Wild dolphins off US Southeast coast found with microplastics in their breath, study says

For the first time, scientists have found evidence that marine mammals could be inhaling microplastics, according to new research that detected the potentially harmful particles in the breath of bottlenose dolphins off the coasts of Louisiana and Florida.

Microplastics are small pieces of plastic defined as less than 5 millimeters long (less than one-fifth of an inch) that have been linked to adverse effects on human and animal health in earlier studies.

Previous research has discovered the tiny particles present in marine mammals’ tissues from exposure through consumption and then movement from the digestive tract into other organs. However, the new study, published Wednesday in the journal PLOS One, is the first to explore inhalation as a viable route for cetaceans to be exposed to microplastics.

“We found that dolphins may be breathing in microplastics, even if they live in rural areas away from high levels of human activity. This demonstrates that these particles are everywhere, regardless of urbanization and human development,” said co-lead author Miranda Dziobak, an environmental scientist and instructor of public health at the College of Charleston in South Carolina.

Airborne microplastics have been found all over the globe, even in the Arctic and other remote locations. The researchers are unsure how inhalation of microplastics will affect dolphins, but they suspect it could have an impact on the creatures’ lung health, according to the study.

With the findings, the study authors were “disappointed, but not surprised,” Dziobak said. “We know that plastics have contaminated virtually every part of the globe, so contamination in wildlife seems almost inevitable.”

Studying dolphin breath

Scientists studying marine mammals and microplastic consumption have long speculated that inhalation was a way in which cetaceans could acquire microplastics in their bodies, similar to how humans have also been found to breathe in the small particles.

“Now we can say with confidence that it is,” said Greg Merrill, a researcher and doctoral student in ecology at Duke University in Durham, North Carolina, who was not part of the new study.

“It opens a myriad of inquiries into the consequences of such an exposure,” said Merrill, who was the lead author of an October 2023 study that found more than half of marine mammals tested had at least one microplastic particle embedded in their tissues.

To test the dolphins’ breath, the researchers took samples from 11 wild bottlenose dolphins — six from Barataria Bay in Louisiana, and five from Sarasota Bay in Florida — during catch-and-release health assessments in May and June 2023. The study team held up petri dishes to the mammals’ blowhole, through which dolphins inhale and exhale. After examining the dishes under a microscope, the scientists found that each dolphin exhaled at least one microplastic particle.

The types of plastics found in the dolphins were similar to those observed in previous human inhalation studies, with the most common being polyester, a plastic commonly used in clothing, Dziobak said.

Merrill pointed to a November 2022 study that estimated large baleen whales, such as blue whales, can consume up to 10 million microplastics each day. “Confirmation that cetaceans inhale microplastics as well as consume them means that our estimates of total microplastic exposure to these species are underestimated,” he added in an email.

Previous research indicates that microplastics within the ocean are flung into the atmosphere through wave activity, so it’s possible that other marine mammals that breathe at the surface such as dolphins could be exposed to the particles as well, Dziobak said in an email.

However, the study authors did not examine other marine or terrestrial mammals, so the impact on other animals can’t be determined, she added.

Coastal dolphins and human health

The authors of the new study hope to do further research on microplastic inhalation in dolphins to understand the types of plastic they are exposed to and potential health risks, Dziobak said.

Bottlenose dolphins have a long lifespan — at least 40 years in the wild — with some populations staying in the same areas year-round. Resident dolphin pods can be useful in detecting disturbances in their local environment and can also provide more information for humans who swim in the same waters, eat the same species of fish and live along the coast, she added.

“This is an important finding but is rather unsurprising owing to the ubiquity of microplastics in the environment,” Merrill said. He is also the lead author of a new study that published Wednesday in the journal Marine Pollution Bulletin. Merrill and his coauthors discovered plastic debris in the water has an acoustic signature similar to that of dead squid, the primary prey for certain whale species that use sound waves to hunt for food.

“We share much of our physiology with marine mammals and consume much of the seafood (they) eat, so this research has considerable implications for human health,” he added.

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