Microplastics have been found in dolphin breath, suggesting the animals could be exposed to the potentially harmful particles through inhalation.

In a study researchers collected samples of exhaled air from five bottlenose dolphins in Sarasota Bay, Florida, and six bottlenose dolphins in Barataria Bay, Louisiana.

They found that all 11 dolphins had at least one suspected microplastic particle in their breath.

Further analysis revealed that they included both fibres and fragments and included several types of plastic molecules, including polyethylene terephthalate (PET), polyester, polyamide, polybutylene terephthalate, and poly(methyl methacrylate), also known as PMMA.

Study authors Miranda Dziobak and Leslie Hart, both of the College of Charleston in South Carolina, US, said: “Not only did we find that many of the dolphins were exposed to these chemicals, but their levels were higher than those found in humans.

“We do not yet know exactly where these chemicals are coming from, but the evidence points to plastic pollution as a possible source.

“There are trillions of tiny plastic particles (microplastics) floating in the oceans, and dolphins are likely exposed to them through what they eat and the air they breathe.

“We’ve been exploring the ingestion component for the past couple of years, finding microplastics in their stomach contents and prey fish. Now it’s time to explore the other primary exposure route.”

They added: “Finding microplastics in the exhaled breath of dolphins highlights how extensive environmental microplastic pollution is.

“Because of their large lung capacity and deep breaths, we are worried that breathing in microplastics may damage their lungs.

“Finally, studies like this also warn us of hazardous exposures that people living and working in the coastal environment may be facing.”

For the study published in the Plos One journal, the researchers held a collection surface over or just above each dolphin’s blowhole as it exhaled in order to collect the samples.

They also sampled the surrounding air near the dolphins, allowing them to confirm the microplastics they detected were not just airborne near the blowholes but were actually exhaled.