Precise characterization of the presence and fate of plastic oligomers in water

Microplastics are synthetic polymers that contribute to water pollution. However, little is known about the presence and fate of microplastic breakdown products, especially oligomers, due to their structural diversity and lack of standards. Here we present Oligomer-Finder, a non-targeted platform that uses repeated neutral losses, retention time prediction and custom-built databases to screen and annotate oligomers. By incubating four commonly used bioplastics in three natural water types, we identified several hundred released oligomers, which entered water quickly but declined over time. Oligomers with shorter chains or modified end structures showed greater stability. Using Oligomer-Finder combined with a suspect screening approach, we detected dozens of oligomers from five polymers and hundreds of potentially new oligomers in wastewater samples from 13 treatment plants. Aquatic toxicity assessments revealed embryotoxicity in zebrafish, highlighting potential ecological risks. Oligomer-Finder, with its user-friendly interface, provides precise identification of oligomers and supports life-cycle risk assessments for plastics. Oligomers are among the various chemical contaminants that can derive from the breakdown of microplastics and that are challenging to detect. A purposely designed platform allows detection of a large number of oligomers, providing an important step towards their risk assessment.