waters,” said study lead author Matthew Pendergraft. “More research is necessary to determine the level of risk posed to the public by aerosolized coastal water pollution. These findings provide further justification for prioritizing cleaning up coastal waters.”

The study is published in the journal Environmental Science & Technology.

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By Chrissy Sexton, Earth.com Editor

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