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Plastic is a ubiquitous environmental contaminant, resulting in widespread exposure across terrestrial and marine spaces. In the environment, plastics can degrade into microparticles where exposure has been documented in a variety of fauna at all trophic levels. Human epidemiological studies have found relationships between inhaled microplastics and oxidative stress and inflammation. Previous studies of bottlenose dolphins (Tursiops truncatus) have reported prevalent exposure to plasticizing chemicals (e.g., phthalates) as well as particle loads in gastrointestinal tracts, but exposure from inhalation has not yet been studied. The objective of this study was to determine if inhalation is a viable route of microplastic exposure for free-ranging dolphins. Exhalation samples were opportunistically collected from dolphins residing in Sarasota Bay, Florida (n = 5) and Barataria Bay, Louisiana (n = 6) during catch-and-release health assessments to screen for microplastic particles. All dolphin samples contained at least one suspected microplastic particle, and polymer composition was determined for 100% of a subset (n = 17) of samples. Additional studies are warranted to better understand the extent of inhaled microplastics, as well as to explore impacts, given potential risks to lung function and health. [ABSTRACT FROM AUTHOR]

Effects of micro- and nanoplastic particles (MNP) on organisms have been increasingly reported in recent years, with a large number of studies conducted on water fleas of the genus Daphnia. Most of the available studies used pristine particles that have not been exposed to the environment or to organic substances. In natural environments, however, organic substances like dissolved organic matter (DOM) attach to the MNP, forming an ecocorona on the particles' surface. How the formation of an ecocorona influences MNP toxicity is still uncertain. While some studies suggest that DOM can mitigate the negative effects of MNP on organisms, other studies did not find such associations. In addition, it is unclear whether the DOM attached to the particles' surface attenuates the effects of MNP directly or whether co-exposure with DOM solved in the medium attenuates MNP toxicity indirectly, for instance by increasing Daphnia's resilience to stressors in general. To draw more solid conclusions about the direction and size of the mediating effect of DOM on MNP-associated immobilization in Daphnia spp., we synthesized evidence from the published literature and compiled 305 data points from 13 independent studies. The results of our meta-analysis show that the toxic effects of MNP are likely reduced in the presence of certain types of DOM in the exposure media. We found similar mediating effects when MNP were incubated in media containing DOM before the exposure experiments, although to a lesser extent. Future studies designed to disentangle the effects of DOM attached to the MNP from the general effects of DOM in the exposure medium will contribute to a deeper mechanistic understanding of MNP toxicity in nature and enhance the reliability of MNP risk assessment. [ABSTRACT FROM AUTHOR]