Researchers at the College of Charleston in South Carolina have discovered microplastic particles in the air exhaled by wild bottlenose dolphins. This indicates that inhalation could be a significant route of exposure to these potentially harmful contaminants. Miranda Dziobak and her team published their findings in the open-access journal PLOS ONE.
Exhaled breath is collected from a wild bottlenose dolphin during a health assessment conducted by the National Marine Mammal Foundation and partners in Barataria Bay, LA. Image Credit: Todd Speakman/National Marine Mammal Foundation. Bottlenose dolphin health assessments were conducted under MMPA/ESA Permit No. 18786-03 in 2018 and MMPA/ESA Permit No. 24359 in 2023, CC-BY 4.0.
Humans and other animals worldwide are exposed to tiny plastic contaminants called microplastics. Exposure to microplastics has been associated with negative health effects in humans and rodents, including oxidative stress and inflammation. The ingestion of food contaminated with microplastics is a significant route of exposure for wildlife and humans. Inhalation of airborne microplastics has also been connected to harmful health effects in humans.
Few studies, however, have investigated inhalation as a possible source of microplastic exposure for wildlife. In this study, during catch-and-release health assessment studies, the research team collected exhaled air samples from five bottlenose dolphins in Sarasota Bay, Florida, and six dolphins in Barataria Bay, Louisiana. They positioned a collection surface over or just above each dolphin's blowhole to capture the air while it exhaled.
Examination of the collected air revealed that all 11 dolphins had at least one possible microplastic particle in their breath. Further examination of the exhaled microplastic particles indicated the presence of fibers and fragments comprising various types of plastic polymers, including polyethylene terephthalate, polyamide, polyester, polybutylene terephthalate, and poly(methyl methacrylate).
The research team also sampled the surrounding air near the dolphins to provide a comparison. This allowed them to confirm that the detected microplastics were not merely airborne near the blowholes but were exhaled by the dolphins.
These results reinforce the notion that inhalation, in addition to ingestion, could be a significant route of microplastic exposure for dolphins. However, the authors caution that their findings are preliminary, highlighting the need for further research to more accurately quantify the extent of inhalation exposure to different types of microplastics in bottlenose dolphins and to assess the potential health impacts, including the risk of lung damage.
The authors added, “We know that microplastics are floating around in the air, so we suspected that we would find microplastics in breath samples. We are concerned by what we are seeing because dolphins have a large lung capacity and take really deep breaths, so we are worried about what these plastics could be doing to their lungs.”
Journal Reference:
Dziobak, M. K., et al. (2024) First evidence of microplastic inhalation among free-ranging small cetaceans. PLOS ONE. doi.org/10.1371/journal.pone.0309377.