Fig. 2.

A pathfinder network of keywords associated with engineered nanomaterials (ENMs) in the field of environmental sciences. The bibliographic search was conducted on the Web of Science database, and the keywords used for article searching were (“Engineered nanoparticle∗” or “Engineered nanomaterial∗” or “Engineered nanopollut∗”) and “Environment∗”, with only research articles published from January 2000 to December 2021 included. The node threshold was set as top 25, and the co-occurrence rings and links within the same year were assigned with a unique color. The hub keywords with high centrality scores were highlighted with purple trims.