Widespread microplastic and nanoplastic contamination in the intestines of birds: A case study from Chengdu, China

Widespread pollution of microplastics (MPs) and nanoplastics (NPs) poses significant threats to organisms and human health. However, the extent of MPs and NPs contamination and their ecological risks to wildlife remain underexplored. In this study, we used Laser Direct Infrared (LDIR) spectroscopy to identify and characterize MPs in the intestinal contents of 49 bird species, and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) to identify NPs in the intestinal contents of five species. LDIR analysis indicated that chlorinated polyethylene (CPE) and polyvinyl chloride (PVC) were the most prevalent plastics among 32 identified types. MP particle sizes below 100 μm were most abundant, and MPs were predominantly in the form of fragments or pellets. We also found that birds with narrower dietary niche breadth had more MPs. Herbivorous and carnivorous birds had higher MP abundance than omnivorous species, which suggests the capacity of MP accumulation across diet categories. The Polymer Hazard Index (PHI) for MPs revealed that most species sampled were classified at hazard levels III or IV. Py-GC/MS identified four types of NPs in bird intestines, including nylon 66 (PA66), PVC, polyethylene (PE), and polypropylene (PP). This study advances our knowledge of plastic pollution ingested by terrestrial organisms and the risks associated with increased plastic pollution in the environment.