Microplastics and nanoplastics in tea: Sources, characteristics and potential impacts

Recent scientific studies have raised concerns about the presence and potential impacts of microplastics and nanoplastics (MNPs) in tea-based drinks. This review critically examines publications relating to MNPs in tea, with focus on the type of sample involved, methods and techniques employed to isolate and identify MNPs, and the main qualitative and quantitative findings. Sources of MNPs in tea include production water, plastic packaging and contaminated tea leaves but the most important source is teabags when steeped in boiling water. Here, more than 10⁹ MNPs have been reported to be released per plastic teabag. However, significant quantities of MNPs are also released when plastic-cellulosic composite and biodegradable bags are steeped. Discrepancies among different studies partly reflect inter-brand and inter-material differences, but a more general cause is the adoption of different analytical protocols, including different size cutoffs used during isolation and constrained by identification. Some studies have also reported leaching of plastic additives and residues on steeping, although it is not clear whether these are released from the intact teabags or MNPs that are subsequently mobilised. As teabags generate concentrations of MNPs greater than other beverages or foodstuffs, potential impacts on human health and the environment are a concern and require further study.